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Inverse-Geometry CT with a Rotating C-Arm: Implementation On the Scanning Beam Digital X-Ray System

J Slagowski

J Slagowski*, M Speidel , University of Wisconsin - Madison, Madison, WI


MO-AB-FS4-5 (Monday, July 31, 2017) 7:30 AM - 9:30 AM Room: Four Seasons 4

Purpose: To present the first inverse geometry CT (IGCT) results generated by rotation of a C-arm mounted multisource x-ray tube and photon-counting detector array.

Methods: Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system that consists of a C-arm mounted multisource x-ray tube and photon-counting detector. A single-view geometric calibration technique was developed to enable C-arm IGCT. CT projection data were acquired by performing simultaneous source scanning and C-arm rotation over a 190 degree short-scan arc in 13 seconds. Image reconstruction was performed using a gridded filtered backprojection algorithm adapted for the SBDX geometry and extended for object truncation. An anthropomorphic thorax phantom containing a high contrast atrium was imaged at 100 kVp and tube currents from 20-100 mAp (9.5-47.6% full power) to evaluate SBDX-CT for cardiac chamber mapping during interventional procedures. The atrium was segmented and compared to a helical CT scan. A histogram of point distances between the reconstructed and reference surfaces was computed and the 99ᵗʰ percentile distance was used as a metric of segmentation accuracy. The modulation transfer function (MTF) was measured using a stainless-steel wire to evaluate spatial resolution. A water cylinder was imaged to assess image artifacts and response uniformity.

Results: Images of the anthropomorphic thorax phantom were successfully reconstructed. For imaging at 100 kVp, 60 mAp, 99% of the segmented atrium surface points were within 2.8 mm of the reference scan. The Sorensen-Dice coefficient was 0.90. The MTF was 11.1 cm⁻¹ at 10% with reconstruction parameters optimized for cardiac chamber segmentation. The MTF measured 17.3 cm⁻¹ at 10% with parameters adjusted to improve spatial resolution. Differences in regions-of-interest at the center and periphery of the water cylinder measured 1 HU.

Conclusion: IGCT data acquisition and reconstruction has been demonstrated using C-arm rotation of a multisource x-ray tube and detector.

Funding Support, Disclosures, and Conflict of Interest: Financial support provided by NIH Grant No. R01 HL084022.

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