This section describes the usage of the NRU developed registration
module for the Interactive Image Overlay (IIO) approach to
coregistration. The method is inspired by that of Pfluger et
The basis of the method is the
assumption that the human eye is good at detecting differences in
shapes. Once the module has been initiated using the main program, the
user interface of the method appears (Figure 20).
The main interface of the IIO module.
On the interface, the reslice image is shown as it directly appears
within the space of the standard image4
Next, adjustment of the reslice and standard Min/Max values should be
made, to adjust the colormaps to the value ranges of the images. The
value of the reslice threshold (which determines the position of the
overlayed green contour should also be adjusted, e.g. to a value
corresponding to the cranial surface.
A first order registration can be done by pressing the 'CM alignment'
button on the IIO interface, which will register the centres of mass
of the two images (Figure 21).
IIO - centres of mass aligned.
Clicking the three lower panes, will navigate the standard image
space. Clicking the coronal pane will update the
corresponding axial an sagital view ports. Clicking one of the three upper
panes will make a zoomed version of that pane visible (left in Figure 22)
Zoomed pane before (left) and after (right) transformation.
By using the keyboard and mouse, the overlayed image and the overlayed
image can now be aligned visually with the underlying standard image:
The pointer keys adjusts the image orientation by translation.
Translation stepsize is adjustable through + and - keys.
The , and . keys adjusts the image orientation by rotation,
in positive/negative direction.
Rotation stepsize is adjustable through * and / keys.
The centre of rotation is selectable using mouse clicking.
Once the image orientation is satisfactory (right
in Figure 22), the window should be
closed using either the keyboard x key or the close button of
the window. Repeating this process on all viewports and navigating the
standard image space will register the two images (Figure 3.2.5).
Once registration is satisfactory, the IIO interface should be closed,
returning the user to the main interface of MARS, where
registration parameters can be saved.
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