C-11 TYROSINE POSITION EMISSION TOMOGRAPHY AND H-1 MAGNETIC-RESONANCESPECTROSCOPY OF THE RESPONSE OF BRAIN GLIOMAS TO RADIOTHERAPY

We monitored 10 patients with unresected (9) or partially resected (1) supratentorial gliomas with C-11-tyrosine position emission tomograph y (TYR-PET) before and after radiotherapy. TYR-PET tumour volumes were measured using a threshold technique, In seven patients the tumour vo lume decreased after radiotherapy, although all gliomas persisted on T YR-PET images. In eight patients the tumour protein synthesis rate (PS R) was calculated using a dynamic study protocol in combination with a PATLAK analysis. There were no changes in PSR after radiotherapy, but the PSR was calculated on the remaining tumour volume using the same threshold technique as before therapy, i.e. the decrease in tumour vol ume was not taken into account. In eight patients the PET data were co mpared with magnetic resonance spectroscopic imaging (H-1-MRSI) perfor med simultaneously. Although there was no statistically significant co rrelation between TYR-PET volume changes and H-1-MRSI choline level we observed a simultaneous decrease in volume and choline in four patien ts.