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  5. Real-Time In-Vivo Dosimetry Using Plastic Scintillation Detector (PSD) Device While Treating Prostate with EBRT

Real-Time In-Vivo Dosimetry Using Plastic Scintillation Detector (PSD) Device While Treating Prostate with EBRT

T Baig1,2*, J Muenkel2 , K Xu2 , Z Xu2 , T Podder1,2 , R Ellis1,2 , (1) Case Western Reserve University, Cleveland, OH, (2) University Hospitals Seidman Cancer Center, Cleveland, OH

Presentations

(Sunday, 7/14/2019) 5:00 PM - 6:00 PM

Room: Stars at Night Ballroom 1

Purpose: To report the real-time in-vivo dose tracking using OARtrac (AngioDynamics, Latham, NY) plastic scintillation detector (PSD) for linac-based prostate EBRT cases and assessment of this dose tracking device for clinical application.

Methods: The OARtrac system has a PSD embedded in the prostate immobilization endorectal balloon (ERB). The PSD provides real-time dose for any photon beam irradiating it. The ERB with a secured PSD sensor was placed proximal to the anterior rectal wall, closely reproducing it’s position during CT-Sim. In-vivo real-time dose was recorded using OARtrac’s dose monitoring software. Expected dose was determined from the treatment plan using Pinnacle (Philips, version 16.2) planning system and CBCT co-registered with planning CT.

Results: Total 75 measurements were taken from 16 different patients who underwent either SBRT or IMRT/VMAT treatment. The measured dose was categorized in two groups based on difficulty of identifying the sensor in the CBCT image. Better sensor detection was achieved when standard CBCT protocol was used; not the fast CBCT scanning protocol. An average deviation of 5% (range: -10.95% to 10.92%) was observed for 69% (n=52) of measurements with standard CBCT. This deviation was increased to 19.8% (range: -11.12% to -35.85%) for 31% (n=23) of the measurements when fast scanning protocol was used for CBCT or any unexpected anatomical change (e.g. bowel movement or presence of gas in rectum)occurred during the treatment time.

Conclusion: The PSD sensor of OARtrac device for real-time in-vivo dosimetry has proven to be useful when it is possible to localize accurately in CBCT image. Clinically the detector improves patient safety with daily or weekly in-vivo dose measurements to reduce the risk for a misadministration. A revised balloon has been developed to help aid in localization of the PSD, and is anticipated to be available in the near future.

Funding Support, Disclosures, and Conflict of Interest: Rodney Ellis, MD has a consulting contract with AngioDynamics, Latham, NY.

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