Abstract: The present invention extends to methods, systems, and computer program products for semantically altering a medical image. A medical image and a transform are accessed. The transform is used to transform the medical image to a simpler image having reduced complexity relative to the medical image. A semantic alteration is made to content of the simpler image. Another (and possibly inverse) transform is accessed. The other transform is used to transform the simpler image to a more complex image having increased complexity relative to the simpler image (e.g., complexity resembling the medical image). Transforming the simpler image to a more complex image can include propagating the semantic alteration with the increased complexity into content of the more complex image. A medical decision is made in view of the semantic alteration and based on at least a portion of the more complex image content.