الفهرس 
MRI in diagnosis and staging of rectal cancerOnly 14 pages are availabe for public view
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Abstract
Rectal cancer is a common cancer and a major cause of mortality in Western countries. The diagnosis is usually established by means of clinical examination (rectal digital examination), endoscopy (sigmoidoscopy and colonoscopy), double-contrast enema examination, and histologic confirmation, supplemented by biochemistry (e.g., blood carcinoembryonic antigen measurement). All of these techniques are poor indicators of the depth of invasion and lymph node involvement, which are both important features for prognosis. Accurate preoperative assessment of these prognostic factors is an important first step in assigning patients to one of the available treatment strategies, which include transanal local excision, transanal endoscopic microsurgery, total mesorectal excision, preoperative irradiation, and preoperative chemotherapy. Noninvasive radiologic modalities such as endoluminal ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging have proved to be important and have been widely used diagnostic tools in the assessment of depth of cancer invasion and/or lymph node involvement. Endoluminal ultrasonography has been known to be an accurate and convenient method for assessing depth of invasion and regional lymph node involvement. (MRI) has been used increasingly because of its benefits of pelvic imaging and it gives more imformation for preoperative staging status than any other diagnostic method. It can show a clear relationship between rectal cancer and any adjacent pelvic organ on sagittal section. It can also show a lateral pelvic lymph node status and any involvement of levator ani muscle beyond the reach of endoluminal ultrasonography. MRI also has been known to be able to provide surgeons with valuable information regarding the presence of sphincter invasion and the surrounding structures in patients with distal rectal cancer, which is important for making a decision on whether to perform sphincter preservation or not. The current role of CT in patients with rectal cancer is controversial. The introduction of MDCT allowed thin-collimation scanning, resulting in improved multiplanar reconstructions (MPRs). These benefits may help to establish MDCT as an effective diagnostic technique in the evaluation of preoperative local staging of rectal cancer. This study aims at discussing the value of endoluminal U/S, CT and MRI in the diagnosis and staging of rectal cancer.