The Diagnosis of Lymph Node Metastasis in Colorectal Cancer Using Helical CT

A method to detect new metastatic lymph nodes from colorectal cancer was devised by making the best use of characteristics of helical CT, and its usefulness was investigated. The use of 1-mm axial images and MPR images, obtained with helical CT, was superior in locality identification to conventional methods. The diagnostic accuracy rate in 51 patients examined was 86.3% for paraintestinal lymph nodes and 82.2% for intermediate lymph nodes. Nodes showing enhancement only in their marginal regions or in the mottled form at 40 seconds after contrast medium injection or those showing no enhancement at either 40 or 120 seconds after injection were considered to be metastasis-positive. The diagnostic accuracy rate in 28 patients, determined according to the qualitative criteria eatablished from the contrast-enhanced findings, was markedly higher, 96.4% for paraintestinal lymph nodes and 94.7% for intermediate lymph nodes, compared with those obtained by conventional methods. In diagnosis with helical CT, the use of 1-mm axial images and MPR images improved the identification of locality, and a nearly perfect diagnosis could be made when a qualitative diagnostic factor was added, indicating extreme usefulness of this diagnostic method.