Biomedical Engineering Reference
In-Depth Information
Figure 22.
Locations of one manually selected landmark point in three orthogonal 2D
images of the atlas and the patient before and after deformable registration. The landmark
point is marked with a green cross. Left to right: atlas image, patient's image with the
manually selected landmark point; patient's image with the warped landmark point from
the atlas with direct use of deformable registration; and the patient's image with the warped
landmark point from the atlas with the proposed approach. Copyright c
2006, Elsevier
B. V. See attached CD for color version.
The estimated tumor model parameters were
c
t
= (109
,
86
,
126),
r
t
=3
.
9
mm,
r
e
=24mm, and
P
=3
.
55 Pa. In order to quantitatively assess the im-
provement in registration accuracy due to the proposed approach, 21 landmark
points were selected around the tumor area in the patient's images and corre-
sponding points were identified by an expert in the atlas. The point coordinates
were mapped through the resulting deformation map with direct deformable reg-
istration, and with the approach described above. The location of one landmark
point in the atlas image and the patient's image before and after registration are
shown in Figure 22. The results for all 21 points are presented in Table 3. The
maximum error was reduced by 71% via the use of the presented approach while
the mean error was reduced by 57.6%.
Similar deformable registration experiments were performed on a simulated
tumor case based on an MR scan of a normal subject. Using the biomechanical
model described in Section 4.3, a simulation was performed on the image of
the normal subject with simulation parameters
c
t
= (106
,
86
,
128),
r
t
=4
.
5 mm,
r
e
=21mm, and
P
=4
.
5 kPa. Using the approach described above, the estimated
values of these parameters were
c
t
= (109
,
85
,
128),
r
t
=4
.
1 mm,
r
e
=23mm,
and
P
=3
.
6 kPa. The warping of some labels associated with the atlas to the
subject's image near the tumor area are shown in Figure 23.
