Ms. Sarah Aubert Profile

Sarah Aubert

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Proceedings Article | 1 April 2024 Presentation + Paper

Jesse Tanguay, Kaitlyn Sims, Sarah Aubert

Proceedings Volume 12925, 129250R (2024) https://doi.org/10.1117/12.3005975

KEYWORDS: Iodine, Angiography, X-rays, Denoising, X-ray detectors, X-ray imaging, Photon counting, Signal processing for photon counting

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Single-exposure, dual-energy x-ray angiography using photon-counting x-ray detectors is a potential alternative to kV-switching dual-energy angiography and digital subtraction angiography (DSA), but is unable to simultaneously suppress anatomic noise from soft tissue and bone. Triple-energy, photon-counting angiography that counts photons in three energy bins during a single x-ray exposure would overcome this limitation but high quantum noise levels compromise image quality. We extended anti-correlated noise reduction (ACNR) for dual-energy angiography to triple-energy photon-counting angiography and evaluated the resulting improvement in iodine signal-difference-to-noise ratio (SDNR). We implemented triple-energy photon-counting imaging of iodine using a cadmium-telluride, photon-counting x-ray detector with analog charge summing for charge-sharing correction. We imaged a phantom consisting of vessel-like structures with diameters of 3mm, 4mm and 5mm embedded in background clutter. The vessels were filled with an iodine solution containing 100mg/ml of iodine. We acquired images at 60kV, 80kV and 100kV using energy thresholds that theoretically maximized SDNR per root entrance air kerma without ACNR. For each tube voltage, we simulated three energy bins by acquiring two separate exposures using two different sets of energy thresholds. The triple-energy images with ACNR had SDNR that was approximately 7.5 times greater than those without. Further increases in ACNR are expected with optimization of tube voltage and energy thresholds in the presence of ACNR. Future work will focus on optimization and frequency-dependent image-quality assessment.

Proceedings Article | 15 February 2021 Poster + Presentation + Paper

Theoretical comparison of energy-resolved and temporal-subtraction angiography

Sarah Aubert, Michael Belli, Jesse Tanguay

Proceedings Volume 11595, 115954J (2021) https://doi.org/10.1117/12.2582010

KEYWORDS: Signal to noise ratio, Angiography, X-ray detectors, Iodine, Data modeling, Spectroscopy, Zinc, X-rays, Systems modeling

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Energy-resolving x-ray detectors may enable producing iodine-specific images of the coronary arteries without the presence of motion artifacts. We refer to this approach as energy-resolved angiography (ERA), which uses basis material decomposition to produce iodine-specific images. We compared the theoretical iodine pixel signal-to- noise ratio (SNR) and the zero-frequency SNR of ERA with that of conventional digital subtraction angiography (DSA), the latter of which produces iodine-specific images by subtracting images acquired before and after iodine injection. For both ERA and DSA, we modeled iodine SNR with and without the response of realistic x-ray detectors. For ERA, we used a validated model of the energy response of a cadmium zinc telluride (CZT) spectroscopic x-ray detector to account for spectral degradation and spatio-energetic cross talk due to charge sharing. For DSA, we modeled the response of a cesium-iodine (CsI)-based detector and validated our model by comparison with published data. Incorporating a realistic energy response for spectroscopic x-ray detectors decreased the pixel SNR and zero-frequency SNR by greater than a factor of two. In the case of DSA, optical blur in the scintillator increased iodine SNR relative to ideal systems, a result attributable to reduced high-frequency noise in the presence of optical blur. Our results suggest that, for the same patient x-ray exposure, the pixel SNR and zero-frequency SNR of ERA will be ~1/6 and ~1/3 of that DSA, respectively.

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