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Optimization of Calcium Inserts for Quality Assurance of Calcium Removal in Dual Energy Computed Tomography

M Lawless1*, L Di Maso1 , J Huang1 , K Ruchala4 , J Miller1 , (1) University of Wisconsin-Madison, Madison, WI, (4) GAMMEX Inc., Madison, WI


(Tuesday, 7/16/2019) 3:45 PM - 4:15 PM

Room: Exhibit Hall | Forum 9

Purpose: To develop calcium inserts that produce accurate results when performing calcium removal on a single-source dual-energy CT (ssDECT) scanner.

Methods: The TwinBeam(TB) and Dual Spiral(DS) ssDECT techniques on the Siemens SOMATOM Definition Edge CT scanner were used to acquire images of the Gammex Multi-Energy CT Phantom containing inserts with concentrations ranging from 0–300 mgCa/ml. The Syngo.via software was used to remove the calcium from the images via material decomposition, which resulted in virtual non-calcium (VNCa) and calcium images for each acquisition technique. Calcium removal was performed using basis pairs of fat/tissue (the default setting) and fat/CB2 plastic. The process was repeated with optimized inserts developed with the manufacturer in which the calcium was mixed with a plastic that has an effective atomic number similar to that of tissue in order to facilitate the use of a fat/tissue basis pair.

Results: For the DS and TB acquisitions of the original inserts, using a basis pair of fat/CB2 resulted in lower residual calcium concentrations in the VNCa image compared to using a fat/tissue basis pair(p(DS)<0.0001, p(TB)=0.0021). In the DS and TB VNCa images of the optimized inserts, the use of a fat/tissue basis pair produced residual calcium concentrations lower than those obtained with the original inserts(p(DS)=0.0015, p(TB)=0.0009).

Conclusion: The choice of basis pair materials in material decomposition can impact the resulting VNCa and calcium images. Using a fat/tissue basis pair yielded incorrect residual calcium concentrations when used on the original calcium inserts of the MECT phantom. This issue was remedied by using a fat/CB2 basis pair; however, a better solution was the creation of optimized inserts, which resulted in accurate identification of calcium while using a fat/tissue basis pair. These inserts allow users to perform QA in a phantom while using the same fat/tissue basis pair that is used clinically.

Funding Support, Disclosures, and Conflict of Interest: Kenneth Ruchala is an employee of Gammex Inc.


Dual-energy Imaging, CT, Phantoms


IM- CT: Dual Energy and Spectral

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