Faculty of Engineering
DEPARTMENT of ELECTRICAL AND
ELECTRONIC ENGINEERING
Biomedical Imaging
BMED 434
Term project
Surgical Navigation
Dr. Shahla Azizi Alikamar
Fall term 2023
Loujayn Ayache
20801170
Kiana Mahtabi Nourani
21009141
Lenah Serai Wangare
20700181
Table of Contents
List of figures .......................................................................................................................................... 3
Introduction ............................................................................................................................................. 4
What this method is ................................................................................................................................ 5
What the device is ................................................................................................................................... 6
How it works ........................................................................................................................................... 7
Function of the surgical navigation system (SNS) .............................................................................. 8
The process of surgical navigation in details ...................................................................................... 9
Data Acquisition.............................................................................................................................. 9
Registration ................................................................................................................................... 10
First method of registration ....................................................................................................... 10
Second method of registration .................................................................................................. 10
Third method of registration ..................................................................................................... 10
Tracking ........................................................................................................................................ 10
Deep Brain Stimulation Lead Placement (DBSL) ............................................................................ 12
Surgical Navigation Advanced Platform (SNAP) ............................................................................. 12
Thoracic Trauma ............................................................................................................................... 13
What are its various parts ...................................................................................................................... 15
Electrical circuit of the device .............................................................................................................. 17
Conclusion ............................................................................................................................................ 19
Reference .............................................................................................................................................. 20
2
List of figures
Figure 1 Application of Surgical navigation ........................................................................................... 5
Figure 2 Variety of navigation platforms ................................................................................................ 6
Figure 3 Common OR setup in spinal surgery ........................................................................................ 7
Figure 4 Basic navigation workflow ....................................................................................................... 7
Figure 5 Tracking procedure via 7D SNS system ................................................................................... 8
Figure 6 Different probe tips that can be used for registration ............................................................... 9
Figure 7 Navigation display .................................................................................................................. 10
Figure 8 Navigation display after 2D to 3D registration....................................................................... 11
Figure 9 Passive trackers ...................................................................................................................... 11
Figure 10 Use of navigation system in surgery..................................................................................... 12
Figure 11 View provided by SNAP for neurocysticercosis surgery ...................................................... 13
Figure 12 positioning of the glass in 3D combined MRI and CT scan using SNAP ............................ 14
Figure 13 Reflective markers, skin markers, and Mayfield adapter ..................................................... 15
Figure 14 The working station .............................................................................................................. 15
Figure 15 Mayfield adapter ................................................................................................................... 15
Figure 16 Different parts of a simple surgical navigation system ......................................................... 16
Figure 17 Circuit diagram representation of the SNS system .............................................................. 17
3
Introduction
As a significant development in the medical field, surgical navigation improves the
accuracy and precision of surgical treatments. Better patient outcomes are ensured by the
revolutionary manner this technology has transformed the way surgeons undertake intricate
surgical procedures. The last 20 years have seen the addition of navigation technology to the
surgeon's toolkit. The goal of performing less intrusive and safer procedures led to the
development of navigation in surgery. Better and more efficient technical instruments became
necessary because of this advancement, which made it possible for novel and more difficult
surgical techniques. With the development of new surgical techniques, navigation has become
an increasingly significant tool for surgical decision-making.
The late nineteenth century saw the commencement of the first significant studies
aimed at accurately localizing particular anatomical structures within the human body. While
a lot has changed since then, the primary obstacle of precisely targeting an anatomical structure
in a less intrusive and safer manner has not altered. Precise and safe targeting of anatomy was
only possible with the development of medical imaging in tandem with the exponential
expansion of computer processing power. Navigation was made possible thanks in large part
to medical imaging. The evolution of navigation in surgery as it exists now was largely driven
by three main factors: stereotaxy, medical imaging, and neurosurgery.
This report provides an overview of surgical navigation systems, including its
definition, the device used, how it works, its applications, the various parts involved, and the
electrical circuits driving the device.
4
What this method is
Surgical navigation is a cutting-edge medical technology that integrates preoperative
imaging data with real-time vision during surgery. It is often referred to as computer-assisted
surgery (CAS) or image-guided surgery. By giving surgeons accurate information, this
technique improves their precision and safety of patient when operating [1].
Every patient must have a unique, high-resolution CT scan performed before the
surgery. This scan acts as a map for the surgeon to use during the procedure. A computer
workstation is loaded with the CT scan on the day of operation to interpret the images and get
positional data from the tracking device. Any surgical navigation treatment starts with a
procedure called "registration," which aligns relevant locations in the preoperative CT scan
with the anatomy of the patient. Registration is a necessary first step in the surgical navigation
technology calibration process [2].
Figure 1 Application of Surgical navigation
(A) The surgical navigation system called StealthStation. (B) Image-to-patient registration
and intraoperative referencing for the navigation unit and image-guided visualization display.
(C) Setting up the magnetic field generator (arrowheads) and reference locations (arrows) in
advance of final draping in order to prepare for registration. (D) Tracer probe registration
without markers.
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What the device is
A PC workstation is usually the main tool used in surgical navigation. Specialized
software that processes and displays medical imaging data, such as CT, MRI, and 3D
reconstructions, is installed on this workstation. Additionally, it communicates with a range of
instruments and tracking devices utilized during the surgical process [3].
The level of flexibility, functionality required, and workflow requirements vary
depending on the surgical specialty, hospital, and surgeon. There are numerous navigation
platforms available to meet every surgical need: For maximum flexibility, the systems can be
carried between hospitals or installed permanently at the ceiling of the OR. They can also
minimize cable clutter, take up less space in the OR, and be mobile platforms that can be used
in multiple ORs at different times [3].
Figure 2 Variety of navigation platforms
A) ceiling-mounted; B) dual display; C) Kick, which is more compact and portable; D) Dash,
the smart mobile option.
Computer-assisted navigation systems can be classified as imageless, fluoroscopic, or
computer tomography (CT) based, depending on how information is referenced. The most
accurate navigation method is CT-based, but it needs more preoperative CT scanning.
Planning takes longer, and radiation exposure increases. Convenient fluoroscopic-based
navigation is possible, and once the patient's tracker is positioned, intraoperatively registered
images can be obtained. In particular, minimally invasive spine surgery and trauma fracture
fixation benefit from it. Images are not needed for imageless navigation. When surgeons
perform the registration by simply pointing at bony landmarks, errors may occur because it
ignores the unique bony anatomy of each individual [3].
6
How it works
Surgical navigation systems function by merging real-time data from tracking devices
with medical imaging data specific to each patient. A stereoscopic camera that emits infrared
light is used by modern surgical navigation systems to determine the three-dimensional
location of prominent structures, such as reflective marker spheres.
Figure 3 Common OR setup in spinal surgery
Spinal OR setup: A stereotactic camera (upper right corner) and a computer screen (center) are
commonly used in ORs that use surgical navigation. Both items are mounted to the ceiling.
Additional marker spheres are firmly fastened to the patient and surgical instruments using a
reference array.
Figure 4 Basic navigation workflow
Basic model-based and image-based navigation workflows. For image-based navigation,
which is usually used for cranial or spinal surgery, preoperative images must be registered to
the patient setup. Model-based navigation, commonly used in orthopedic surgery, does not
require imaging data and registers the patient's anatomy to a virtual model.
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Function of the surgical navigation system (SNS)
For better understanding of how SNS system works we can describe it by a simple
example of GPS tracking for a moving object. In simple words we can define surgical
navigation as techniques that will project the position of the instrument using real time x-ray
imaging in order to help the surgeon to track the position of the instrument. Comparing the
function of the GPS and SNS, the moving object in GPS is the surgical instrument that is being
imaged in real time in SNS system. The tracking process of the system is made by a computer
and specialized software, which the software does the tracking in either optical or
electromagnetic way. Most surgeons prefer electromagnetic tracing. For having better
preoperative planning of the surgical procedure, anatomical mapping, tumor or classification
localizing, navigation calibration, and some specific patient consideration, before using
surgical navigation system, the patient undergoes a special high resolution CT scan. This CT
scan will act like a map during the surgery and the scan is loaded into a computer to process
the images and collect positional data from the tracking system [4].
Registration is the second step after performing the scan. Registration acts as a marker
in such a way that it corresponding point in the patient anatomy (that are the suspension point
which are going to be removed by surgical process) and preoperative CT scan are aligned. This
step is also considered an essential step for calibration of the SNS system before string the
surgery. Using registration will allow the surgeon to follow the position of the projected
instrument on the preoperative imaging.
Figure 5 Tracking procedure via 7D SNS system
In general, registration is critical for all image guided navigation procedures, such as
angioplasty, which employs fluoroscopy as a real-time imaging approach, or surgical
navigation, which uses a combination of planar and tomographic imaging. Registration will
match the patient's 3D location (as determined by the general scan obtained before surgery) to
the preoperative images that will be utilized for navigation, and all of this is accomplished
through a computerized process.
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Registration can be done in three ways, depending on the application. One of these
choices is Point Merge, which requires the user to predefine landmarks on the patient's scans
and touch them in the same sequence on the patient. Touch-and-go is another option. At the tip
of the probe, Go holds a ball. This ball-shaped tip fits neatly in the middle of the fiducial. A
software program will assist the user in touching the fiducials in any sequence. Tracer
registration is the final option. As the name implies, it will gather 300 points from the patient's
face and scalp tracing and map them to the patient's geometry from the pre-op scan.
Because the tracer probe may be run down the scalp via the patient's hair, it gives the
user more flexibility in gathering points, which might be considered a benefit of tracer
registration over other registration alternatives. Whatever registration method is used, pressure
is a crucial issue to consider since it might lead to mapping the scalp surface, which is not
necessary for the operation. To avoid this, the user should use a soft touch to avoid applying
pressure to the spot [4].
Figure 6 Different probe tips that can be used for registration
The process of surgical navigation in details
Data Acquisition
Both preoperative and intraoperative data collection is possible. Digital Imaging and
Communications in Medicine (DICOM) is the format in which all medical images are stored.
The navigation system receives the preoperative medical images (CT/MR) in DICOM format,
allowing for image analysis and surgical planning to be completed prior to the procedure. A
bone model that is created from the many CT datasets that have been stored and fitted to the
designated bony surface points is produced once surgeons have identified anatomical bony
landmarks using a navigation pointer. After that, these details are used for tracking and
registration [5].
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Registration
Through the process of "image-to-patient registration," surgeons identify anatomical
landmarks for the computer to use in determining the location of the bone in the space. As a
result, it establishes a connection between the patient's anatomy at the surgical site and the
medical images (Xray, CT, MRI, or the patient's 3D bone model).
First method of registration
The first technique involves placing fiducial markers or tracker pins at the target bones
while acquiring 2D and 3D images. Following the acquisition of images or the identification
of the fiducial markers during surgery, registration is finished.
Second method of registration
The surface-matching technique is the second approach. Paired-points matching is used
to initiate the initial registration process. In the surgery, the patient's anatomical features are
aligned with four to five predetermined points on the preoperative images. More surface points
are taken from the target bone and compared to the form of the bone surface model created
from preoperative CT scans in order to increase the registration accuracy even further.
Third method of registration
The 2D–3D registration technique is the third. Following manual image adjustment,
two intraoperatively acquired fluoroscopic images are automatically matched with
preoperative CT images.
Tracking
During surgery, 3D optical or magnetic sensors track the target bones and the relative
position of the surgical instruments to the target bone. While surgical instruments are connected
to another tracker, trackers are positioned at the target bones.
Figure 7 Navigation display
The navigation display following surface registration and paired-points during a CT-based
navigated resection in a patient with a right pubic malignant tumor.
10
Figure 8 Navigation display after 2D to 3D registration
The navigation display following 2D to 3D registration (CT-fluoro matching) in a patient
undergoing a CT-based navigated procedure for a proximal tibia tumor is depicted in the
above figure.
Figure 9 Passive trackers
(a) the active trackers with infrared light-emitting diodes (b) attached to the surgical
instruments and patient bones.
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Applications of surgical navigation
As with other medical instrument and equipment’s, surgical navigation has been
influenced by the advancement pf technology and is gaining new applications day by day, so
that today it is used in various surgeries including, biopsy, tumor dissection and resection,
catheter placement, deep brain stimulation lead placement (DBSL), spine decompression or
fusion, spinal or pelvic fixation, and sacral and thoracic trauma. Among all these applications,
this project will only investigate DBSL, and thoracic trauma applications.
Deep Brain Stimulation Lead Placement (DBSL)
Numerous medical specialties, such as neurosurgery, orthopedics, ENT (ear, nose, and
throat), dental implantation, laparoscopic, and robotic-assisted surgeries, use surgical
navigation. Additionally utilized for spine and neurosurgery procedures such as biopsies, tumor
resections, implanting catheters, placing leads for deep brain stimulation, and spinal
decompression or fusion pelvic or spinal fixation [6].
Figure 10 Use of navigation system in surgery
The figure shows using the iPod screen next to the surgical field, the surgeon can easily
navigate the bone resection when performing a total knee replacement [7].
Surgical Navigation Advanced Platform (SNAP)
SNAP was first used at Mayfield Hospital in Ohio to aid neuroscience research after
receiving FDA approval. This platform entered the field of surgery and microscopic surgeries
due to the complexities in the structure of the brain and the challenges to access some brain
regions during surgery. Neurocysticercosis, is a brain condition in which larvae (are immature,
often worm-like, forms of insects and certain other invertebrates) will cause parasitic infection
of the central nervous system and it will follow symptoms such as seizure, nausea, loose in
coordination, sudden memory lost, and heart attack [8].
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SNAP has application in surgical approach of neurocysticercosis. As patients with
condition are having multiple cysts (5 to 7) which each of them contains larvae inside, so the
surgeon must be so precise and swift while suctioning the cysts. It is important that the surgeon
has a good vision of the cysts and meantime have delicacy control over the region. For this
reason, a camera that can provide a combinational MRI and CT scan embedded inside the
patient’s brain to provide 3D images. The surgeon has advanced visualization of tools and
anatomy of the brain via the interconnections between the SNAP system and operation room
navigation devices. Crile hemostat or Crile forceps are a type of non-toothed instrument that
helps the surgeon to grasp or dissect tissue. These instruments are inserted into the patient's
brain through the ICP line, and in this way, the surgeon will have an excellent vision of the
cysts and make the correct cut or suction.
Figure 11 View provided by SNAP for neurocysticercosis surgery
Thoracic Trauma
Also, SNAP plays a role in surgeries of GSW and trauma cases. An Example of SNAP
application in heart- lung surgery is a case reported in 2019 in Chicago city for a trauma patient
that a crystal chandelier weighted about 20 kg fall on him. Since the crystal is a type of ceramic
glass and follows the mechanical properties of ceramic, after entering the body, it is broken
into smaller pieces due to change in pressure and moves towards the vessels and vital organs
such as the heart and aorta. Knowing that aorta it’s the main vessel responsible to deliver
oxygenated blood from the lungs toward the heart and from the heart to all the body organs a
3D coordination of the exact location of the glass particles together with excellent vision of the
distance between the glass particle and other organs was detected by SNAP platform in a 7hour surgery. While if the medical team wanted to do the surgery by using open heart surgery
without having any information of the glass and its broken particle could increase the risk of
surgery and survival rate of the patient [9].
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Figure 12 positioning of the glass in 3D combined MRI and CT scan using SNAP
14
What are its various parts
Surgical navigation systems consist of several key components such as:
Computer Workstation which is the central unit that processes and displays imaging data and
tracking information. A Tracking Devices is a device that is attached to surgical instruments
and the patient to continuously monitor their positions. Surgical Instruments are equipped
with markers or sensors for tracking. Imaging Equipment like CT scanners, MRI machines,
or other imaging devices for preoperative data acquisition. Lastly is a specialized software
that integrates imaging data, performs registration, and provides real-time guidance [10].
Figure 14 The working station
Figure 13 Reflective markers, skin markers,
and Mayfield adapter
Figure 15 Mayfield adapter
Namely, 3 main components of this technology are field generator, connection panel,
and monitor cart. The electromagnetic field around the patient is done by a field generator. This
part acts as a dynamic arm, that can move around the patient and location of the surgery to
provide optimized patient setup. The interface between the tracking and navigation system is
the part known as connection panel. This part of the system can be housed inside the OR table
or even inside the monitor cart.
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Finally, to perform a smooth surgical procedure, a system setup is required to prove the
user for a real time animated workflow to ensure about positioning of the instrument during
surgery. Knowing that surgical navigation system offers electromagnetic and optical tracking
opportunity to the user by using devices like microscope and ultrasound, all the mentioned
parts need to work together to provide the most saucerful and efficient procedure [11].
Figure 16 Different parts of a simple surgical navigation system
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Electrical circuit of the device
Knowing the surgical navigation consists of different part and components including
imaging and surgical instruments that all together will produce a platform that is known as
Navigation Theater or StealthStation it’s hard to investigate circuit diagram of each part
separately. Based on this, the report is trying to explain the general electrical circuit of two
main parts of the device which are field generator and connection panel by describing each of
their components and functions briefly.
Figure 17 Circuit diagram representation of the SNS system
As mentioned above, field generators are being used to provide either optical or
electromagnetic field that later on clinicians will use to track their instruments during surgery
in real time using CT scan or MRI. Based on today’s technologies used in SNS systems, most
surgeons prefer to use electromagnetic fields. To produce this electromagnetic field, coil arrays
that can be made of coils or sensors are embedded inside a casing that is going to be placed
near the patient. These arrays will collect signals from the patient using tracking instruments
while at the same time the produce a low strength, sterile field within the surgical area.
Inside the connection panel there are various parts. Staring from power supply that as
it comes from its name, it will provide the device with electrical current and make the device
or system functional. The current produced by the power supply is sent to the generator field
to produce or convert this electrical current to magnetic field using coil arrays. Then the
electromagnetic field is sent to the cooling system via cables and wiring in order to maintain
the device temperature during surgical procedure and cool the device using a special oil if it
requires [12].
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Next, there is a control unit that acts like a manager in the panel as it controls the
operation of the different parts of the system including processor, communicator, and calibrator.
Control units are connected to a part known as display and user interface. Depending on the
generation of the system, a touchscreen or a combination of buttons and screen can be used in
interface to let the operator control the system manually. To make sure of the proper tracking
and navigation, a part called calibration tool is being utilized right after the interface. A crucial
part in the design of the system is the safety feature that takes place between the calibration
tool and coil array. The duty of this component is to send alarms and provide safe mechanisms
to ensure the patient’s safety. It’s noticeable that in some generations of the device, an
emergency stop button is used for this aim [12].
Data interface is the part that makes the communication of the device with other
medical devices such as imaging and robotic systems possible. Malfunctioning of the part can
cause big trouble during the surgical procedure. Finally, external devices or equipment like
monitors and instruments are connected to the system using communication ports. In contrast
with other medical instruments, 3 types of cable or wiring are being used in the structure of the
SNS system including data, power, and shielding cable. Transmitting signals to the field
generator branch is being done by data cable, where power supply is being connected to the
field generator using power cables and finally shielding cables are used for safety purposes.
[12][13]
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Conclusion
Surgical navigation has revolutionized the field of medicine by enhancing the precision
and safety of surgical procedures. By combining preoperative imaging data with real-time
tracking and visualization, surgeons can perform complex operations with greater accuracy,
ultimately leading to improved patient outcomes. As technology continues to advance, surgical
navigation systems are likely to become even more sophisticated, further benefitting both
patients and medical professionals in the years to come.
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