Imaging Performance of the Onboard Kilo-Voltage Fan-Beam Computed Tomography for Ring Gantry Therapy Unit
G Gibbard, J Tan, Y Park, M Lin, K Wang, W Lu, R Reynolds, A Godley, A Pompos, S Jiang, B Cai*, T Zhuang, University of Texas Southwestern Medical Center, Dallas, TX
Presentations
PO-GePV-M-155 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
ePoster Forums
Purpose: This study aims to evaluate the performance of the kV Fan-Beam Computed Tomography (kV-FBCT) system on the RefleXion® X1 by use of standard image quality metrics. The RefleXion X1 is a novel ring-gantry radiotherapy platform that incorporates kV-FBCT and on-board PET for image guided radiotherapy (IGRT) and Biology-guided Radiotherapy.
Methods: Images of a physical phantom (Catphan 604, The Phantom Laboratory, New York, NY) were acquired using two different imaging protocols of 120 kV/1.25 mm with 0.5 pitch/150 mA (medium dose medium couch noted as MM) or 0.2222 pitch/133 mA (high dose slow couch noted as HS), respectively. Images were reconstructed in a 512x512 grid with 50 cm field-of-view. Image quality metrics, including slice thickness accuracy, spatial resolution, low-contrast resolution, geometric accuracy, CT Hounsfield unit (HU) number accuracy, and image uniformity, were evaluated.
Results: For both medium dose and high dose protocols, the spatial resolution is 6 lp/cm; the slice thickness is within 0.1 mm of expected; the geometric accuracy tests passed within 0.5 mm at a 50 mm distance; the image uniformity is within 2.8 HU; the CT numbers are within expected range for most inserts, except for “air”,”teflon”, and “bone 50%”. The CT number for “bone 50%” is outside the expected range by less than 15 HU. The low contrast visibility is higher with high dose mode. The diameter of the smallest visible target in the 1% contrast group is about 3 mm and 4mm in the HS and MM protocols respectively.
Conclusion: All major image quality metrics were within vendor-recommended tolerances for both MM and HS protocols. The onboard kV-FBCT system on the RefleXion X1 meets specifications for clinical implementation of IGRT.
Funding Support, Disclosures, and Conflict of Interest: This work is partially supported by a grant from RefleXion Medical, Inc.
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