11C-MET and 18F-FLT-PET as tracers for tumour activity in comparison to perfusion and diffusion MR imaging

Introduction: In the differentiation of malignant brain tumours the apparent diffusion coefficient (ADC) and the relative cerebral blood volume (rCBV) obtained by MRI have been evaluated1. Aim of this study was to investigate the relation between 11C-MET and 18F-FLT as amino acids for the assessment of proliferation in PET to rCBV respectively to the ADC.

Marterial and methods: In total 19 patients with primary glioma were included. All patients underwent 11C-MET PET investigation, 10 patients 11C-MET and 18F-FLT PET. DW and PW images were performed in 17 of 19 patients. The relative cerebral blood volume (rCBV), the apparent diffusion coefficient (ADC), 11C-MET uptake and 18F-FLT uptake were determined by using a region of interest (ROI) approach.

Results: Maximal rCBV ratios within in the tumour are strongly related to the highest 11C-MET and 18F-FLT uptake ratios (MET: r=0.89, p<0.001; FLT: r=0.68, p=0.05). After co-registration in the tumour with the highest rCBV also increased 11C-MET uptake/18F-FLT ratios were found (MET: r=0.66, p=0.004; FLT: r=0.77, p=0.016). An inverse correlation was observed between the ADC ratio and the uptake ratios of 11C-MET and 18F-FLT (11C-MET: r=–0.76, p=0.001; 18F-FLT: r=–0.77, p=0.73).

Conclusion: The strong relation between high metabolism of 11C-MET and 18F-FLT and rCBV ratios respectively ADC ratios indicates that high proliferating parts of the tumour as depicted by PET are associated to a high perfusion and a high cellular density detected by MR.

References:

1. Calli, C., O. Kitis, et al. (2006). “Perfusion and diffusion MR imaging in enhancing malignant cerebral tumors.“ Eur J Radiol 58(3): 394–403.

„Supported in part by EC-FP6-project DiMI, LSHB-CT-2005–512146 and EMIL, LSHB-CT-2004–503569“