الفهرس 
Anatomy of the ColonOnly 14 pages are availabe for public view
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Abstract
Cancer colon is one of the commonest neoplasms all over the world, and is considered a leading cause of death among different neoplasms.
For ages cross sectional imaging play limited role in diagnosis of cancer colon. The recent innovations in the field of cross sectional imaging, with the development of spiral and then multislice CT, producing volumetric data made a revolution in the role of CT in diagnosis of colonic lesions.
Virtual colonoscopy is one of the recent advances in the field of CT post processing technique. It represents a type of 3D reconstruction technique which is capable of elaborating endoscopic endoluminal display of the colon without use of real endoscope and hence it was named virtual colonoscopy.
The aim of our thesis is to evaluate the role of virtual colonoscopy in colonic neoplasia. Results were compared to conventional colonoscopy and documented by histopathology in all cases.
The main steps to perform virtual colonoscopy technique incorporate excellent colonic preparation, proper colonic air insufflation and scanning the patient in both supine and prone positions.
The optimum scanning parameters should include thin beam collimation, short scanning time and lowest dose possible. In data analysis it is emphasized on reviewing both 2D and endoluminal 3D images to get more guarantees of precise results.
The results in our study showed that conventional colonoscopy is a little bet ahead in front of virtual colonoscopy, yet the results are more or less comparable to each other.
Also in our study, a comparative study for the sensitivity of polyp detection according to size was done and it also showed comparative results especially in large polyps and masses.
The main causes of false positive and negative results in virtual colonoscopy were inadequate colonic distension with collapsed colonic segments and improper preparation with residual fecal matter and water lakes.
CT Virtual colonoscopy provides a total colonic examination of the patients, even in those who have distal occlusive colorectal cancer and in circumstances of incomplete colonoscopy.
In our study in stenotic lesions which conventional colonoscopy could not bypass, virtual colonoscopy easily bypassed the stenotic segments and navigated through the proximal colon.
In our study, the axial 2D images included in virtual colonoscopy, gave the technique another advantage examining the extra colonic abdominal organs. For example, hepatic deposits were found in two patients, peritoneal deposit in one patient, local infiltration of the surrounding organs in one patient.
Another issue is the patient compliance which is easily achieved in virtual colonoscopy as compared to conventional colonoscopy and thus it is preferred as a screening tool.
Finally we can say that virtual colonoscopy is a recent modality that finds its way among the diagnostic tools for colonic lesions. It will not replace conventional colonoscopy, but it is expected to prove itself as a valuable auxiliary method in directing and improving colon pathology patient care.