CLINICAL RELEVANCE OF TL-201-CHLORIDE SPET IN THE DIFFERENTIAL-DIAGNOSIS OF BRAIN-TUMORS

Magnetic resonance imaging (MRI) and computed tomography (CT) may not be reliable in the differential diagnosis of tumour necrosis, scar and recurrent tumour. We compared Tl-201-chloride SPET with CT and MRI fo r the differential diagnosis of these cerebral lesions. Brain SPET was performed in 40 patients after the intravenous injection of Tl-201-ch loride. All 40 patients also had a CT or MRI scan, and a histological diagnosis was available for 27 of the patients. For each patient, the ratio of counts in the lesion region of interest (ROI) to counts in th e contralateral ROI was calculated and found to be between 0.58 and 9. 60. The ratios for high-grade gliomas, metastases and meningiomas were high (> 2.7), especially in tumours with good vacularization. A low r atio (< 1.7) was noted in patients with low-grade astrocytoma, necrosi s or ischaemic lesions. There were two exceptional cases of ischaemic lesions in the luxury perfusion stage (ratios of 3.61 and 3.87), as ve rified by HMPAO-SPET. We found that Tl-201-chloride SPET helps to diff erentiate between malignant tumours, poorly vascularized benign lesion s and necrosis. Differentiation between low-grade astrocytoma and non- malignant lesions was not possible, but there was a trend towards diff erentiating between low-grade astrocytoma and ischaemic infarction. Th e timing of the investigation is important to avoid false-positive res ults in hyperperfused ischaemic tissue. ((C) 1998 Chapman & Hall Ltd.) .