Proton beam spot size and position measurements using a multi-strip ionization chamber

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Proton therapy requires precise beam characterization for effective treatment.
• Accurate measurement of proton beam spot size and position is critical for quality assurance.

Purpose of the Study:

• To develop and characterize a large-area multi-strip ionization chamber (MSIC).
• To enable efficient measurement of proton beam spot size and position in proton therapy.

Main Methods:

• A 420 mm x 320 mm MSIC with 240 vertical and 180 horizontal strips was designed.
• Characterization involved irradiating proton spots across 17 energies (73.5-235 MeV) and comparing with EBT3 film.
• Analysis included beam profiles, spot sizes, positions, measurement stability, and sensitivity.

Main Results:

• The MSIC demonstrated excellent agreement with EBT3 film for spot size (±0.18 mm) and position (±0.17 mm) measurements.
• The detector exhibited good short-term measurement stability and low noise performance.
• Accurate characterization was achieved across the clinical proton beam energy range.

Conclusions:

• The developed large-area MSIC provides efficient and accurate proton beam spot characterization.
• The MSIC is suitable for commissioning and quality assurance in pencil beam scanning proton therapy.
• This technology supports fast quantification of spot size and position for improved treatment delivery.