Mr. Jayasai R. Rajagopal Profile

Jayasai R. Rajagopal

Postdoctoral Research Associate

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Publications (8)

Proceedings Article | 15 February 2021 Poster + Presentation + Paper

Multivariate SNR in spectral computed tomography

Jayasai Rajagopal, Faraz Farhadi, Ayele Negussie, Ehsan Abadi, Pooyan Sahbaee, Babak Saboury, Ashkan Malayeri, William Pritchard, Elizabeth Jones, Ehsan Samei

Proceedings Volume 11595, 115954I (2021) https://doi.org/10.1117/12.2581079

KEYWORDS: Signal to noise ratio, Spectral computed tomography, CT reconstruction, Iodine, Scanners, Photons, Matrices, Computing systems, Computed tomography

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Proceedings Article | 15 February 2021 Poster + Presentation + Paper

An experimental evaluation of material separability in photon-counting CT

Jayasai Rajagopal, Faraz Farhadi, Ayele Negussie, Ehsan Abadi, Pooyan Sahbaee, Babak Saboury, Ashkan Malayeri, William Pritchard, Elizabeth Jones, Ehsan Samei

Proceedings Volume 11595, 115954K (2021) https://doi.org/10.1117/12.2581081

KEYWORDS: Scanners, Mahalanobis distance, Iodine, Gadolinium, Receivers, Photon counting, Computed tomography

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Proceedings Article | 16 March 2020 Paper

Optimization of energy thresholds in photon-counting CT via a virtual clinical trial

Ehsan Abadi, Jayasai Rajagopal, Thomas Sauer, Elizabeth Jones, W. Paul Segars, Ehsan Samei

Proceedings Volume 11312, 113121Y (2020) https://doi.org/10.1117/12.2549055

KEYWORDS: Sensors, Liver, Tumor growth modeling, Image quality, Clinical trials, Photons, Aorta, Monte Carlo methods, X-ray computed tomography, Photodetectors

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In photon-counting CT, detector energy thresholds directly affect image quality attributes such as contrast and noise. The purpose of this study was to identify optimum energy thresholds using a comprehensive virtual clinical trial platform. The virtual trial was done using a computational, anthropomorphic phantom and a photon-counting CT simulator. The phantom (adult male, 50^th percentile body mass index) was chosen from the library of extended cardiac-torso (XCAT) phantoms. A vessel growth algorithm was used to model detailed hepatic arteries within the liver. Five computational lesions were inserted to the liver. The phantom was “imaged” with iodinated contrast at three contrast phases, i.e. arterial, portal venous, and delayed phases. All virtual sinograms were simulated using a validated CT simulator (DukeSim) modeling a prototype photon-counting scanner (CounT, Siemens Healthcare). The simulator included an energy- and threshold-dependent detector model accounting for X-ray and electronic effects and noise. At each contrast phase, the phantom was imaged at 35 detector energy threshold combinations with five lower-energy thresholds (20-40 keV) and seven upper-energy thresholds (50-80 keV). For each scan, two “threshold” images (photons detected beyond a threshold) and one “bin” image (photons detected between the two thresholds) were acquired. Noise magnitude, image contrast, and contrast-to-noise ratio (CNR) were measured in the aorta and the liver lesions. Optimum energy thresholds were identified as those yielding higher CNRs. From the simulations, noise magnitude was found to increase and CNR decrease with the increase in energy thresholds. Keeping the low threshold constant, the noise decreased and CNR increased with the increase in the upper energy threshold. Therefore, our results suggest that a combination of a lower threshold at 20-30 keV and upper threshold at 80 keV maximize the image quality. This study demonstrates an application of a virtual trial platform to quantify and optimize the quality of photon-counting CT.

Proceedings Article | 1 March 2019 Paper

A framework for realistic virtual clinical trials in photon counting computed tomography

Ehsan Abadi, Brian Harrawood, Jayasai Rajagopal, Shobhit Sharma, Anuj Kapadia, Martin Sedlmair, Juan Carlos Ramirez, Karl Stierstorfer, W. Paul Segars, Ehsan Samei

Proceedings Volume 10948, 109484F (2019) https://doi.org/10.1117/12.2512898

KEYWORDS: Monte Carlo methods, Photon counting, Computed tomography, Clinical trials, Scanners, Medicine, Computer simulations

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Proceedings Article | 1 March 2019 Paper

Image quality in photon-counting CT images as a function of energy threshold

Jayasai Rajagopal, Elizabeth Jones, Ehsan Samei

Proceedings Volume 10948, 109484M (2019) https://doi.org/10.1117/12.2512957

KEYWORDS: Photon counting, Image quality, Computed tomography, Image resolution, X-ray computed tomography, Radiology

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Proceedings Article | 1 March 2019 Paper

Impact of energy threshold on material quantification of contrast agents in photon-counting CT

Jayasai Rajagopal, Pooyan Sahbaee, Ehsan Abadi, Ayele Negussie, William Pritchard, Brad Wood, Elizabeth Jones, Ehsan Samei

Proceedings Volume 10948, 109484N (2019) https://doi.org/10.1117/12.2512944

KEYWORDS: Photon counting, Iodine, Gadolinium, Bismuth, X-ray computed tomography, Computed tomography, Radiology

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Proceedings Article | 1 March 2019 Paper

Accuracy and variability of radiomics in photon-counting CT: texture features and lung lesion morphology

Jayasai Rajagopal, Jocelyn Hoye, Marthony Robins, Elizabeth Jones, Ehsan Samei

Proceedings Volume 10948, 109484J (2019) https://doi.org/10.1117/12.2512934

KEYWORDS: Photon counting, Computed tomography, Lung, Imaging systems, X-ray computed tomography, Radiology

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Proceedings Article | 9 March 2018 Presentation + Paper

Evaluation of statistical breast phantoms with higher resolution

Jayasai Rajagopal, Gregory Sturgeon, Xinyuan Chen, Thomas Sauer, Yinhao Ren, W. Segars, Joseph Lo

Proceedings Volume 10573, 1057307 (2018) https://doi.org/10.1117/12.2294049

KEYWORDS: Breast, Principal component analysis

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Showing 5 of 8 publications

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