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Improved Single-Scan Dual-Energy CT Using Primary Modulation

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M Petrongolo

M Petrongolo1*, L Zhu2, (1) Yale-New Haven Hospital, New Haven, CT, (2) Georgia Institute of Technology, Atlanta, GA


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

Purpose: Compared with conventional CT, dual energy CT (DECT) provides better material differentiation but requires projection data with two different effective x-ray spectra. Current DECT scanners use either two-scan settings or costly imaging components, which are not feasible or available on open-gantry cone-beam CT systems. We propose a hardware-based method (PM-DECT) which utilizes primary modulation to enable single-scan DECT on a conventional CT scanner. Improvements to the modulator design and image reconstruction algorithm have enhanced PM-DECT’s capabilities while retaining the possibility for future combination with effective scatter correction on the same CT scanner.

Methods: We insert an attenuation sheet with a spatially-varying pattern -primary modulator- between the x-ray source and the imaged object. During the CT scan, the modulator selectively hardens the x-ray beam at specific detector locations. Thus, PM-DECT simultaneously acquires high and low energy data. From the sparse projection data, high and low energy CT images are jointly reconstructed and simultaneously decomposed into basis materials via an iterative reconstruction algorithm with gradient weighting. PM-DECT’s performance is assessed using Catphan© 600 and anthropomorphic head phantoms. Electron density calculations are used to quantify its decomposition accuracy.

Results: Results on the Catphan© phantom indicate improved image quality compared to previously presented preliminary studies. PM-DECT retains spatial resolution rivaling that of a conventional CT scan and limits electron density error to 1.1%. Head phantom images show retention of fine, intricate structures. By applying correction algorithms and using all of the acquired projection data, we can also reconstruct a single-energy CT image of comparable quality to conventional CT images.

Conclusion: This work shows great promise in using a primary modulator to perform high-quality single-scan DECT imaging. Future studies will focus on combining PM-DECT with scatter correction via primary modulation during a single cone-beam CT scan.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH Grant no. R21EB019597.

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