scholarly journals The Evolution of Lateral Dose Distributions of Helium Ion Beams in Air: From Measurement and Modeling to Their Impact on Treatment Planning

2022 ◽  
Vol 9 ◽  
Author(s):  
Judith Besuglow ◽  
Thomas Tessonnier ◽  
Benedikt Kopp ◽  
Stewart Mein ◽  
Andrea Mairani

To start clinical trials with the first clinical treatment planning system supporting raster-scanned helium ion therapy, a comprehensive database of beam characteristics and parameters was required for treatment room-specific beam physics modeling at the Heidelberg Ion-Beam Therapy Center (HIT). At six different positions in the air gap along the beam axis, lateral beam profiles were systematically measured for 14 initial beam energies covering the full range of available energies at HIT. The 2D-array of liquid-filled ionization chambers OCTAVIUS from PTW was irradiated by a pencil beam focused at the central axis. With a full geometric representation of HIT’s monitoring chambers and beamline elements in FLUKA, our Monte Carlo beam model matches the measured lateral beam profiles. A second set of measurements with the detector placed in a water tank was used to validate the adjustments of the initial beam parameters assumed in the FLUKA simulation. With a deviation between simulated and measured profiles below ±0.8 mm for all investigated beam energies, the simulated profiles build part of the database for the first clinical treatment planning system for helium ions. The evolution of beamwidth was also compared to similar simulations of the clinically available proton and carbon beam. This allows a choice of treatment modality based on quantitative estimates of the physical beam properties. Finally, we investigated the influence of beamwidth variation on patient treatment plans in order to estimate the relevance and necessary precision limits for lateral beam width models.

2006 ◽  
Vol 5 (2) ◽  
pp. 121-128 ◽  
Author(s):  
J. C. L. Chow ◽  
G. N. Grigorov ◽  
R. Jiang

A recently released Pinnacle treatment planning system software, v7.4f includes some new physics features such as modeling of the rounded multi-leaf collimator (MLC) leaf ends and the tongue-and-groove structure between leaves. In this study, the above physics modeling improvements were verified by comparing the peripheral dose profiles for the small MLC fields calculated by the new Pinnacle v7.4f and the old Pinnacle v6.2b with those obtained from measurements experimentally. Three test MLC fields with different jaw sizes were prepared, and specific dose profiles (along cross-line, in-line and diagonal axis) at different depths were measured using a Varian 21 EX linear accelerator with 120-leaf Millennium MLC, big scanning water tank and photon diode. Estimated dose profiles for the test fields were calculated using Pinnacle v6.2b and v7.4f. By comparing the measured and calculated results, it was found that both v6.2b and v7.4f performed well in calculating the cross-line (along the gap between the longitudinal lengths of two leaves) and diagonal axis dose profiles at different depths. However, v7.4f gave calculated dose values closer to the measured field for in-line (gap between junctions of two rounded leaf ends) axis dose profiles at different depths. For the shape of the profile along the in-line axis, v7.4f calculated a flat “platform” dose profile of about 34.3% (inter-bank leakage) at depth dmax> beyond the MLC field edge using a clinical dose grid size of 0.4×0.4×0.4cm3, compared to the “zigzag” dose profile varying between 35.4% and 42.1% measured using the water tank and diode. However, both Pinnacle v6.2b and v7.4f calculated the percentage depth dose for the test fields well compared to the measurements.


2000 ◽  
Vol 27 (7) ◽  
pp. 1588-1600 ◽  
Author(s):  
O. Jäkel ◽  
G. H. Hartmann ◽  
C. P. Karger ◽  
P. Heeg ◽  
J. Rassow

2009 ◽  
Vol 92 ◽  
pp. S253-S254
Author(s):  
E. Wieslander ◽  
T. Knöös ◽  
P. Engström

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