Disclosed is an automated technique for analyzing the affected region due to an embolism in an organ. A segmented image of the organ vasculature is generated using image volume data received, for example, from a Computed Tomography (CT) machine. An embolus is then identified (either manually or automatically) within the segmented image, and the volume of the organ affected by the embolism is automatically determined. The volume of the organ affected by the embolism may be determined by computing a sub-tree within the segmented image, where the sub-tree comprises vessels that are distal to the identified embolus point. In one embodiment, the sub-tree is generated by determining a plane perpendicular to a vessel at the embolus point such that the sub-tree comprises a distal portion of the vasculature with respect to the plane. Unwanted overlapping trees are identified (e.g., by analyzing branch angles) and removed from the sub-tree. The volume of the organ affected by the embolism is determined by calculating a volume of the organ that is perfused by the sub-tree. The affected volume may be adjusted by scaling the volume based on the percentage occlusion of the partial embolus.