الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
rectal cancer is the second most common cause of cancer in Females and the third most common in Males it is the fourth most common cause of cancer death after lung, stomach, and liver cancer.. It is more common in developed than developing countries . Risk factors include polyposis syndromes, inflammatory bowel disease, dietary imbalance between fat, protein and fiber.
- mr imaging has become the most accurate technique in local staging of rectal cancer, this is due to advances in terms of imaging equipment, coils, and sequences that have progressively improved the technique, with a parallel increase in accuracy. mri can provide information regarding the site of tumor, the depth of mural and extramural tumor spread, involvement of the circumferential resection margin and indicate the extent of any sphincter involvement
- the main pitfalls that can be faced during an mri is the difficulty in differentiation between y1, t2 and t2, t3 stages (moderate accuracy for t-staging), however this can have little impact on the management of patients.
- identification of nodal disease continues to be a problem for radiologists. The problem for morphologic imaging is their dependence on size criterion for diagnosis. , the presence of an irregular contour and inhomogeneous signal were found to be the most reliable MRI criteria for lymph node metastasis. uspio-enhanced mri is a new promising approach to detect metastatic lymph nodes and are especially of additional benefit in the evaluation of small nodes.
- gd - enhanced mri isthe highlysensitiveFor detection of hepatic metastases; which represent the commonest site for distant metastatic spread. mri can also be used after chemoradiotherapy for locally advanced rectal cancer to evaluate treatment response and to determine the new tumor extent.
- the recent introduction of powerful whole-body mri systems enables imaging of the whole body in a single session through repeated table movements. This technique may be used for rectal cancer staging in the future allowing for local staging and whole-body staging in a single session.
- diffusion weighted imaging and perfusion mri (dse-mri) have a growing role in rectal cancer staging, while some other functional imaging modalities such and mr spectroscopy remain research-based, with limited clinical experience. dwi can play a role in detection, staging and restaging of patients in terms of prognosis, therapy planning and monitoring.