A piecewise-focused high DQE detector for MV imaging

A piecewise-focused high DQE detector for MV imaging

Citation

Star-Lack, J., Shedlock, D., Swahn, D., Humber, D., Wang, A., Hirsh, H., ... & Fahrig, R. (2015). A piecewise‐focused high DQE detector for MV imaging. Medical physics, 42(9), 5235-5249. 

Keywords

  • Electronic Portal Imagers (EPIDs)
  • Detective Quantum Efficiency (DQE)
  • Megavoltage (MV) Imaging
  • Cone-Beam Computed Tomography (CBCT)
  • Cadmium Tungstate (CWO)
  • Cu-GOS 

Brief

This article describes an efficient piecewise-focused pixelated strip scintillator for MV imaging that offers more than a 20-fold dose efficiency improvement over Cu-GOS. 

Summary

This 2015 article in Medical Physics, authored by Josh Star-Lack, Daniel Shedlock, and others, describes the development and testing of a new type of medical imaging detector designed for use with megavoltage (MV) x-ray beams, typically used in radiation therapy.

Here are the key takeaways:

  • Problem: Existing electronic portal imagers (EPIDs) used in radiation therapy suffer from low detective quantum efficiency (DQE). This means they require high radiation doses to produce usable images, which is not ideal for patient safety.
  • Proposed Solution: The article reports on a new EPID design using a "piecewise-focused" array of cadmium tungstate (CWO) crystals coupled to an active matrix flat panel imager (AMFPI).
  • Advantages of CWO: CWO was chosen for its desirable properties as a scintillator, including:
    1. High light output
    2. High density
    3. Radiation hardness
    4. Optical transparency
  • Piecewise Focusing: This technique helps maintain high spatial resolution across the entire imaging field of view, a significant improvement over previous designs.
  • Results: The new CWO-based EPID demonstrated:
    1. Significantly higher DQE than conventional EPIDs (over 20 times greater). This means much lower radiation doses are needed to achieve the same image quality.
    2. Improved spatial resolution, comparable to that of kV-based CBCT systems commonly used in image-guided radiotherapy (IGRT).
  • Benefits for IGRT: This technology has the potential to enhance IGRT by enabling:
    1. Higher quality imaging for real-time tracking of tumor motion during treatment.
    2. More accurate 3D image reconstruction (CBCT) for better patient positioning and treatment planning.
  • Future Directions: The researchers highlight areas for further investigation, including:
    1. Optimizing the design to further reduce image artifacts.
    2. Exploring ways to eliminate the fiber optic plate (FOP) used for focusing to potentially reduce production costs.

The article concludes that this new CWO-based EPID represents a major step forward in MV imaging technology for radiation therapy.

Origin: https://aapm.onlinelibrary.wiley.com/doi/full/10.1118/1.4927786

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