3-[123I]Iodo-a-Methyltyrosine and [Methyl-11C]-L- Methionine Uptake in Cerebral Gliomas: A Comparative Study Using SPECT and PET

This study compares the uptake of the nonmetabolizable amino acid analog 3-[123l]iodo-a-methyltyrosine (IMT) and of [methyl-11C]-L-methionine (MET) in cerebral gliomas. Methods: In 14 patients with cerebral gliomas, IMT uptake was measured using SPECT (10 dynamic, 4 static SPECT acquisitions) and, on the same day, MET uptake by dynamic PET. The IMT and MET data were compared with respect to tracer kinetics, tumor to brain ratios (T/B) and tumor size after converting the resolution of the PET scans to that of the SPECT scans (14 mm FWHM). Results: All gliomas showed in creased uptake of both tracers in relation to normal brain tissue. Visual comparison of the scans yielded no differences in tumor size and shape with both methods. IMT showed a maximal tracer uptake in brain and in tumors at about 15 min postinjection which was followed by a washout of 45.0 % ±13.5 % in gliomas (mean ±s.d., p < 0.001, n = 10) and 35.3 % ±5.4 % in normal brain (p < 0.001