Gastric Neuroendocrine Carcinoma Presenting as a Wandering Exophytic Mass: A Case Report

We describe a case of poorly differentiated gastric neuroendocrine carcinoma presenting as a wandering exophytic mass. CT imaging revealed a 14.5x10.0x8.0 cm, lobulated, solid mass with a multifocal necrotic portion at the right of the peritoneal cavity. It was attached to the antrum of the stomach by a broad stalk, and shown by MR imaging to be well-defined, lobulated and solid, with a multifocal necrotic portion, and at the left of the peritoneal cavity. Isointensity was apparent at T1-weighted imaging, and slightly hyperintensity at T2-weighted imaging, and after gadolinium injection, enhancement was stronger than at precontrast imaging.

In Vitro of MR Imaging of the Resected Normal Gastric Wall: Radiologic-Histologic Correlation

PURPOSE: To evaluate normal human gastric wall layers in vitro using magnetic resonance*(MR) imaging, to correlate the results with the histologic findings, and to determine the optimal technique for evaluation of the gastric wall. MATERIALS AND METHODS: Forty-one normal resected gastric specimens obtained from 25 patients were dissected and placed in a polyethylene tube filled with normal saline. MR imaging with four MR sequences, T1-weighted FLASH*(T1FLASH), fat-saturated T1-weighted FLASH, T2-weighted TSE*(T2TSE), and True-FISP, was performed. The number of gastric wall layers and signal intensity of each layer were determined, and after correlating MR images with the histologic findings, the conspicuity of each layer*(mucosa, submucosa, and muscle), the distinction between each layer, and overall image quality were assessed. RESULTS: The gastric wall was shown by TIFLASH to have two (n=6, 14-6%), three (n=31, 75.6%) and four layers (n=4, 9.8%); by fat-saturated TIFLASH to have two (n=6, 14.6%) and three (n=35, 85.4%) ; by T2TSE to have three (n=24, 58.5%), four (n=11, 26.8%), and five (n=6, 14.6%); and by True-FISP to have one (n=2, 4.9%), two (n=8, 19.5%), three (n=23, 56%), four (n=4, 9.8%), and five (n=4, 9.8%) . The signal intensity of each layer at T1FLASH and fat-saturated T1FLASH was high-intermediate from the lumen in two-layer cases, high-low-high/intermediate in three-layer cases, and high-low-high-intermediate in four-layer cases. The signal intensity of each layer at T2TSE was intermediate/high-low-intermediate in three-layer cases, intermediate low-high-intermediate/low in four-layer cases, and low-high-low-high-low in five-layer cases. Three-layered gastric wall corresponded mostly to mucosa, submucosa, and muscle from the inner to outer layers, respectively. T1FLASH, fat-saturated T1FLASH, and T2TSE were superior to True-FISP in evaluating the gastric wall. T1FLASH and fat-saturated T1FLASH were the best sequences for demonstrating mucosa (p<0.05), and T2TSE was the best for submucosa and the distinction between this and muscle (p<0.05). Both T1FLASH and T2TSE provided the best overall image quality (p<0.05). CONCLUSION: In-vitro MR imaging is an excellent technique for the evaluation of layers of normal gastric wall. T2TSE is the sequence which best demonstrates the conspicuity of submucosa, the distinction between submucosa and muscle, and overall image quality.

MR Imaging of Advanced Gastric Cancer: Comparison between T1-weighted FLASH, T2-weighted TSE, and TrueFISP

PURPOSE: To compare the usefulness of three MR sequences for the depiction and staging of advanced gastriccancer (AGC). MATERIALS AND METHODS: MR imaging was performed in 20 patients in whom AGC was proven by endoscopy.Axial scans with T1-weighted fast low-angle shot (FLASH), T2-weighted turbo spin-echo (TSE), and true fast imagingwith steady state precession (TrueFISP) MR sequences were obtained. We measured the signal-to-noise ratio (S/N) ofgastric cancer and signal difference-to-noise ratio (SD/N) between cancer and intraluminal fluid, cancer and thepancreas, and cancer and perigastric fat in each MR sequence. We also graded lesion conspicuity (poor, fair, orgood), and the degree of serosal invasion in each sequence. All results were correlated with histopathologicfindings. RESULTS: TrueFISP was superior to FLASH or TSE in lesion conspicuity, and showed the highest value ofSD/N between cancer and intraluminal fluid. FLASH showed the highest value of SD/N between cancer and thepancreas, and cancer and perigastric fat. The accuracy of T-staging of AGC with MRI was 75% using FLASH, 70% usingTrueFISP, and 60% using TSE. FLASH sequence understaged in three cases(15%) and overstaged in two (10%). In Usingthe TrueFISP sequence, six cases(30%) were overstaged. CONCLUSION: TrueFISP showed the best lesion conspicuity,but tended to overstage the lesion. T1-weighted FLASH sequence showed the highest value of SD/N on theextraluminal side of the gastric wall, and was better than T2-weighted TSE or TrueFISP for T-staging of AGC.