A Case of Rectal Dissemination of Gastric Cancer Diagnosed by Simultaneous F-18-FDG PET/MRI

Metastatic rectal cancer is rare and difficult to differentiate from primary rectal cancer. A 79-year-old man with a rectal mass detected by CT during postoperative follow-up of gastric cancer underwent F-18-FDG PET/MRI. Fused PET/MRI images revealed a lower FDG uptake within the mass, which appeared to surround the outside of the rectum, than in the rectal wall, suggesting rectal dissemination of gastric cancer. PET/MRI was useful for differentiating between mass and rectal wall uptake, because of the high contrast resolution of MRI and precise image fusion made possible by simultaneous image acquisition.

Automated summary

Metastatic rectal cancer was detected in a 79-year-old male patient with a rectal mass during postoperative follow-up of gastric cancer. F-18-FDG PET/MRI was performed, and the fused images showed lower FDG uptake around the mass compared to the rectal wall, indicating rectal dissemination of gastric cancer. PET/MRI was valuable for differentiating mass uptake from rectal wall uptake due to the high contrast resolution of MRI and precise image fusion enabled by simultaneous image acquisition.