Result evaluation

Figure 5.4: Yet Another screen shot of the RegistrationTool. This figure shows the comparison mode. On the left the fuse opacity option has been chosen while this is the grid option on the right. Parameters of these options can be changed on the control panel on the left.

As said before, evaluating the accuracy of the results is an important issue of such a software. Hence we provide several ways of doing so.

At any moment, you can press this button to evaluate the registration accuracy. It provides two modes of comparison. Fig. 5.4 (left) shows the first mode that fuses the registered moving image (i.e. moving image resampled w.r.t. the transform - being rigid, affine or non-linear) with the fixed image by blending them with an alpha value that the user can change: .

The second mode (Fig. 5.4 right) uses a checkerboard technique: the view is divided in squares (the number of squares can be changed), and one square out of two contains the moving image and the fixed image, alternatively.

Either the percentage of the moving image related to the fixed image, or the size of the squares can be manually set by a slider in the control panel.

Use this button to output a snapshot of the current comparing-mode window.

Note that the window-level cannot be changed in the comparison mode as soon as it corresponds to a mix of the two input images. In order to change the window level you must go back to the double panel mode by pressing again the ``comparison mode'' button, change the window level of each image as desired and then go once again in the comparison mode.

Figure 5.5: This figure shows a comparison mode after non-linear registration. In the control panel you can choose to display the resulting deformation field (right) in parallele to the comparison view (left). The deformation field is in fact wrapped into a regular grid. Note that this feature is only available for 3D image registration.

As soon as one performed a non-linear registration process (or loaded a deformation field as input), one can visualize this field in the compare mode. It can be done by clicking the ``Deformation Field'' checkbox in the control panel. The deformation field is used to wrap a regular grid with it. The output grid is then shown in parallel of the comparison view (see 5.5).