Revista Espanola De Medicina Nuclear | 2019
Segmentation of gliomas in 18F-fluorocholine PET/CT. A multiapproach study.
Abstract
Abstract Aim Our aim was two-fold, to study the interobserver agreement in tumour segmentation and to search for a reliable methodology to segment gliomas using 18F-Fluorocholine PET/CT. Methods 25 patients with glioma, from a prospective and non-randomized study [FuMeGA (Functional and Metabolic Glioma Analysis)], were included.Interobserver variability in tumour segmentation was assessed using fixed thresholds. Different strategies were used to segment the tumours. First, a semi-automatic tumour segmentation was performed, selecting the best SUVmax-% threshold for each lesion. Next we determined a variable SUVmax-% depending on the SUVmax. Finally a segmentation using a fixed SUVmax threshold was performed. To do so, a sampling of 10 regions of interest (ROIs of 2.8\xa0cm2) located in the normal brain was performed. The upper value of the sample mean SUVmax\xa0±\xa03 SD was used as cut-off. All procedures were tested and classified as effective or not for tumour segmentation by two observer s consensus. Results In the pilot segmentation, the mean\xa0±\xa0SD of SUVmax, SUVmean and optimal SUVmax-% threshold were: 3.64\xa0±\xa01.77, 1.32\xa0±\xa00.57 and 21.32\xa0±\xa08.39, respectively. Optimal SUVmax-% threshold showed a significant association with the SUVmax (Pearson\xa0=\xa0−0.653, p\xa0=\xa00.002). However, the linear regression model for the total sample was not good, that supported the division in two homogeneous groups, defining two formulas for predicting the optimal SUVmax-% threshold. As to the third procedure, the obtained value for the mean SUVmax background\xa0+\xa03 SD was 0.33. This value allowed segmenting correctly a significant fraction of tumours, although not all. Conclusion A great interobserver variability in the tumour segmentation was found. None of the methods was able to segment correctly all the gliomas, probably explained by the wide tumour heterogeneity on 18F-Fluorocholine PET/CT.