Development of high quantum efficiency flat panel detectors for portal imaging: intrinsic spatial resolution

Area of Science:

• Medical Physics
• Radiological Imaging
• Detector Technology

Background:

• Flat panel detectors (FPDs) show better image quality than conventional electronic portal imaging devices (EPIDs).
• Current FPDs have low quantum efficiency (QE) (2-4%), limiting their use in portal imaging.
• Increasing FPD conversion layer thickness improves QE but reduces spatial resolution due to x-ray scatter.

Purpose of the Study:

• To theoretically investigate the intrinsic spatial resolution of a high QE FPD.
• To explore the potential of a novel, denser, and thicker energy conversion layer for FPDs.
• To determine if high QE and high spatial resolution can be achieved simultaneously in FPDs.

Main Methods:

• Developed a theoretical model to calculate the modulation transfer function (MTF) of the FPD system.
• Utilized a novel approach employing an analytical expression for absorbed dose.
• Investigated the impact of varying conversion layer materials, density, and thickness.

Main Results:

• Achieved a theoretical high QE of approximately 60% for the FPD.
• Demonstrated that optimized conversion layer materials yield an intrinsic MTF superior to current EPIDs.
• Identified design principles for conversion layers to enhance QE, spatial resolution, and detective quantum efficiency (DQE).

Conclusions:

• High QE flat panel detectors with advanced conversion layers can surpass current EPIDs in both image quality and efficiency.
• Careful selection of materials for the energy conversion layer is crucial for optimizing FPD performance.
• The study provides guidelines for designing next-generation FPDs for portal imaging applications.