Investigation of time-resolved proton radiography using x-ray flat-panel imaging system

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Proton beam therapy offers precise dose delivery due to the Bragg peak.
• Range uncertainties in proton therapy stem from inaccuracies in stopping power estimation and water-equivalent path length (WEPL).
• Accurate in vivo WEPL measurement via proton radiography is crucial for improving treatment precision.

Purpose of the Study:

• To develop and validate a novel proton radiography technique using a flat panel imager (FPI).
• To assess the feasibility of using time-resolved dose measurements for proton radiography.
• To evaluate the accuracy of WEPL measurements and the FPI's performance under low-dose conditions.

Main Methods:

• Utilized a 226 MeV pencil beam and a custom range modulator wheel (MW) to create a time-varying broad beam.
• Employed a flat panel imager (FPI) to capture time-resolved dose rate functions (DRFs) at various depths.
• Acquired proton radiographs of phantoms with varying configurations, analyzing dose rate patterns and WEPL accuracy.

Main Results:

• The FPI successfully generated high spatial resolution, low-noise proton radiographs.
• Measured relative stopping powers demonstrated accuracy within approximately 2% for CT tissue surrogates.
• The FPI exhibited robustness, with no significant radiation damage observed after substantial cumulative dose exposure.

Conclusions:

• A practical and effective method for generating proton radiography using an FPI has been successfully demonstrated.
• This technique shows promise for in vivo WEPL measurements, potentially reducing range uncertainties in proton therapy.
• The FPI-based proton radiography system offers a low-dose, high-resolution imaging solution for enhancing proton therapy precision.