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  4. Detecting Iodine Enhancement with Dual-Energy Computed Tomography: How Low Can We Go?

Detecting Iodine Enhancement with Dual-Energy Computed Tomography: How Low Can We Go?

M Jacobsen1,2*, E Cressman1 , X Duan3 , D Cody1 , D Schellingerhout1 , R Layman1 , (1) University of Texas MD Anderson Cancer Center, Houston, TX (2) University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX (3) UT Southwestern Medical Center, Dallas, TX

Presentations

(Thursday, 8/2/2018) 7:30 AM - 9:30 AM

Room: Room 202

Purpose: Multiple studies have proposed diagnostic thresholds based on Dual-Energy Computed Tomography (DECT) iodine maps. However, it is critical to determine the minimum detectable iodine concentration for DECT systems to establish the clinical significance of various measured quantities for these image types.

Methods: Seven serial dilutions of iohexol were made with concentrations from 0.03 to 2.0 mg Iodine/mL in 50 mL centrifuge tubes. The dilutions and one blank with distilled water were scanned five times each in two scatter conditions: a 20.0 cm diameter (Head) phantom and a 30.0 cm x 40.0 cm elliptical (Body) phantom. We utilized six scanners from three vendors, including fast-kVp switching, dual-source, dual-layer detector, and split-filter DECT. Scan parameters and dose were matched as closely as possible across systems, and iodine maps were reconstructed using each vendor’s software. Regions-of-Interest were placed centrally within each vial on the iodine map. Mean and standard deviation were calculated across the five scan acquisitions, and linear calibration curves were calculated for each scanner. Using standard analytical methods, the signal region corresponding to a 95% likelihood of measuring only water was defined as the Limit of Blank (LOB). Subsequently, the Limit of Detection (LOD) in the signal domain was defined as the LOB plus 1.645 times the standard deviation of the 0.5 mg/mL insert and was converted to a concentration using the calibration curves.

Results: The range of LOD was 0.021 – 0.484 mg I/mL in the head phantom and 0.125 – 0.547 mg I/mL in the body phantom. Higher kVp levels on a given system generally performed better than lower kVp settings in the body phantom.

Conclusion: DECT systems available in today’s marketplace can detect iodine concentrations as low as 0.125 mg I/mL in an anthropomorphic body phantom, which corresponds to an enhancement of approximately 3.2 HU at 120-kVp.

Keywords

Dual-energy Imaging, CT, Quantitative Imaging

Taxonomy

IM- CT: Dual Energy and Spectral

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