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Dual Energy CT Protocol Optimization for Increased Blood Detectability of Virtual Non-Contrast Images in a Single Source Dual Energy CT System: A Phantom Study

C Olguin*, S Leon, I Barreto, R De Jesus, M Arreola, University of Florida College of Medicine, Gainesville, FL

Presentations

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

Room: AAPM ePoster Library

Purpose: To optimize the dual energy CT stroke protocol to increase blood detectability in stroke patients. Dual Energy CT (DECT) differentiates between residual iodinated contrast and hemorrhagic blood; however, by optimizing the protocol to brain specific tissues, microhemorrhage detectability may improve.

Methods: A multi-energy CT phantom with stroke-mimicking materials was scanned in a single source sequential DECT scanner. To create iodine and virtual non-contrast (VNC) images, the input of two virtual monochromatic images (VMI) with equivalent 135-kVp and 80-kVp soft tissue Hounsfield Units (HU) is required. VMIs were reconstructed over a range of 35-135 keVs. By least squares optimization, soft tissue equivalent VMIs were identified. The iodine contrast slope was measured for the optimized VMIs. General adipose tissue and grey matter HUs were measured in the VMIs to create an optimized stroke protocol. Iodine and VNC images were reconstructed with the vendor-recommended and the newly-optimized settings. The enhancement of inserts mimicking iodine, acute and chronic blood was measured in iodine maps and VNCs using both settings.

Results: The optimized VMIs were identified as 71 keV and 57 keV, whereas the vendor-recommended VMIs were 66 keV and 52 keV. The optimized VMI contrast slope changed from 0.55 to 0.60. Iodine enhancement on the new iodine map decreased on average by 20 HU, but the sensitivity limit of 0.2 mg I/mL remained detectable (7.84 HU). Chronic blood enhanced on the iodine map using vendor-recommended settings but did not enhance with the new settings (4.80 HU and 0 HU, respectively). Acute and chronic blood HU increased in the new VNC by 2.94 and 11.71 HU, respectively.

Conclusion: DE CT vendor-recommended stroke protocols may need optimization for specific clinical tasks such as for microhemorrhage detection. This phantom study optimized the stroke protocol and increased blood enhancement in the VNC.

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Funding Support, Disclosures, and Conflict of Interest: Funding provided by Canon Medical Systems to the radiology's department's budget. Grant money funded partial PhD student's tuition costs at the University of Florida. No co-author directly received payment for this work. No conflicts of interest to disclose.

Keywords

Dual-energy Imaging, Optimization, Stroke

Taxonomy

IM- CT: Dual Energy and Spectral

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