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Technical Assessment of Dose and 3D Imaging Performance for a New Mobile Isocentric C-Arm for Intraoperative Cone-Beam CT

N Sheth1*, T De Silva1 , A Uneri1 , M Ketcha1 , R Han1 , R Vijayan1 , G Kleinszig2 , S Vogt2 , J Siewerdsen1 , (1) Johns Hopkins University, Baltimore, MD, (2) Siemens Healthineers, Erlangen, Germany


(Sunday, 7/14/2019) 1:00 PM - 2:00 PM

Room: 304ABC

Purpose: To characterize the dose and 3D imaging performance of a recently FDA-approved mobile isocentric C-arm equipped with a flat-panel detector (FPD) for intraoperative cone-beam CT (CBCT) (Cios Spin 3D, Siemens Healthineers) and identify potential improvements to imaging protocols for pertinent imaging tasks.

Methods: The C-arm features a 30 x 30 cm² FPD and isocentric gantry (116.4 cm source-detector distance) with computer-controlled motion of rotation (0-195°), angulation (±220°), and height (0-45 cm). Standard and custom scan protocols were evaluated in quantitative phantom studies, including variation of number of projections (100-400) and exposure (3-22 mAs). Image reconstruction was based on 3D filtered backprojection with smooth, standard, and sharp reconstruction filters. A new QA phantom designed specifically for CBCT physics testing was used to evaluate uniformity, linearity, contrast, noise (noise-power spectrum, NPS), and spatial resolution (modulation transfer function, MTF), and noise-equivalent quanta (NEQ). Radiation dose was measured for each protocol in terms of the weighted central and peripheral absorbed dose (air kerma, Dw).

Results: The dose (Dw) varied with imaging protocol from ~1-5 mGy (~0.17 mGy/mAs) for head scan protocols to ~6-37 mGy (~0.05 mGy/mAs) for body scan protocols. The axial MTF was consistent with sub-mm resolution, with f�₀ (frequency at 10% modulation) of 0.64 mm�¹, 1.0 mm�¹, and 1.5 mm�¹ for smooth, standard, and sharp filters, respectively. The NPS and NEQ exhibited expected 3D spatial-frequency dependence and provided a guide to selection of technique protocols according to pertinent clinical imaging tasks (e.g., visualization of bone architecture, find instrumentation, or soft-tissue boundaries).

Conclusion: The studies provided objective assessment of the dose and 3D imaging performance of this newly released C-arm, offering an important basis for technique selection, and a benchmark for QA.

Funding Support, Disclosures, and Conflict of Interest: The research was supported by academic industry partnership with Siemens Healthineers (Erlangen, Germany). Gerhard Kleinszig and Sebastian Vogt are employees of Siemens Healthineers.


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