Registration of emission and transmission whole-body scintillation-camera images

In this work, a method for registration of whole-body (WB) scintillation-ca mera images is presented. The primary motive for the development is to perf orm activity quantification using the conjugate view method on an Image bas is. Accurate image registration is required for sequential anterior and pos terior scans, for serial emission images for analysis of the biokinetics, a nd for transmission and emission images for a pixel-based attenuation corre ction. Methods: Registration is performed by maximization of the mutual inf ormation. The spatial transformation has been tailored for the registration of WB images and is composed of global and local transformations, includin g rigid, projective, and curved transformations. A coarse registration is f irst performed using cross-correlation and direct pixel scaling. Optimizati on is then performed in a sequence, beginning with the 2 legs independently , followed by the upper body and head. Evaluation is performed for clinical images of an I-131-labeled monoclonal antibody and for Monte Carlo-simulat ed images. An anthropomorphic WB computer phantom, which has been especiall y modified to match the patient position during WB scanning, is used for th e simulations. Results: For simulated images, registration errors are withi n 1 pixel (<3.6 mm) for a sufficient image count level. Separate evaluation of the influence of noise shows that the errors increase below a total ima ge count of approximately 10(5) (signal-to-noise ratio, approximately 4). F or clinical evaluations, the deviations between point markers are 9 +/- 5 m m. Conclusion: An automatic registration method for WB images has been deve loped, which is applicable to emission-emission and transmission-emission r egistration. This method has been applied in more than 50 clinical studies and has shown to be robust and reliable.