Reply to the comments on “Setup error analysis in helical tomotherapy based image-guided radiation therapy treatments” by Slav Yartsev

Abstract

Sir,The aim of our study was to assess the patient setup errors for various tumor sites based on clinical data treated with helical tomotherapy using pretreatment image guidance (IG) based on the institutional practice. In addition, we also calculated and compared the planning target volume (PTV) margins for all disease sites based on the analysis of systematic and random errors. The motivation of this study was to analyze our institution’s specific setup errors considering the fact that setup errors vary according to each immobilization system and patient which in turn influence the PTV margins. We have divided the tumor sites into various categories as brain, head and neck, thorax - abdomen, pelvis, and craniospinal irradiation. Planning computed tomography (CT) images were obtained on lightSpeed Xtra (GE Health care Pvt Limited , India.) with a slice thickness of 3 mm for all the disease sites as per the protocol. For thorax and abdominal tumors, four-dimensional CT scans were obtained, from which internal target volume was generated for planning purposes. studies which is our results. we agree fast CT studies for planning may be suboptimal for IG purposes, and untagged average studies may be used.