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A 3D RANGE MODULATOR FOR ULTRA-SHORT PROTON FLASH IRRADIATION
Abstract
Background and aims
In the pursuit of optimal parameters for FLASH irradiation, all components involved in the beam delivery should be compatible with requirements spread in an extreme and wide unexplored regime. Aiming for minimal total irradiation times with modulated proton beams, which deliver a flat depth-dose distribution along tumors, a static range modulator has been developed to accommodate ultra-short beam durations regardless of their time structure. The design goals were set to match the functionality of the rotating wheel used for in-vivo and in-vitro FLASH investigations at HZB.
Methods
Having the form of a ridge filter extended to an additional dimension, a hexagonal-pyramid pattern was configured to an incoming beam of 23 MeV energy with > 1 mm radius, in order to create a 6 mm uniform field with a flat dose range of 5 mm at the target. The manufacturing was done with a 3D printer using VeroWhite, a material similar to PMMA. The lateral and distal dose distribution of both modulators were measured using a Markus Chamber (PTW-Freiburg, Germany) in a water phantom and a radioluminescent screen mounted in front of CCD camera, respectively.
Results
The developed modulator created very flat dose distributions as designed, with negligible differences to the reference rotating wheel. The positioning tolerances were evaluated as relatively relaxed, with offsets of 2 cm and an angle of 5 degrees not compromising the desired performance.
Conclusions
The developed static modulator allows systematic proton FLASH studies on small organs using a broad range of timing schemes, disentangled from temporal and spatial incoherencies.
Content
Author and article information
References
Kourkafas Georgios, Bundesmann Juergen, Fanselow Timo, Denker Andrea, Ehrhardt Vincent Henrique, Gollrad Johannes, Budach Volker, Weber Andreas, Kociok Norbert, Joussen Antonia M., Heufelder Jens. FLASH proton irradiation setup with a modulator wheel for a single mouse eye. Medical Physics. Vol. 48(4):1839–1845. 2021. Wiley. [Cross Ref]