Waveform simulation based on 3D dose distribution for acoustic wave generated by proton beam irradiation
Schematic diagram of the experimental setup.
2D measurement method of symmetric proton beam irradiation. The IP was inserted into the gap between the two oblique edges formed by PMMA holders.
Schematic image of the pressure calculation. An imaginary component of 3D dose distribution is added above the water surface of the original 3D dose distribution.
Depth dose and quenching factor. The amount of the modulation weights of range-shifted PSL curves and depth doses from 125 MeV proton beam are relative. As a reference, the quenching factor, which was simply scaled down from Ref. 11, and the calculated dose by quenching factor at the Bragg peak were shown.
Calculated 3D dose distribution for the Bragg curve: (a) Image in the plane and depth dose profile on beam axis and (b) image in the plane and lateral dose profile at the Bragg peak. Profiles before and after 3D calculation are represented by solid lines and dotted lines, respectively.
Steps of waveform calculation and results.
Acoustic waveforms calculated for one point at the center of the detector, for distributed five points in axis of the detector and for distributed 300 points in which the size of each element is equal to the voxel size of 3D dose matrix. This calculation was done for the beam at the Bragg peak of 65 mm depth and for the hydrophone at 90 mm depth.
Influence of the correction factor of the PSL quenching on the calculated acoustic waveform. waveforms were calculated for , , the adequate correction, and no-correction at the Bragg peak. These calculations were done for the beam with the Bragg peak of 65 mm depth and for the hydrophone at 140 mm depth.
Influence of the proton range on the waveform [(a), (b), (c)] and influence of off-axis measurement on the waveform [(d), (e), (f)]. Solid lines indicate the calculated pressure waveforms, while the dotted lines indicate the experimental waveforms detected by the hydrophone in water. waveforms (a), (b), and (c) were normalized using the first maximum. waveforms (d), (e), and (f) were normalized using the first maximum of the on-axis measurement.
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