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  4. Real-Time Dose Verification for HDR Brachytherapy Using PSD Sensor in Cervical Cancer Patient

Real-Time Dose Verification for HDR Brachytherapy Using PSD Sensor in Cervical Cancer Patient

T Baig1,2*, B Traughber1,3 , J Muenkel2 , E Harris1,2 , R Ellis1,2 , T Podder1,2 , (1) Case Western Reserve University, Cleveland, OH, (2) University Hospitals Seidman Cancer Center, Cleveland, OH, (3) Cleveland VA Medical Center, Cleveland, OH

Presentations

(Thursday, 7/18/2019) 7:30 AM - 9:30 AM

Room: 301

Purpose: To report the first ever study on in-vivo real-time dose tracking of cervical cancer patients using OARtrac system (AngioDynamics, Latham, NY) using plastic scintillating detector (PSD) for HDR brachytherapy applications.

Methods: From October 2018 to February 2019 real-time in-vivo dose measurement were performed for three patients diagnosed with FIGO stage IIB and IIIB cervical cancer who underwent HDR brachytherapy treatment using Venezia (Elekta, Stockholm) gynecological applicator. OARtrac PSD sensor was placed, prior to the CT scan, in one of the interstitial needles that were inserted along the periphery of applicator. PSD sensor was contoured on planning CT; D90 of the PSD was obtained using Oncentra (Elekta) planning system and used as expected dose. The PSD was carefully placed at the same location and real-time dose was measured using OARtrac software. Distance to agreement (DTA) and dose range along the length of the sensor were computed.

Results: Total seven measurements were obtained from three patients. Difference between expected D90 dose to measured dose for all measurements was 6.4% (range: -19.5% to 14.5%). Five of the seven measured dose were within 4.0% of the expected/planned dose. Larger dose differences of -19.5% and 14.5% could be attributed to possible movement of the anatomy or catheter/needle with PSD between CT-Sim and treatment delivery due to presence of gas in patient’s rectum. DTA for six of the seven measurements were within 1.8mm. 5.2mm DTA was measured for largest dose discrepancy of -19.5%.

Conclusion: With less anatomical deviation during treatment (5 of the 7 cases) dose measured using OARtrac sensor showed an agreement within 4.0% of the planned dose. It appears that the OARtrac device is capable of verifying the real-time dose monitoring for HDR applications within clinically acceptable limit. Using multiple PSD measurements in additional positions may reduce the potential variation due to motion.

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

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