O-(2-[ 18 F]fluoroethyl)-L-tyrosine PET in gliomas: influence of data processing in different centres.

Background: PET using O-(2-[ ¹⁸ F]fluoroethyl)-L-tyrosine ( ¹⁸ F-FET) is an established method for brain tumour diagnostics, but data processing varies in different centres. This study analyses the influence of methodological differences between two centres for tumour characterization with ¹⁸ F-FET PET using the same PET scanner. Methodological differences between centres A and B in the evaluation of ¹⁸ F-FET PET data were identified for (1) framing of PET dynamic data, (2) data reconstruction, (3) cut-off values for tumour delineation to determine tumour-to-brain ratios (TBR) and tumour volume (T _vol ) and (4) ROI definition to determine time activity curves (TACs) in the tumour. Based on the ¹⁸ F-FET PET data of 40 patients with untreated cerebral gliomas (20 WHO grade II, 10 WHO grade III, 10 WHO grade IV), the effect of different data processing in the two centres on TBR _mean , TBR _max , T _vol , time-to-peak (TTP) and slope of the TAC was compared. Further, the effect on tumour grading was evaluated by ROC analysis.
Results: Significant differences between centres A and B were found especially for TBR _max (2.84 ± 0.99 versus 3.34 ± 1.13; p < 0.001), T _vol (1.14 ± 1.28 versus 1.51 ± 1.44; p < 0.001) and TTP (22.4 ± 8.3 min versus 30.8 ± 6.3 min; p < 0.001) and minor differences for TBR _mean and slope. Tumour grading was not influenced by different data processing.
Conclusions: Variable data processing of ¹⁸ F-FET PET in different centres leads to significant differences especially for TBR _max and T _vol . A standardization of data processing and evaluation is needed to make ¹⁸ F-FET PET comparable between different centres.