Projects:DBP2:Harvard:Registration Documentation

Registration

Slicer 3 contains a number of different ways to register two images. In this document we will examine the results of these modules on three different cases. The convention used will be (moving image) -> (fixed image) = (resulting moved image). The cases are:

• Registering a t2 weighted image to an arbitrary t1, then registering this transformed image back to the original t2. Ideally this will produce a identical image.
• Registering a DTI baseline image to the corresponding realigned t2 weighted image, and vice-versa. This is a realistic test of one of our (the PNL) everyday uses of registration.
• Registering a realigned t2 weighted image to another t2.

Tasks completed

Affine

Affine case 1: Minor loss of detail.

• 53-t2 -> 31-t1 = aff1
• aff1 -> 53-t2 = aff2

The image shows these side by side. The are nearly the same except for the loss of fine detail.

• DTI-baseline -> 53-t2 = aff3

Image shows the 53-t2 target image and the registered image side by side. DTI distortion remains but aligned well to ventricles in center.

• 53-t2 -> DTI-baseline = aff4

The registered image does not stretch to the full extent of the DTI at the midline, though the match is quite close more laterally.

Linear

Linear case 1: Minor shift at front, loss of detail.

• 53-t2 -> 31-t1 = lin1
• lin1 -> 53-t2 = lin2

The image shows lin2 and 53-t2 side by side. The image shows there appears to be some change beyond loss of detail, possibly a L-R shift in the front.

• DTI-baseline -> 53-t2 = lin3

Middle is clearly matched, coronal slices look okay, sagittal shows DTI distortions remain.

• 53-t2 -> DTI-baseline = lin4

Brainstem and cerebellum matched well, normal DTI distortions still present.

Rigid

Rigid case 1: Significant loss of detail.

• 53-t2 -> 31-t1 = rig1
• rig1 -> 53-t2 = rig2

Significant blurring, but every feature is in it's proper place.

• DTI-baseline -> 53-t2 = rig3

Brainstem aligned, normal DTI distortions present.

• 53-t2 -> DTI-baseline =rig4

Similar.

Deformable B-spline

• 53-t2 -> 31-t1 = Bspline1
• Bspline1 -> 53-t2 = Bspline2

Superior frontal enlargement, odd upward shifting in rear of brain, distortions everywhere.

• DTI-baseline -> 53-t2 = Bspline3

Fits the cortex on the baseline to the skull on the t2. Retry with a skull stripped t2.

• DTI-baseline-masked -> 53-t2-masked = Bspline4

Bad registration, numerous deformations, midline shift in frontal lobe, right side deformations, cerebellum doesn't fit any more.

Diffeomorphic Demons

• 53-t2 -> 31-t1 = Demons1
• Demons1 -> 52-t2 = Demons2

Multiple deformations. Much larger ventricles. Small errors everywhere, expansions, contractions, shifts. Roughly in the same place overall.

Register Volumes Module

• 53-t2 -> 31-t1 = init1
• init1 -> 53-t2 = init2

Initial

Huge shift in count values, rigid translation down ~4 pixels, left ~1 pixel.

Rigid

Huge shift in grey values. Few other problems.

Affine

Again, shift in grey values, mostly okay otherwise. Slight rightward shift.

B-Spline

Again grey values shift. Minor distortion in frontal lobe and cerebellum.

• DTI-baseline -> t2

TAKES FOREVER. Inferior frontal, temporal, stretched downwards. Cerebellum is terrible. Very top of the brain is stretched. Pretty bad overall.