Finding an improved amorphous-silicon x-ray flat-panel detector configuration for the in-line geometry

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Detector Engineering

Background:

• Conventional amorphous-silicon flat-panel detectors (FPDs) have been explored for intrafractional image guidance in an in-line geometry.
• This setup allows simultaneous monitoring of the patient and the treatment beam by separating diagnostic (kV) and treatment (MV) signals.
• Existing FPDs face challenges in this configuration, including beam attenuation and signal saturation.

Purpose of the Study:

• To propose and investigate a novel FPD design with reduced upstream areal density for improved intrafractional image guidance.
• To enhance the performance of FPDs in an in-line geometry for radiotherapy applications.
• To minimize signal interference and saturation while maintaining accurate imaging.

Main Methods:

• Utilized Monte Carlo simulations to model and validate the proposed FPD design.
• Conducted experimental irradiations using simple rectangular fields to assess detector component impact.
• Investigated the effects of removing detector components like the support structure and phosphor screen on signal measurements.

Main Results:

• The proposed FPD design demonstrated a 60% decrease in megavoltage (MV) beam attenuation compared to conventional FPDs.
• A 20% reduction in the MV signal within the primary field region was observed, mitigating FPD saturation.
• Long-range scatter from the MV beam into the kilovolt (kV) region of the detector was significantly reduced.

Conclusions:

• The novel FPD design offers superior performance for intrafractional image guidance in radiotherapy.
• Reduced areal density enhances MV beam transmission and minimizes scatter, leading to improved image quality and detector reliability.
• This optimized FPD configuration is better suited for simultaneous patient and treatment beam monitoring.