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

PET using O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (¹⁸F-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 ¹⁸F-FET PET using the same PET scanner. Methodological differences between centres A and B in the evaluation of ¹⁸F-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 ¹⁸F-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.

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.

Variable data processing of ¹⁸F-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 ¹⁸F-FET PET comparable between different centres.