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Potential Benefits of Photon Counting CT in Cerebral CT Angiography

E Harvey*, R Zhang , X Ji , G Chen , K Li , University of Wisconsin, Madison, WI


(Wednesday, 8/1/2018) 10:15 AM - 12:15 PM

Room: Room 207

Purpose: The aim of this work was to investigate the clinical benefit of a photon counting CT (PCCT) system in cerebral CT angiography (CCTA) imaging. The rationale behind the investigation was that PCCT could improve the image quality of CCTA due to equal weighting applied to the low- and high-energy photons and relaxed tradeoff between image noise and spatial resolution offered by the photon counting detector (PCD).

Methods: The experimental benchtop PCCT system was developed using a 51 cm collinear PCD (CdTe-based, native pixel size 100 µm) and rotating anode angiographic tube (Varian medical System, Palo Alto, CA). A custom angiographic CT head phantom containing contrast-enhanced healthy cerebral artery models (diameters ranging from 0.5 to 4.0 mm) was scanned using the PCCT system and a clinical MDCT system with a clinical CCTA protocol where radiation dose level, detector collimation, kV, in-plane pixel size, and slice thickness were matched between the two CT systems. PCD-CT images were reconstructed with both a standard ramp and a Gaussian-apodized ramp reconstruction kernel. Apodization was applied to match the spatial resolution of the standard reconstruction generated at the MDCT console. CNR was measured at both proximal and distal branches of ICA and MCA, and line profiles of the vessels were compared.

Results: The effective dose of the CCTA scan was 1.23 mSv for both CT systems. With matched spatial resolution, the CNR of the proximal arteries (diameter 4.0 mm) was 44.7±12.2 in the clinical MDCT while the CNR of PCCT-CCTA was 87.5±22 (p=0.0003). For the distal and smaller artery branches (0.5 mm) the CNR was found to be 11.3±6.3 while PCCT provided a higher CNR (17.3±6.1, p=0.013). Line profiles of the vessels confirmed PCCT’s superior image quality compared to MDCT.

Conclusion: This study demonstrated PCCT could potentially improve the image quality of CCTA imaging.


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