PMOD supports two types of spatial transformations:
Combination of Transformations
The PMOD fusion tools support the analytical combination of spatial transformations, avoiding hereby multiple interpolations. For example, when image A is matched to image B by the rigid transformation R1, and B is matched to image C by the rigid transformation R2, A is inherently matched to C by the combination R1*R2 of the transforms.
In PMOD, an arbitrary number of rigid transformations can be combined, but only one elastic transformation at the end of the chain. So for example:
All the automatic methods can not only return the matching transformation, but also the inverse transformation which applies if the role of the Reference and the Input is reversed. Additionally, PMOD can always calculate the inverse of the current transformation, even if it was created by combining transformations.
Transformation of VOIs
The spatial transformations can not only be applied to reslice images to reference images, but also to project VOIs from the reference space to the target image space. An application of particular interest is the use of standard VOIs which are defined in the MNI space for the analysis of patient images. This can be achieved with the following steps:
As a result the standard VOIs, adjusted for the particular patient anatomy, are available in the VOI tool as outline contours. The user can adjust them if needed, then save them and calculate image statistics on the unchanged patient data.