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

BACKGROUND Cerebral radionecrosis is a possible complication of brain radiation therap y in patients with primary or metastatic tumors. This retrospective study e valuated the role of Tc-99m hexamethyl propyleneamine oxime (HMPAO) scintig raphy in monitoring the effects of radiation on the brain. METHODS Ninety-eight patients (41 female, 57 male) with a mean age of 51 years (ran ge, 16-82 years) underwent 128 sets of single photon emission computed tomo graphy studies. TI-201 and Tc-99m HMPAO single-photon emission computed tom ography studies were performed for tumor localization and evaluation of the effect of radiation on the cerebral cortex. Thirty concomitant neuropsycho logical tests and 96 anatomic imaging (computed tomography/magnetic resonan ce 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 16 0 mCi of I-125 EGFr concomitantly, The average follow-up period was 34 mont hs. 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 neuropsycholog ical 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%) patient s versus 24/67 (36%) patients before radiation therapy. HMPAO imaging after radiation therapy revealed significantly more perfusion abnormalities. The re were significant differences between ail of the aforementioned parameter s. CONCLUSION Tc-99m HMPAO imaging is useful in the evaluation of the effects of radiatio n therapy on the brain and is highly concordant with neuropsychological tes ting. It is superior to anatomic studies in identifying radiation-induced c hanges.