Performance evaluation of adaptive aperture's static and dynamic collimation in a compact pencil beam scanning proton therapy system: A dosimetric comparison study for multiple disease sites.

p.aythelady61 shared this article with you from Inoreader Performance evaluation of adaptive aperture's static and dynamic collimation in a compact pencil beam scanning proton therapy system: A dosimetric comparison study for multiple disease sites. Via Head and Neck Related Articles Performance evaluation of adaptive aperture's static and dynamic collimation in a compact pencil beam scanning proton therapy system: A dosimetric comparison study for multiple disease sites. Med Dosim. 2020 Dec 02;: Authors: Grewal HS, Ahmad S, Jin H Abstract A compact pencil beam scanning (PBS) proton therapy system, Mevion S250i with Hyperscan, is equipped with adaptive aperture (AA) to collimate the beam with 2 different techniques: Static aperture (SA) and dynamic aperture (DA). SA (single aperture) collimates the outermost contour of the target and DA (multi-layer aperture) collimates each energy layer of the proton beam. This study evaluates dosimetric performance of SA and DA for different disease sites. This study includes 5 disease sites (brain, head and neck (HN), partial breast, lung, and prostate), and 8 patients for each. A total of 80 patient treatment plans (5 sites × 8 patients per site × 2 collimation techniques) were created using 2 to 4 proton beams. Both SA and DA plans were made using the same plan and optimization parameters calculated by a Monte Carlo dose algorithm. Multi-field optimization (MFO) was used for HN treatment plans, whereas treatment plans for the other sites were made with single-fie ld optimization (SFO). All plans were robustly optimized with 3 mm (brain and HN) or 5 mm (breast, lung, and prostate) position uncertainty along with 3.5% range uncertainty. Treatment plans were normalized such that 99% of the clinical target volume (CTV) received 100% of the prescribed dose. Dose volume histogram (DVH) parameters were evaluated for CTV and organs at risk (OARs). The CTV was also evaluated for dose homogeneity, dose conformity, and dose gradient. In general, the DA plan made CTV hotter, while it saved OARs better. DA produced better conformity with sharper dose falloff around CTV, while SA generated better homogenous target coverage. DA decreased Dmax to brainstem (1.2% = [(SA-DA)/DA × 100%]) for brain, Dmax to the spinal cord (137.3%) for HN, D1% of the ipsilateral lung (50.5%) for breast, and Dmax to the spinal cord (74.0%) for lung. The dose reduction in bladder and rectum for prostate plans with DA was less than 2.5%. The DA plans reduced the dose to O ARs for all disease sites but escalated the target maximum dose for the same target coverage than the SA plans. The OAR saving and dose escalation depended on CTV size, proximity of the OARs to CTV, and the plan complexity. PMID: 33279369 [PubMed - as supplied by publisher] View on the web Inoreader. Take back control of your news feed. Follow us on Twitter and Facebook.