H Zhong*, J Garcia Alvarez, K Kainz, G Chen, A Tai, E Ahunbay, X Li, Medical College of Wisconsin, Milwaukee, WI

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  H Zhong

PO-GePV-T-310 (Sunday, 7/25/2021)   [Eastern Time (GMT-4)]

Purpose: To develop an independent dose mapping program for verification of adaptive radiotherapy (ART) for patients treated with helical tomotherapy.

Methods: An in-house developed ART platform (Hertz) was adapted to verify dose accumulations performed in a commercial ART system (PreciseART, Accuracy Inc.). Specifically, in PreciseART, deformable image registrations were performed from daily MV-CTs to a planning kV-CT. The resultant displacement vector fields (DVFs) were used to map doses from the MV-CTs to the kV-CT. All the CTs, doses and DVFs were exported to Hertz. In Hertz, HU-to-mass density tables for kV and MV-CTs were used to convert HU and dose to mass density and energy. DVFs were used to generate their pseudo-inverse DVFs. An energy-and-mass congruent mapping (EMCM) method was implemented to reconstruct the deformed doses on the planning CT using the pseudo-inverse DVFs. The doses reconstructed by the two methods were compared to verify the accuracy of dose accumulation in PreciseART. The doses reconstructed by EMCM and PreciseART were converted to energy using the mass densities of the daily MV-CT and planning kV-CT, respectively. Energy distributions derived from the planned, delivered, and reconstructed doses were compared with each other to detect potential DVF errors, mass changes or imaging artifacts in each organ. The program was tested with the data acquired from three tomotherapy patients.

Results: The dose and energy reconstructed by PreciseART and Hertz were compared within six representative structures. The dose difference averaged over all the structures is 2.7±1.7% and energy difference is 5.4±0.8%. Compared to the energy on the daily images, the reconstructed energy on the planning images changed by 4.1±0.4% for Hertz and 8.4±4.0% for PreciseART.

Conclusion: An independent dose reconstruction program has been developed to verify dose accumulations in PreciseART. This program may also help calculate energy distributions within each organ for root cause analysis.

Funding Support, Disclosures, and Conflict of Interest: This project was funded in part by NIH/NIBIB R01-EB028324.

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Keywords

Not Applicable / None Entered.

Taxonomy

TH- External Beam- Photons: tomotherapy

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