Characterization of proton pencil beam scanning and passive beam using a high spatial resolution solid-state
Linh T Tran1, Lachlan Chartier1, David Bolst1
1Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.
Medical Physics
|September 10, 2017
Summary
This study demonstrates a silicon microdosimeter
Area of Science:
- Medical Physics
- Radiation Oncology
- Nuclear Instrumentation
Background:
- Proton therapy utilizes pencil beam scanning (PBS) and passive double scattering (DS) for precise radiation delivery.
- Characterizing the relative biological effectiveness (RBE) is crucial for optimizing proton therapy outcomes.
- Silicon on insulator (SOI) microdosimeters offer potential for detailed radiation field characterization.
Purpose of the Study:
- To characterize proton pencil beam scanning (PBS) and passive double scattering (DS) systems.
- To measure parameters for the relative biological effectiveness (RBE) using a novel silicon microdosimeter.
- To assess and compare dose equivalents outside clinical proton treatment fields.
Main Methods:
- Utilized a novel silicon microdosimeter with well-defined 3D sensitive volumes (SVs) capable of detecting low lineal energies.
- Placed the microdosimeter in a water phantom at various depths and increments within the spread-out Bragg peak (SOBP).
- Derived RBE values using measured microdosimetric lineal energy spectra and the modified microdosimetric kinetic model (MKM), validated with Geant4 simulations.
Main Results:
- Measured dose-mean lineal energy (yD¯) increased significantly towards the distal edge of the Bragg peak (BP) for PBS.
- Derived RBE for PBS increased from 0.97 at the entrance to 1.57 at the distal part of the BP.
- DS system showed a substantial RBE increase from 1.29 to 1.43 at the distal edge of the SOBP.
Conclusions:
- The SOI microdosimeter effectively characterizes proton radiation fields with submillimeter resolution.
- RBE modeling using the MKM showed an increase from 1.14 to 1.6 in the BP and its distal part for a physical dose of 1.82 Gy.
- Experimental and simulation results showed good agreement, confirming the SOI microdosimeter's utility for quality assurance in proton therapy.
Keywords:
RBE3D sensitive volumemicrodosimetrypencil beam scanning (PBS)proton therapysilicon on insulator (SOI)More Related Videos
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