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In ten patients with malignant gliomas the regional cerebral metabolic rate for glucose (rCMRGlc) was studied with positron emission tomography (PET) using 2-18F-deoxyglucose (18FDG) before and within 1 to 7 days after intra-arterial chemotherapy with the nitrosourea derivative ACNU (iaACNU). Three patients were studied before and after two iaACNU courses and one patients before and after three iaACNU courses. The early effects of iaACNU on tumour rCMRGlc were highly variable and appeared to be more pronounced after the first course of iaACNU than in later iaACNU courses, i.e. more pronounced in untreated patients. Although there was no clear correlation between the change of rCMRGlc following the first course of iaACNU and the clinical outcome in this small group of patients, the patient with the most pronounced decrease of tumour metabolism (-16.5%) after the first course of iaACNU exhibited full tumour remission for 12 months, while the patient with the most pronounced increase of tumour metabolism (+65%) after the first course of iaACNU developed rapid tumour progression. The first results indicate that early effects of intra-arterial chemotherapy may be observed with 18FDG PET, especially following the first course of iACNU. Further studies are needed to evaluate the predictive value of such studies for therapy response.

The cerebral uptake of 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) as measured with the use of single photon emission computed tomography (SPECT) was studied in 66 patients with various types of brain tumours and quantified by tumour-to-cerebellum ratios. The uptake of 99Tcm-HMPAO by gliomas and meningiomas showed wide ranges of values. There were no significant differences among primary malignant gliomas (0.75 +/- 0.27, n = 25), recurrent malignant gliomas (0.81 +/- 0.25, n = 14) and benign gliomas (0.77 +/- 0.21, n = 9). Compared to gliomas, meningiomas exhibited a significantly higher 99Tcm-HMPAO uptake (1.14 +/- 0.31, n = 13, p less than 0.001) while the remaining four patients with tumours of various histopathology showed a low 99Tcm-HMPAO uptake. Three of the 66 patients were scanned immediately and again 2 h after injection and they revealed a decrease in tumour activity. No changes in the pattern of uptake were observed in two patients with gliomas which were studied before and after intra-arterial chemotherapy, but a decrease in tumour uptake was found in the glioma patient who was studied before and after radiotherapy. The results obtained with 99Tcm-HMPAO SPECT are in agreement with those on regional cerebral blood flow (rCBF) in brain tumours reported in the literature.