Computer-assisted surgery (CAS) uses computer technology like 3D modeling to help plan and guide complex surgical procedures. It involves creating a virtual 3D model of the patient's anatomy from scans and then using tracking technology to match the virtual model to the actual patient during surgery. CAS has applications in sinus, maxillofacial, ENT, and neurological surgeries where it helps locate lesions and vital structures more safely and accurately.

1. COMPUTER ASSISTED
SURGERY
Dr. Deepa Shivnani

5. CAS
 Computer-assisted surgery (CAS) represents a
surgical concept and set of methods, that use
computer technology for surgical planning, and for
guiding or performing surgical interventions.
 Synonyms for this technology include,
 computer-aided surgery,
 computer-assisted intervention,
 image-guided surgery and
 surgical navigation.

6. TECHNIQUE
 During computer assisted surgery, specialized
software creates a virtual 3-D model of the
patient’s head and sinuses.
 During surgery the surgeon matches the patient’s
actual anatomy to the 3-D model displayed on a
monitor.

7.  International Society for Computer-Aided Surgery (ISCAS)
defined the scope of computer-aided surgery (CAS) as
 encompassing ‘all fields within surgery, as well as
biomedical imaging and instrumentation, and digital
technology employed as adjunct to imaging in diagnosis,
therapeutics, and surgery’. CAS, therefore, includes
 surgical navigation,
 virtual reality,
 computer-aided image review,
 stereotactic surgery,
 robotic surgery,
 telemedicine,
 computer-aided tumour modelling and many other
applications.

8. HISTORY
 Maxillofacial surgeons were among the first to
make use of computers for surgical planning.

9. STRYKER’S CAS TECHNOLOGY CONSISTS
OF:
 1.) infrared navigation camera,
 2.) Smart Instruments with light-emitting diode (LED) technology
 3.) a computer with specialized surgical navigation software.
CT scan
 imported in to the navigation computer
 create the virtual 3-D model of the patient’s sinus anatomy
 staff places a sticker-like mask (embedded with LEDs) on the
patient’s face.
 with the navigation camera, is used to match the patient’s true
anatomy with the virtual 3-D model.
These 3D reconstructions can be used to
 plan surgery (surgical planning),
 practise a certain surgical procedure (surgical simulation) or
 to navigate during the surgical procedure (image-guided surgery).

10. PROCESS
Two fundamental processes are required for
intraoperative image guidance,
 registration and tracking.
 Registration is the process that relates the
patient in the operating theatre to preoperatively
acquired image data sets.
 Tracking is the mechanism of following the
position of the patient or an instrument within
the operative field.

11. IGS SYSTEM COMPONENTS
Hardware
 Computer workstation
 Display system
 Tracking system
 Surgical instrumentation
Software
 Data management
 Image review
 Surgical navigation

12. REGISTRATION
 2 methods
 by locating anatomical landmarks visible both on the
patient and image data using a probe that is visible to
the tracking device. surgeon would point to pre
specified landmarks, such as the tragus, outer canthus
and nasion. This is usually sufficient to achieve a
registration accuracy or error of 3-4 mm..

13. REGISTRATION CONT…
 Some types of IGS systems make use of fiducial
markers that are applied to the patient before
scanning on the day of surgery. These markers
are clearly visible in both MR and CT data sets
and, of course, on the patient when in theatre.
They help to improve the accuracy of registration

15. TRACKING
 Sensors that provide dynamic positional
information are known as 'tracking devices'.
 In surgical practice, tracking systems must be
 very precise,
 consistently accurate,
 fast enough to provide more than 25 readings
per second
 be insensitive to changes in air temperature
 unaffected by metal objects
 and able to track two objects simultaneously.

16. TRACKING SYSTEM
 The tracking systems can be
 optical (infrared light tracks surgical instruments
and headframes, both equipped with optical
sensors),
 electromagnetic (transmitter located near
operative site, corresponding receiver located on
surgical instruments), or
 electromechanical (mechanical arm with several
mechanical linkages and articulating joints
between the instrument and a computer
processor, special sensors measure angular
rotations at these joints.

17.  Infrared light sensors are the most commonly
used image-guided surgical systems. They are
referred to as either active or passive devices.
 Active devices sense infrared light from light-
emitting diodes (LED) attached to the patient or
location probe.
 Passive tracking devices detect infrared light
reflected from metallic balls attached to the
patient or probe

19. APPLICATIONS
 Revision sinus surgery.
 Distorted sinus anatomy of development, postoperative, or traumatic
origin.
 Extensive sino-nasal polyposis.
 Pathology involving the frontal, posterior ethmoid and sphenoid
sinuses.
 Disease abutting the skull base, orbit, optic nerve or carotid artery.
 CSF rhinorrhea or conditions where there is a skull base defect.
 Benign and malignant sino-nasal neoplasms.
 decompression surgery for endocrine orbitapathy
 facial reconstruction maxillo-facial surgery
 In the field of otology, IGS has been used to aid the surgeon in locating
the facial nerve, identifying and localizing lesions of the petrous apex
tumours, particularly in the internal auditory meatus. (These include
meningiomas and vestibular schwannomas)

20. THE AMERICAN ACADEMY OF OTOLARYNGOLOGY -
HEAD AND NECK SURGERY GAVE THE EXAMPLES OF
INDICATIONS FOR IGS IN ENDOSCOPIC SINUS
PROCEDURE AS FOLLOWS:
● Revision sinus surgery
● Distorted intranasal anatomy
● Large or massive nasal polyp
● Lesions in the posterior ethmoid, sphenoid or
frontal sinus
● Lesions along the vital structures such as skull
base, orbit or optic nerve
● Skull base defect or cerebrospinal fluid leakage
● Sino-nasal neoplasm

35. ADVANTAGES OF COMPUTER AIDED ESS
 Advantages
 Accurate localisation of lesions:
 – Increased safety of patients. reduces the risk of
major intracranial or intraorbital complications
 – Surgeon reassurance.
 – Simplification of complex operations.
 Sagittal reconstruction and a three dimensional
imaging capacity:
 – Understanding of complex anatomy.
 – Improved learning curve for residents

36. LIMITATIONS AND DISADVANTAGES
 Preoperative computed tomography:
 Longer operating room time (expected to be
reduced when more experience is gained).
 Expensive equipment.
 Satisfactory registration is critical for accurate
surgical navigation .
 Intraoperation surgical navigation uses
preoperative imaging data
 IGS is not a substitute for surgical expertise .

37. CONCLUSION
 Image-guided surgery (IGS) assists the experienced surgeon in
delineating ambiguous or distorted landmarks. It is not a
replacement for thorough anatomical training
 Accuracy within 2 mm is the norm
 Based on experience with both of the currently used systems,
registration can be accomplished with minimal additional
operating room time
 Inconveniences related to the logistical setups of either system
are minimal and do not affect the value of the technology
 Image-guided surgery (IGS) allows the surgeon to routinely
perform a more complete exploration of the paranasal sinuses.
 Difficult sphenoid sinus and ethmoid sinus anatomy can be
approached with more surgical confidence using computer-
guided dissection
 Frontal sinus anatomy can be approached with greater
confidence.
 Teaching aid for trainee doctors.