Dosimetric impact of systematic spot position errors in spot scanning proton therapy of head and neck tumor.

Purpose: The spot position is an important beam parameter in the quality assurance of scanning proton therapy. In this study, we investigated dosimetric impact of systematic 15 spot position errors (SSPE) in spot scanning proton therapy using three types of optimization methods of head and neck tumor.

Materials And Methods: The planning simulation was performed with ± 2 mm model SSPE in the X and Y directions.

Dosimetric effects of quality assurance-related setup errors in passive proton therapy for prostate cancer with and without a hydrogel spacer.

The purpose of this study was to evaluate the effect of quality assurance (QA)-related setup errors in passive proton therapy for prostate cancer with and without a hydrogel spacer. We used 20 typical computed tomography (CT) images of prostate cancer: 10 patients with and 10 patients without spacers. The following 12 model errors were assumed: output error ± 2%, range error ± 1 mm, setup error ± 1 mm for three directions, and multileaf collimator (MLC) position error ± 1 mm.