REGISTRATION OF SYNTHETIC TOMOGRAPHIC PROJECTION DATA SETS USING CROSS-CORRELATION

Tomographic registration, a method that makes possible accurate patien t registration directly from projection data, consists of three proces sing steps: (i) manual coarse positioning, (ii) tomographic projection set acquisition, and (iii) computer mediated refined positioning. In the coarse positioning stage, the degree of patient alignment is compa rable with that achieved with the standard radiotherapy set-up. Howeve r, the accuracy requirements are somewhat more relaxed in that meticul ous alignment of the patient using external laser indicators is not ne cessary. Instead, tomographic projection sets are compared with planni ng CTs in order to achieve improved patient set-up. The projection set s are cross-correlated to obtain the best-fit translation and rotation offsets. The algorithm has been tested on synthetic data with the inc orporation of varying amounts of Gaussian pseudo-random noise. These t ests demonstrate the algorithm's stability and also confirm that align ment can be achieved with an accuracy of less than one projection pixe l.