Ms. Olivia F. Sandvold Profile

Olivia F. Sandvold

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Proceedings Article | 6 May 2024 Poster + Paper

PixelPrint: generating patient-specific phantoms for spectral CT using dual filament 3D printing

Pouyan Pasyar, Jessica Im, Kai Mei, Leening Liu, Olivia Sandvold, Michael Geagan, Peter Noël

Proceedings Volume 12925, 1292527 (2024) https://doi.org/10.1117/12.3006512

KEYWORDS: Metals, 3D printing, Printing, Computed tomography, Scanners, Bone, Tissues, Medical imaging, Matrices, Image restoration

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In recent years, the importance of spectral CT scanners in clinical settings has significantly increased, necessitating the development of phantoms with spectral capabilities. This study introduces a dual-filament 3D printing technique for the fabrication of multi-material phantoms suitable for spectral CT, focusing particularly on creating realistic phantoms with orthopedic implants to mimic metal artifacts. Previously, we developed PixelPrint for creating patient-specific lung phantoms that accurately replicate lung properties through precise attenuation profiles and textures. This research extends PixelPrint's utility by incorporating a dual-filament printing approach, which merges materials such as calcium-doped Polylactic Acid (PLA) and metal-doped PLA, to emulate both soft tissue and bone, as well as orthopedic implants. The PixelPrint dual-filament technique utilizes an interleaved approach for material usage, whereby alternating lines of calcium-doped and metal-doped PLA are laid down. The development of specialized filament extruders and deposition mechanisms in this study allows for controlled layering of materials. The effectiveness of this technique was evaluated using various phantom types, including one with a dual filament orthopedic implant and another based on a human knee CT scan with a medical implant. Spectral CT scanner results demonstrated a high degree of similarity between the phantoms and the original patient scans in terms of texture, density, and the creation of realistic metal artifacts. The PixelPrint technology's ability to produce multi-material, lifelike phantoms present new opportunities for evaluating and developing metal artifact reduction (MAR) algorithms and strategies.

Proceedings Article | 1 April 2024 Presentation + Paper

Hybrid spectral CT system with clinical rapid kVp-switching x-ray tube and dual-layer detector for improved iodine quantification

Olivia Sandvold, Roland Proksa, Heiner Daerr, Amy Perkins, Kevin Brown, Nadav Shapira, Thomas Koehler, J. Webster Stayman, Grace Gang, Ravindra Manjeshwar, Peter Noël

Proceedings Volume 12925, 129251K (2024) https://doi.org/10.1117/12.3006451

KEYWORDS: Iodine, X-rays, X-ray computed tomography, Imaging systems

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Spectral computed tomography (CT) is a powerful diagnostic tool offering quantitative material decomposition results that enhance clinical imaging by providing physiologic and functional insights. Iodine, a widely used contrast agent, improves visualization in various clinical contexts. However, accurately detecting low-concentration iodine presents challenges in spectral CT systems, particularly crucial for conditions like pancreatic cancer assessment. In this study, we present preliminary results from our hybrid spectral CT instrumentation which includes clinical-grade hardware (rapid kVp-switching x-ray tube, dual-layer detector). This combination expands spectral datasets from two to four channels, wherein we hypothesize improved quantification accuracy for low-dose and low-iodine concentration cases. We modulate the system duty cycle to evaluate its impact on quantification noise and bias. We evaluate iodine quantification performance by comparing two hybrid weighting strategies alongside rapid kVp-switching. This evaluation is performed with a polyamide phantom containing seven iodine inserts ranging from 0.5 to 20mg/mL. In comparison to alternative methodologies, the maximum separation configuration, incorporating data from both the 80kVp, low photon energy detector layer and the 140kVp, high photon energy detector layer produces spectral images containing low quantitative noise and bias. This study presents initial evaluations on a hybrid spectral CT system, leveraging clinical hardware to demonstrate the potential for enhanced precision and sensitivity in spectral imaging. This research holds promise for advancing spectral CT imaging performance across diverse clinical scenarios.

Proceedings Article | 7 April 2023 Presentation + Paper

Spectral CT thermometry with improved temperature sensitivity for image-guided thermal ablation

Leening Liu, Rizza Pua, Derick Rosario-Berrios, Olivia Sandvold, Kevin Brown, Grace Gang, Michael Soulen, Nadav Shapira, Peter Noël

Proceedings Volume 12463, 124630P (2023) https://doi.org/10.1117/12.2649111

KEYWORDS: Denoising, Thermometry, Ablation, Computed tomography, Tumors

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Percutaneous ablation procedures have been increasingly utilized to non-invasively treat tumors, such as hepatocellular carcinoma, by heating tumor cells beyond the lethal threshold. Intraprocedural temperature monitoring via spectral CT thermometry with a sensitivity less than 3 °C can reduce local recurrence rates by ensuring the tumor and its surrounding safety margin reach lethal temperatures. Because temperature sensitivity is reliant on noise, the effect of additional denoising, radiation dose, slice thickness, and iterative reconstruction levels on temperature sensitivity was evaluated on physical density slices utilized to generate temperature maps. Three different denoising algorithms (total variation, bilateral filtering, and non-local means) were applied to input images prior to generating physical density maps. Differences in noise in physical density and temperature sensitivity were calculated for each combination of parameters. All three denoising algorithms did not significantly affect quantification with an average difference of 1 x 10^-4 g/mL from standard reconstructions, while generally non-local means denoising performed best with noise decreasing to 2 x 10^-4 g/mL. The reduction in noise corresponded to temperature sensitivity decreasing from 15 ± 4 °C with standard reconstructions to 3 ± 2 °C with non-local means denoising at 2 mGy with 2 mm slices. Overall, temperature sensitivity at low radiation doses improved to clinically satisfactory levels with additional denoising. These accurate temperature maps from spectral CT thermometry will enable real-time, non-invasive temperature monitoring to ensure critical structures are not thermally damaged and the entire tumor and safety margin reach the lethal threshold, reducing local recurrences.

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