Computer assisted decision making after portal imaging

Abstract

The verification of patient positioning during radiotherapy relies on the comparison of portal iamges to a reference image which may be a simulator film or a digitally reconstructed radiograph (DRR) from the computerised treatment planning system. While the comparison has been traditionally done by physicians and/or radiation therapists, much research has been undertaken in recent years to determine the differences between simulator and portal images utilising automatic and quantitative systems (1–4). The outcome is a numerical value for the shift and/or rotation of the treatment field as determined in each portal image in relation to the simulator image.