Biomedical Engineering Reference
In-Depth Information
Figure 3.3:
MR prostate image with labeled features used to analyze registration
error. This transverse image is from the reference volume of prostate cancer
patient P3. The prostate boundary was manually segmented near the image
center. The four vertical dash lines from left to right indicate the rim of the
right acetabular socket, the right and left rims of the prostate, and the rim of
the left acetabular socket, respectively. The five crosses from bottom to top
indicate the coccyx, the prostate posterior rim, the 2D centroid automatically
calculated from the segmented prostate area, the anterior rim, and the pubic
symphysis. The image also shows the bottom of the bladder, the rectum, the
pubic symphysis, and hip joints.
3.2.3
Evaluation of Registration
3.2.3.1
Registration Accuracy Based on Bony Landmarks
We evaluate the registration of the pelvis by measuring the displacement of
bony landmarks following registration. There are six easily found bony land-
marks consisting of two great sciatic notches, two lesser sciatic notches, the
pubic symphysis, and the coccyx, some of which are illustrated in Fig. 3.3. Pre-
viously, sciatic notches and the pubic symphysis were used to register CT and
MRI images for prostate conformal radiation [28]. To measure landmark dis-
placements, we use visualization software such as
RegViz,
a program written
