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BEST IN PHYSICS (IMAGING): Abdominal CT with Three K-Edge Contrast Materials Using a Whole-Body Photon-Counting Scanner: Initial Results of a Large Animal Experiment

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M Lakshmanan

M Lakshmanan*, R Symons , T Cork , C Davies-Venn , K Rice , A Malayeri , V Sandfort , D Bluemke , A Pourmorteza , National Institutes of Health Clinical Center, Bethesda, MD

Presentations

WE-FG-207B-1 (Wednesday, August 3, 2016) 1:45 PM - 3:45 PM Room: 207B


Purpose:
To demonstrate the feasibility of in vivo three-material decomposition techniques using photon-counting CT (PCCT) with possible advantage of resolving arterial and venous flow of an organ simultaneously.

Methods:
Abdominal PCCT scans were acquired using a prototype whole-body PCCT with four energy thresholds (25/50/75/90keV) in a canine. Bismuth subsalicylate (60 mg) was administered orally one day prior to scanning. Immediately prior to CT scan, gadoteric acid (60 ml, Dotarem, Guerbet) was intravenously injected, followed in ten minutes by a 20mL injection of iodinated contrast (iopamidol 370 mg/mL, Bracco). Scans were acquired every ~20 seconds, starting from the time of iodine injection. Linear material decomposition was performed using the least mean squares method to create concentration maps of iodine, gadolinium, and bismuth. The method was calibrated to vials with known concentrations of materials placed next to the animal. The accuracy of this method was tested on vials with known concentrations.

Results:
The material decomposition algorithm’s accuracy was confirmed to be within ±4mM in the test vials. In the animal, we could estimate the concentration of gadolinium in delayed-enhanced phase (10 minutes post-injection) in the abdomen. We could follow the wash-in and wash-out of iodine in arterial, venous, and excretory flow of the kidneys (20s, 80s, and 120s post-iodine injection) while gadolinium was present in the delayed-enhanced phase. Bismuth, which was used as a contrast agent for the gastro-intestinal tract, was easily differentiable from the other two contrast agents in the small intestine.

Conclusion:
This study shows the feasibility of using photon-counting CT with four energy thresholds to differentiate three k-edge contrast agents in vivo. This can potentially reduce radiation dose to patients by combining arterial and venous phases into a single acquisition.


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