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A Novel High Quantum Efficiency MV X-Ray Detector for Image-Guided Radiotherapy

J Liu1*, A Teymurazyan2 , Y Xu3 , G Pang4 , (1) Ryerson University, Toronto, Ontario, (2) University of Regina, Regina, Saskatchewan, (3) Ryerson University, Toronto, Ontario, (4) TSRCC, Toronto, ON


(Thursday, 8/2/2018) 1:00 PM - 3:00 PM

Room: Room 202

Purpose: To develop a new scintillating-fiber-based electronic portal imaging device (EPID) with a high quantum efficiency (QE) and an adequate spatial resolution.

Methods: Scintillating fibers with a diameter of 1 mm were embedded in lead to form a honeycomb pattern. The distance between the centers of neighboring fibers is 1.35 mm. The prototype detector has a thickness of 2 cm. The QE, line spread function (LSF), and anti-scatter properties of the detector were measured using 6 MV beam on a Linac machine. To characterize the spatial resolution, Fourier transform of the LSF was performed to yield the modulation transfer function (MTF).

Results: The QE of the prototype detector is 35%, about an order of magnitude higher than that of current EPIDs. The scatter to primary ratio (SPR) measured by the detector at 10 cm air gap and 20×20 cm² field size is approximately 25% lower than that of ionization-chamber-based detectors with a comparable QE. The f₅₀ of the MTF is 0.2 mm�¹ at 6 MV, which is comparable to that of video-based EPIDs.

Conclusion: This work indicates that using scintillating fibers to generate and guide imaging signals, it is possible to increase the thickness of the detecting materials, therefore the QE of the detector, and maintain an adequate spatial resolution for MV x-ray imaging. Due to the application of lead as the spacing material, the new detector also has anti-scatter property, which will help improve the signal-to-noise ratio of the images. Further investigation to optimize the design of the detector and achieve a better combination of QE and spatial resolution is warranted.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).


Scintillators, Megavoltage Imaging


IM/TH- RT X-ray Imaging: Detector development & evaluation

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