Accuracy of High-Resolution MRI with Lumen Distention in Rectal Cancer Staging and Circumferential Margin Involvement Prediction

OBJECTIVE: To evaluate the accuracy of magnetic resonance imaging (MRI) with lumen distention for rectal cancer staging and circumferential resection margin (CRM) involvement prediction. MATERIALS AND METHODS: Seventy-three patients with primary rectal cancer underwent high-resolution MRI with a phased-array coil performed using 60-80 mL room air rectal distention, 1-3 weeks before surgery. MRI results were compared to postoperative histopathological findings. The overall MRI T staging accuracy was calculated. CRM involvement prediction and the N staging, the accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were assessed for each T stage. The agreement between MRI and histological results was assessed using weighted-kappa statistics. RESULTS: The overall MRI accuracy for T staging was 93.6% (k = 0.85). The accuracy, sensitivity, specificity, PPV and NPV for each T stage were as follows: 91.8%, 86.2%, 95.5%, 92.6% and 91.3% for the group < or = T2; 90.4%, 94.6%, 86.1%, 87.5% and 94% for T3; 98,6%, 85.7%, 100%, 100% and 98.5% for T4, respectively. The predictive CRM accuracy was 94.5% (k = 0.86); the sensitivity, specificity, PPV and NPV were 89.5%, 96.3%, 89.5%, and 96.3% respectively. The N staging accuracy was 68.49% (k = 0.4). CONCLUSION: MRI performed with rectal lumen distention has proved to be an effective technique both for rectal cancer staging and involved CRM predicting.

Assessment of the Prognostic Factors for a Local Recurrence of Rectal Cancer: the Utility of Preoperative MR Imaging

OBJECTIVE: To determine the utility of MR imaging in evaluating the prognostic factors for a local recurrence of rectal cancer following a curative resection. MATERIALS AND METHODS: The preoperative MR images obtained from 17 patients with a local recurrence and 54 patients without a local recurrence, who had undergone a curative resection, were independently evaluated by three radiologists. The following findings were analyzed: the direct invasion of the perirectal fat by the primary rectal carcinoma, involvement of the perirectal lymph nodes, perirectal spiculate nodules, perivascular encasement, and an enlargement of the pelvic wall lymph nodes. The clinical and surgical profiles were obtained from the patients' medical records. The association of a local recurrence with the MR findings and the clinicosurgical variables was statistically evaluated. RESULTS: Of the MR findings, the presence of perivascular encasement (p = 0.001) and perirectal spiculate nodules (p = 0.001) were found to be significant prognostic factors for a local recurrence. Of the clinicosurgical profiles, the presence of a microscopic vascular invasion (p = 0.005) and the involvement of the regional lymph nodes (p = 0.006) were associated with a local recurrence. Logistic regression analysis showed that the presence of perirectal spiculate nodules was an independent predictor of a local recurrence (odds ratio, 7.382; 95% confidence interval, 1.438, 37.889; p = 0.017). CONCLUSION: The presence of perirectal spiculate nodules and perivascular encasement on the preoperative MR images are significant predictors of a local recurrence after curative surgery for a rectal carcinoma. This suggests that preoperative MR imaging can provide useful information to help in the planning of preoperative adjuvant therapy.

Differentiation of Recurrent Rectal Cancer and Postoperative Fibrosis: Preliminary Report by Proton MR Spectroscopy

PURPOSE: To know the differences of proton MR spectroscopic features between recurrent rectal cancer and fibrosis in post-operative period, and to evaluate the possibility to discriminate recurrent rectal cancer from post-operative fibrosis by analysis of proton MR spectra. MATERIALS AND METHODS: We evaluated the proton MR spectra from 25 soft tissue masses in perirectal area that developed in post-operative period after operation for the resection of rectal cancer. Our series included 11 cases of recurrent rectal cancer and 14 of fibrotic mass. All cases of recurrent rectal cancer and post-operative fibrosis were confirmed by biopsy. We evaluated the spectra with an attention to the differences of pattern of the curves between recurrent rectal cancer and post-operative fibrosis. The ratio of peak area of all peaks at 1.6 -4.1ppm to lipid (0.9 - 1.6ppm) [P (1.6 -4.1ppm)/P (0.9 -1.6ppm)] was calculated in recurrent rectal cancer and post-operative fibrosis groups, and compared the results between these groups. We also evaluated the sensitivity and specificity for discriminating recurrent rectal cancer from post-operative fibrosis by analysis of 1 H-MRS. RESULTS: Proton MR spectra of post-operative fibrosis showed significantly diminished amount of lipids compared with that of recurrent rectal cancer. The ratio of P (1.6 -4.1ppm)/P (0.9 -1.6ppm) in post-operative fibrosis was much higher than that of recurrent rectal cancer with statistical significance (p < .05) due to decreased peak area of lipids. Mean (standard deviations of P (1.6 -4.1ppm)/P (0.9 -1.6ppm) in post-operative fibrosis and recurrent rectal cancer group were 2.71 +/-1.48 and 0.29 +/- 0.11, respectively. With a cut-off value of 0.6 for discriminating recurrent rectal cancer from post-operative fibrosis, both the sensitivity and specificity were 100% (11/11, and 14/14). CONCLUSION: Recurrent rectal cancer and post-operative fibrosis can be distinguished from each other by analysis of proton MR spectroscopic features, and 1 H-MRS can be a new method for differential diagnosis between recurrent rectal cancer and post-operative fibrosis.

MR Evaluation of Rectal Carcinoma: Pelvic Phased-Array Coil versus Endorectal-Pelvic Phased-Array Coil

PURPOSE: To compare the accuracy of MR imaging using an endorectal-pelvic and a pelvic phased-array coil forpreoperative local staging of rectal carcinoma. MATERIALS AND METHODS: To determine preoperative staging, 38patients with rectal carcinoma underwent MR imaging. All patients were examined with both an endorectal-pelvic anda pelvic phased-array coil. All underwent surgery and staging was pathologically confirmed. Two radiologistsblinded to pathologic stage analyzed perirectal invasion and perirectal node metastasis, and scored according to afour-point scale. Radiologic and pathologic findings were correlated. Receiver operating characteristic (ROC)analysis of Wilcoxon statistic (W values) was used to compare diagnostic accuracy between the two different MRmethods. Interobserver variation was measured using kappa statistics. RESULTS: For perirectal invasion, T1WIendorectal-pelvic phased-array coil images (reader 1: 0.854, reader 2: 0.818) showed higher W values than pelvicphased-array coil images (reader 1: 0.755, reader 2: 0.811). On T2WI, W values were higher according to pelvicphased-array coil images (reader 1: 0.828, reader 2: 0.861) than according to endorectal-pelvic phased-array coilimages (reader 1: 0.813, reader 2: 0.786). For perirectal node metastasis, pelvic phased-array coil images (reader1: 0.745, reader 2: 0.792) showed higher W values than endorectal-pelvic phased-array coil images (reader 1:0.722, reader 2: 0.775), according to both reader 1 and 2. The defference kappa values between the two readers wasless than 0.4 ; agreement between them was poor. CONCLUSION: The use of an endorectal-pelvic phased-array coildid not significantly improve the accuracy of assessment of perirectal invasion and perirectal node metastasis,and in MR imaging of rectal corcinoma, the routine use of an endorectal coil is not advocated.

MRI with Endorectal Coil in Rectal tumor Staging: Is Gadolinium Enhancement Helpful?

PURPOSE: To determine whether gadolinium enhancement is helpful in rectal tumor staging determined by MRI and using an endorectal surface coil. MATERIALS AND METHODS: Between January 1995 and July 1996, we studied 17 MRI scans in which the scanning procedure had involved the use of an endorectal coil ; this was a prostate coil in six patients, and a colon coil in eleven. Eight patients were male and nine were female ; they were aged between 39 and 77 (mean, 59) years, and the tumors which had presented were adenocarcinoma (n=15), lymphoma (n=1) and villous adenoma (n=1). Precontrast scanning showing invasion of the rectal wall and perirectal fat were interpreted, and postcontrast T1WI and pathological findings were then compared. Fifteen patients underwent surgical resection but the other two (one adenocarcinoma and one lymphoma) underwent only an endoscopic biopsy. RESULTS: On precontrast scanning with the prostate coil, accurate staging was possible in three cases (one of stage T2, and two of stage T3) ; we overstaged two cases of stage T2 as stage T3. On postcontrast T1WI, however, we additionally understaged one case of stage T3 as stage T2. In a case of adenocarcinoma proven by biopsy, no definite difference was noted between pre- and postenhanced scan. On precontrast scan using a colon coil, accurate staging was possible in six cases (two of stage T1, one of stage T2 and three of stage T3). We overstaged a case of stage T2 as stage T3 and understaged three cases of stage T3 as stage T2. On postcontrast T1WI, however, we accurately diagnosed one additional case of stage T3, not diagnosed on precontrast scan. In one case of bioptically-proven lymphoma, no definite difference was noted between pre- and postenhanced scan. CONCLUSION: In rectal tumor staging, pre- and postenhanced scans are both 60% accurate. In MRI using an endorectal surface coil, gadolinium enhancement is not, therefore significantly helpful.