Image Processing Reference
In-Depth Information
Time-Point Interpolation.
We evaluate the capacity of the deformations
computed using the proposed models to interpolate between time-points. For
this, we remove every second time-point from the synthetic series before com-
puting the serial registrations. We then scale each velocity field
v
t
by a factor
1
2
to account for the larger gaps between observations and compute the residual
to the complete series. The resulting registration errors are shown in Figure
7
.
Interpolated time-points are indicated on the x-axis.
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Time
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(a) Single Sulcification
(b) Pairwise Sulcification
Fig. 7.
Registration Error using half the image data (orange: no, blue: uniform, green:
spatially adaptive temporal smoothing)
While the registration error is higher than when using the full series, the
results show that the spatially adaptive temporal smoothing prior enables a more
accurate prediction of the missing images in both experiments. Spatially uniform
smoothing on the other hand leads to worse performance during most of the
single-sulcification and the first half of the pair-wise sulcification experiments.
We attribute this to oversmoothing at the beginning of sulcification, where its
effect is not yet strongly visible (Figure
3
). While not completely avoiding it, the
spatially adaptive method however reduces this effect. This yields results that
are comparable to the naive method in the first experiments and a decrease in
registration error in the second. Interestingly, the registration error could also
be reduced for those time-points that have been used for registration.
3.2 Fetal Brain Development
Based on the publicly available atlas [
25
], we compute a model of brain develop-
ment in the human fetus between Gestational Weeks (GW) 23 and 35. As in the
synthetic case, we evaluate the registration error and smoothness of the result-
ing overall deformation. In order to render the registration robust to intensity
changes during development due to tissue maturation, we optimize the Residual
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