Abstract
Objective : This study was conducted to evaluate the usefulness of conventional lowfield MR imaging (MRI) as a daily clinical examination to detect and stage rectal carcinoma. Materials and Methods : The subjects were 54 patients (32 males and 22 females) who were evaluated preoperatively using a 0.5-T MR scanner and a whole-body CT scanner. For both MRI and CT, the rectum was inflated with 300-600 ml of air using a barium enema syringe before examination. For MRI examination, T1 -, T2-weighted images and gadopentetate dimeglumine (Gd-DTPA) -enhanced T1-weighted images were obtained in all patients. For CT examination, contrast-enhanced images were obtained using iopamidol in 49 patients. The chi-square test was performed for independent variables to compare the staging accuracy of MRI with that of CT. Results : Tumor depiction rate was 93.9% with CT and 94.4% with MRI. The diagnostic accuracy of tumor depth infiltration was 37.0% with CT and 56.9% with MRI and the difference between the two techniques was significant (P<0.05). The sensitivity of both modalities for diagnosis of lymph node metastasis was poor, being 15.0% for CT and 4.8% for MRI. Conclusion : The diagnostic accuracy of MRI for tumor depth infiltration was superior to that of CT, but the sensitivity for diagnosis of lymph node metastasis was poor with both modalities. The diagnostic capability of the low-field MR scanner we employed was poorer than that reported previously for a high-field MR scanner or an investigative low-field MR scanner. To improve the diagnostic capability of the low-field MR scanner, a phased-array coil and fast SE sequence should be employed.
