Comparison of ¹²³I-α-Methyltyrosine SPECT and ¹¹C-L-Methionine PET in Patients with Brain Tumors

Summary

PET studies using ¹¹C-L-methionine (MET) have been shown to yield useful information in patients with brain tumors. The aim of this study was to investigate, whether SPECT studies using ¹²³I-α-methyltyrosine (IMT) can produce similar results.

9 patients with cerebral gliomas (four glioblastomas WHO grade IV, two astrocytomas WHO grade II,two astrocytomas WHO grade III and one anaplastic astrocytoma WHO grade IV) were investigated by MET-PET and IMT-SPECT. SPECT was performed from 15 to 60 minutes after i.v. injection of 370–550 MBq IMT using a modern three-headed SPECT system (Triad, Trionix). Two hours later a PET study was carried out 15–60 minutes after i.v. injection of 740–1110 MBq MET using the Scanditronix PC-4096-15WB. The PET and SPECT scans were visually compared and evaluated by ROIs and tumor to non-tumor ratios (TINT).

Although MET-PET yielded a better spatial resolution than IMT-SPECT there was no obvious difference in tumor extent and uptake between the two methods. The T/NT ratios showed a significant correlation (r=0.76; p<0.001).

The first results indicate that IMT-SPECT is comparable to MET-PET in patients with brain tumors. Thus IMT-SPECT offers the possibility of cerebral amino acid uptake studies in departments without PET.