Diagnosis of Primary Colorectal Cancer and Its Metastasis to Lymph Nodes by MRI Diffusion-weighted Imaging (MRI DWI)

Abstract

Twenty-three patients were enrolled in this study, including 12 colon cancer patients and 11 rectal cancer patients in whom laparotomy was performed to resect tumors, as well as lymph node dissection. Primary lesions and lymph nodes were visualized by MRI DWI and the mean maximum diameters of resected primary lesions and the largest lymph node were determined using fixed samples. In addition, the largest lymph node on MRI DWI was measured.
Primary lesions could be delineated in 18 cases (78%). The mean maximum diameter of the delineated primary lesions was 50mm, which was significantly different from that of five lesions that measured 20mm and could not be well delineated (p<0.01). Of the 18 cases, lymph nodes could be visualized in 11, and five cases were found to be metastasis-positive by histological examination. For these five cases, the mean maximum diameter of all metastasis-positive lymph nodes visualized in the fixed samples was 10.8mm (range 6-15mm). In these cases, the mean maximum diameter of lymph nodes on MRI DWI was 10.8mm (range 4-14mm) and these sizes were similar. On the other hand, seven cases whose lymph nodes could not be visualized were found to have no lymph node metastases based on histological examination and the mean maximum diameter of the lymph nodes was 8mm (range 4-14mm), not indicating a significant difference from the former. Therefore, lymph nodes that could be visualized were likely to contain metastases.