Role of Residual Setup Errors and Intrafraction Motion in the Evaluation of Planning Target Volume Margins for Prostate Cancer Radiation Therapy

Abstract

Traditional setup techniques rely on skin marks aligned to room-based lasers or on the alignment of bony structures. However, these techniques do not take into account that the prostate moves relative to both skin marks and bony anatomy. With daily online correction based on implanted fiducial markers as a surrogate for prostate position, a significant improvement of the accuracy of daily prostate localization can be achieved. However, residual set-up errors (RSE) reflecting inaccuracies in the imaging and repositioning systems as well as intrafraction motion may become limiting factors in prostate targeting accuracy.