METHODS TO IMPROVE HEATING EFFICIENCY OF 27 MHZ DIATHERMY
SYSTEM BY USING REFLECTOR CONTROL
Siddharth Mangavally
B.Tech., J N T University, India, 2007
Raghuram Pulijala
B.Tech., J N T University, India, 2007
PROJECT
Submitted in partial satisfaction of
the requirements for the degrees of
MASTER OF SCIENCE
in
ELECTRICAL AND ELECTRONIC ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
SPRING
2011
METHODS TO IMPROVE HEATING EFFICIENCY OF 27 MHZ DIATHERMY
SYSTEM BY USING REFLECTOR CONTROL
A Project
by
Siddharth Mangavally
Raghuram Pulijala
Approved by:
__________________________________, Committee Chair
Preetham B Kumar, Ph.D.
__________________________________, Second Reader
Fethi Belkouche, Ph.D.
____________________________
Date
ii
Students: Siddharth Mangavally
Raghuram Pulijala
I certify that these students have met the requirements for format contained in the
University format manual, and that this project is suitable for shelving in the Library and
credit is to be awarded for the project.
__________________________, Graduate Coordinator
Preetham B Kumar, Ph.D.
Department of Electrical and Electronic Engineering
iii
___________________
Date
Abstract
of
METHODS TO IMPROVE HEATING EFFICIENCY OF 27 MHZ DIATHERMY
SYSTEM BY USING REFLECTOR CONTROL
by
Siddharth Mangavally
Raghuram Pulijala
This project will focus on the methods of improving the heating effects of 27.12 MHz
Mettler Diathermy system by using reflector networks, for potential use in Hyperthermia
systems for the treatment of cancer. Currently, the Mettler system is tested by heating wet
absorber material, which is chosen since its electrical properties are identical to the
biological human tissue. However, previous studies using the same system have showed
that the applicator needs to be very close to the heating surface, to obtain any significant
increase in temperature; additionally, the surface also requires to be heating for at least 60
minutes to increase the temperature by 10-15 degrees. The aim of the current study is to
study any possible increase in efficiency, by using different types of reflector networks,
which are metallic structures that help to focus the RF energy from the Mettler source.
Our goal would be to achieve the temperature of the treatment within the desired time,
while maintaining a suitable distance between applicator and treatment surface.
, Committee Chair
Preetham B Kumar, Ph.D.
______________________
Date
iv
ACKNOWLEDGMENTS
We would like to take this opportunity to convey our sincere regards to Dr.
Preetham Kumar, faculty Member, EEE department and Graduate Advisor, for valuable
guidance, giving us the opportunity to take on this project and being very helpful
throughout this project. His support and encouragement helped the project to start and
end at the right time. We thank him again for his constructive feedback throughout the
course of our fieldwork.
We would also like to acknowledge and thank Professor Fethi Belkouche, Faculty
Member, EEE department for being part of the review committee and extending his
guidance for better formulation of our project. We also thank him for his review and
comments on the project report.
Our sincere appreciation goes to all our family members and friends for their love and
support during the entire duration of our coursework and this project.
v
TABLE OF CONTENTS
Page
Acknowledgments............................................................................................................... v
List of Tables .................................................................................................................... ix
List of Figures ..................................................................................................................... x
Chapter
1. INTRODUCTION ....................................................................................................... 1
2. HISTORY OF MICROWAVE HYPERTHERMIA AND ITS APPLICATIONS ...... 4
2.1. Hyperthermia Therapy ..................................................................................... 4
2.1.1. Mechanisms of Hyperthermia Treatment ................................................6
2.2. Methods in Hyperthermia Treatment ............................................................... 8
2.2.1. Local Hyperthermia .................................................................................9
2.2.2. Regional Hyperthermia ..........................................................................10
2.2.3. Whole-body Hyperthermia ....................................................................11
2.3. Risks in Hyperthermia ....................................................................................11
2.4 Benefits of Hyperthermia .................................................................................12
3. REFLECTOR NETWORKS & EQUIPMENT DESCRIPTION ............................... 14
3.1. Traditional Reflector Systems.........................................................................14
3.2. Reflector Networks Developed for Hyperthermia Applications ....................16
3.2.1. Circular Vane Reflector Structure .........................................................16
3.2.2. Rectangular Array Grid Reflector ..........................................................17
vi
3.3. Mettler Autotherm Equipment Details............................................................19
3.4. Mettler in Heat Therapy ..................................................................................21
3.5. Technical Specifications of Mettler Autotherm Equipment ...........................22
3.6. Precautions While Using Autotherm ..............................................................23
3.7. Infrared Digital Thermometer .........................................................................25
4. EXPERIMENTAL RESULTS OF DIELECTRIC HEATING USING DIATHERMY
SYSTEM WITH REFLECTOR ATTACHMENT ................................................ 26
4.1. Experimental Setup for Diathermy Heating Measurements ...........................27
4.2. Measurements with Applicator at a Distance 13.5cms from the Absorber
Material without the use of Reflector .............................................................29
4.3. Measurements with Applicator 12.5cms Away and without Reflector ..........31
4.4. Measurements with Applicator 1cm Away and without Reflector .................32
4.5. Measurements with Applicator at a Distance 12.5cms from the Absorber
Material with the Use of Circular Vane Reflector..........................................34
4.6. Measurements with Applicator at a Distance 10cms from the Absorber
Material with the Use of Circular Vane Reflector .........................................36
4.7. Measurements with Applicator at a Distance 5cms from the Absorber
Material with the Use of Circular Vane Reflector .........................................38
4.8. Measurements with Applicator at a Distance 1cm from the Absorber Material
with the Use of Circular Vane Reflector ........................................................40
4.9. Measurements with Applicator at a Distance 21.5cms from the Absorber
Material with the Use of Rectangular Array Grid Reflector ..........................42
4.10. Comparison of Readings Recorded on the Clay Medium and Absorber
Medium ...........................................................................................................44
5. CONCLUSION AND FUTURE SCOPE ......................................................................47
vii
Bibliography .....................................................................................................................49
viii
LIST OF TABLES
Page
1.
Table 4.1.Variation of temperature rise with time (Head of the Applicator 13.5cms
away from absorber material without reflector) .........................................................30
2.
Table 4.2.Variation of temperature rise with time (Head of the Applicator 12.5cms
away from absorber material without reflector) .........................................................31
3.
Table 4.3.Variation of temperature rise with time (Head of the Applicator 1cm away
from absorber material without reflector) ..................................................................33
4. Table 4.4.Variation of temperature rise with time (Head of the Applicator 12.5cms
away from absorber material using Circular Vane reflector) .....................................35
5.
Table 4.5.Variation of temperature rise with time (Head of the Applicator 10cms
away from absorber material using Circular Vane reflector) .....................................37
6.
Table 4.6.Variation of temperature rise with time (Head of the Applicator 5cms
away from absorber material using Circular Vane reflector) .....................................39
7.
Table 4.7.Variation of temperature rise with time (Head of the Applicator 1cm away
from absorber material using Circular Vane reflector) ..............................................41
8.
Table 4.8.Variation of temperature rise with time (Head of the Applicator 21.5cms
away from absorber material using Rectangular Array Grid reflector) .....................43
9.
Table 4.9.Comparison between Clay Medium and Absorber Medium (Head of the
applicator 1cm away from the absorber material) ......................................................45
ix
LIST OF FIGURES
Page
1.
Figure 2.1a Typical Hyperthermia System ...................................................................4
2.
Figure 2.1b Hyperthermia Ranges ................................................................................5
3.
Figure 2.1c Radiation Hyperthermia ...........................................................................6
4.
Figure 2.1d Denaturation Process ................................................................................7
5.
Figure 2.1e Microwave Hyperthermia System .............................................................8
6.
Figure 2.2. Local Hyperthermia System .......................................................................9
7.
Figure 3.1a Corner Reflector Structure ......................................................................14
8.
Figure 3.1b Types of Parabolic Reflectors .................................................................15
9.
Figure 3.2a Circular Vane Reflector Structure ...........................................................17
10. Figure 3.2b Equipment for Rectangular Array Grid Reflector ..................................18
11. Figure 3.2c Mettler Autotherm Diathermy with Circular Vane Reflector Structure .19
12. Figure 3.3a Mettler Autotherm Diathermy Unit ........................................................20
13. Figure 3.3b Control Knobs on Mettler Autotherm .....................................................21
14. Figure 3.3c Patient Input Meter for Autotherm ..........................................................21
15. Figure 3.4.Relative Absorption of RF Power Generated by the Autotherm
Equipment ...................................................................................................................22
16. Figure 3.5 Infrared Digital Thermometer ...................................................................25
17. Figure 4.1.Experimental Diathermy Setup without Reflector ....................................27
18. Figure 4.1a Experimental Diathermy Setup Using Circular Vane Reflector .............28
x
19. Figure 4.1b Experimental Setup Using Rectangular Array Grid Reflector ...............29
20. Figure 4.2.Graphical Representation of Temperature vs Time (Head of the
Applicator 13.5cms away from absorber material without reflector) ........................30
21. Figure 4.3.Graphical Representation of Temperature vs Time (Head of the
Applicator 12.5cms away from absorber material without reflector) ........................32
22. Figure 4.4.Graphical Representation of Temperature vs Time (Head of the
Applicator 1cm away from absorber material without reflector) ...............................34
23. Figure 4.5.Graphical Representation of Temperature vs Time (Head of the Applicator
12.5cms away from absorber material using Circular Vane reflector) ........................36
24. Figure 4.6.Graphical Representation of Temperature vs Time (Head of the Applicator
10cms away from absorber material using Circular Vane reflector) ...........................38
25. Figure 4.7.Graphical Representation of Temperature vs Time (Head of the Applicator
5cms away from absorber material using Circular Vane reflector) .............................40
25. Figure 4.8.Graphical Representation of Temperature vs Time (Head of the Applicator
1cm away from absorber material using Circular Vane reflector) ..............................42
26. Figure 4.9.Graphical Representation of Temperature vs Time (Head of the Applicator
21.5cms away from absorber material using Rectangular Array Grid reflector) ........44
27. Figure 4.10.Graphical Representation of Temperature vs Time (Recorded for Clay
Medium and Absorber Material) .................................................................................46
xi
1
Chapter 1
INTRODUCTION
RF and Microwaves play a major role in therapeutic medicine: one major field of
use in medicine is for treatment of tumors or also called Hyperthermia therapy. A specific
band of frequencies, such as 27 MHz, 900 MHz and 2450MHz fall among RF and
microwaves, which are allocated for the treatment of biological tissues. The 27 MHz, also
termed as Industrial Scientific and Medical (ISM) band, is being used for Hyperthermia
treatment. Currently, Hyperthermia treatment is primarily used as an adjuvant to radiation
or chemotherapy for cancer treatment in humans and animals [1]. The addition of
hyperthermia to conventional cancer treatment methods has been proven to enhance the
effects of radiation or chemotherapy alone.
This project is based on an experimental setup, involving the 27 MHz Mettler
Autotherm 300 diathermy system.
The fundamental idea behind conducting this
experiment is to test the heating properties of the system on wet absorber material, which
has similar dielectric and conductive properties to human tissue. The additional aim is to
achieve accurate and efficient heating different depths and distances with respect to the
experimental test object by using enhanced equipment and improved methods to extract
maximum output with the provided Hyperthermia equipment. By doing such
experiments, we could pave a strong foundation for upcoming research and study of
Hyperthermia .
2
The Mettler Autotherm 300 is used in our experiments to generate microwaves at
27MHz.This equipment is very much portable, inexpensive compared to that of its
contemporaries. Due to its inexpensive and flexible nature, many medical centers can
afford this equipment for Hyperthermia therapy. Here the material under test is absorber
material, which portrays similar properties of biological tissue. The temperature changes
in the material, due to incident radiation, are monitored with Infrared thermometer
compared to that of plastic Head of the Applicator digital thermometer (used in previous
experiments). Infrared thermometers have many advantages compared to plastic head of
the applicator thermometers [2]. They are usually termed as non-contact thermometers,
since a laser is used to measure the emissivity (here heat in temperature) from a distance,
by which the human intervention or direct contact of test object is evaded, hence
improving the efficiency of the reading taken with a very minimal prone of errors .
In order to improve heating efficiency, reflector networks were designed and tested
along with the Mettler system. Two kinds of reflector systems were tested: a rectangular
grid array reflector, and a circular vane reflector, or also called as a nonagon reflector.
These reflector networks were constructed and used in this experiment for concentrated
heat radiation on the absorber material. Temperatures were noted down with absorber
material kept at specific distances and with specific time intervals to understand different
variations from the heat source throughout the experiment.
This project report is organized as follows: This first chapter hence deals with
introduction to the work done in this project .Chapter II gives a background on
3
Hyperthermia therapy in the treatment of cancer. Chapter III deals with the design and
structure of reflector networks that were developed in this work. Chapter IV details the
experimental results on heating with the Mettler system, with and without reflector
networks. Finally, Chapter V gives conclusions on this work, followed by references.
4
Chapter 2
HISTORY OF MICROWAVE HYPERTHERMIA AND ITS APPLICATIONS
2.1 Hyperthermia Therapy:
In Hyperthermia treatment, temperature of the tumor to be treated in animal or
human body is increased to 42 degrees C or 108 degrees Fahrenheit. This increased
temperature is sustained for about 30 min, so that the tissue under treatment is made more
susceptible for the following radiation or chemotherapy process. A typical hyperthermia
system is shown in figure 2.1a below. Skin health can be affected if the heat
concentration is deviated from the target tumor location, it can lead to side effects such a
burnt skin. These side effects can be reduced by regulating the temperature and
maintaining it not to rise above a threshold level. Figure 2.1b shows different ranges of
hyperthermia [1,2].One feature which assists the success of this type of therapy is
confining heat to affected area. By killing cancer cells and damaging proteins and
structures within cells, hyperthermia not only shrinks tumors but also makes them
susceptive and responsive for the radiation or chemotherapy, which follows [2].
Figure 2.1a Typical Hyperthermia System [1]
5
Hyperthermia is capable of making cancer cells sensitive or even kills them where the
process of radiation cannot. Both the therapies if given and given within an hour range.
Hyperthermia temperature levels and a typical equipment schematic are shown in figures
2.1b and 2.1c respectively. Apart from giving effective treatment, Hyperthermia enhances
the effect of few anti cancer drugs. Hyperthermia is studied and proved effective when
used along with other thermal therapies such as chemotherapy, immunotherapy and
biological therapies [4].
Figure 2.1b Hyperthermia Ranges [1]
The above figure 2.1b shows different ranges of hyperthermia temperature calibrated in
both Fahrenheit and Centigrade. Figure 2.1c below depicts a typical equipment used for
administering hyperthermia. Essentially, it consists of an applicator around the patient
6
bed, along with a temperature monitoring system. The latter system is essential to
maintain the right temperature of 42 degrees C on the tumor area.
Figure 2.1c Radiation Hyperthermia [3]
2.1.1 Mechanisms of Hyperthermia Treatment:
A tumor is a solid lesion formed by an abnormal growth of cells (termed neoplastic)
which looks like a swelling [4]. Hyperthermia might kill or weaken tumor cells by high
thermal radiation which will cause denaturation (a process in which proteins lose their
tertiary structure and secondary structure by application of some external stress or
compound, such as a strong acid or base, a concentrated inorganic salt, an organic
solvent, or heat). Figure 2.1d shows the denaturation process. The blood in the area of the
body exposed to this kind of radiation is warmed, by which perfusion in tumors is
doubled, whereas the perfusion in normal tissue is increased to ten times or even more.
This process enhances the work of medication at these effected tumor sites. Since the
7
area is warm, oxygen flow is also increased which may make radiation to kill cell protein
structures and to prevent rejuvenating the damaged cell structures happened during
radiation session [7].
Figure 2.1d Denaturation Process [1]
Biological tumors have high-water content, when microwave energy is used for
treatment of such tumors; results will be outstanding since microwave energy is very
effective in heating cancerous tissues. When such high water percentage tissues are
exposed to high power microwaves, they heat very rapidly.Microwaves can be pin
pointed to a particular location by specially designed antennas located adjacent to
patient’s body. A clinical adaptive microwave hyperthermia system for treating cancer
deep in the body is show in figure 2.1e below [8].
8
Figure 2.1e Microwave Hyperthermia System [3]
Microwaves antennas are used for tumor treatment, which in turn depend upon
the location and size of the tumor in the body, these antennas work in such a way that
body tissues with high-water content that are irradiated with significant amounts of
microwave energy are heated. The microwave energy (oscillating about a billion times a
second) when flows through the tissue, water molecules are vibrated and frictional forces
are created between the water molecules in the tissue .This results in the heating of the
tissue. Microwave energy can be concentrated and can be made possible to selectively
heat tumors and protect healthy tissues. In the same way, synchronized radiating antennas
produce concentrated microwaves [8].
2.2 Methods in Hyperthermia Treatment:
Many methods of hyperthermia are currently under study: local, regional, and
Whole-body hyperthermia.
9
2.2.1. Local Hyperthermia:
Heat is applied to a small area, such as a tumor, usually using an applicator such
as the Mettler diathermy system that is being studied in this project. The cells affected
with cancer are heated to a maximum temperature of 108° F by using heating elements
such as microwave, antennas, heating rods, ultra sound. A typical Local hyperthermia
system is shown in figure 2.2.1 below.
Figure 2.2. Local Hyperthermia System [1]
Depending on the tumor location, there are several approaches to local hyperthermia such
as external, intra-luminal and interstitial [9].
a. External Approach: Used to treat tumors that are in or just below the skin. External
applicators are positioned around or near the appropriate region, and energy is focused on
the tumor to raise its temperature.
b. Intra-luminal or Endocavitary: Used to treat tumors within or near body cavities,
such as the esophagus or rectum. Head of the Applicators are placed inside the cavity and
inserted into the tumor to deliver energy and heat the area directly.
10
c. Interstitial: Used to treat tumors deep within the body, such as brain tumors. This
technique allows the tumor to be heated to higher temperatures than external techniques.
Under anesthesia, Head of the Applicators or needles are inserted into the tumor. Imaging
techniques, such as ultrasound, may be used to make sure the Head of the Applicator is
properly positioned within the tumor. The heat source is then inserted into the Head of
the Applicator. Radiofrequency ablation (RFA) is a type of interstitial hyperthermia that
to heat and kill cancer cells.
2.2.2. Regional Hyperthermia:
Heat is applied to a larger part of the body, such as an entire organ or limb. Usually, the
goal is to weaken cancer cells so that they are more likely to be killed by radiation and
chemotherapeutic medications. This may use the same techniques as local hyperthermia
treatment, or it may rely on blood perfusion in which the patient's blood is removed from
the body, heated up, and returned to blood vessels that lead directly through the desired
body part. Various approaches used to heat large areas of tissue, such as a body cavity,
organ, or limb are deep tissue, regional perfusion and continuous hyperthermic peritoneal
perfusion (CHPP) [10].
a. Deep Tissue Approach:
It may be used to treat cancers within the body, such as cervical or bladder cancer.
External applicators are positioned around the body cavity or organ to be treated, and
microwave or radiofrequency energy is focused on the area to raise its temperature.
11
b. Regional Perfusion Technique:
It can be used to treat cancers in the arms and legs, such as melanoma, or cancer in some
organs, such as the liver or lung. In this procedure, some of the patient’s blood is
removed, heated, and then pumped back into the limb or organ. Anticancer drugs are
commonly given during this treatment [11].
c. Continuous Hyperthermic Peritoneal Perfusion (CHPP) Technique:
It is used to treat cancers within the peritoneal cavity (the space within the abdomen that
contains the intestines, stomach, and liver), including primary peritoneal mesothelioma (a
cancer of the lining of the abdominal cavity) and stomach cancer. During surgery, heated
anticancer drugs flow from a warming device through the peritoneal cavity. The
peritoneal cavity temperature reaches 106–108°F [11].
2.2.3. Whole-body Hyperthermia:
Heat is applied to the entire body to temperatures of about 107–108°F. It is typically used
to treat metastatic cancer (cancer that spreads in many parts of the body).Techniques
include infrared hyperthermia domes which include the whole body apart from the head,
putting the patient in a very hot room, or wrapping the patient in hot, wet blankets [9].
2.3. Risks in Hyperthermia:
Hyperthermia side effects for the external methods include pain, unpleasant sensations
and burns in a small percentage of patients. In the case of the internal pyrogens(a
substance inducing fever), which are sometimes bacterial toxins, the situation is more
12
complicated, as bacterial toxins can induce serious, even fatal reactions in humans,
depending on dosage [2]. Ultrasound hyperthermia in areas where the tumor is over a
bone will cause bone pain. Whole body hyperthermia is a more radical form of heat
treatment, and has not been approved in the FDA yet, since it has increased potential for
side effects due to large-volume heating. Extracorporeal systemic hyperthermia is another
mode, where the blood is routed from the body as in dialysis, for example, and is heated
before returning to the body [2]. It has two advantages, higher possible temperatures and
heating that is more homogeneous. The figure 2.3 above shows different temperature
conditions. The side effects, however, have been considerable frequent persistent
peripheral neuropathies, abnormal (and sometimes lethal) blood coagulation, some
damage to liver and kidneys, and brain hemorrhaging and seizures. Hyperthermia should
be administered to patients who are awake and can report any problems as they
experience them. Analgesics can be administered if a patient has difficulty lying still for
the duration of the session. Patient’s vital signs must be monitored frequently during the
session. Cardiovascular disease and sometimes pace makers (depending on the heat
delivery method) are a contraindication for the treatment [10].
2.4. Benefits of Hyperthermia:
Hyperthermia, when used alone, leads to impressive results, eradicating 10-15% of
tumors. These results usually do not last, and the tumors grow again. Hyperthermia raises
the body temperature above normal to a maximum of 108 ° F as this reduces the foreign
organism presence and the impurities in the body. When compared to the body tissues,
13
the invading foreign organisms cannot survive in the high temperatures. This is a certain
benefit as the temperature can be increased above certain level which kill the unwanted
organisms, bacteria and virus, and thereby killing the cancer cells [8].
Hyperthermia and radiation combined together in the treatment has been reported
to yield higher and durable responses than radiation alone. In deep-seated tumors, the
effect of this combined treatment is under research for deep-seated tumors. Though it is
difficult to increase human tumor temperature, recent clinical trials has shown that
radiation with hyperthermia is far more successful in controlling many human tumors
radiation alone. Hyperthermia may also provide additional advantage in drug delivery.
Several studies have shown that the delivery of monoclonal antibodies is enhanced by
using hyperthermia, particularly to the tumors with resultant improvement in anti tumor
effects. The spread of carried chemo drugs into the tissues of liposome is increased
considerably with higher temperature when compared to that under normal temperature.
Much of the information and research has emerged from hyperthermia studies in several
other treatments that may become valuable in the future [9].
14
Chapter 3
REFLECTOR NETWORKS & EQUIPMENT DESCRIPTION
Reflectors are devices that guide or focus electromagnetic waves. Reflectors used in
Hyperthermia systems to improve efficiency in heating biological tissues are similar;
however, size is a critical factor, which changes based on operating frequency, and
structure of the original diathermy system.
3.1 Traditional Reflector Systems:
The most common type of reflector types are corner reflectors, parabolic reflectors and
flat reflectors. [8]. Figure 3.1a shows a typical corner reflector that is used in
communication systems, to focus the radiation in a particular preferred direction.
Figure 3.1a Corner Reflector Structure [8]
15
A corner reflector is a retro reflector consisting of three mutually perpendicular; which
reflects waves back directly towards the source. Unlike a simple mirror, they work for a
relatively wide-angle field of view. Corner reflectors are easy to construct from a metal
sheet such as aluminum but care must be taken that the surfaces join exactly at 90 degrees
and must be robust enough. There are two types of reflectors: Dihedral and Trihedral
reflectors. The dihedral has two surfaces that are orthogonal planes and trihedral has three
surfaces respectively [11].
Figure 3.1b shows typical examples of parabolic reflectors.
Figure 3.1b Types of Parabolic Reflectors [7]
16
A parabolic reflector is a reflective device used to collect or project energy such as light,
sound or radio waves. It is in the shape of a circular paraboloid that is the surface
generated by parabola moving around the axis. The parabolic reflector transforms the
incident plane wave into a spherical wave converging towards the propagating as a
collimated beam along the axis. In this project, we have made use of two types of
reflectors namely circular vane reflector and rectangular array grid reflectors [12].
The plane reflector is the simplest form of reflector antenna. When a plane reflector is
placed in front of the feed, energy is radiated in desired direction. To increase the
directivity of the antenna, a large flat sheet can be kept as a plane reflector in front of a
half dipole. The main advantage of the plane reflector is that for a dipole, backward
radiations are reduced and the gain in forward direction increases. To increase directivity,
we can use array of two half-wave dipoles in front of plane reflectors.
3.2. Reflector Networks Developed for Hyperthermia Applications:
In the current work, two types of reflector networks were designed and tested, with the
main aim of improving the efficiency of the diathermy unit, and essentially focusing the
RF power coming out of the unit. These reflector networks are described below:
3.2.1. Circular Vane Reflector Structure:
The photograph of the circular vane reflector is show below in Figure 3.2a. The reflector
consists of nine metallic sections connected to the common baseboard in a circular
formation. The radius of the reflector vane base is 30cm, and the outer radius of the vane
circle is 150cm.
17
Fig 3.2a Circular Vane Reflector Structure
The Circular Vane Reflector is also named as a Nonagon (9) reflector structure. To
stop the heat dissipation, to improve heating efficiency with respect to time and to
acquire the desired temperature in confined time, this reflector structure helps us to
reflect the heat from the Autotherm and concentrate this dissipated heat back to the
absorber material so that temperature increase would be faster in the absorber material
[11].
3.2.2 Rectangular Array Grid Reflector:
The second reflector network developed in our lab is the Rectangular Array Grid
Reflector, which is shown below in Figure 3.2b.
18
Fig 3.2b Equipment for Rectangular Array Grid Reflector
The dimensions of the rectangular array reflector are 160x40cm. It consists of 10 linear
vanes separated at a distance of 4cm.
The experimental setup for Diathermy with reflector network is shown below in
Figure 3.2c. The figure clearly shows that the Reflector points towards the head of the
absorber medium. Several experiments were carried out with the head of the reflector
being varied from an inch to several centimeters to calculate the temperature rise in
regular intervals of time [10].
19
Fig 3.2c Mettler Autotherm Diathermy with Circular Vane Reflector Structure
The next chapter deals with experimental results where several reading were
taken with two types of reflecto: Rectangular Array Reflector and the Circular Vane
Reflectors. The distance between the
absorber test medium and the diathermy the
applicator has been varied from an 1 cm to several cm for attaining the maximum
temperature within small time; graphical representations have been depicted to show the
variation of temperature with time [11].
3.3. Mettler Autotherm Equipment Details:
In this project, all the measurements of the experiment were conducted with the
Mettler Autotherm equipment shown in the Figure 3.3a. The Autotherm is a equipment
which possesses unique induction field circuitry which produces a short wave frequency
20
of 27.12 MHz This wave can penetrate into muscle tissue with negligible heating in the
fatty layer or bone [10].
Figure 3.3a. Mettler Autotherm Diathermy Unit
The Autotherm 300 is a continuous shortwave diathermy unit, which is designed
to be economical and lightweight. It is capable of automatic tuning which ensures proper
frequency response of the equipment. It is portable with a roller coaster base and is
flexible. The arm is made adjustable, so that it can reach different parts of the body and
can heat accordingly. This equipment is mainly used where deep heat is required such as
the low back, shoulder, neck and hip [7]. This equipment is economical and is easy to
operate since it only has two controls, a timer knob and an intensity control knob as
shown in figure 3.3b respectively
21
Figure 3.3b Control Knobs on Mettler Autotherm
The Autotherm has a timer, which is designed to the variation of 0 to 30 minutes.
The timer helps to know the timing of treatment. The power meter, as shown in Figure
3.3c, displays the energy levels absorbed by body surface. It also monitors the current
from the power supply and displays the energy absorbed.
Figure 3.3c Patient Input Meter for Autotherm
3.4. Mettler in Heat Therapy:
Mettler Autotherm is used when deep heat therapy has to be done for any part of
the body. It operates with short wave diathermy and is a safe for subcutaneous body
22
tissues. The electro-magnetic field is generated between the equipment and the body. The
heat penetrates deep into muscle tissue, eases the tensions, and brings relief. This therapy
is mainly used for back pain, chronic arthritis, bursitis and other musculo-skeletal
conditions [10]. The heat therapy modality is shown below in figure 3.4.
Figure 3.4. Relative Absorption of RF Power Generated by the Autotherm Equipment [3]
3.5. Technical Specifications of Mettler Autotherm Equipment:
Input: 100–240 VAC, 50-60Hz
Frequency: 27.12 MHz (Wavelength λ= 11.06 meters)
RF output: Continuous mode 100 W Average Power, Pulsed mode 200 W Peak
Power Continuous mode: 100-Watts Average Power
Pulsed Mode: 200-Watts Peak Power
Pulse frequency: 10 Hz, 20 Hz, 50 Hz, 100 Hz, 400 Hz
Pulse duration: 65 μs, 100 μs, 200 μs, 300 μs and 400 μs
23
Treatment time: 1–30 minutes [10]
Weight: Unit: 30 pounds
Dimensions: 40 in (H) x 18 in (W) x 18 in (D), (100 cm (H) x 46 cm (W) x 46cm (D))
3.6. Precautions While Using Autotherm:
The use of Autotherm for shortwave and microwave diathermy treatment, tissues are
heated by use of electromagnetic energy. This induces or radiates from the head of
diathermy unit. This is absorbed in the electrically conductive tissues of the human body
and is converted to heat [11]. In most of the shortwave diathermy units, a radio-frequency
field exists around the cables in the equipment and carries electrical energy from the
source generator to the equipment head. Microwave diathermy units have well-shielded
leads within the equipment between the generator and head of the applicator. The
generator and applicator head are integrated, and there is normally very little radiation
from other source except that of the applicator [12]. There is very little or no heating of
the air surrounding the cables since it absorbs little energy from the radio-frequency
fields. Table 4.1 shows the variation pattern of electric and magnetic fields in the
diathermy unit as a function of distance within the treatment volume. Heating occurs only
when conductive or partially conductive material is located within the electric or
magnetic field produced by the cables or applicator. The Canadian Bureau of Medical
Devices mentions in its data that certain plastics and synthetics such as nylon, polyvinyl
chloride, and polyethylene terephthalate and some fabric blends which are usually
24
regarded as good insulators, can also be heated certain temperatures by shortwave and
microwave diathermy units [7]. However, two other synthetics widely used in medical
practice for several applications, silicone and polytetrafluoroethylene usually called
Teflon are relatively very less affected by electromagnetic fields [9].
The amplitude of heating depends on a number of factors, including the output
setting of the generator and the degree to which the electromagnetic energy waves are
concentrated in a small area of the body. A very high-density field exists because of three
reasons: When a cable is located near a grounded or conductive object, when the cables
are positioned at a very less distance. There are some recommendations which will
minimize the risk involved in equipment damage and injury and can also reduce the risk
of fire associate with equipment [8].When generator is activated leaning on the
equipment or holding the cables may cause unwanted heating or radiation to the body. If
done so the cable might break and expose the user to high voltages or radiation. Cables
should be spaced apart for each other. We should not keep anything in between these
cables to avoid the damage of cables. We should keep all line cords away; there should
be no contact between diathermy unit cables. The operating diathermy unit should be
kept away from coil line cords. The cables should be kept at least several inches away
from any objects or material. There should be no contact between cables and metal or
grounded objects. There may be some synthetic or plastic objects which may be
nonconductive but may be heated by the diathermy unit [9].
25
3.7
Infrared Digital Thermometer:
Figure 3.5. Infrared Digital Thermometer [5]
In the first phase of this project, the thermometer with metal Head of the
Applicator was used. In this phase of the project, we have used the Fluke 62 Mini digital
thermometer with plastic Head of the Applicator as shown in above figure 3.8. It is
perfect introduction to infrared (IR) thermometers for the professional [6]. The Fluke 62
Mini Infrared Thermometer offers quick and reliable surface temperature readings
infrared thermometer is a non-contact diagnostic tool for quick basic temperature checks
in applications where a technician is close to the target object.
Simple to use, the Fluke 62 Mini enables technicians to discover temperature
discrepancies before they become problems. In this experiment the intervention of the
thermometer in the path of the medium might affect the values of temperature while
calibration, by using this Infrared thermometer we measure temperature from a safe
distance and can make sure about the readings taken [11].
26
Chapter 4
EXPERIMENTAL RESULTS ON DIELECTRIC HEATING USING DIATHERMY
SYSTEM WITH REFLECTOR ATTACHMENT
We have discussed about the Mettler diathermy system and associated reflector
networks in the earlier chapter. In this chapter, we outline the experiments that were
carried on the diathermy system, with and without reflectors, with the aim of studying the
heating properties for potential hyperthermia application.
In the first phase of
experiments, [1] absorber materials of two different types were used, one with more
water content and one with less water content in it. The absorber material content
resembles the human skin in many properties such as plasticity, absorbency and cohesion.
As with the part of absorbency, oxygen, nitrogen and carbon dioxide can diffuse into the
epidermis in small amount constituting to high content of water in the skin [2]. Similar is
the case with the absorber material that it contains 40% of natural water that fills up all
the minute pores between all the mineral grains [5]. The plasticity of the absorber
material and the human skin depends on the proportion of water content in them, which
makes them exhibit similar properties.
In the set of experiments done in the first phase, a contact digital thermometer
was used, and there were significant fluctuations in the thermometer display. These
fluctuations occurred because the long metal probe of the thermometer experienced
considerable interference with the RF radiation emanating from the Autotherm unit. We
tried to cover the part of the metal probe of the thermometer with absorber material;
27
however, that did not help to stop the fluctuations with the thermometer. Hence, it was
decided to use thermometer, which does not have a probe, that can act as an antenna to
the thermometer. We researched and got a infrared non-contact thermometer without a
metallic probe, which could not potentially interfere with the radiation from diathermy
unit.
4.1. Experimental Setup for Diathermy Heating Measurements:
Figure 4.1 shows a typical setup for diathermy measurement. This setup does not
include reflector networks, it comprises mainly of the diathermy unit, or more
specifically, the applicator head, focusing on the absorber material that will be heated to
the appropriate temperature. The aim is to raise the temperature on the absorber material
to the hyperthermia temperature of ~ 42 degrees C or 107 degree F. The heating is not
instantaneous, and takes 30-60 minutes to heat the absorber to at least 10 degrees above
the normal room temperature.
Figure 4.1. Experimental Diathermy Setup without Reflector
28
All the readings were taken with utmost accuracy taking in consideration the time
and the distance of the applicator’s head from the absorber material. All the readings
were taking with high intensity on the Autotherm unit [7].
Figure 4.1a shows a typical setup for diathermy measurement, with the circular
vane reflector. It comprises of the diathermy unit, the circular reflector unit. , focusing on
the absorber material that will be heated to the appropriate temperature. The aim is to
raise the temperature on the absorber material in a shorter time, as compared to the case
without reflector networks.
Figure 4.1a Experimental Diathermy Setup Using Circular Vane Reflector
Figure 4.1b shows a typical setup for diathermy measurement, with the
rectangular array grid network. It comprises of the diathermy unit, the rectangular
reflector unit. , focusing on the absorber material that will be heated to the appropriate
29
temperature. The aim is to raise the temperature on the absorber material in a shorter
time, as compared to the case without reflector networks.
Figure 4.1b Experimental Setup Using the Rectangular Array Grid Reflector
4.2. Measurements with Applicator at a Distance 13.5cms from the Absorber
Material without the Use of Reflector:
This set of readings was taken with head of the applicator placed at distance of 13.5 cm
away from the absorber material. All the readings were taken with interval of 10 minutes
for 1 hour. The table 4.1 below shows that the readings were recorded without the
reflector and placing the head of the applicator at a distance of 13.5cm.
30
CASE 1
Distance
–
Reflector –
13.5cms
No
Time(Minutes) Temperature(F)
0
71
10
71.5
20
68
30
68.5
40
68.5
50
68.5
60
69
Table 4.1. Variation of Temperature rise with time (Head of the Applicator 13.5cms away
from absorber material without reflector)
Without Reflector and distance 13.5cms
72
71.5
Temperature(oF)
71
70.5
70
69.5
Temperature
69
68.5
68
67.5
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.2. Graphical Representation of Temperature vs Time (Head of the Applicator
on 13.5cms away from absorber material without reflector)
The above Figure 4.2. shows the graphical representation of temperature rise as a
31
function of time.As we can see from the graph that the change in temperature was only
seen in the first 10 minutes of the experiment. After 30 minutes of heating the absorbing
medium, there was a difference of only 2° F for the next 60 minutes.
4.3. Measurement with Applicator 12.5cms Away and without Reflector:
These set of readings were taken with the absorber material that was just an inch away
from the diathermy head. This step was taken, as there was no much increase in the
temperature after 30 minutes of heating, these readings were taken by keeping the head of
the applicator on the surface. These readings were taken with an interval of 15 minutes
for 60 minutes. Table 4.3 shows the readings taken with the distance of 12.5cms and
without reflector.
CASE 2
Distance
–
Reflector -
12.5cms
No
Time(Minutes) Temperature(F)
0
72.5
10
71
20
70.5
30
70.5
40
71.5
50
71.5
60
71.5
Table 4.2. Variation of Temperature rise with time (Head of the Applicator 12.5cms away
from absorber material without reflector)
32
The above table 4.2. depicts that the readings were recorded without the reflector and
placing the head of the applicator at a distance of 12.5cms.
Without Reflector and distance 12.5cms
73
Temperature(oF)
72.5
72
71.5
Temperature
71
70.5
70
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.3. Graphical Representation of Temperature vs Time (Head of the Applicator
on 12.5cms away from absorber material without reflector)
From the above graph, we can see that there was only considerable change throughout the
process until 40 minutes then there was no temperature increase.
4.4. Measurements with Applicator 1cm Away and without Reflector:
We even tried taking readings without using the Reflector so that we can have the both
the incident and reflected wave which in turn results in temperature rise in less time. In
this set of readings, we have placed the applicator 1 cm away from the absorber material.
33
CASE 3
Distance – 1
Reflector -
cm
No
Time(Minutes) Temperature(F)
0
76
10
78.5
20
81.5
30
84
40
85.5
50
86
60
87.5
Table 4.3. Variation of Temperature rise with time (Head of the Applicator 1cm away
from absorber material without reflector)
The above table 4.3. shows that the readings were recorded without the reflector placing
the head of the applicator at a distance of 1cm.
34
Without Reflector and distance 1cm
90
Temperature(oF)
88
86
84
82
80
Temperature
78
76
74
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.4. Graphical Representation of Temperature vs Time (Head of the Applicator
on 1cm away from absorber material without reflector)
From the above graph representation, we can see that there is a gradual increase in
temperature along with time. We can observe that temperature gradually increases from
10 minutes up to 60 minutes. There is an increase of nearly 10° F within one hour but
beyond that the temperature remained constant and there was not much of considerable
change in the temperature rise of the absorber material [11].
4.5. Measurements with Applicator at a Distance 12.5cms from the Absorber
Material with the Use of Circular Vane Reflector:
These set of readings are taken with Head of the applicator placed at a distance of 12.5
cm away from the absorber material and with the Reflector.
35
CASE 4
Distance
– Reflector -Yes
12.5 cm
Time(Minutes) Temperature(F)
0
81
10
76
20
73.5
30
72.5
40
72
50
72
60
72.5
Table 4.4. Variation of Temperature rise with time (Head of the Applicator 12.5cms
away from absorber material using Circular Vane reflector)
The above table 4.4. shows that the readings were recorded with the reflector and placing
the head of the applicator at a distance of 12.5cms.
36
Temperature(oF)
With Reflector and distance 12.5cms
82
81
80
79
78
77
76
75
74
73
72
71
Temperature
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.5. Graphical Representation of Temperature vs Time (Head of the Applicator
on 12.5cms away from absorber material using Circular Vane reflector)
The above graph clearly depicts that Temperature gradually decreases as time time
increases with Nanogon Reflector.We observe that Temperature falls down from 81°F to
72° F within 40 minutes.But temperature remains constant for the next 2 intervals and
again starts rising. From the previous readings we draw to a conclusion that temperature
gradually decreases as the distance between the head of the applicator and absorber
material increases [4].
4.6. Measurements with Applicator at a Distance 10cms from the Absorber Material
with the Use of Circular Vane Reflector:
The next set of readings is taken by placing the head of the applicator at a distance of 10
cm away from the absorber material in the presence of reflector.
37
CASE 5
Distance – 10 Reflector -Yes
cm
Time(Minutes) Temperature(F)
0
70.5
10
71
20
71.5
30
72.5
40
73
50
74
60
71.5
Table 4.5. Variation of Temperature rise with time (Head of the Applicator 10cms away
from absorber material using Circular Vane reflector)
The above table 4.5. shows that the readings were recorded with the reflector and placing
the head of the applicator at a distance of 10cms.
38
With Reflector and distance 10cms
74.5
74
Temperature(oF)
73.5
73
72.5
72
Temperature
71.5
71
70.5
70
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.6. Graphical Representation of Temperature vs Time (Head of the Applicator on
10cms away from absorber material using Circular Vane reflector)
The above table and graph suggest that temperature slowly rises from 70.5°F to 74°F
remains constant for nearly 30 min and slowly starts decreasing after 20 min to 71.5°F.
This supports our previous assumption that as distance between the head of the applicator
and absorber medium decreases the Temperature rises with respect to time [7].
4.7. Measurements with Applicator at a Distance 5cms from the Absorber material
with the Use of Circular Vane Reflector:
These measurements are taken with head of the applicator 5 cm away from the absorber
material.
39
CASE 6
Distance – 5cm
Reflector -Yes
Time(Minutes)
Temperature(F)
0
67
10
69.5
20
71
30
71.5
40
73.5
50
74.5
60
75
Table 4.6. Variation of Temperature rise with time (Head of the Applicator 5cms away
from absorber material using Circular Vane reflector)
The above table 4.6. shows that the readings were recorded with the reflector and placing
the head of the applicator at a distance of 5cms.
40
Temperature(oF)
With Reflector and distance 5 cms
76
75
74
73
72
71
70
69
68
67
66
Temperature
0
10
20
30
40
50
60
70
Time(Min)
Figure 4.7. Graphical Representation of Temperature vs Time (Head of the Applicator on
5cms away from absorber material using Circular Vane reflector)
The above table and graph suggest that temperature slowly rises from 67.5°F to 75°F.The
temperature rises constantly for each interval of time and hence this proves the
assumption that as distance between the head of the applicator and absorber medium
decreases the temperature rises with respect to time.
4.8. Measurements with Applicator at a Distance 1cm from the Absorber Material
with the Use of Circular Vane Reflector:
The final set of readings that have been recorded with head of applicator placed at a
distance of 1cm above the absorber material. The below table and readings describe the
temperature with respect to time and suggests the maximum temperature rise as the
distance decreases.
41
CASE 7
Distance – 1cm
Reflector -Yes
Time(Minutes)
Temperature(F)
0
72.5
10
77.5
20
82
30
85.5
40
88
50
90
60
91
Table 4.7.Variation of Temperature rise with time (Head of the Applicator 1cm away
from absorber material using Circular Vane reflector)
The above table 4.7. shows that the readings were recorded with the reflector and placing
the head of the applicator at a distance of 1cm.
42
Figure 4.8. Graphical Representation of Temperature vs Time (Head of the Applicator on
1cm away from absorber material using Circular Vane reflector)
The above table and graph suggest that temperature constantly rises from 72.5°F to 91°F
for each interval of time and hence this proves the assumption that as distance between
the head of the applicator and absorber medium decreases, the temperature rises with
respect to time.
4.9. Measurements with Applicator at a Distance 21.5cms from the Absorber
Material with the Use of Rectangular Array Grid Reflector:
The set of readings have been recorded with the head of the applicator at a distance of
21.5 cm away from the absorber material using Rectangular Array Grid Reflector as
show in Fig 4.2. The values recorded are represented in the table and the graphical
representation has been depicted.
43
CASE 8
Distance
– Reflector -Yes
21.5cm
Time(Minutes)
Temperature(F)
0
81
10
76
20
73.5
30
72.5
40
72.0
50
72.0
60
72.5
Table 4.8. Variation of Temperature rise with time (Head of the Applicator 21.5cms
away from absorber material using Rectangular Array Grid reflector)
The above table 4.8. shows that the readings were recorded with the reflector and by
placing the head of the applicator at a distance of 21.5cms.
44
With reflector and distance 21.5cms
80
Temperature(oF)
78
76
74
72
70
Temperature
68
66
64
0
10
20
30
40
50
60
Time(Min)
Figure 4.9. Graphical Representation of Temperature vs Time (Head of the Applicator at
a distance of 21.5 cm away from Absorber material using Rectangular Array Grid
reflector)
The above graph suggest that temperature slowly falls from 81°F to 72.5°F.The
temperature falls down constantly for each interval of time and hence this proves the
assumption that as distance between the head of the applicator and absorber medium
increases the temperature decreases with respect to time.
4.10. Comparison of readings recorded on the Clay Medium and Absorber Medium:
In this section, we have attempted to give a brief summary of the readings recorded by
the earlier reports where clay medium, and its comparison with absorber material
measurements. It is observed that the absorber material measurements show enhanced
heating, as compared with clay medium. Hence, the absorber material was used in all
later measurements, since it represented a better match.
45
CASE 8
Distance –
On Clay
On Absorber
1cm
Medium
Material
Time(Minutes)
Temperature(F)
Temperature(F)
0
69
72
10
69.5
77.5
20
71.2
82
30
72
85.5
40
72.5
88
50
72.5
90
60
73
91
Table 4.9. Comparison between Clay Medium and Absorber Medium (Head of the
applicator 1cm away from the absorber material).
The above table 4.9. represents readings recorded for clay medium and for the wet
absorber material by placing the head of the reflector at a distance of 1cm.
46
Figure 4.10. Graphical Representation of Temperature vs Time (Recorded for Clay
Medium and Absorber Material)
From the above table 4.9 and Graphical representation figure 4.10. it could be clearly
understood that there was a huge improvement in the temperature rise after the
construction of Rectangular reflector and Circular reflector where more effective heating
could be done with minimum microwave interference and leading to better results.
47
Chapter 5
CONCLUSION AND FUTURE SCOPE
The focus of this project is to study the heating effects of the 27 MHz Mettler
diathermy unit on sample absorber material, with potential for application in clinical
hyperthermia treatment of cancer. However, the significant change in the heating
mechanism is the addition of reflector networks to improve the heating efficiency of the
overall system. The efficiency is measured by reducing the heating time to attain the
required temperature, and by increasing the distance between applicator and heating
surface. An additional enhancement in temperature measurement was to include an
Infrared contact-free thermometer to record measurements, as compared to the contact
probe thermometer that was used previously. The new temperature protocol was
successful in eliminating the earlier interference between the diathermy radiation and the
measuring probe of the contact thermometer.
The major success of this project came from the following changes: Firstly,
replacing clay medium with absorber material as the testing material showed increased
RF energy absorption, and increased the ability to get meaningful results. Secondly, the
measurements recorded with the replacement infrared thermometer helped us in giving
accurate non-fluctuating temperature measurements. Thirdly, construction of reflectors
like rectangular array grid reflector and circular vane reflectors helped in increase of
temperature within very less time, which would be very beneficial in hyperthermia
applications. Though we were not able to replicate exactly how the human body responds
48
to the heat we have made a considerable achievement in understanding the way heat can
be effectively transmitted through the auto therm equipment.
Despite taking at most care in recording the measurement using the Infra Red
thermometer with the hand, there were minor fluctuating errors, which can be avoided
using a fixed stand. At present, we were able to achieve temperatures up to a maximum
of 100 degrees F. Future efforts will aim on getting higher temperature goals, to near the
hyperthermia temperature of 42 degrees C or 108 degrees F.
49
BIBLIOGRAPHY
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on
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http://www.scribd.com/doc/6130660/Microwave-Diathermy on February 11 2011.
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50
11. Typical RF fields close to Diathermy devices retrieved from website http://www.hcsc.gc.ca/ewh-semt/pubs/radiation/83ehd-dhm98/fields-rf-champs-eng.php February
21 2011.
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