Role of Magnetic Resonance Imaging in Staging Rectal Carcinoma

Introduction: Recent advances in management of rectal cancer have lead to emphasis on accurate preoperative staging, determination of Circumferential Resection Margin (CRM) and mesorectal fascia involvement. Because of superior soft tissue contrast and multiplanar capability, MRI is currently imaging modality of choice. Aim: To study imaging characteristics of different rectal tumors. To evaluate accuracy of MRI in local ‘T’ staging of rectal tumor. Determination of CRM and mesorectal fascia involvement and to evaluate accuracy of MRI in nodal (N) staging. Materials and Methods: A prospective study of 64 patients presenting with rectal mass/bleeding was conducted in Department of Radiodiagnosis at tertiary care hospital in Goa (Goa Medical College), over a period of 2 year by using 1.5 Tesla superconductive unit. Results: Overall accuracy of MRI for ‘T’ staging was 95.75%, the accuracy was 97.49% for T1 tumor, 94.11% for T2 tumor, 91.66% for T3 tumor and 100% for T4 tumor. MRI was 100% accurate in diagnosing mesorectal fascia invasion. Conclusion: MRI is currently the only modality that enables accurate evaluation of tumor extent, involvement of CRM and mesorectal fascia. This enables to carefully select those patients who will benefit from neo-adjuvant chemotherapy or primary surgery. R ad io lo g y S ec tio n Role of Magnetic Resonance Imaging in Staging Rectal Carcinoma SitaRam BaRath, Jeevan a veRnekaR, Sachin ShaShikant amate InTROduCTIOn Colorectal cancer is the third most common cancer worldwide [1]. Accurate preoperative diagnostic and staging of rectal carcinoma is essential for treatment planning and prognosis. This can be achieved with both endorectal ultrasound (USG) and computed tomography (CT) scan. The most important anatomical landmark for the evaluation of local tumor extent of carcinoma rectum is mesorectal fascia [2]. MRI because of its multiplanar capability and superior soft tissue contrast is currently modality of choice to depict mesorectal fascia and its relation to tumor margin. The other advantage of MRI is lack of ionizing radiation and nephrotoxicity from iodinated contrast material. This study emphasize on role of MRI and its significance for planning an effective therapeutic strategy for the individual patient and also to study imaging characteristics of different histological type of rectal tumor. MATeRIAlS And MeThOdS The prospective hospital based study was carried out on 64 cases in Department of Radiology, Goa Medical College and hospital from October 2010 to October 2012, over a period keywords: Circumferential resection margin, Mesorectal fascia, Rectal adenocarcinoma of 2 years. Inclusion Criteria: 1) Rectal mass on per rectal examination; 2) Rectal mass on colonoscopy; 3) Biopsy proven carcinoma rectum. exclusion Criteria: 1) Patients with cardiac pacemaker in situ; 2) Patients with pelvic metallic implants. Ethical Clearance for the study was obtained before commencement of the study from Institutional Ethics Committee, Goa Medical College, Bambolim Goa. All patients underwent routine clinical, histopathological and radiological workup. Every patient was given a cleansing enema one hour before the MRI. Informed consent of patient/attendant was taken. The MRI was performed without distending rectum except in patients with smaller lesions which was difficult to characterize. Ultrasound gel was used as a distending agent. Intramuscular injection of Buscopan 20mg was given just prior to the procedure. MRI performed on 1.5 Tesla (Siemens MAGNETOM Avanto) imaging system with an external body array coil. The following sequences were used: