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Intrafraction Imaging: Simultaneous KV Image Acquisition During MV Treatment Delivery to Monitor Patient and Target Motion

L Sensoy1, A Hernandez2, D Hernandez3, D Campos4, Y Rong5, S Benedict6*, (1) UC Davis Medical Center, Sacramento, CA, (2) University of California-Davis, Sacramento, CA, (3) Univ of California, Davis, Sacramento, CA, (4) Allegheny Health Network, Pittsburgh, PA, (5) University of California-Davis, Sacramento, CA, (6) UC Davis Cancer Center, Sacramento, CA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

A Novel Application for Intrafraction Imaging has been developed commercially to provide kV image acquisition during MV delivery, including kV CBCT imaging during VMAT delivery. Demonstration of features of intrafraction imaging are examined, including effects of MV scatter on kV acquisition relative to conventional or SBRT fractionation, motion detection and internal target volume coverage evaluation, and registration and display strategies to assess departures from simulation and initial planning.

Imaging was performed using geometric phantoms (Catphan600), anthropomorphic phantom (Kyoto N1 Multipurpose Lung Phantom), and the lung motion phantom (Quasar Respiratory Motion Phantom). Image quality analysis including noise power spectrum, MTF, and CNR and
HU linearity was performed in accordance with established techniques, and presented in terms of degradation with beam on, dose rate, and motion range induced.

Our studies confirm that simultaneous kV CBCTs may be used to perform image registration for post-treatment ITV verification. Geometric tests, including resolution of line-pairs, and integrity of Hounsfield were minimally affected, with only a low contrast visibility test demonstrating degradation. In this study we also analyze the MV scatter correction that works by acquiring images on the XVI panel when the kV beam is OFF, subtracted out from the kV ON images which then go into reconstruction.

The effects of scatter, motion, dose rate, and kV/mA technique have been assessed for a new commercially available Intrafraction imaging application for simultaneous image acquisition during MV delivery. The results indicate that intrafraction imaging has the potential for substantial clinical utility in the clinical workflow for conventional and SBRT treatments. An IRB approved limited study of Intrafraction Imaging with SBRT lung patients is proposed to evaluate clinical workflow, perform daily assessment of patient positioning and motion, and provide feedback on treatment planning and potentially adaptive planning strategies relative to ITV margins and OAR.


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