1. A medical imaging system comprising: a detector array; and a computer coupled to the detector array, the computer configured to access a first series of images acquired using a computed tomography (CT) imaging modality; receive predetermined pixel intensity values that indicate an organ of interest; threshold each image slice in the first series of images using the predetermined pixel intensity values to identify pixels in each image slice that indicate the organ of interest; automatically select a single image slice from the first series of images that best represents the organ of interest; automatically place a first visual indicator designating a region of interest (ROI) in the single image slice that best represents the organ of interest; automatically transfer the first visual indicator representing the ROI to the remaining image slices in the first series of images; automatically analyze the ROI designated by the first visual indicator within the first series of images based on first ROI pixel intensity values; automatically propagate a second visual indicator, designating the ROI, onto at least one second image from a second series of images using a second imaging modality based on a final position of the ROI in the first series of images; automatically analyze the ROI designated by the second visual indicator within the second image based on second ROI pixel intensity values; and automatically reposition the second visual indicator based on at least the first ROI pixel intensity values and the second ROI pixel intensity values.