AUTOMATIC ESTIMATION OF PATIENT SET-UP ERRORS IN RADIOTHERAPY BY REGION-BASED ALIGNMENT OF PORTAL AND PRE-TREATMENT IMAGES

摘要

In radiotherapy, eradication of a tumour without causing complications in normal tissues surrounding the tumour depends on the accuracy of patient set-up, i.e. the position of the patient with respect to the radiation beams. In this paper, an automatic method is presented to estimate patient set-up errors by region-based alignment of portal images captured during treatment delivery and pre-treatment images obtained from conventional X-ray film by digitisation. The method utilises the axes and grid lines produced by the collimating system on both images to achieve automatic extraction of the corresponding sub-image pairs, and exploits the mutual information between the corresponding sub-image pairs to achieve automatic alignment. Using real radiotherapy images, the patient errors estimated are shown to be consistent with manual alignment.