Dose-related fluorodeoxyglucose uptake in acute radiation-induced hepatitis.

Therapeutic assessment with fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is sometimes problematic after radiation therapy. Herein we describe a patient with acute radiation-induced hepatitis in which PET showed dose-dependent FDG uptake. A 50-year-old man underwent FDG PET for staging of esophageal cancer. Chemoradiotherapy was delivered concurrently with a radiation field that expanded from the esophagus into the upper stomach to cover metastasis of the gastric wall. The patient also underwent FDG PET 26 days and 4 months after chemoradiotherapy to evaluate the therapeutic effect. Twenty-eight days after chemoradiotherapy, hematochemistry revealed elevated hepatic enzymes and postcontrast computed tomography showed band-like hypoattenuation in the liver with parenchymal swelling corresponding to the radiation field. FDG PET performed 26 days after chemoradiotherapy showed a wedge-shaped hypermetabolic area in which the degree of FDG uptake correlated with the prescribed radiation dose. Follow-up PET 4 months after therapy showed no abnormal uptake in the liver. Acute radiation-induced hepatitis can be a potential cause of false-positive findings of malignancy on FDG PET scans, and PET images should carefully be compared with the distribution of prescribed dose. Threshold dose might be higher for metabolic changes than for morphologic changes.