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Using EPID in Vivo Dosimetry to Quantify Treatment Delivery Accuracy in Canine Head and Neck Tumors

J Lambeck1*, S Saad2 , K Hansen3 , M Kent3 , S Dieterich4 , (1) University of California Davis, Sacramento, CA, (2) The William R. Prichard Veterinary Medical Teaching Hospital, School of Veterinary Medicine,UC Davis, Davis, CA, (3) Department of Surgical and Radiological Sciences, UC Davis School of Veterinary Medicine, Davis, CA, (4) UC Davis Medical Center, Sacramento, CA


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To assess dose delivered during a course of treatment to the PTV and critical organs of 15 canine nasopharynx cancer patients using the Sun Nuclear PerFRACTION 3D EPID dosimetry software. The secondary goal was to validate the PerFRACTION IMRT delivery quality assurance (DQA) tool.

Methods: Varian Eclipse software was used to create IMRT plans based on a simulation CT scan. The DQA was performed twice, first using the Sun Nuclear MapCHECK device and then with the PerFRACTION in air EPID tool. Results were evaluated for gamma pass rate at 3%/ 3mm for both systems. Patients were set-up on a Varian TrueBeam linear accelerator using CBCT image guidance. EPID fluence maps were captured for each fraction. The PerFRACTION software was used to calculate and record radiation dose delivered from exit fluence data. Radiation dose delivered to PTV and critical organs were compared to planned treatment values.

Results: All patients had QA gamma pass rates with PerFRACTION of over 90%, except for one patient at 89.4%. Over 92% of 104 total fractions delivered met or exceeded 95% of planned treatment dose to PTV. 27% of patients had at least 1 fraction deliver less than 95% of planned dose to PTV with 1 fraction only delivering 89%. 1 patient never had treatment dose to PTV higher than 92% of planned, despite QA showing greater than 95%, both with PerFraction and MapCHECK. All critical organs received less than 105% of planned treatment dose for over 80% of fractions, except for the Left Inner Ear at 62% of fractions.

Conclusion: This work demonstrates the ability to chart dose variability over the course of a patient’s treatment, allowing for the implementation of adaptive radiotherapy practices. This work also validates the PerFRACTION IMRT DQA tool, with all but one patient receiving 90% gamma pass rate.

Funding Support, Disclosures, and Conflict of Interest: S. Dieterich has a beta testing agreement with SNC Inc.


Electronic Portal Imaging, In Vivo Dosimetry, Image-guided Therapy


TH- External beam- photons: Quality Assurance - IMRT

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