الفهرس 
Acknowledgment
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Abstract
Functional endoscopic sinus surgery (FESS) using rigid endoscopes has quickly become the standard of care for opening obstructed outflow tracts of the paranasal sinuses with over 500,000 procedures estimated to be performed yearly in the United States. Unfortunately, the endoscope provides only a two dimensional view requiring surgeons to localize instruments based in part on their depth of penetration and tactile sensation. The narrow confines of the sinonasal tract and the complex relationships with adjacent vital structures, demands a high degree of technical precision and provides little room for surgical error.
Image-guidance systems were developed to provide assistance with real time intraoperative localization of surgical anatomy. These systems function to identify surgical instruments, calculate the location of the instrument tip in relation to the patient, and project the instrument location onto a previously-obtained imaging study (usually a CT scan).
Anon et al first described computer-assisted endoscopic sinus surgery in 1994 using a frameless stereotactic system.
The technology has dramatically improved since then, with several accurate and easy to use tracking systems currently available. Image guidance systems track surgical instruments in the operative field using either electromagnetic or optical based technologies. Both platforms have been shown to be accurate to within 2 mm, and account for intraoperative head movement by fastening a headset to the patient.
The sinonasal cavities are an ideal environment for the application of image-guidance technology since the bony borders of the sinonasal tract provide a constant framework that resists extensive shift of tissues and loss of accuracy; major issue in the application of the technology for soft tissue navigation. Further, several of these borders are ‘fixed’ landmarks that are not to be violated or altered during the course of surgery, such as the lamina papyracea of the orbit, the skull base, and sphenoid face.
The application of image guidance can be viewed as one way to improve overall visualization during the course of ESS but it is not substitute for surgical expertise.
Clinical application of Image guided surgery:-
The American Academy of Otolaryngology – Head and Neck Surgery recommends image guidance in the following cases:-
• Revision sinus surgery
• Distorted sinus anatomy of developmental, postoperative, disease or traumatic origin.
• Extensive sino-nasal polyposis.
• Pathology involving the frontal, posterior ethmoid, or sphenoid sinuses.
• Disease abutting the skull base, orbit, optic nerve or carotid artery.
• Cerebral spinal fluid (CSF) leak or conditions where a skull base defect exists.
• Benign and malignant sino-nasal neoplasms.
• Orbital and optical nerve decompression procedures
• Sinus procedures such as maxillary antrostomies, ethmoidectomies, sphenoidotomies/sphenoid explorations, turbinate resections, and frontal sinusotomies.
• Encephalocele procedures.
• Endoscopic dacryocystorhinostomy.
• CSF rhinorrhea or conditions where there is a skull base defect.
Advantages of image-guided surgery :-
• Procedures are less invasive than the open surgical approaches that were once standard
• Precision is greater, resulting in lower risk to the patient
• Allows for more complete surgical dissections
• Patient discomfort is minimal with potential for reduced recovery time
• Less tissue trauma
• Faster healing time
• Fewer and smaller scars
Disadvantages of image-guided surgery:-
• Image Guided Surgery (IGS) is an expensive but extremely useful tool for better anatomical orientation.
• It is not for every surgeon.
• It is not for every patient.
• In no case it can substitute the surgeon’s surgical experience and anatomical knowledge.
Aim of work
The purpose of this essay is to delineate:-
1- Uses of Image-Guided Surgery.
2- Advantages of image-guided surgery over functional endoscopic sinus surgery (FESS).
3- Advantages of image-guided surgery for Skull Base Surgery (An Advanced Solution to Traditional Surgery).
4- Types of commercially available systems.
5- Costs and contraindications of Image Guidance.
6- Radiological anatomy.
7- Types and technique of registration.