The role of Tc-99m HMPAO functional brain imaging in detection of cerebral radionecrosis.

BACKGROUND

Cerebral radionecrosis is a possible complication of brain radiation therapy in patients with primary or metastatic tumors. This retrospective study evaluated the role of Tc-99m hexamethyl propyleneamine oxime (HMPAO) scintigraphy in monitoring the effects of radiation on the brain.

METHODS

Ninety-eight patients (41 female, 57 male) with a mean age of 51 years (range, 16-82 years) underwent 128 sets of single-photon emission computed tomography studies. TI-201 and Tc-99m HMPAO single-photon emission computed tomography studies were performed for tumor localization and evaluation of the effect of radiation on the cerebral cortex. Thirty concomitant neuropsychological tests and 96 anatomic imaging (computed tomography/magnetic resonance imaging) were performed. The average radiation dose was 52 Gy delivered as 1.8 to 2 Gy/fraction. Thirty-two patients received an average dose of 160 mCi of I-125 EGFr concomitantly. The average follow-up period was 34 months. Abnormalities away from the tumor site were interpreted as positive on HMPAO studies, neuropsychological testing, or anatomic imaging; otherwise, they were classified as negative.

RESULTS

There were 10/45 (22%) and 75/83 (90%) abnormal HMPAO study results before and after radiation therapy. The HMPAO studies compared with neuropsychological testing showed 3/13 (23%) and 14/17 (82%) concordant abnormalities in addition to tumor site in patients pre- versus postradiation therapy. There was better concordance of HMPAO and anatomic imaging in 22/30 (76%) patients versus 24/67 (36%) patients before radiation therapy. HMPAO imaging after radiation therapy revealed significantly more perfusion abnormalities. There were significant differences between all of the aforementioned parameters. CONCLUSION Tc-99m HMPAO imaging is useful in the evaluation of the effects of radiation therapy on the brain and is highly concordant with neuropsychological testing. It is superior to anatomic studies in identifying radiation-induced changes.