A method and apparatus for generating a computer model from scan data from a patient, comprising: (1) acquiring the scan data from the patient; (2) selecting a plurality of key frames from the scan data; (3) hand segmenting the selected key frames, whereby to identify specific anatomical structures; (4) automatically generating segmented intervening frames for the regions between the key frames using an interpolation process; (5) merging the automatically segmented intervening frames with the hand segmented key frames so as to generate a complete set of segmented frames; (6) obtaining a first measurement of a selected feature of the complete set of segmented frames; (7) hand segmenting at least one additional key frame and replacing a corresponding intervening frame with said one additional key frame within the complete set of segmented frames; (8) re-interpolating the set of segmented frames based upon the updated set of key frames; (9) obtaining a second measurement of the selected feature of the re-computed set of segmented frames; (10) comparing said second measurement with said first measurement; and (11) if the second measurement differs from the first measurement by a statistically significant amount, replacing the first measurement with the second measurement and repeating the process from Step 7.