Kj. Langen et al., 3-[I-123]IODO-ALPHA-METHYLTYROSINE AND [METHYL-C-11]-L-METHIONINE UPTAKE IN CEREBRAL GLIOMAS - A COMPARATIVE-STUDY USING SPECT AND PET, The Journal of nuclear medicine, 38(4), 1997, pp. 517-522
This study compares the uptake of the nonmetabolizable amino acid anal
og 3-[I-123]iodo-alpha-methyltyrosine (IMT) and of [methyl-C-11]-L-met
hionine (MET) in cerebral gliomas. Methods: In 14 patients with cerebr
al gliomas, IMT uptake was measured using SPECT (10 dynamic, 4 static
SPECT acquisitions) and, on the same day, MET uptake by dynamic PET. T
he IMT and MET data were compared with respect to tracer kinetics, tum
or to brain ratios (T/B) and tumor size after converting the resolutio
n of the PET scans to that of the SPECT scans (14 mm FWHM). Results: A
ll gliomas showed increased uptake of both tracers in relation to norm
al brain tissue. Visual comparison of the scans yielded no differences
in tumor size and shape with both methods. IMT showed a maximal trace
r uptake in brain and in tumors at about 15 min postinjection which wa
s 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, n = 1
0) at 60 min postinjection. MET concentration in tumor tissue or brain
tissue between 15 and 60 min remained constant. T/B ratios of IMT SPE
CT and MET PET showed a significant correlation at 15 min postinjectio
n (r = 0.69, n = 10, p = 0.03), a low correlation for the mean values
of the scans from 15-60 min postinjection (r = 0.54, n = 14, p = 0.05)
and no correlation at 60 min postinjection (r = 0.09, n = 10, n.s.).
Conclusion: IMT and MET uptake in gliomas is similar in the early, tra
nsport dominated phase. There are some differences in tumor to brain r
atios between both tracers within the first hour postinjection that ar
e mainly caused by variable washout of IMT. Imaging of tumor extent wi
th IMT SPECT is comparable to MET PET. Thus, amino acid SPECT using IM
T is a promising tool to evaluate the biological activity and intracer
ebral infiltration of gliomas.