MOSFET dose measurements for proton SOBP beam

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Proton therapy utilizes spread-out Bragg peaks (SOBP) for precise dose delivery.
• Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are used for dose measurements but exhibit dependence on Linear Energy Transfer (LET).
• Correcting MOSFET response to LET variations is crucial for accurate dosimetry in proton beams.

Purpose of the Study:

• To develop a computational scheme for correcting LET dependence in MOSFET response for SOBP proton beams.
• To enable accurate dose measurements in water phantoms using MOSFET detectors.

Main Methods:

• Investigated LET dependence of MOSFETs, attributing it to the stopping power ratio of SiO2 to H2O and fractional hole yield.
• Derived formulas for dose-weighted correction factors using literature stopping power values and measured fractional hole yields.
• Applied derived formulas to a clinical 190-MeV proton SOBP beam.

Main Results:

• Computed dose-weighted correction factors for a clinical 190-MeV proton SOBP beam.
• Predicted MOSFET outputs using correction factors for a beam composed of weighted monoenergetic Bragg peaks.
• Observed good agreement between predicted and measured MOSFET responses.

Conclusions:

• Applying LET-dependent correction factors to MOSFET data allows for accurate dose verification in proton therapy.
• This method enhances the quality assurance of dosimetry using MOSFET measurements.
• Facilitates reliable dose verification for clinical proton beam applications.