A medical imaging system (900, 1000, 1100, 1200) for acquiring medical image data from an imaging volume, wherein the medical imaging system is a magnetic resonance imaging system, the medical imaging system comprising: - a tissue treating system (910, 1080, 1180, 1190, 1280, 1290) for treating a target volume of a subject; - a computer system comprising a processor, wherein the computer system is adapted for controlling the medical imaging system; and - a memory containing machine readable instructions (954, 956, 958, 962, 964, 966, 968, 970, 972, 974) for execution by the processor, wherein execution of the instructions cause the processor to: - acquire (100, 200, 308) medical image data by controlling the medical imaging system, wherein the medical image data is magnetic resonance data; - reconstruct (102, 202, 310) a medical image using the medical image data; - derive (104, 204, 312) an image segmentation seed (600, 934) from a treatment plan, wherein the treatment plan is descriptive of the target volume; and - identify (106, 210, 314) a treated volume (400, 700, 800) in the medical image by segmenting the medical image in accordance with the image segmentation seed; wherein the instruction cause the processor to identify the treated volume in the medical image by: - thresholding the medical image; and - floodfilling the thresholded medical image in accordance with the image segmentation seed; and - identifying the treated volume in accordance with the floodfill in the thresholded medical image. - a tissue treating system (910, 1080, 1180, 1190, 1280, 1290) for treating a target volume of a subject; - a computer system comprising a processor, wherein the computer system is adapted for controlling the medical imaging system; and - a memory containing machine readable instructions (954, 956, 958, 962, 964, 966, 968, 970, 972, 974) for execution by the processor, wherein execution of the instructions cause the processor to: - acquire (100, 200, 308) medical image data by controlling the medical imaging system, wherein the medical image data is magnetic resonance data; - reconstruct (102, 202, 310) a medical image using the medical image data; - derive (104, 204, 312) an image segmentation seed (600, 934) from a treatment plan, wherein the treatment plan is descriptive of the target volume; and - identify (106, 210, 314) a treated volume (400, 700, 800) in the medical image by segmenting the medical image in accordance with the image segmentation seed; - acquire (100, 200, 308) medical image data by controlling the medical imaging system, wherein the medical image data is magnetic resonance data; - reconstruct (102, 202, 310) a medical image using the medical image data; - derive (104, 204, 312) an image segmentation seed (600, 934) from a treatment plan, wherein the treatment plan is descriptive of the target volume; and - identify (106, 210, 314) a treated volume (400, 700, 800) in the medical image by segmenting the medical image in accordance with the image segmentation seed; - thresholding the medical image; and - floodfilling the thresholded medical image in accordance with the image segmentation seed; and - identifying the treated volume in accordance with the floodfill in the thresholded medical image.