NAGARJUNACOLLEGE OF ENGINEERING AND TECHNOLOGY
VENKATAGIRIKOTE, DEVANAHALLI, BENGALURU– 562 110
Guidelines for the Preparation of Project Evaluatiuon Internal-II (18ECP83 Report)
1. Project report should be typed (Times New Roman style) neatly on one side of the paper with 1.5
line spacing on a A4 size bond paper. The margins should be: Left-1.25”, Right-1” and Top & Bottom0.75”.
2. Report should besoft bounded with EC report color(Purple)
3. Abstract should not be more than One Page.
4. Sequence of pages to be followed as:
1. Cover Page
2. Certificate
3. Acknowledgment
4. Abstract
5. Table of Content
6. List of Figures
7. List of Tables
8. Chapter-I
• Introduction
• Objective
9. Chapter -II
• Literature Survey (At least 12 Papers)
10. Chapter -III
• Methodology/ Working Model
11. Chapter -IV
• Block Diagram
• Flow Diagram
12. Chapter- V
• System Requirements
13. Chapter- VI
• Results and Discussions
14. Chapter- VII
• Conclusion and Future work
15. References (At least 30 Papers)
16. Appendix
Note: Total number of pages 50-55(Approx.)
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
BELAGAVI
Project Evaluation-18ECP83
Report on
“Treatment of Hepatocellular carcinoma using 5-Slot Microwave
Ablation Antenna at 2.45 GHz”
Submitted in the partial fulfillment of the requirement for the award of the degree in
Bachelor of Engineering
In
Electronics & Communication Engineering
Submitted by
Mr. P. VIJAY KUMAR REDDY
Mr. P. NIRANJAN
Mr. P. JANARDHANA REDDY
Mr. T. NAVEEN KUMAR REDDY
1NC18EC063
1NC18EC064
1NC18EC069
1NC18EC093
Under the Guidance of
Dr. Ajay Kumar Dwivedi
Associate Professor
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
NAGARJUNA COLLEGE OF ENGINEERING AND TECHNOLOGY
(An Autonomous Institution under VTU, Belgavi-590018)
VENKATAGIRIKOTE, DEVANAHALLI, BENGALURU– 562164
2021-2022
DEPARTMENT OF ELECTRONICS AND COMMUNICATIONENGINEERING
CERTIFICATE
This is to Certify that the project work entitled “Treatment of Hepatocellular carcinoma using 5-Slot
Microwave Ablation Antenna at 2.45 GHz”carried out by MR P. Niranjan(1NC18EC064), MR P. Vijay
Kumar Reddy(1NC18EC063),MR P. Janardhana Reddy(1NC18EC069), MR T. Naveen Kumar Reddy
(1NC18EC093) a bonafide students of Nagarjuna College of Engineering and Technology, an autonomous
college under Visvesvaraya Technological University, Belagavi, in partial fulfillment for the award of
Bachelor of Engineering in ELECTRONICS & COMMUNICATION ENGINEERING during the year
2021-2022.
It is certified that all corrections/suggestions indicated for internal assessment have been incorporated in
the Report deposited in the departmental library. The project report has been approved, as it satisfies the
academic requirements in respect of project work prescribed for the said degree.
Signature of the Guide
Signature of the HoD
Signature of the Principal
Dr. Ajay Kumar Dwivedi
Dr. Nagesh K N
Dr. B V Ravishankar
Internal/External
Name of the Examiners
1.
2.
Signature with date
ACKNOWLEDGEMENT
Every project begins with an idea and materializes with concrete efforts. In the beginning, we would like
to thank the almighty God and our parents who gave us the strength and capability to work on this project
and complete it successfully.
We are extremely grateful to our project guide Dr. Ajay Kumar Dwivedi, Associate Professor,
Department of Electronics and Communication Engineering for the guidance and encouragement.
It is indeed gratifying to have the privilege to express our sense of gratitude to our project coordinators
Dr. Nagesh K.N, HoD of ECE & Dr. H. Venkatesh Kumar, Professor, Department of Electronics
and Communication Engineering, NCET for his scholarly guidance during the course of
investigation.We extend our sincere gratitude to Dr.Nagesh K N, Head of the Department, Electronics
and Communication Engineering, NCET, for his consistent assistance and guidance during the course
of the project work.
We also express our gratitude to Dr. B V Ravishankar, Principal, Nagarjuna College of Engineering
and Technology for his help and support.
Finally, we express our immense pleasure and thanks to all Teaching staff and Non- teaching staff of
the Department of Electronics and Communication Engineering, NCET for their co-operation and
support.
P Niranjan (1NC18EC064)
P Vijay Kumar Reddy (1NC18EC057)
T Naveen Kumar Reddy (1NC18EC093)
P. Janardhana Reddy (1NC18EC089)
ABSTRACT
Every year, about 7 lakh Indians succumb to cancer, with an additional 10 lakh being newly diagnosed.
In most cases, surgical removal of hepatocellular carcinoma is not a viable option. It has been shown that
microwave coagulation therapy (MCT) is an effective alternative to resection in tissue and that it is safe.
Other thermal ablation treatments have the advantage of being more rapid and producing an ablation
region that is instantaneously hypoechoic on real-time ultrasound monitoring, as opposed to laser ablation.
An intrusive technique is used in this treatment, which entails introducing a thin microwave coaxial slot
antenna (operating at 5GHz) into the tumour in order to coagulate the cancer cells. When it comes to
analyzing complex structures, the finite element approach is applied. According to the world health
organization, more than half of the world’s population does not have access to conventional diagnostics
tumor imaging due to its inflated cost. This number is even worse in developing countries like India.
herefore, microwave imaging has attracted much focus as an alternative to conventional ionizing radiation
methods such as CTs and mammography due to its non-ionizing characteristics and significantly lower
cost.
Microwave imaging of human tissue has been investigated exhaustively in recent years. Still, limited
detection capabilities, complex computational techniques, and variation in tissue electrical parameters
have restrained the practical implementation in actual clinical outcomes. Since malign breast tumors have
significantly different electrical properties than healthy tissue, microwave technology resulted in a
promising technique in breast tumor detection. This technique is analogous to the ground-penetrating radar
technology with certain modifications; electromagnetic waves are transmitted at microwave frequency
using arrays of microstrip antenna, and the reflected signal from the malign tissue containing the electrical
properties is recorded. In contrast, the performance characteristic comprises large bandwidth and highly
directional antenna, which can be accomplished using antenna arrays.
PREAMBLE
CHAPTER 1: INTRODUCTION
Every year, about 7 lakh Indians succumb to cancer, with an additional 10 lakh being newly
diagnosed. In most cases, surgical removal of hepatocellular carcinoma is not a viable option.
It has been shown that microwave coagulation therapy (MCT) is an effective alternative to
resection in tissue and that it is safe. Other thermal ablation treatments have the advantage
of being more rapid and producing an ablation region that is instantaneously hypoechoic on
real-time ultrasound monitoring, as opposed to laser ablation. An intrusive technique is used
in this treatment, which entails introducing a thin microwave coaxial slot antenna (operating
at 5GHz) into the tumour in order to coagulate the cancer cells. When it comes to analyzing
complex structures, the finite element approach is applied. According to the world health
organization, more than half of the world’s population does not have access to conventional
diagnostics tumor imaging due to its inflated cost. This number is even worse in developing
countries like India.
CHAPTER 2
LITERATURE SURVEY
Chapter 2 Contains The Litreature Survey of the Different papers of different papers.
In [8] author presented a technique to reduce overall diameter of antenna by introducing air
filled coaxial cable. At design frequency of 7 GHz the S11 obtained was -24 dB. Lesion area
obtained was 4.1 x 2.7 cm. Obtained higher reflection coefficient with reduced diameter by
15% but at a cost of elongated ablation zone.
In [9] tapered balun technique was incorporated at the outer conductor of coaxial cable.
At the designed frequency of 6 GHz the S11 obtained was -20 dB.Lesion area obtained was
4.6 x 3.5 cm2. Tapered balun reduced the surface current on the outer conductor resulting
in more spherical ablation but SAR obtained was asymmetrical. Also there was 30 dB
reduction in SAR as compared to conventional design.
In [10] the author proposed a copper tube spiral antenna.At designed frequency of 2.45 GHz
the S11 was -20 dB.Lesion diameter obtained was 3-4 cm. Obtained effective antenna
cooling technique and also more spherical ablation but addition of water increases the
diameter of the antenna making it more invasive.
CHAPTER 3: SYSTEM REQUIREMENTS
This Chapter Explains About The System Requirements For Our Project. We required
COMSOL MULTIPHYSICS Software Tool to Design the antenna and to calculate the
amount of HCC Tissue is Ablated And Temparature Distrubution.
3.2 BLOCK DIAGRAM
This section explains the Block Diagram of Treatment for Heptacellular Carcinoma Using
Microwave Ablation Antenna.
CHAPTER 4: METHODOLOGY
The Finite Element Method is an effective approach for analysing complicated structures
that allows modifying the antenna's configuration. This approach involves expressing a
domain using geometrically simple forms from which approximation functions may be
generated. Using COMSOL multiphysics, a 2D finite element model calculates the absorbed
power and temperature distribution around a single thin microwave coaxial antenna. In order
to test the antenna model for FM analysis, the outer conductor of the narrow coaxial wire
was chopped to 1mm wide ring form. The antenna is encased in a PTFE sleeve (catheter) for
hygiene reasons. In microwave coagulation treatment, the antenna operates at 2.45 GHz. The
antenna shape is 2D modeled and studied with varied slot dimensions of 1mm, 1.2mm,
1.5mm,1.7 mm and 1.9 mm from the tip.
CHAPTER 5: RESULT DISCUSSION
For the evaluation of MWA results in treating HCCs, the local and tumor control rate, overall
survival (OS), mean and medium survival rate, as well as PFS are essential parameters. For
the treatment of HCCs, clinical guidelines categorize ablation therapies not only as equal to
surgery but even better than surgery in small or very small HCCs (oligonodular tumors ≤ 3
cm). The main reason for this recommendation is the fact that ablation leads to much less loss
in the normal liver parenchyma compared to surgical resection. The therapeutic response of
MWA in HCCs in 53 patients was evaluated and compared in a retrospective study. Complete
local tumor control was documented in 84.4 % of lesions treated with RFA and in 88.9 % of
lesions treated with MWA.
CHAPTER 7: CONCLUSION & FUTURE WORK
We analyse an axisymmetric model with a narrow microwave coaxial antenna in COMSOL
Multiphysics. The mesh statistics of the model, as well as the SAR pattern and temperature
distribution in tissue, are all analysed in detail. The models offer temperature distribution,
surface temperature on tissue, and power absorption in tissue with variable electric, thermal,
and geometric variations. By steady-state tissue temperature distribution for 40 W microwave
input.In the designed antenna we introduced a total of 5 slots with variable diameter which
improves the overall ablation zone and more spherical ablation zone.
TABLE OF CONTENTS
Chapter
No
CHAPTER NAME
PAGE NO
Acknowledgment
Abstract
Preamble
Table of Contents
List of Figures
Abbrevations
List of Tables
Introduction
Literature survey
i
ii
iii
vi
vii
viii
ix
1-11
12-16
Chapter 3
Chapter 4
System requirements and Block Diagram
17-27
System Design and Methodology
28-29
Chapter 5
Results and Discussions
21
Chapter 6
Conclusion and Future work
22
Chapter 1
Chapter 2
References
39-42
Appendix
43
LIST OF FIGURES
FIGURE
NO
2.1
2.2
4.1
6.1
6.2
6.3
6.4
FIGURE NAME
Microwave Ablation tools and components
Research gap summary
Block diagram
Simulated antenna environment
Power dissipation
Fraction of Damage
Temperature Distribution
PAGE NO
14
17
29
31
31
32
33
LIST OF TABLES
TABLE NO
1
2
TABLE NAME
Microwave Ablation System
Study Between Papers
\
PAGE NO
7
14
ABBREVIATIONS
HCC
Heptacellular Carcinoma
WHO
World Health Organization
MRI
Magnetic Resonance Image
MWA
Microwave Ablation
Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
CHAPTER 1
INTRODUCTION
Hepatocellular carcinoma (HCC) is the third most common organspecific cause of cancer-related
mortality in the world with an average survival rate of less than six months if untreated, and a five-year
survival of only 5 – 9 % from the time of diagnosis [1]. Furthermore, the liver is the most common site of
distant metastases in patients with colorectal cancer with a cumulative incidence rate of up to 50 %.
Surgical techniques like resection or transplantation are still considered the gold standard for the treatment
of primary and secondary liver cancer. However, in more than 75 % of cases surgical resection is not
possible [2]. The same applies to systemic chemotherapy. Different alternative interventional modalities
for the treatment of unresectable liver tumors are available.
In interventional oncology two different therapeutic approaches can be used for the treatment of liver
malignancies: first, transarterial procedures with administration of chemotherapeutic agents such as
transarterial chemoperfusion (TACP), transarterial chemoembolization (TACE) or transarterial
embolization (TAE) or radioactive material such as selective internal radioembolization (SIRT); second,
thermal ablation techniques such as radiofrequency ablation (RFA), microwave ablation (MWA) and
laser-induced interstitial thermotherapy (LITT) as well as irreversible electroporation (IRE) and
cryotherapy.
These are potential minimally invasive treatment modalities especially in early-stage HCC and
oligonodular metastases (three or less lesions), particularly in non-resectable liver lesions or if the patient
is not a candidate for liver transplantation or is in poor general condition [3]. This paper reviews the
evidence supporting the use of MWA in the treatment of HCC and hepatic metastases. Furthermore, basic
principles, theoretical background, tools and techniques, technical problems, and the latest MWA
protocols will be discussed. The advantages, limitations, and technical considerations of MWA treatment
will be provided.Microwave ablation (MWA), a type of PLA, is a recent development in the feld of tumor
ablation. It has emerged as an alternative treatment for HCC and is increasingly used for the inactivation
of tumor cells. In some cases, operative MWA is performed using a laparoscopic technique. MWA uses
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
electromagnetic (EM) waves to create a microwave near-feld with direct tissue heating. However, the
major limitation of conventional MWA systems is the lack of predictability of the ablation zone size and
shape. Therefore, a specifc newer generation MWA system, the Emprint™ Ablation System with
Thermosphere™ Technology (Covidien, Boulder, CO, USA), was designed to create predictable large
spherical zones of ablation that are not impacted by varying tissue environments. This review highlights
the efcacy and complications of MWA performed with conventional systems and the newer generation
system in patients with HCC.
with the latter being the most commonly used frequency. The category of 2450 MHz is the one most
commonly employed, whereas the frequency of 915 MHz can facilitate deeper penetration, which
potentially leads to the creation of larger ablation zones [13]. MWA systems create a large active heating
zone (up to 2 cm surrounding the antenna for conventional systems), thus permitting more uniform
necrosis in the target lesion. However, the major limitation of all heat-based thermal ablation devices is
the lack of predictability of the ablation zone size and shape. In addition, the shape of the EM feld, which
is elliptical with conventional systems, cannot be modifed according to the presence of adjacent vessels
(Fig. 1b). These limitations must be overcome to achieve the desired outcomes.
1.1 Introduction and Background of Cancer Treatment Technique
Cancer is responsible for around 1 in every 7 deaths globally. Primary hepatobiliary system malignancies
are a substantial public health concern globally, and their therapy provides considerable difficulties for
the hepatobiliary specialist. In India, the incidence of hepatobiliary cancers is growing. Hepatobiliary
malignancy (liver cancer) is the fifth most frequent kind of cancer in males globally (7.5%) and the ninth
most common type of cancer in women (9.5%). (3.4 percent ). It is mostly an issue in less developed
nations, accounting for 83% (and 50% in China alone) of the projected 782,000 new cancer cases globally
in 2012. This is because hepatocellular carcinoma (HCC) is associated with chronic hepatitis B (HBV)
and hepatitis C (HCV) infections. approximately 781,631 deaths in 2018 (8.2 percent ). Liver cancer has
an extremely dismal prognosis (overall ratio of mortality to incidence is 0.95). In India, liver cancer is the
ninth most frequent kind of cancer in males (incidence 3.5 and death 3.3) and the twelfth most common
type in women (incidence 3.5 and mortality 3.3). (ASR incidence and ASR mortality 1.9). HCC accounts
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
for 70%–85% of primary liver cancer cases in the majority of nations. with the illness load projected to
grow in the future years. The combination of cancer and chronic liver disease complicates therapy
significantly. The varying regional incidence of liver cancer is
similar to that of HCV and HBV infections, which account for 75% of global cases. Organ transplantation,
surgical resection, chemotherapy, radiation therapy, laser hyperthermia, radio-frequency ablation,
cryotherapy, and microwave ablation are all options for cancer treatment. [1]
1.2 Present treatment technologies and Drawbacks
•
Surgical re-section-It is the most commonly used technique for early stage cancer treatment however
for advance stage where cancer cells are located at multiple and unfavorable points, surgical resectioning may hinder the performance of the organ [1].
•
Chemotherapy-It is not suitable for selected region cancer treatment within the body and has a
drawback of damaging large portion of healthy parts of the body [2].
•
Radiation therapy-It uses high energy to destroy the DNA of cancer cells but due to high frequency
application collateral damage to nearby healthy organ is evident [3].
•
Laser Ablation-This method uses fiber optics to deliver laser energy pulses which heats and
evaporates targeted tissue however it is the most expensive treatment and penetration of laser inside
blood vessels is the main drawback [4].
•
Cryo-Ablation-It is the oldest method and uses nitrogen and argon mixture to reach temperature as
low as -75 degree C. The lesion zones thus created cannot be controlled for variable size tumors and
it also has limitation of time constraints [5].
•
Lastly, the Radio Frequency Ablation techniques (RFA) in which radio waves produces electrical
current to heat up the tumor cell up to the level of irreversible damage (necrosis) but the main problem
with RFA is the unpredictable ablation zone and less ablation volume [6].
At higher frequency the Microwave Thermal Ablation (MWA) process which is a minimally invasive
technique to destroy tumor tissue by the way of high localized temperature induced absorption of
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
electromagnetic wave by the targeted tissue. Such high temperature (i.e. 55-60°C) causes irreversible
tissue damage (necrosis).
Background on Cancer Treatment Techniques:
Cancer is the uncontrolled growth and spread of cells. It can affect almost any part of the body for example
lung, liver, kidney, breast and bones. Therefore, it is desirable to remove the cancer from the human body
as soon as possible. Cancer causes 1 in 8 deaths worldwide and is rapidly becoming a global pandemic.
The global cancer burden is expected to nearly double to 21.4 million cases and 13.5 million deaths by
2030 (Siegel, et al., 2015). Treatment options for cancer patients include surgical resection, chemotherapy,
radiation therapy, transplantation and tumour ablation techniques. Surgical resection is considered the
gold standard treatment option for cancer patients.
However, it is limited for patients with early stage cancer and ineffective for treating metastasis stage
where cancer cells have grown into blood vessels and produce cancer recurrence in other part of the body.
Surgical resection is also not an option for patients with too spread cancer cells as it might hinder the
functional capability of the organ after the operation (Petrich-Munzinger, et al., 2014). In addition, only
small percentage of patients with metastasis tumours are amenable to surgical resection due to high
surgical risk or un-favourable tumour location.
Eligibility of organ transplant for cancer patients depends on finding the suitable organ donor which is not
always possible. Chemotherapy is not suitable for treating selected tumour tissues within the body and it
comes at the expense of damaging large portion of healthy tissues (Kassner, 2000). Radiation therapy uses
high energy levels to kills the cancer cells by destroying their DNA but on the other hand, it destroys the
DNA of healthy tissues surrounding the tumour (Bentzen, 2006).
All the treatments mentioned measures prove to be ineffective as the tumour can reoccur in the patients in
any part of their body which is called cancer metastasis. (Thongsopa & Thosdeekoraphat, 2013). Such
limitations give rise to the development of thermal ablative techniques to be less invasive more effective
in eradicating tumours that cannot be treated using the conventional treatment options.
The main purpose of ablative treatments is the ability to treat patients who cannot be treated through
surgery, resection or any other means as there is high surgical risk, or unfavourable tumour location.
Sometimes, these treatments are also used in patients waiting for organ transplant or during surgery to be
sure the treatment aimed at the right place. Ablation refers to the method of selectively killing a wellDEPT.ECE, NCET, Bengaluru
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
defined target tissue by the application of heat based (radiofrequency ablation and microwave ablation),
cold (cryotherapy), chemicals Chapter One Introduction and Background of Cancer Treatment Techniques
3 (percutaneous ethanol injection), or laser hyperthermia techniques directly to a tumour causing cell
death. The most common cancers treated by thermal tumour ablation are liver, lung, kidney (renal) and
bone cancers. Ablative treatments typically do not require a hospital stay and more than 90% of patients
are released from the hospital the day after the procedure.
Ablation is an image guided treatment which refers to the method of killing selectively targeted tumour
tissues by the application of heat-based therapy such as Radio frequency ablation, microwave ablation,
cold based therapy (Cryo-ablation), focused ultrasound ablation and Laser ablation and direct current
catheter ablation. Each of these techniques work in different ways in order to eradicate tumour tissues
with saving as much surrounding healthy tissues as possible, all while maintaining minimally invasive
and relatively less painful procedure to the patient. Ablation can be performed in open surgery using a
catheter based applicator or percutaneously by inserting a needle or probe - which is called applicator into the tumour through the skin. This requires only a tiny hole, usually less than 3 mm via which the
probe is introduced (McGahan & Raalte, 2005; Kaur & Maini, Surita, 2014).
Ultrasound, Computer Tomography (CT) scanning or Magnetic Resonance Imaging (MRI) are used to
guide the needle or the probe into the tumour (Vrba Jr, Jan & Vrba, David, 2014). When the probe is
within the cancer, it is connected to a generator which provide the required power to “burn” or “freeze”
the cancer. “Burning” refers to increasing the temperature of the tumour to such a level that causes internal
coagulation which results in cell death. This is usually achieved by radio or microwave frequency probes,
referring to the type of energy used to increase the tissue temperature. “Freezing” refers to Cryo-ablation
which decreases the temperature to -75 °C which also kills the cancer cells.
Thermal ablation is not only limited to treat cancer patients, but also has a numerous beneficial clinical
effects for example, it is used to provide an efficient means for coagulating vessels to stop bleeding during
open surgery or carefully eradicate tissues that may not be cancerous e.g. cardiac arrhythmias, prostatic
hypertrophy and varicose veins (Prasantamrongsiri, S, et al., 2012; Suseela, Sreekala, et al., 2013; Rosen,
Arye, et al., 2002). Both RF and microwave-based tumour ablation techniques are used to ablate tissue by
heating it to cytotoxic temperatures. Temperatures in excess of 60 °C are known to cause relatively
instantaneous cell death, while temperatures from 50-60 °C will induce coagulation and cell death in a
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
matter of minutes, depending upon temperature, previous thermal injury (Brace, 2009). Chapter One
Introduction and Background of Cancer Treatment Techniques 4 Despite both RF and microwave energy
can heat tissue to cytotoxic levels, the mechanisms of RF and microwave heating are quite different and
must be considered for ablation of different tissue types
1.3 Benefits of Microwave ablation compared to other thermal ablation Techniques:
Most important factor that distinguishes microwaves from other sources of thermal therapy techniques
that microwaves can propagate through all types of tissues including dehydrated, charred and desiccated
tissues created during the ablative process unlike RF, laser and ultrasound Chapter One Introduction and
Background of Cancer Treatment Techniques 9 energies can be substantially affected by different tissue
types, especially as a result of thermal ablation. Microwaves also offer more direct and fast heating than
other ablation energies, making them more potent in organs with high blood perfusion or near vascular
heat sinks and provide shorter treatment time (Singal, et al., 2018; Yhamyindee, P, et al., 2012; Luyen, et
al., 2017). Despite RF ablation is the most widely used modality in cancer treatment, it has several
limitations and shortcomings which gave rise to the development of microwave ablation with less invasive
and more effective method in cancer treatment. The differences between RF and microwave heating in
each organ given that the properties of each tissue type, are demonstrated in Table 1. As illustrated in
Table 1, RF heating is limited in areas of high blood perfusion rate (kidney and liver), in tissues with poor
electrical and thermal conductivity (lung and bone), while microwaves offer all of the same benefits as
RF energy for thermal ablation, but are not as dependent on tissue properties, have the ability to heat faster
in a larger volume, less affected by perfusion and may be able to penetrate deeper into low conductivity
materials (lung and bone) (Suseela, Sreekala, et al., 2013; Rosen, Arye, et al., 2002; McGahan & Raalte,
2005; Kaur & Maini, Surita, 2014; Tacke, et al., 2004; Lee, et al., 2003; Hulsey, et al., 2015; Phairoh, et
al., 2015; Sanpamch, et al., 2015; Brace, 2009).
1.4 Microwave ablation system:
Microwave ablation system consists of Microwave power source such as solid state semiconductor devices
or vacuum tube devices such as magnetron. Coaxial cable is used to carry the microwave power from the
generator to the antenna. Most thermal ablation devices intended for percutaneous use are currently
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
between 1.5 mm and 3 mm in diameter. Smaller antenna diameters are preferred for percutaneous
applications while larger needle diameters are associated with increased risk of complications such as
bleeding. On the other hand, small diameter coaxial cables have lower power handling ability which is
not desirable in microwave ablation system. Increased power delivery has been associated with faster and
potentially more effective treatments, particularly when targeting large tumours (Brace, Christopher L,
2010; Vojackova, Lucie, et al., 2014; Phairoh, C, et al., 2013). At the same time, input powers exceeding
the cable power rating can have detrimental effects. Using only smaller size antenna will facilitate active
cooling and antenna arrays can help increase energy delivery and hence produce larger ablation zones
(Taj-Eldin, Mohammed & Prakash, Punit, 2014). The antenna contains a rigid shaft and the radiating
section at the distal end of the applicator as shown in Fig. 1.
Lung
Liver
Organ
RF Ablation
-It is limited only to treat only small tumours
less than 3 cm in diameter.
-It is ineffective to ablate tumours in high
perfusion regions such as tumours near large
vessels of diameter 3mm (Hancock, et al., 2015;
Singal, et al., 2018).
Microwave Ablation
-It can ablate tumour tissues around large vessels due
to faster heating, higher temperature levels provided
by microwaves in high perfusion region (e.g. Liver)
(Hancock, et al., 2015).
-higher effective conductivity attained in microwave
ablation produced larger ablation lesions Increasing
(Brace, 2009).
- RF current isnot able to penetrate through low
conductivity aerated lung.
-It has limited amount of power deposited into
tissue due to the increased impedance seen by
generator (Brace, 2009).
-Poor thermal conductivity of aerated lung
during RF ablation results in small ablation zone
(Brace, Christopher L, 2010; Wonnell, et al.,
1992).
-The lower permittivity and conductivity of aerated
lung allows deeper microwave penetration
(Sanpamch, et al., 2015).
-Microwave heating is not substantially hampered by
low-conductivity tumour tissue which can actively
produce larger ablation zones (Lee, et al., 2003).
-Due to better propagation of microwave in low
conductivity lung, better thermal gradient achieved
maximum temperature exceeds 150 °C (Colebeck,
Erin, et al., 2013).
-Change in tissue properties during ablation
procedures won’t affect microwave energy as much
as RF energy (Hulsey, et al., 2015).
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Kidney
Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
-It is Limited only to treat small tumours due to
high perfusion rate of kidney (Pop, Mihaela, et
al., 2010).
-Tissue dehydration hampers RF current as the
temperature increases during the procedure
-It is Ineffective for treating large tumours (>3
cm in diameter) or centrally located tumours
(Brace, 2009; Goldberg, SN, et al., 1998).
-Higher heating rate is observed during microwave
ablation procedure due to high water content of
kidney (Brace, 2009).
-Less sucesptable to tissue dehydration as It allows
better microwave propagation (Hancock, et al.,
2015).
-Faster heating ability of microwave energy will
overcome the high perfusion rate of kidney (Suseela,
et al., 2015).
Bone
-Limited ablation zones due to poor
conductivity and thermal conduction of bone
(Brace, 2009; Solazzo, et al., 2005).
-Microwave penetration is more effective due to low
permittivity and conductivity of bone tumours
(Gamez, ES, et al., 2013).
-Microwave applicators are developed to provide
more precised controlled ablation lesions and
achieve more functioning limb after the procedure
(Phairoh, et al., 2015; Martínez-Valdez, R., et al.,
2017; Luján, et al., 2017).
Table 1.1 Microwave Ablation System
1.5 Problems and Limitations Found in Microwave Ablation Technology:
Despite microwave ablation is the most recent ablative technique and has several advantages over other
complementary methods for cancer treatment such as low cost, smaller antenna size, shorter recovery
time and effective prevention of the metastasis of tumour cells, there are still shortcomings and
challenges accompanied with microwave ablation therapy needed to be fulfilled.
•
The tissue impedance increases as the water content evaporates during the tissue ablation which
results in shifting in the resonating frequency of the antenna. Therefore, the return loss will
increase and as most of the current microwave ablation systems use narrowband antenna, this will
create elongated ablation zone and damage the surrounding healthy tissues (Hulsey, et al., 2015;
Hancock, 2011; Brace, Christopher L, et al., 2004; Brace, Christopher L, et al., 2005)
•
The overheating of cabling used to transfer power from the generator to the applicator due to high
mismatch losses between the antenna and coaxial cable while increasing unwanted heating of the
antenna shaft. In extreme cases, high return loss may necessitate short ablation times to prevent
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thermal damage along the antenna shaft and damage of the healthy tissues along the antenna shaft
and lead to shorter ablation time (Luyen, et al., 2015).
•
The most common frequencies used in microwave ablation are 433, 912 and 2450 MHz which
produce non uniform SAR pattern resulting in unsuccessfully ablated areas within the target tissue
(Luyen, Hung, et al., 2014; Luyen, Hung, et al., 2014; Luyen, et al., 2013; Hancock, Chris P, et
al., 2013; Sawicki, et al., 2015; Hodgson, et al., 1999; Yoon, et al., 2011; Komarov, 2014; HinesPeralta, Andrew U, et al., 2006; Ahn, Hee-Ran & Lee, Kwyro, 2005). Recent studies demonstrated
that nanosecond pulsed electric fields (nsPEF) used as purely electrical cancer therapy without the
need of hyperthermia or drugs. nsPEF electrodes can provide acceptable level of homogeneity in
SAR pattern. However, the SAR homogeneity is only confined in a small volume within the
separation of the 2 electrodes and inhomogeneous in the vicinity surrounding the electrodes. It was
observed that the Chapter One Introduction and Background of Cancer Treatment Techniques 13
homogeneity of SAR pattern depends on the distance between the electrodes (Beebe, et al., 2002;
Soueid, et al., 2015).
•
The need of using baluns increases the size of the antenna which results in less comfortable and
less invasive treatment procedures for percutaneous applicators which may cause complications
after surgery (Lin, James C & Wang, Yu-Jin, 1996; Hancock, Chris P, et al., 2013; Maini, Surita
& Marwaha, Anupma, 2012; Maini, Surita & Marwaha, Anupama, 2013; Luyen, et al., 2015;
Luyen, Hung T., et al., 2015; Longo, Iginio, et al., 2003; Maini, 2016; Lara, et al., 2015).
Several scenarios have been investigated in literature regarding antenna designs proposed for microwave
ablation. Nonetheless, high reflection and lack of control over heating due to use of high input power still
represent the main shortcomings associated with these designs. High reflection encountered during
ablation due the change of tissue properties with the increase of temperature which can be attributed to
narrow band feature which hinders large portion of microwave power from being deposited within targeted
tissue. This yielded using high input power to force eradication of targeted tumour at the expense of
overheating of the cable and lack of control over heating. These drawbacks give rise to claim a novel
antenna design to alleviate complications and overcome limitations of previously proposed applicator
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designs achieve successful ablation using low microwave power by confinement of heating within the
targeted tissues rather than its surroundings.
1.6 Research Aim and Objectives:
Major concern of this work is to alleviate complications and overcome limitations of previously proposed
applicator designs especially regarding control overheating of the cable, overly-treated lesions and
unconfined heating. The aim of this research is to design and develop a compact microwave antenna for
treating focal tumours to achieve confined heating within targeted tumour by using low input power
producing minimum reflection over a wider bandwidth.
The research aim can be achieved via the following objectives:
•
Review recent research about tissue ablation therapy highlighting the pros and cons found in
previously proposed work which is consolidated in a comprehensive literature.
•
Determine limitations of previously proposed solutions regarding applicator designs which gave
rise to the problems encountered in microwave ablation.10 Chapter One Introduction and
Background of Cancer Treatment Techniques 14
•
Design less invasive antenna structure by choosing to operate the antenna at high microwave
frequency bands which will provide smaller compact design and targeted higher thermal
conductivity yielding higher absorption by the targeted region. • Apply analytical solutions by
solving Maxwell equations and boundary conditions to determine current distribution required on
the antenna surface to attain highly directed axial near-field radiation which yields confined
heating within targeted tumour model.
•
Synthesize the antenna structure using numerical simulations so that it has less abrupt transitions
which will be exploited in achieving minimum reflection over wide bandwidth.
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
•
Apply parametric studies to the antenna structure so that it has minimum backward radiation and
directed axial radiation towards the targeted tumour which helps achieving homogenous
absorption within targeted tumour and reaching the temperature levels required for ablation at low
power level while alleviating radiation towards healthy tissues surrounding the targeted tumour.
•
Apply embedded choke approach in the antenna structure which yields compact sized applicator
and minimizes return currents excited in the outer conductor of the coaxial cable. This controls
overheating of the cable and reduces the damage of healthy tissues along the antenna shaft.
•
Manufacturing and testing the developed antenna in either real biological tissues or synthesized
solutions to prove the efficacy of the proposed design as microwave coagulator in providing
successful ablation at low input power by exploiting directed axial radiation and determine the
total ablated volume obtained after the procedure.
OBJECTIVE
The Main Objective of This Project is the Ablation of Hepatocellular carcinoma using 5- Slot Microwave
Antenna at 2.45 GHz Frequency. As we all know the more than half million people are suffering from
cancer and there is no proper health care and the Treatment is very costly and most of the middle-class
people can’t afford it so we are using the Technique for ablation of Cancer With using 5-Slot antennas
and cost will be less so that middle class people and poor people can also afford it.
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CHAPTER 2:
LITERATURE SURVEY:
2.1 Microwave Ablation-literature review:
The shortcomings of previously mentioned cancer treatment techniques necessitate the investigation of an
alternative technique to maintain high success rate while reducing the complications. Microwave Ablation
technique is a special case of dielectric heating. Dielectric heating occurs when polar water molecules
present in the tissue tends to align themselves with the alternation electromagnetic fields. During such
process dielectric rotation of the molecules takes place thereby increasing the kinetic energy and hence
the temperature the tissue.
2.2 Microwave Ablation tools and technique:
Microwave ablation system includes a microwave power source. It may be a solid state power amplifier
or a magnetron. Connected to it is a co-axial cable which is used to carry the generated power from
generator to antenna. The co-axial cable should be of optimum design in order to maintain trade-off
between power handling capacity and minimally invasiveness.
The antenna section connected to coaxial cable consists of rigid shaft and a radiating element. The
radiation pattern in general should be broad side whereas axial mode of pattern may be useful in certain
conditions such as cardiac arrhythmia.
The overall system requires specialized software which allows prediction of different component
accurately in order to maintain clinical ethics while actual use. These components include design of
feasible antenna for penetration into the soft target tissue.
The heating rate in a biological tissue near the radiating element must be predicted accurately in order to
get desired, minimally invasive results. Below is the Fig.1 of Microwave Ablation tools and components
[7].
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Fig.2.1 Microwave Ablation tools and components
2.3 Comparative study between different papers
Table 2.1 Study Between Papers
In this paper
author presented a
technique
to
reduce
overall
diameter
of
antenna
by
introducing
air
filled
coaxial
cable. [8]
At design
frequency of 7
GHz the S11
obtained was 24 dB.
In this paper
tapered
balun
technique
was
incorporated at the
outer conductor of
coaxial cable. [9]
At
the
designed
frequency of 6
GHz the S11
obtained was 20 dB.
Obtained higher reflection coefficient with reduced
diameter by 15% but at a cost of elongated ablation zone.
Lesion area
obtained was
4.1 x 2.7 cm2.
Tapered balun reduced the surface current on the outer
conductor resulting in more spherical ablation but SAR
obtained was asymmetrical. Also there was 30 dB reduction
in SAR as compared to conventional design.
Lesion
area
obtained was
4.6 x 3.5 cm2.
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In this paper the
author proposed a
copper tube spiral
antenna. [10]
At
the Good reflection coefficient obtained but the pattern
designed
obtained was of rectangular shape and low operating
frequency of frequency causes inhomogenous SAR patterns.
2.45 GHz the
S11 obtained
was -37 dB.
Lesion
area
obtained was
4.5 x 2 cm2.
In this paper
authors
used
higher
rated
power source for
faster ablation and
water as cooling
agent for the
heated
antenna
and
co-axial
cable. [11]
At designed Obtained effective antenna cooling technique and also more
frequency of spherical ablation but addition of water increases the
2.45 GHz the diameter of the antenna making it more invasive.
S11 was -20
dB.
The authors in this
paper
designed
balun free antenna
for localised SAR
pattern.[12]
At designed Obtained more spherical ablation without the use of baluns
frequency of but the reflection coefficient was low resulting in higher
1.9 GHz the power requirement of upto 50 W to obtain agreeable results.
S11 was -12
dB.
Lesion
diameter
obtained was
3-4 cm.
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Lesion
area
obtained was
3.8 x 3.3 cm2.
2.4 Research Gaps
The successful outcome depends largely upon the shape of ablation, dimension of the antenna, location at
which the applicator is inserted, temperature vs. time of application, characteristics of the tissue (ex-vivo
or in-vivo) and the frequency of operation.
Few reputed journals have been published so far regarding ablation zone and time of application. Various
antenna types such as monopoles, slotted, tri-axial-slot, helical antenna have been proposed for various
clinical trial on ex-vivo bovine livers and showed some promising results. The above mentioned
techniques however do not solve the problem of asymmetric thermal ablation.
A major disadvantage of microwave ablation is the requirement of high input power up to 50W which is
necessary for the tissue ablation but the diameter of the applicator antenna must be small as possible in
order to get easily inserted in the tissue, this in turns reduces power carrying capacity of the antenna
resulting in its malfunction. Another major research area that can be explored is the continuous flow of
blood through the tissue (blood perfusion rate) which can seriously alter the ablation outcomes when
compared to ex-vivo clinical trials. Yet another major research area is the use of detection and treatment
technique incorporated in a single device which several newly published articles lacked.
The physical, biological and thermal complexity that can alter the preferred outcome need to be evaluated
in advance which somehow not tackled accurately by many journals.
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The tissue impedance increases with the time of application as the water evaporates during ablation. Such
change in impedance may shift the resonant frequency.
Also, use of baluns increases the size of antenna diameter resulting in less confortable ablation.
Thus a comparative strategy and balance between theoretical and measured results need to be taken to
account while incorporating novel techniques in applicator design for detection and treatment.
Fig.2.2 Research gap summary
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CHAPTER 3:
METHODOLOGY
3.1 ANTENNA DESIGN
The Finite Element Method is an effective approach for analysing complicated structures that allows
modifying the antenna's configuration. This approach involves expressing a domain using geometrically
simple forms from which approximation functions may be generated. Using COMSOL multiphysics, a
2D finite element model calculates the absorbed power and temperature distribution around a single thin
microwave coaxial antenna. In order to test the antenna model for FM analysis, the outer conductor of the
narrow coaxial wire was chopped to 1mm wide ring form. The antenna is encased in a PTFE sleeve
(catheter) for hygiene reasons. In microwave coagulation treatment, the antenna operates at 2.45 GHz.
The antenna shape is 2D modeled and studied with varied slot dimensions of 1mm, 1.2mm, 1.5mm,1.7
mm and 1.9 mm from the tip as shown in Fig. (2).
The wire is shorted at the tip and a 1.5 mm wide ring hole is cut 6mm from the tip. In addition to the
slot's axial and radial dimensions, the pin's radial dimensions provided excellent energy interaction
between the microwave source and the tissue. The COMSOL multi-physics user interface includes CAD
tools for modeling 2D and 3D coaxial antennas
3.2 THERMAL SETUP
Figure (2) depicts a three-dimensional arrangement with FEM boundary conditions. MWA is classified as
a kind of dielectric heating. Because of the dielectric heating, polar water molecules in tissue align
themselves with electromagnetic fields. The dielectric rotation of the molecules raises the kinetic energy
of the molecules and, as a result, the temperature of the tissue.. Because tissue is made up of many veins
and arteries, a simplified assumption is required to assess the bioheat transfer model. Applying thermal
boundary conditions to a 100micro-m diameter is difficult. The impact of adding or altering thermoDEPT.ECE, NCET, Bengaluru
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
physical factors in the equation of conduction is handled as though the tissue area of interest had no blood
vessels Penne's bioheat equation over a restricted volume is one example[7].
 c
t t
v

Tt (r , t )dV =  k t  2Tt (r , t )dV +   b  b cb [Tart ( x, t ) − Tt ( x, t )] + Qm
t
v
v
……….(1)
Where the term qm. refers to the metabolic heat production in the tissue and the term qb-blood. refers to
the contribution of blood flow to the local tissue temperature distribution, respectively. Similarly, 𝜌 is the
tissue density [kg/𝑚3 ], C is Specific heat capacity expressed in [J/kg.K] and 𝑘 is Thermal conductivity
expressed inW/m.K.
3.3 ELECTROMAGNETIC SETUP
Simulated design of the unique antenna was carried out, and the impact of thermoelectrical parameters on
tissue models was explored. An electromagnetic-bioheat transfer model was developed that includes a
temperature-dependent thermo-electrical tissue property as well as the evaluation of thermally induced
tissue injury. Specifically, the following are the Maxwell's equations for a transverse electromagnetic
mode, which are determined by the transverse electromagnetic mode.[8]
𝐴𝑒 𝑗(𝜔𝑡−𝑘𝑧)
𝐸(𝑟) = (
𝐻(𝑟) =
𝑟
𝐴𝑒 𝑗(𝑤𝑡−𝑘𝑧)
𝑟
) 𝑟…………………(2)
. 𝑍𝑖𝑛 𝜙 … … … . … … .. (3)
Where E and H are the electric and magnetic field in r and φ directions and the propagation direction of
electromagnetic waves is represented by z.
3.4 MODELING COMPUTATION DOMAIN
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
The antenna was numerically modeled and analyzed using finite element approach. It includes breaking
up a complicated geometry into tiny pieces for a set of partial differential equations. The microwave
source is at the coaxial cable tip. Table 1 shows the material volume put in the antenna. Several factors
influence the capacity of a tissue to create heat when subjected to a time-varying electric field. These
factors include conductivity, relative permittivity, and thermal conductivity
S.
No.
1
parameters
Rho_blood
Cp_blood
2
Omega_
3
4
5
6
7
8
T_blood
value
s
1000k
g/m^3
3639J
/(kg.k
)
0.003
6000
1/s
310.1
5K
2.03
2.6
2.45G
Hz
Eps_diel
Eps_cat
Relative
blood
permittivity
, Catheter
P_in
20 W
description
Density of the blood
Blood specific heat.
The rate of blood perfusion
Temperature of blood
Relative permittivity
Catheter Permittivity
The frequency of microwave
Microwave power at the source
Table 2.3 parameters
Indication for MWA:
Tumor ablation indications are divided into either a curative or palliative intention. In a curative ablation
the goal is the complete eradication of all tumor cells in order to produce a tumor-free condition. In a
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
palliative intention the main goal of MWA or RFA is to ablate a sufficient portion of the index tumor in
order to achieve symptom relief. The aim of debulking is the reduction of tumor burden or controlling
disease progression. This is of great importance, in particular, for pain reduction due to capsular or
intestinal tumor infiltration or reduction of symptoms from metastatic neuroendocrine tumors [4].
The Barcelona Clinic Liver Cancer (BCLC) staging and treatment strategy has been widely endorsed as
the optimum treatment option for HCC liver cancer. One of the key aspects in patient management is the
optimum timing for systemic treatment initiation and for declaring tumor progression and/or treatment
failure. The treatment strategy for the effective treatment of HCCs with the usual priority selection is from
very early stage HCC (resection, transplantation, ablation) to intermediate stage (TACE) to advanced stage
(sorafenib). For very early stages of HCC, BCLC stage 0 (single lesion ≤ 2 cm, Child-Pugh A, PSO 0),
ablation treatment of the lesion is the recommended first-line treatment option for patients who are not
potential candidates for liver transplantation. For early stages of HCC (BCLC stage A), surgical resection,
liver transplantation and ablation are the recommended lines of treatment as defined by the BCLC staging
system and based on specific selection criteria for each option.
Although resection can be performed in some of these patients with advanced liver disease, the mortality
is higher and liver transplantation or ablation could be more beneficial. Although recommendations of
BCLC and the guidelines of the American Association of the Study of the Liver Disease (AASLD) refer
only to RFA, studies have proved that MWA has comparable local control rates and similar survival rates
to RFA [16]. The treatment algorithm established by the AASLD recommends local treatment for earlystage HCCs (≤ 3 cm in size and ≤ 3 lesions) or early-stage HCCs (≤ 2 cm) with complications such as
portal hypertension. However, for early-stage HCCs (single or ≤ 3 lesions and ≤ 3 cm) without
complications like portal hypertension, cirrhosis or high bilirubin, liver resection should be considered as
the best treatment option.
Total tumor volume > 70 % of the liver volume, multiple tumor nodules, high extrahepatic tumor burden,
clinical evidence of liver failure, such as massive ascites, hepatic encephalopathy or other organ failure,
severe blood coagulation dysfunction including prothrombin time longer than 30 s, prothrombin activity
below 40 %, platelet count below 30,000, acute or active inflammatory and infectious lesions in other
organs are considered as absolute contraindications [18].
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Metallic materials like surgical clips and pacemakers are not contraindications for MWA. In the treatment
of non-HCC liver malignancies like liver metastases, in general a tumor size of more than 5 cm or more
than five liver lesions or considerable ascites can be considered as absolute contraindications for
interventional MWA. A tumor location close to vital structures such as the bowel, gallbladder, major bile
ducts or major blood vessels; active infection; cholestasis; bile duct dilatation or previous anastomotic
surgery might be considered as relative contraindications [19]. The European Society for Medical
Oncology (ESMO) recommends treating oligometastatic disease with a strategy of local ablative therapy,
the spectrum of which includes surgical R0 resection, percutaneous ablation and intra-arterial therapies,
the choice of treatment being left to the multidisciplinary team. [20]. Microwave ablation has been used
to treat hepatic metastases from solid tumors, e. g. colorectal cancer, breast cancer, lung cancer and
carcinoid tumors [20 – 22]. Compared to surgery, microwave ablation can provide comparable results in
treating liver metastases from colorectal cancer. A study by Shibata et al. compared the survival between
surgical resection and MWA of colorectal cancer liver metastases. The 1-, 2-, and 3-year survival rates
and mean survival times were 71 %, 57 %, 14 %, and 27 months, respectively, in the microwave group,
whereas they were 69 %, 56 %, 23 %, and 25 months, respectively, in the hepatectomy group [23].
Complete tumor ablation near major vessels can be difficult to achieve. In rare cases MWA might be
performed in order to debulk hepatic tumors and reduce local pain or symptoms from compressing
neighboring structures.
Procedure:
Patient preparation and monitoring:
Before the start of therapy, the patient’s record should be discussed in an interdisciplinary tumor board
including experts from hepatobiliary surgery, hepatology and oncology. Written informed consent should
be obtained before treatment. Patients should be informed about alternative therapy modalities like
surgery, radiooncological therapy, possible complications and side effects. Preinterventional blood tests
should include routine blood counts, WBC, RBC count and PLT, liver function and kidney tests.
Depending on the underlying disease coagulation parameters are essential: thrombocytes should be equal
to or more than 30,000. Pre-ablation imaging like CT or preferably MRI should be performed (should not
be older than 1 month). Furthermore, the medical history and complete drug history of the patient should
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
be obtained, especially for previous treatment protocols. Patient should fast for at least 6 hours before
ablation. Percutaneous MWA is also feasible as an in- and outpatient procedure under local anesthesia
and analgosedation with at least 6 hours of observation after the procedure. Depending on the clinical
status of the patient, a one night hospital stay is preferable and mostly practiced [24]. Some groups focus
on outpatient procedures [25].
MWA technique:
For the performance of MWA, various interventional approaches (percutaneous, laparoscopic or
intraoperative) and methods of guidance (CT, MRI and ultrasound) are available. Generally one, rarely
more antennas are placed directly into the tumor. For ablation, an electromagnetic microwave is emitted.
Each generator is capable of producing different powers, for example 45 to 100 W at a frequency of 915
MHz or 2450 MHz, depending on the device type [11].
Different protocols for the temporal course of the energy are in use. One protocol starts the ablation
procedure first with low energy and gradually increases the power, while monitoring the ablation zone
and possible complications. Adequate monitoring of oxygen level via pulse oximetry should be provided
during intervention. Blood pressure should also be measured before and after treatment. In order to
devascularize the hepatic malignancy and to reduce the bleeding risk, neoadjuvant transarterial lipiodolbased emboVogl TJ et al. Microwave Ablation (MWA):… Fortschr Röntgenstr 2017; 189: 1055–1066
1059 This document was downloaded for personal use only.
Unauthorized distribution is strictly prohibited. lization (TACE) can be performed before ablation. In
addition, transarterial lipiodol embolization can help to mark the lesion for the planned ablation. To
decrease potential damage to nearby structures and to minimize complications, a “hydrodissection”
technique might be used. In this case 0.9 % saline or 5 % dextrose in water is injected between the targeted
lesion and adjacent organs like the intestine, kidney or vessels in order to protect them from possible
thermal damage.
The visibility of the fluid can be improved on CT by using a 1:50 ratio of iodinated contrast in the fluid.
Other available methods are air or carbon dioxide instillation, balloon placement and leveraging of the
ablation zone away from vulnerable structures using the antenna [26 – 29]. In a prospective study, artificial
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
ascites as separation in ultrasound-guided percutaneous MWA was used in 36 hepatic tumors adjacent to
the gastrointestinal tract. The separation success rate and technical effectiveness of MWA were reported
to be 88.9 % and 96.9 %, respectively [30].
Recently in experimental studies, a thermoprotective gel was successfully injected [26, 27]. Accurate and
reliable methods for near real-time imaging assessment during ablation are essential to determine the
adequacy of therapy in order to prevent under- or overtreatment of a lesion [31]. Using ultrasound
monitoring during thermal ablation, a hyperechogenic focus can often be seen surrounding the distal part
of the applicator, which is caused by microbubbles and gas released from the heated tissue. This does not
correlate with adverse tissue coagulation. The presence of gas bubbles in the liver parenchyma during
MWA can affect ultrasound evaluation by overestimating the size of the ablated areas. This phenomenon
will often disappear completely within 1 h after ablation [10]. In contrast, positioning an MWA antenna
and monitoring via CT allow precise online visualization of the vaporization process and early detection
of possible complications, like bleeding or pneumothorax.
When should thermal ablation be interrupted?:
In the case of a major complication during the procedure including massive bleeding, severe pain, severe
pneumothorax or perforation of adjacent organs, the procedure should be stopped immediately. In severe
bleeding, an immediate CT angiography scan should be performed, and in case of arterial hemorrhage,
interventional angiography and embolization should be initiated. In the case of minor complications like
pneumothorax or minimal perihepatic bleeding, the patient’s vital functions must be monitored. After the
procedure, the puncture site will be covered with a sterile dressing and the patient should be observed for
a minimum of 6 hours. During this period regular assessment of the patient’s vital signs and pain should
be performed. A contrast-enhanced CT or MRI examination should be performed within 24 hours after
treatment to determine the volume of ablation and evaluate if the residual tumor requires retreatment.
Although there are no scientific data proving this concept, it is practiced in many institutions.
Post-procedural imaging:
Postprocedural imaging findings can be considered as a rough guide to the success of ablation therapy
because microscopic foci of residual disease cannot be detected with standard imaging. “Ablation zone”
is used to describe the radiologic region or zone of induced treatment effect in the area of gross tumor
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
destruction, which is visualized by imaging. In pathologic findings a central “white zone” of coagulation
induced in most thermal therapies is generally accepted to represent coagulated tissue. This is surrounded
by a variable “red zone” of hyperemia, which is best documented on MRI [17].
On delayed contrast images, peripheral rim enhancement (e. g. for CT < 20 HU), which often surrounds
the region of coagulation, can be identified. The rim usually indicates an inflammatory reaction due to
thermally damaged cells [10]. This can be considered pseudoenhancement or alternatively represent
minimal enhancement from leaky capillaries at the treatment margin [4]. A bulky irregular rim at the edge
of a treatment site is the most common appearance of an incompletely treated lesion [10]. Hence, after the
ablation procedure, the following different imaging findings are identified: zones with decreased perfusion
and changes in signal intensity on MRI, higher echogenicity on US, higher attenuation on CT or tracer
uptake on PET [32].
The gross pathologic appearance of treated tissue should be referred to as coagulation-like pathologic
findings associated with high-temperature thermal injury. As the ablation actively leads to tumor
destruction, the more generalized term “coagulation” is preferred to “coagulative necrosis”, as it has a
well-defined meaning in pathology including the absence of visible nuclei within the dead cells. The term
“lesion” should not be used for ablation zone, as ablation zone refers to both the ablated area as well as
the underlying tumor to be ablated [4]. MRI follow-up findings should be evaluated according to the
presence or absence of gadolinium enhancement in the treated region. At the 3-month follow-up, the
ablation area appears to be homogenous, while the MRI examination within 3 days after ablation shows
heterogeneous alteration on unenhanced T1- and T2-weighted images and diffusion-weighted sequences,
which can be caused by focal hemorrhage. Most likely an uneven evolution of the necrotic area and the
host response to thermal damage lead to a change in the variability of signal intensity throughout the
ablated region. In gadolinium-enhanced images, a thin rim of enhancement after treatment is usually
detected and, similar to CT scans on which the rim appears bulky, can represent a residual tumor [10].
Although the gross extent of induced coagulation can be identified on imaging, the accuracy is limited by
both spatial and contrast resolution to approximately 2 – 3 mm depending on the imaging modality used.
At 6 – 12 months after ablation, regression of the ablation zone is detected.
Most commonly, a less than 20 % reduction in volume of the non-enhanced peripheral rim is documented
[10]. There is a lack of consensus on a standard follow-up strategy for follow-up imaging. The most
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common approaches include contrast-enhanced imaging (US, CT, MRI, or PET-CT) within 1 day of the
initial ablation to determine whether additional ablation therapy is 1060 Vogl TJ et al.
Microwave Ablation (MWA):… Fortschr Röntgenstr 2017; 189: 1055–1066 Review This document was
downloaded for personal use only. Unauthorized distribution is strictly prohibited. required. In many
centers this evaluation is even performed on the day of the initial procedure, every 1 – 4 months thereafter
and at longer intervals over the course of time, depending on imaging findings, underlying tumor and
patient risk factors
Assessment of Technical Effectiveness:
When the ablation zone completely overlaps or encompasses the target tumor plus an ablative safety
margin, it can be classified as “technically successful” [4]. An appropriate safety margin of about 5 to 10
mm of apparently healthy tissue surrounding the lesion and beyond the borders of the tumor is necessary
in order to achieve complete tumor destruction. Thus, possible micro-metastases or microscopic foci can
also be destroyed and the risk of local recurrence is minimized. However, data to support precise
recommendations regarding the ideal margin size are currently lacking [33, 34]. Extension of the desired
or intended ablative margin is not always necessary, as this can increase the risk of complications, but an
insufficient ablative margin is defined as an independent significant risk factor for local tumor progression
[8, 33]. Residual microscopic malignant foci, particularly at the periphery of a treated lesion with its
normally high blood perfusion, can continue to grow and then lead to therapy failure. Therefore longterm
imaging follow-up plays a significant role in documenting successful ablation [10].
Side effects and complications:
According to the SIR classification (Society of Interventional Radiology), a major complication is an
event that leads to substantial morbidity and disability and increases the level of care, or results in hospital
admission, or significantly lengthens the hospital stay (classifications C–E), also including any case in
which blood transfusion or interventional drainage procedure is needed.
All other complications like small bleeding or hematoma are considered 70-year-old woman with
pathologically proven HCC/CCC mixed tumor. After three courses of TACE, the size of the tumor could
be reduced from 24 mm to 19 mm. However, a major safety rim was necessary in order to achieve A0
ablation. a Gradient-echo MR sequence T1 VIBE DIXON TRA TR/TE 6.69/2.39, gadolinium-enhanced.
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Verification of the necrotic part of the tumor central in the hyperenhanced rim surrounding the tumor after
chemoembolization. b CT-guided navigation with positioning of the antenna tip (Emprint™, Covidien) in
the central part of the tumor. c T1w contrast-enhanced tra TR/TE 6.69/2.39. Follow-up MRI 24 hours after
ablation demonstrates a spherical ablation zone of 55 mm in size with minimum peripheral rim
enhancement. d Gadolinium-enhanced MR imaging follow-up (TR/TE 500/17) demonstrates the
reduction of the ablation volume and complete A0 ablation after 3 months. e Further reduction in size and
homogenization after 6 months.
T1 sequence TR/TE 6.69/2.39.70 jährige Frau mit pathologisch nachgewiesenem HCC/CCC (gemischter
Tumor). Nach 3 TACE-Sitzugen konnte der Tumor von 24 mm auf 19 mm reduziert werden. Ein größerer
Sicherheitssaum war jedoch notwendig, um eine A0 Ablation zu erreichen. a Gadolinium-verstärkte
Gradienten-Echo MR-Sequenz T1 VIBE DIXON TRA TR/TE 6.69/2.39. Verifikation des nekrotischen
Tumoranteils zentral im hyperverstärkten Rand um den Tumor post Chemoembolisation. b CT-gesteuerte
Navigation mit Positionierung der Nadelspitze (Emprint™, Covidien) im Zentrum des Tumors. c T1w
Kontrastverstärkte tra TR/TE 6.69/2.39. Follow-up 24 Stunden nach Ablation zeigt eine kugelförmige
Ablationszone von 55 mm mit minimalem peripherem Rand-Enhancement. d Gadolinium-verstärktes
MRT Follow-Up (TR/TE 500/17) zeigt eine Reduktion des Ablationsvolumens und eine vollständige A0
Ablation nach 3 Monaten. e Weitere Größenreduktion und Homogenisierung nach 6 Monaten.
T1 sequence TR/TE 6.69/2.39. Vogl TJ et al. Microwave Ablation (MWA):… Fortschr Röntgenstr 2017;
189: 1055–1066 1061 This document was downloaded for personal use only. Unauthorized distribution
is strictly prohibited. minor. Several complications such as pneumothorax or tumor seeding can be
considered either a major or minor complication, depending on their severity [35].
Undesired consequences of the ablation procedure that commonly occur include pain, post-ablation
syndrome (PAS), asymptomatic pleural effusions and minimal asymptomatic perihepatic (or renal) fluid
or blood collections. Furthermore, imaging evidence of asymptomatic minimal thermal damage of
adjacent structures without other “collateral damage” can be expected. For example, when the ablation
zone extends beyond the liver capsule and includes small portions of the diaphragm, this should not be
considered a major complication, as these side effects do not require an increased level of care and followup control or admission to the hospital. During ablation procedures, pain is a relatively common
complication. Patients might experience pain even with an appropriate local anesthesia technique.
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Moreover, in many patients grade 1 to 2 pain can persist for several days, even for 1 to 2 weeks after
ablation depending on the organ site.
PAS is a transient, usually self-limiting symptom with low-grade fever ≤ 37.8, nausea, vomiting, residual
soreness of the treated area and malaise for up to one week. Its duration depends on the tumor volume,
the volume of necrosis produced and the overall condition of the patient. If relatively large areas of the
liver are ablated, the syndrome may persist for 2 to 3 weeks. Pain reduction is usually fast and occurs
within the first 24 hours in some patients and during the first week in most of patients. After ablation of
small tumors, patients are unlikely to experience PAS at all. For large tumors the incidence of PAS is
higher, hence it might be feasible to prophylactically use antipyretic medication and a pain killer. In almost
all PAS cases, symptomatic treatment with antipyretic medication or pain killer is sufficient. Pleural
effusion may also occur. Bile duct damage, severe bleeding, infection of ablation cavity which can lead
to liver abscess, colonic perforation, and tumor cell seeding are the most serious complications. Postprocedure bleeding and tumor cell seeding can be prevented by attempting to obliterate damaged vessels
and tumor cell destruction via heating of the puncture channel during withdrawal of the probe with
microwave [7].
Compared to RFA, the most frequent complication of MWA is bleeding, which rarely requires transfusion
(< 1 %). Furthermore, pneumothorax (< 1 %), liver abscess (about 1 %) and injury of bile or gallbladder
vessels (< 1 %) were reported. Overall complication rates are reported to be around 3 – 7 %, when using
a non-cooled shaft antenna. Moreover, multiple MWA sessions are associated with a higher rate of major
complications [13, 36]. A survey including 16 studies and 2062 patients in which MWA was compared to
RFA for hepatic lesions using meta-analytical techniques showed significantly better 6-year overall
survival rates for MWA than RFA (odds ratio: 1.64, 95 % confidence interval: 1.15 – 2.35) in 3 of 16
articles. Moreover, the 1 – 5-year overall survival, disease-free survival, local recurrence rate, and adverse
events showed comparable results. Regarding safety and efficacy outcomes, MWA and RFA can be
currently considered effective local hepatic therapy techniques [37].
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CHAPTER 4:
BLOCK DIAGRAM
4.1 Block diagram
It Consists Of Vector Network Analyser Which Is Used To calculate the Reflection Coefficeint and SAR
(Specefic Absorption Rate). The Resulted Signal is Treansmitted Through Transmitter and it is Passed
Through 3D Liver Model And The 5-D Slot Antenna will work by using Microwave Power Source and
calculates the Value and it Checks the value with the reference value.
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SYSTEM REQUIREMENTS
• COMSOL MULTIPHYSICS Software
• Laptop
• 8 GB Ram
COMSOL MULTIPHYSICS Software Modeling is useful together with experiments for optimizing
processes and devices quicker and often more efficiently and accurately than running experimental
methods or testing prototypes alone. By developing experimentally validated models for your analyses,
you can gain a deeper understanding of the design or process because you can study it in a more convenient
manner than in the lab.
Multiphysics is often a necessity for accurately modeling your design or process. As a user of COMSOL
Multiphysics®, you are free from the restrictive nature generally associated with simulation software and
have complete control over all aspects of your model. You can be creative in a way that is impossible, or
a lot harder, with traditional approaches, thanks to the ability to couple any number of physics phenomena
together. For even further customization, input user-defined physics descriptions, with associated
equations and expressions, directly in the user interface.
Accurate multiphysics models consider a wide range of possible operating conditions and physical effects.
This makes it possible to use models for understanding, designing, and optimizing processes and devices
for realistic operating conditions
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CHAPTER 5:
RESULTS AND DISCUSSIONS
Fig. 6.1 Simulated antenna environment
Fig. 6.2 power dissipation
A longitudinal plane is shown in Figs. (6.1) and (6.2), where 2D modelling is used to depict the antenna
environment and surface power distribution in the liver tissue at the completion of the heating process (the
steady state).
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Fig. 6.3 Fraction of Damage
Fig. 6.4 Temperature Distribution
Fig.(6.3) shows fraction of damage to the tissue with respect to time. The value of 1 indicate 100 percent
of the tissue damage. The position of observation point is fixed at the longitutional direction and variable
along transversal direction. It can be seen that faster rate of ablation is reached at closer observational
point along transversal direction. Fig.6.4 shows temperature distribution till 10 min. of time.
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Fig. 6.5 SAR Pattern
Fig.6.6 Temperature Contour
Fig.(6.5) shows specific absorption rate (SAR) along the arc length of the antenna ablation zone. Fig(6.6)
show isothermal temperature contour due to dielectric heating
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Fig 6.7 Thermal Damage
Fig. 6.7 shows ablation zone due to microwave ablation. Since 5 slots were introduced in the antenna a
higher amount of ablation is seen. Slots improve field distribution along the transversal direction of
antenna.
MWA results in HCC :
For the evaluation of MWA results in treating HCCs, the local and tumor control rate, overall survival
(OS), mean and medium survival rate, as well as PFS are essential parameters. For the treatment of HCCs,
clinical guidelines categorize ablation therapies not only as equal to surgery but even better than surgery
in small or very small HCCs (oligonodular tumors ≤ 3 cm).
The main reason for this recommendation is the fact that ablation leads to much less loss in the normal
liver parenchyma compared to surgical resection. The therapeutic response of MWA in HCCs in 53
patients was evaluated and compared in a retrospective study. Complete local tumor control was
documented in 84.4 % of lesions treated with RFA and in 88.9 % of lesions treated with MWA.
However, in both groups technical success was achieved in lesions < 2 cm. The recurrence rates at 3, 6, 9
and 12 months were 6.3 %, 3.1 %, 3.1 % and 3.1 % in RFA vs. 0 %, 5.6 %, 2.8 % and 2.8 % in MWA,
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
respectively. The PFS rates at 1, 2, and 3 years were 96.9 %, 93.8 %, and 90.6 %, respectively for patients
treated with RFA and 97.2 %, 94.5 % and 91.7 %, respectively, for patients treated with MWA [38].
In a retrospective study Zhang L et al. [39] compared the therapeutic efficacy of percutaneous RFA to
MWA in HCCs ≤ 5 cm by evaluating 155 patients. Technical success was achieved in 83.4 % for RFA
vs. in 86.7 % for MWA. Moreover there was no significant difference in the 1-, 3-, and 5-year overall
survival and the 1-, 3-, and 5-year disease-free survival rates between the RFA and MWA groups. Even
in relatively large HCCs, technical success can be achieved.
Contrast-enhanced ultrasound (CEUS)-guided MWA was performed by Liu F et al. [40] in 107 patients
with large HCCs (mean maximum diameter: 19.5 ± 8.5 mm) with a technical success rate of 98.13 %.
Regarding comparative evaluation of MWA vs. transarterial chemoembolization (TACE) in large HCCs,
Abdelaziz et al. analyzed 64 patients with large HCCs [41]. MWA showed higher rates of complete
ablation (75 %) with fewer sessions and a lower incidence of tumor recurrence (p = 0.02) with 13.7 months
of survival. In summary, MWA showed better results in comparison to TACE alone even in large HCCs
[6]. Huang H et al. retrospectively assessed 136 patients with HCC adjacent to the gallbladder who
underwent US-guided percutaneous MWA.
They were followed up for a median period of 30.1 months. In all patients two sessions were performed.
In case of incomplete ablation, percutaneous ethanol injection (PEI) and other therapies were performed.
They concluded that US-guided percutaneous MWA in combination with PEI is a safe and effective
treatment option for HCC adjacent to the gallbladder. MWA can be considered as an alternative to RFA,
especially when the tumor is located in the vicinity of large vessels. Furthermore, several other studies
showed similar results in terms of local tumor control. In a study with 102 patients, Lu et al. reported a
technical success rate of 95 % for MWA compared to 93 % for RFA.
In a prospective study 94 patients with HCC ≤ 7 cm underwent RFA or MWA combined with TACE or
alone. Combination therapy in the treatment of HCC ≤ 7 cm was superior to RFA or MWA alone regarding
survival by reducing arterial and portal blood flow due to embolization with iodized oil via TACE before
ablation [9]. The data for laparoscopic or intra-operative MWA are rather limited. Cillo U et al. described
a laparoscopic MWA technique combined with portal vein ligation for staged hepatectomy [44].
Laparoscopic MWA was successfully applied in patients with multiple colorectal liver metastases and
single HCC nodules. Itoh S et al. [14] described 143 cases of surgical MWA for unresectable initial and
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recurrent HCC performed in 60 patients. The median follow-up period was 19 months. The 1-, 3-, and 5year overall survival rates after the surgical MW procedure were 93.9, 53.8, and 43.1 %, respectively.
Medhat E. et al. evaluated US-guided MWA in large HCCs (5 – 7 cm) in 26 patients. According to the
size of the lesion, multiple needle insertions were performed in one or two sessions resulting in complete
ablation in about 73 % of cases. Local tumor progression was 19.2 % and distant tumor progression within
the liver was 23.1 % with a mean survival of 21.5 months. No major complications or deaths related to
the procedure were recorded [46]. In a bilateral tumor, a combination of MWA and TACE or surgery can
achieve better tumor debulking and better survival rates. However, compared to surgery, MWA has
significantly more recurrence rates, which for HCC is about 13.1 % at 1 year after the treatment and 21.1
% at 3 years [47]. It should be considered that incomplete ablations and larger lesions could theoretically
lead to an increased recurrence rate of liver tumors. Dong et al. retrospectively compared the safety and
efficacy of RFA versus MWA for the treatment of localized HCC and found no significant difference
between RFA and MWA.
MWA results in liver metastases:
In oligonodular liver metastases, the indication for MWA is unresectability or central position of
metastases Patients with up to 5 liver metastases and a size of ≤ 4 cm are eligible candidates for local
ablation. As previously mentioned, comparable survival results to surgical resection can be reached using
different ablation techniques for colorectal cancer liver metastases [23]. In a retrospective analysis
Engetal. treated 49 tumors (0.5 to 5.5 cm in size) in 33 patients who underwent intraoperative MWA of
colorectal cancer liver metastases [49]. Tumor recurrence was documented in 13 patients. The median
time to first recurrence was 364 days. The overall survival was 35.2 % at 4 years with a disease-free
survival of 19.3 % at 3.5 years. In a 9-year retrospective analysis of 64 patients wisingle metastases who
underwent MWA, Alexander ES et al. [22] reported a technical success rate of 95 %.
They included a large spectrum of metastatic lesions including colorectal cancer, breast cancer, carcinoid,
melanoma, lung cancer and anal cancer. There was no statistically significant relationship between time
to recurrence and tumor size, number of activations, number of antennas, and treatment time. Regarding
the local recurrence at 1 year after ablation there was a recurrence of 45.7 % in colorectal metastases and
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70.8 % in other metastases compared to 39.8 % in HCC. Furthermore, the 30-day post-ablation mortality
rate was 0 % with no procedure-related deaths. The rate of complications including
nausea, pain requiring analgesics, pneumothorax, and pneumonia, which according to SIR classifications
are A-D complications, was 23.4 %. The survival rates were 36.3 months for colorectal cancer metastases,
and 13.9 months for other histological types compared to 38.3 months in HCC patients. In a cohort study
of 1136 patients who underwent MWA as treatment for malignant liver tumors, Liang et al. showed that
it is a well-tolerated technique with an acceptably low rate of major complications. Major complications
can be reduced by using a cooled-shaft antenna and performing fewer MW sessions [13].
Wang XH et al. retrospectively analyzed 898 primary liver tumors which were treated in 1111 MWA
sessions in order to evaluate the major complications of percutaneous cooled-tip MWA in the treatment
of liver cancer. The mean tumor diameter and range were 2.5 ± 1.2 cm and 0.4 – 10.0 cm, respectively.
They reported 2 deaths because of pulmonary embolism and hepatorenal syndrome, and also 27 major
complications including 10 cases of tumor cell seeding [50]. In a case control study with 89 patients, Li
M. et al. evaluated the safety and effectiveness of US-guided percutaneous MWA of 96 hepatic lesions
adjacent to the diaphragm. For the control group they selected 100 patients with 127 hepatic lesions not
adjacent to the diaphragm, with a minimum distance more than 10 mm from the lesion to the diaphragm
and the first or second branch of the hepatic vessels. Complete ablation was achieved in 94.8 % in the
study group and 96.9 % in the control group. The local tumor progression rate was 18.8 % in the study
group and 16.5 % in the control group with no major complication
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CHAPTER 6:
CONCLUSION AND FUTURE WORK
CONCLUSION:
We analyse an axisymmetric model with a narrow microwave coaxial antenna in COMSOL
Multiphysics. The mesh statistics of the model, as well as the SAR pattern and temperature distribution
in tissue, are all analysed in detail. The models offer temperature distribution, surface temperature on
tissue, and power absorption in tissue with variable electric, thermal, and geometric variations. By
steady-state tissue temperature distribution for 40 W microwave input.In the designed antenna we
introduced a total of 5 slots with variable diameter which improves the overall ablation zone and more
spherical ablation zone.
FUTURE WORK:
Due to the long-time taken to ethically approve the experimental work in actual tissues, TDFT will be
further tested on real tumour tissues to validate its performance as a microwave coagulator. In addition,
the effect of varying the input power and application time on measuring heat generation and the total
ablated volume within the actual tissues. Nevertheless, TDFT antenna has significantly enhanced features
exploited in microwave cancer ablation, it is highly efficient for treating focal nearly spherical tumours of
diameter ≤20 mm. As TDFT antenna has a capability of thermal energy confinement in the longitudinal
direction, this can be further exploited in eradicating tumours that exist near large vessels without
damaging the vessel wall by inserting the antenna perpendicular to the vessel axis. Furthermore, TDFT
antenna can be tuned and tested to perform local hyperthermia at power range from 1 to 2W for shorter
application time to intentionally create reversible changes in tissue properties and increase the potency of
drugs in chemotherapy.
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In addition, testing TDFT antenna at different frequencies in real biological tissues to investigate the
antenna performance in real-time in-vivo ablation experiments and the effect of changing frequency of
operation on the size of ablated volume, temperature levels reached and confinement of heating.
Investigating different antenna designs is inevitable as cancer can be formed in any shape and inhabit
critical locations of human body where one of which can be very critical to treat. For instance, bone cancer
or osteosarcoma is very critical to treat as ablation of bone tumour or sometimes called bone drilling
requires precise and directional thermal heating in both zenith and elevation planes to minimize the
damage that might be encountered in the surrounding healthy organ and reduce the possibility of organ
malfunction after the treatment. Moreover, there are still limitations regarding the antenna manufacturing
as the feasibility of producing compact antennas is still limited as it will be very beneficial in achieving
less invasive Chapter Six Conclusion and Future Work 161 ablation treatment and eradicating tumours
inhabit critical locations that cannot be reached using traditional antenna size
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[37] Farina, L., Amabile, C., Nissenbaum, Y., Cavagnaro, M., Lopresto, V., Pinto, R., Goldberg, S. “Ex
vivo tissue shrinking in microwave thermal ablation” 2015 9th European Conference on Antennas and
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
APPENDIX
Paper Published : BOOK CHAPTER (SCOPUS INDEXED)
P. Niranjan, P. Vijay Kumar Reddy, P.J Reddy, T.N reddy, V. Singh, A.K Dwivedi*, Treatment of
Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz”, International
Conference on Intelligent Systems and Smart Infrastructure” (ICISSI 2022), Taylor & Francis (CRC
Press). (Under Production) (*Corresponding author).
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna
at 2.45 GHz
P. Niranjan1, T. Naveen Kumar Reddy1, P. Vijay Kumar Reddy1, P. Janardhana Reddy1, Vivek Singh2, Ajay Kumar Dwivedi2*
1
Undergraduate Students, Nagarjuna College of Engineering and Technology, Bengaluru
Associate Professor, Nagarjuna College of Engineering and Technology, Bengaluru
E-mail: niranjanpothamsetty@gmail.com, naveenchinnu144@gmail.com, vijju2234@gmail.com,
janardhanareddy5597@gmail.com, vivek.10singh@gmail.com, er.ajaydwivedi@gmail.com*
2
Abstract
Every year, about 7 lakh Indians succumb to cancer, with an additional 10 lakh being newly diagnosed. In most cases, surgical
removal of hepatocellular carcinoma is not a viable option. It has been shown that microwave coagulation therapy (MCT) is
an effective alternative to resection in tissue and that it is safe. Other thermal ablation treatments have the advantage of being
more rapid and producing an ablation region that is instantaneously hypoechoic on real-time ultrasound monitoring, as opposed
to laser ablation. An intrusive technique is used in this treatment, which entails introducing a thin microwave coaxial slot
antenna (operating at 5GHz) into the tumor in order to coagulate the cancer cells. When it comes to analyzing complex
structures, the finite element approach is applied
Keywords: Microwave Coagulation Therapy (MCT), Cancer cells, Coaxial Slot Antenna, Thermal Ablation.
Introduction
In MWA, interventional procedures include exposure to very high temperatures, which results in tissue necrosis. The treatment
employs an antenna probe that is image-guided to the tumor’s target area and eliminates it with high-frequency dielectric
heating. This therapy is safe when used to treat malignancies of the kidney, liver, bone, lung, and other soft tissue. Additionally,
owing to its cost-effectiveness, it has become a commonly used approach in immunology and oncology research [1].
Thermal ablation (MWA) is a minimally invasive treatment that may be done under local anesthesia and may result in same-day
discharge. As a result, it is commonly used in the treatment of hepatocellular carcinoma (HCC). Each year, around 7,60,000 new
HCC cases are reported globally, with India accounting for more than 50000 instances; hence, HCC accounts for one in every
six cancer patients [2]. Additionally, according to a research performed by ILBS, New Delhi (2020) on the demographic
distribution of HCC patients, Uttar Pradesh accounts for 24% of the entire cases which is a significant proportion [3]. Age,
gender, and alcohol use are all prominent risk factors for HCC, and as life expectancy increases globally, the direct association
between older patients and HCC is becoming an increasing source of worry [4]. Certain kinds of hepatitis may also result in
HCC, and Uttar Pradesh alone accounts for 25000 cases of viral hepatitis each year according to the study conducted in 2019,
which can progress to HCC if left untreated [5]. According to some reports, surgical resection is the primary line of therapy for
HCC, with thermal ablation reserved for those who are not surgical candidates. However, as stated in a recent paper [6], the
death rate associated with surgical resection has risen in older patients relative to younger patients, and numerous surgical
resections may impair a patient’s quality of life and are a very invasive and costly procedure. Additionally, significant
technological and clinical breakthroughs have been documented in the years since the microwave ablation treatment was
introduced. This development comprises a matching antenna applicator, the employment of a state-of-the-art antenna structure,
the optimization of the antenna applicator site, the reduction of the elongated ablation pattern, and a larger and quicker ablation
zone to compensate for the thermo-regulatory impact.
The purpose of this research is to demonstrate a new minimally intrusive antenna and also to study the influence of different
physical and thermal parameters of a biological system on ablation. A three-dimensional finite element model (FEM) is
utilized to simulate the ablation environment. It includes thermo physical heat properties, Penne's bioheat model, and
Arrhenius kinetics.
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Antenna Design
The Finite Element Method is an effective approach for analyzing complicated structures that allows modifying the antenna's
configuration. This approach involves expressing a domain using geometrically simple forms from which approximation
functions may be generated. Using COMSOL Multiphysics, a 2D finite element model calculates the absorbed power and
temperature distribution around a single thin microwave coaxial antenna. In order to test the antenna model for FM analysis,
the outer conductor of the narrow coaxial wire was chopped to 1mm wide ring form. The antenna is encased in a PTFE sleeve
(catheter) for hygiene reasons. In microwave coagulation treatment, the antenna operates at 2.45 GHz. The antenna shape is
2D modeled and studied with varied slot dimensions of 1mm, 1.2mm, 1.5mm,1.7 mm and 1.9 mm from the tip as shown in
Fig. 1. The wire is shorted at the tip and a 1.5 mm wide ring hole is cut 6mm from the tip. In addition to the slot's axial and
radial dimensions, the pin's radial dimensions provided excellent energy interaction between the microwave source and the
tissue. The COMSOL multi-physics user interface includes CAD tools for modeling 2D and 3D coaxial antennas.
Thermal Setup
Figure (2) depicts a three-dimensional arrangement with FEM boundary conditions. MWA is classified as a kind of dielectric
heating. Because of the dielectric heating, polar water molecules in tissue align themselves with electromagnetic fields. The
dielectric rotation of the molecules raises the kinetic energy of the molecules and, as a result, the temperature of the tissue.
Because tissue is made up of many veins and arteries, a simplified assumption is required to assess the bioheat transfer model.
Applying thermal boundary conditions to a 100micro-m diameter is difficult. The impact of adding or altering thermo-physical
factors in the equation of conduction is handled as though the tissue area of interest had no blood vessels Penne's bioheat
equation over a restricted volume is one example [7].
 c
t t
v

Tt (r , t )dV =  k t  2Tt (r , t )dV +   b  b cb [Tart ( x, t ) − Tt ( x, t )] + Qm
t
v
v
…………………..(1)
Where the term qm. refers to the metabolic heat production in the tissue and the term q b-blood. refers to the contribution of
blood flow to the local tissue temperature distribution, respectively. Similarly, 𝜌 is the tissue density [kg/𝑚3 ], C is Specific
heat capacity expressed in [J/kg.K] and 𝑘 is Thermal conductivity expressed inW/m.K.
Electromagnetic Setup
Simulated design of the unique antenna was carried out, and the impact of thermoelectrical parameters on tissue models was
explored. An electromagnetic-bioheat transfer model was developed that includes a temperature-dependent thermo-electrical
tissue property as well as the evaluation of thermally induced tissue injury. Specifically, the following are the Maxwell's
equations for a transverse electromagnetic mode, which are determined by the transverse electromagnetic mode [8]
𝐸(𝑟) = (
𝐻(𝑟) =
𝐴𝑒 𝑗(𝜔𝑡−𝑘𝑧)
𝑟
𝐴𝑒 𝑗(𝑤𝑡−𝑘𝑧)
𝑟
) 𝑟…………………………………………………..(2)
. 𝑍𝑖𝑛 ……………………………………..(3)
Where E and H are the electric and magnetic field in r and φ directions and the propagation direction of electromagnetic waves
is represented by z.
Modeling Computational Domain
The antenna was numerically modeled and analyzed using finite element approach. It includes breaking up a complicated
geometry into tiny pieces for a set of partial differential equations. The microwave source is at the coaxial cable tip. Table 1
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
shows the material volume put in the antenna. Several factors influence the capacity of a tissue to create heat when subjected
to a time-varying electric field. These factors include conductivity, relative permittivity, and thermal conductivity.
Table 1: Parameters for model
S.No
1
2
3
4
5
6
7
8
Parameters
Rho_blood
Cp_blood
Omega_
Values
1000kg/m^3
3639J/(kg.k)
0.0036000 1/s
T_blood
310.15 K
Eps_diel
Eps_cat
Relative blood
permittivity,
Catheter
P_in
2.03
2.6
2.45GHz
Description
Density of the blood
Blood specific heat.
The rate of blood
perfusion
Temperature of
blood
Relative permittivity
Catheter Permittivity
The frequency of
microwave
20 W
Microwave power at
the source
Results and Discussion
Fig. 1. Simulated antenna environment
Fig.2. power dissipation
A longitudinal plane is shown in Figs. (1) and (2), where 2D modelling is used to depict the antenna environment and surface
power distribution in the liver tissue at the completion of the heating process (the steady state).
Fig. 3. Fraction of Damage
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
Fig. 4. Temperature Distribution
Fig. 3 shows fraction of damage to the tissue with respect to time. The value of 1 indicate 100 percent of the tissue damage.
The position of observation point is fixed at the longitutional direction and variable along transversal direction. It can be seen
that faster rate of ablation is reached at closer observational point along transversal direction. Fig. 4 shows temperature
distribution till 10 min. of time.
Fig. 5. SAR Pattern
Fig. 6. Temperature Contour
Fig. 5 shows specific absorption rate (SAR) along the arc length of the antenna ablation zone. The arc length is the distance
between two point along line drawn from ablation boundary along axial direction. Fig. 6 show isothermal temperature contour
due to dielectric heating.
Fig. 7. Thermal Damage
Fig. 7 shows ablation zone due to microwave ablation. Since 5 slots were introduced in the antenna a higher amount of ablation
is seen. Slots improve field distribution along the transversal direction of antenna.
Conclusion
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Treatment of Hepatocellular carcinoma using 5-Slot Microwave Ablation Antenna at 2.45 GHz 2021-22
We analyse an axisymmetric model with a narrow microwave coaxial antenna in COMSOL Multiphysics. The mesh statistics
of the model, as well as the SAR pattern and temperature distribution in tissue, are all analysed in detail. The models offer
temperature distribution, surface temperature on tissue, and power absorption in tissue with variable electric, thermal, and
geometric variations. By steady-state tissue temperature distribution for 40 W microwave input.In the designed antenna we
introduced a total of 5 slots with variable diameter which improves the overall ablation zone and more spherical ablation zone.
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