An experimental evaluation of material separability in photon-counting CT

Jayasai R. Rajagopal; Faraz Farhadi; Ayele H. Negussie; Ehsan Abadi; Pooyan Sahbaee; Babak Saboury; Ashkan A. Malayeri; William F. Pritchard; Elizabeth C. Jones; Ehsan Samei

doi:10.1117/12.2581081

15 February 2021 An experimental evaluation of material separability in photon-counting CT

Jayasai R. Rajagopal, Faraz Farhadi, Ayele H. Negussie, Ehsan Abadi, Pooyan Sahbaee, Babak Saboury, Ashkan A. Malayeri, William F. Pritchard, Elizabeth C. Jones, Ehsan Samei

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Proceedings Volume 11595, Medical Imaging 2021: Physics of Medical Imaging; 115954K (2021) https://doi.org/10.1117/12.2581081
Event: SPIE Medical Imaging, 2021, Online Only

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Abstract

Signal separability is an important factor in the differentiation of materials in spectral computed tomography. In this work, we evaluated the separability of two such materials, iodine and gadolinium with k-edges of 33.1 keV and 50.2 keV, respectively, with an investigational photon-counting CT scanner (Siemens, Germany). A 20 cm water equivalent phantom containing vials of iodine and gadolinium was imaged. Two datasets were generated by either varying the amount of contrast (iodine – 0.125-10 mg/mL, gadolinium 0.125-12 mg/mL) or by varying the tube current (50-300 mAs). Regions of interest were drawn within vials and then used to construct multivariate Gaussian models of signal. We evaluated three separation metrics using the Gaussian models: the area under the curve (AUC) of the receiver operating characteristic curve, the mean Mahalanobis distance, and the Jaccard index. For the dataset with varying contrast, all three metrics showed similar trends by indicating a higher separability when there was a large difference in signal magnitude between iodine and gadolinium. For the dataset with varying tube current, AUC showed the least variation due to change in noise condition and had a higher coefficient of determination (0.99, 0.97) than either mean Mahalanobis distance (0.69, 0.62) or Jaccard index (0.80, 0.75) when compared to material decomposition results for iodine or gadolinium respectively.

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Jayasai R. Rajagopal, Faraz Farhadi, Ayele H. Negussie, Ehsan Abadi, Pooyan Sahbaee, Babak Saboury, Ashkan A. Malayeri, William F. Pritchard, Elizabeth C. Jones, and Ehsan Samei "An experimental evaluation of material separability in photon-counting CT", Proc. SPIE 11595, Medical Imaging 2021: Physics of Medical Imaging, 115954K (15 February 2021); https://doi.org/10.1117/12.2581081

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