Variation in appearance of glioma on serial thallium-201 single photon emission computed tomography--case report.

A 63-year-old female presented with recurrent glioblastoma at the site of a right parietal glioblastoma which was diagnosed 1 year before. She was treated at that time by total removal of the tumor, irradiation, and chemotherapy. Four months after the initial treatment, serial thallium-201 single photon emission computed tomography (201Tl SPECT) showed increased uptake at the edge of the original tumor site. The index, the ratio of 201Tl uptake in the lesion to the normal brain, was 2.9 which suggested a recurrent tumor. Magnetic resonance images with gadolinium over the next 7 months demonstrated an enhanced mass lesion at the site of primary tumor resection and a new enhanced mass in the right temporal lobe. The lesion in the right parietal lobe had a 201Tl uptake index of 2.5, while the lesion in the right temporal lobe had an index of 1.5. Re-craniotomy and total resection of the tumors in the right parietal and temporal lobes were performed. The histological diagnosis of both tumors was glioblastoma. The proposed use of 201Tl SPECT for the differential diagnosis of recurrent glioma and radiation necrosis should be carefully considered because the 201Tl uptake index can vary in tumor with the same malignancy grade.