%0 Generic
%A Altenstein, Georg
%D 2014
%F heidok:17776
%K Rotationstherapie, Dosisberechnung, Bestrahlungsplanung, zeitabhängige Monte-Carlo-Dosisberechnung  
%R 10.11588/heidok.00017776
%T A Novel Collimator Concept for Fast Rotational IMRT
%U https://archiv.ub.uni-heidelberg.de/volltextserver/17776/
%X The 2D binary multileaf collimator (2D-bMLC) is a novel collimator concept specially dedicated to fast rotational radiotherapy treatments. The 2D-bMLC consists of individually controlled absorber channels arranged side by side to form a 2D aperture. The design, which leads to radiation fields characterized by a striped pattern, aims at very quick aperture modulations. Using a Monte Carlo (MC) method we established the dosimetric model of a theoretical flattening filter free medical linac equipped with a 2D-bMLC. We further developed a treatment planning system for rotational 2D-bMLC treatments with a new optimization method and a MC framework for exact calculation of the dose. In plan comparison studies, 2D-bMLC plans were calculated for various clinical indications and compared to clinically accepted IMRT and Helical Tomotherapy plans. The design of the 2D-bMLC might be especially sensitive to geometrical misalignments of the collimator on the one hand, and to intrafraction motion on the other hand. Both aspects have been investigated in additional MC studies. The results of  the planning studies showed that the 2D-bMLC concept is in principal adequate for rotational radiotherapy treatments with potential delivery times considerably below those of IMRT techniques applied in the clinics today. Clinically acceptable 2D-bMLC plans with delivery times below 30 seconds were calculated for all investigated tumour sites. Dosimetric parameters were comparable to those of the reference plans. Already very small geometrical misalignment of the 2D-bMLC can cause severe under-dosage, and especially high demands on manufacture tolerances as well as on quality assurance will be necessary, if a 2D-bMLC should be produced for clinical use. Consideration of intrafraction motion, however, did not lead to significant changes in the accumulated doses calculated for prostate plans with standard fractionation.