Volumetric assessment with [18F]fludarabine PET/CT and illustration of a delineation of MAVT. (a) Tumour growth in rituximab-treated (n = 5) and vehicle-treated mice (n = 5) - RM two-way ANOVA, *** p < 0.001. Error bars: ± standard error of the mean (SEM). (b) Contouring of metabolically active part of tumour (MAVT) based on segmentation with background (muscle) as threshold. The volume of non-avid tissues was assessed by subtracting the MAVT from the total tumour volume.