Radiation fibrosis: differentiation from recurrent tumor by MR imaging.

TLDR

Radiation fibrosis typically shows low T2 signal like muscle, whereas tumors are higher, but high T2 signal can also arise from other conditions such as pneumonitis, infection, hemorrhage, or fibrosis. The study compared MR images from 21 post‑radiation patients with 15 untreated tumor patients. T2‑weighted images were most effective at distinguishing recurrent tumor from radiation fibrosis, with tumor signal always higher than muscle.

Abstract

Magnetic resonance (MR) images of 21 patients who had undergone radiation therapy were analyzed and compared with those of 15 patients who had untreated tumors. T2-weighted images (TR = 1,500 msec, TE = 90 msec) were most helpful in distinguishing recurrent tumor from radiation fibrosis. Radiation fibrosis, like muscle, usually remained low in signal intensity on T2-weighted images, while tumor demonstrated higher signal intensity. In no patient was the signal intensity of tumor the same or less than muscle on the T2-weighted images. However, relatively high signal intensity on T2-weighted images is not specific for tumor recurrence and may be seen in acute radiation pneumonitis, infection, hemorrhage, and even pulmonary radiation fibrosis.