Comparison of Surface and Saddle Endoanal Coil to Evaluate anal Sphincter in Infants and Young Children: Experimental Study Using Phantom and Cats

PURPOSE: We designed an inside-out-type endoanal surface and saddle coil to evaluate the anal sphincter of young children who have difficulty in controlling defecation after the correction of anorectal malformation, and compared two coils using an imaging phantom and cats. MATERIALS AND METHODS: Using two coils, T1- and T2-weighted axial and coronal images of the phantom and of the anorectal region of cats were obtained, and the results were compared in terms of changes in signal intensity and SNR according to the distance from the coil's surface. We also compared the capability of the coils to delineate the internal and external anal sphincter of cat anorectum, both of which are important in the control of defecation. RESULTS: The saddle coil was slightly superior to the surface coil in terms of SNR, but inferior in terms of the signal intensity of the region of interest of the cat's anorectum. Moreover, artifacts of low signal intensity appeared in an azimuthal direction on axial images acquired using the saddle coil and prohibited delineation of the whole of the anal sphincter. In terms of image quality, the surface coil was therefore superior to the saddle coil. CONCLUSION: Our findings suggest that among inside-out-type endoanal coils, the surface coil may be superior to the saddle coil in MR imaging to evaluate the anal sphincter of young children.

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.

Stage 1 Carcinoma of Cervix: Value of Endovaginal Surface Coil MR Imaging in Determining Depth of Invasion

PURPOSE: The purpose of this study was to determine the usefulness, with respect to depth of invasion, ofendovaginal surface coil (EVC) MR imaging for the evaluation of early-stage cervical cancer. MATERIALS AND METHODS: We retrospectively analyzed the MR images of 49 patients with pathologically-confirmed stage one cervicalcarcinoma who underwent EVC MR before hysterectomy. The tumor seen on MR images was identified as a high signalintensity lesion replacine the normal low signal intensity cervical stroma seen on T2WI. Depth of invasion, asseen on MR images and in pathologic specimens was divided into3-5mm, and the results werecompared. RESULTS: Depth of invasion in pathologic specimens was 5mm in25 patients(mean 6.34mm). On MR imaging, tumor was detected in 42 patients. Depth of invasion on MR was 5mm in 25 patients (mean 6.59mm). MR failed to detect tumors which infiltratedless than a certain depth;this cut-off point was 1mm in two patients, 2mm in two, and 3.5mm in one. All tumorswhich invaded more than 5mm were detected on EVC MR. There was no significant difference between depth of invasion seen on MR and in pathologic specimens(p=.59). The 95% confidence interval for difference in the value ofdepth of invasion between MR and on pathologic specimens ranged from -0.7mm to 1.2mm. CONCLUSION: EVC MR imagingmay be useful for assessing the depth of invasion of stage one cervical carcinoma.