1. A method for linking volumes of interest (VOIs) across timepoints and across modalities, comprising: loading a first image dataset comprising image data acquired at a first timepoint using a first imaging modality selected from one of: computed tomography (CT), positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance (MR) and ultrasound; loading a second image dataset comprising image data acquired at a second timepoint using a second imaging modality selected from one of: computed tomography (CT), positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance (MR) and ultrasound, wherein the first imaging modality is different from the second imaging modality; registering the first image dataset and the second image dataset with each other; displaying the first image dataset and the second image dataset on a computer screen at the same time; receiving a manually drawn boundary to demarcate a VOI in the first image dataset; automatically copying the VOI from the first image dataset to a corresponding area in the second image dataset, wherein the corresponding area is obtained by applying a transformation using a result of the registration; and linking the VOI in the first image dataset the VOI copied to the second image dataset, wherein the method is performed using a processor.