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BEST IN PHYSICS (THERAPY) - A Novel Multi-Point Plastic Scintillation Detector for in Vivo Dosimetry and Quality Assurance in Radiation Therapy

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F Therriault-Proulx

F Therriault-Proulx1,2*, L Beaulieu2,3, L Archambault2,3, S Beddar1, (1) University of Texas MD Anderson Cancer Center, Houston, TX, (2) Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec,QC, (3) Centre Hospitalier Univ. de Quebec, Quebec, QC

WE-G-BRB-4 Wednesday 4:30:00 PM - 6:00:00 PM Room: Ballroom B

Purpose: To develop a novel multi-point plastic scintillation detector (mPSD) capable of accurately measuring dose at multiple positions simultaneously with the use of a single optical guide.

Methods: We built a new generation of plastic scintillation detectors composed of multiple scintillating elements along a same optical transmission line. Three different scintillating fibers were optically coupled to a single collecting optical fiber. A primary challenge for this new type of detector is that the output signal is a superposition of multiple scintillation spectra and contaminating elements. Acquisition with a spectrometry setup allows for the implementation of a new hyperspectral approach that accounts for each light-emitting component separately, and allows spectral unmixing. The mPSD and an ion chamber were irradiated in a water phantom with a 6 MV photon beam. Profiles and depth-dose curves were measured and compared between detectors. This detector and the corresponding calibration approach were also applied to Ir-192 HDR brachytherapy.

Results: Doses measured with the mPSD were in good agreement with the ion chamber measurements for external beam irradiations. Average relative differences of (2.3±1.1)%, (1.6±0.4)% and (0.32±0.19)% were observed for each scintillating element. The mPSD measurements tended to be at least as accurate as published measurements from single-point PSDs. For the Ir-192 HDR brachytherapy application, the average difference between the treatment planning system and the measurements were (4.6±1.0)% per dwell-position and (2.1±1.0)% per catheter. The accuracy of each scintillating element was shown to depend on light attenuation and on the similarity of its scintillation spectrum in comparison to the other light emitters.

Conclusions: The feasibility and accuracy of mPSDs using a single transmission line was demonstrated. In addition to well-documented advantages of single-point PSDs, the multi-point capability of this single-fiber detector makes mPSDs a very promising new technique for quality assurance and on-line in vivo dosimetry.

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