1. A method comprising: receiving an input image of a region of interest (ROI) of an individual, the input image being a medical image acquired by a first imaging modality; generating a first feature image based on the input image, the first feature image including a designated anatomical feature of the ROI; obtaining an anatomical atlas, the atlas including a reference image of the ROI of at least one other individual and an organ model, the reference image being a medical image acquired by a second imaging modality that is different from the first imaging modality; and determining a transformation function by registering the first feature image with a second feature image that is based on the reference image and includes the designated anatomical feature.