An image processing device comprising: an electronic processor; and at least one non-transitory storage medium storing instructions readable and executable by the electronic processor to perform an image segmentation process on a medical image depicting activity of a radiopharmaceutical in an imaged patient, the image segmentation process including: performing image segmentation to generate an initial segmented representation of an anatomical structure in the medical image; fitting parameters of a geometric shape to the segmented anatomical structure in the medical image to produce initial fitted shape parameters; assigning, from a set of classifications, a classification for the anatomical structure in the medical image using at least one classifier operating on the initial fitted shape parameters and the initial segmented representation of the anatomical structure, the set of classifications including at least one activity leakage classification and at least one partial or missing activity uptake classification; and generating a final segmented representation of the anatomical structure in the medical image by operations including repeating the image segmentation using the classification as prior knowledge. an electronic processor; and at least one non-transitory storage medium storing instructions readable and executable by the electronic processor to perform an image segmentation process on a medical image depicting activity of a radiopharmaceutical in an imaged patient, the image segmentation process including: performing image segmentation to generate an initial segmented representation of an anatomical structure in the medical image; fitting parameters of a geometric shape to the segmented anatomical structure in the medical image to produce initial fitted shape parameters; assigning, from a set of classifications, a classification for the anatomical structure in the medical image using at least one classifier operating on the initial fitted shape parameters and the initial segmented representation of the anatomical structure, the set of classifications including at least one activity leakage classification and at least one partial or missing activity uptake classification; and generating a final segmented representation of the anatomical structure in the medical image by operations including repeating the image segmentation using the classification as prior knowledge. performing image segmentation to generate an initial segmented representation of an anatomical structure in the medical image; fitting parameters of a geometric shape to the segmented anatomical structure in the medical image to produce initial fitted shape parameters; assigning, from a set of classifications, a classification for the anatomical structure in the medical image using at least one classifier operating on the initial fitted shape parameters and the initial segmented representation of the anatomical structure, the set of classifications including at least one activity leakage classification and at least one partial or missing activity uptake classification; and generating a final segmented representation of the anatomical structure in the medical image by operations including repeating the image segmentation using the classification as prior knowledge.