NONINVASIVE GRADING OF PRIMARY BRAIN-TUMORS - RESULTS OF A COMPARATIVE-STUDY BETWEEN SPET WITH I-123 ALPHA-METHYL TYROSINE AND PET WITH F-18 DEOXYGLUCOSE

Use of iodine-123-alpha-melhyl tyrosine (I-123-IMT) allows investigati on of the amino acid transport rate in gliomas. It was the aim of this study to compare the value of measurement of glucose metabolism with that of measurement of I-123-IMT uptake for the non-invasive grading o f brain tumours. The study population comprised 23 patients with histo pathologically proven primary brain tumours, 14 had high-grade gliomas , and nine low-grade brain neoplasms, Glucose metabolism was studied u sing an ECAT EXACT 47 positron emission tomography (PET) camera and fl uorine-18 fluorodeoxyglucose (F-18-FDG); I-123-IMT uptake was measured with the triple-headed single-photon emission tomography (SPET) camer a, MULTISPECT 3. F-18-FDG and I-123-IMT uptake was quantified as ratio s between the uptake by the tumour and contralateral regions of refere nce. Glucose metabolism and amino acid uptake of the brain tumours cor related significantly (r = 0.71, P < 0.001). Assuming discrimination t hresholds between high-grade and low-grade tumours of 0.8 for F-18-FDG uptake and 1.8 for I-123-IMT uptake, the accuracy values of F-18-FDG PET and I-123-IMT SPET for differentiating between high-grade and low- grade rumours were 21/23 (91%) and 19/23 (83%), respectively. The diff erence in diagnostic performance was not significant on receiver opera ting characteristic analysis (P > 0.4). It is concluded that there is no major difference between the PET investigation of glucose metabolis m and the less expensive SPET measurement of amino acid uptake in term s of their accuracy in evaluating the malignancy grade of primary brai n tumours, This encourages the performance of further studies to analy se the potential impact of I-123-IMT SPET on the therapeutic managemen t of patients with brain tumours.