To incorporate the anatomical detail needed for better diagnosis or guidance in
radiotherapy, image fusion of whole body functional F-18 FDG PET or SPECT with
anatomical CT, or MRI can be performed.
Linear and non-linear image registration
techniques can be applied.
Linear techniques are suitable if the patient body
configuration and breathing conditions are similar between the separate scans.
If PET
images are acquired with different breathing patterns and in a different body
configuration than CT, or MRI, then rigid-body image registration may not be sufficient.
We have developed both linear and non-linear techniques for PET/CT/MRI image
registration based on mutual information techniques. We have designed a practical, fast
and fully automated algorithm for elastic 3D image registration of whole-body PET and
CT thoracic images, which compensates for the non-linear deformation due to the breathhold imaging technique and variable body configuration. We employ 3D computer
graphics techniques for fast deformation of image volumes.
Similar registration
approaches can be used for the follow-up assessment and comparison of serial scans
during the course of therapy. Image registration and fusion enhances the use of sensitive
functional modalities such as PET as a guide for the radiation therapy planning.