Differentiation of benign vs. malignant mass in a postirradiation cerebral arteriovenous malformation by 2-deoxy-2-[ 18F] fluoro-D-glucose positron emission tomography

Abstract

This report demonstrates the findings on two 2-deoxy-2-[ 18F]fluoro-D-glucose positron emission tomography (FDG-PET) brain scans of a 16-year-old girl with previous radiation therapy for an arteriovenous malformation (AVM) that was transformed by radiation therapy to a mass in a deep and relatively inaccessible cerebral location. Clinical neurologic examination, brain CT without and with contrast, 1.5 T MRI of the brain without and with contrast, magnetic resonance angiography (MRA), 1H magnetic resonance spectroscopic imaging (MRSI) of the brain, and two FDG brain PET scans were performed to characterize the lesion. Magnetic resonance imaging (MRI) and 1H MR spectroscopic findings showed a mass and surrounding vasogenic edema in the deep left parietal lobe suggestive of malignant angiosarcoma. However, an FDG-PET scan of the brain identified a large area of hypometabolism involving the left parietal lobe. The PET findings were unchanged compared to a FDG-PET scan performed one year prior, suggesting that the lesion was benign. In addition, an MRI performed six months after the second PET scan was also consistent with a benign lesion, and was unchanged from the MRI performed two years prior. We present the first detailed imaging characteristics of a mass of high clinical suspicion for malignancy resulting from transformation of an arteriovenous malformation after radiosurgery treatment. Two FDG-PET scans performed for a one-year time interval provided a noninvasive method to establish that the lesion had nonmalignant characteristics.