Dr. Michael C. Soulen Profile

Dr. Michael C. Soulen

at Univ of Pennsylvania

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Publications (3)

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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.

Proceedings Article | 18 October 2022 Open Access

Non-invasive real-time thermometry via spectral CT physical density quantifications

Nadav Shapira, Leening Liu, Rizza Pua, Derick Rosario, Johoon Kim, David Cormode, Gregory Nadolski, Matthew Hung, Michael Soulen, Peter Noël

Proceedings Volume 12304, 1230404 (2022) https://doi.org/10.1117/12.2647018

KEYWORDS: Thermometry, Computed tomography, Liver, Liver cancer, X-rays

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Efficient removal of solid focal tumors is a major challenge in modern medicine. Percutaneous thermal ablation is a first-line treatment for patients not fit for surgical resection or when the disease burden is low, mainly due to expedited patient recovery times, lower rates of post-operative morbidity, and reduced healthcare costs. While continuously gaining popularity, ~100,000 yearly thermal hepatic ablation procedures are currently performed without actively monitoring temperature distributions, leading to high rates of incomplete ablations, local recurrences, and damage to surrounding structures. Recent advancements in computed tomography (CT), especially spectral CT, provide promising opportunities for lowering these rates. The additional information available with spectral CT can provide the necessary capabilities to achieve accurate, reliable, on-demand, and non-invasive thermometry during ablation procedures. By taking advantage of our newly developed spectral physical density maps and their direct relation with temperature changes, we performed experiments on phantoms and ex vivo tissue to develop, evaluate, optimize, and refine a method for generating thermometry maps from spectral CT scans. Our results validate the accuracy of the spectral physical density model, allowing “whole-organ” mass quantifications that are accurate within one percent, as well as demonstrate an ability to extract temperature changes (linear correlation coefficient of 0.9781) non-invasively and in real-time.

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Proceedings Article | 4 April 2022 Presentation + Paper

Real-time spectral CT thermometry via physical density for image-guided tumor ablation

Leening Liu, Matthew Hung, Michael Soulen, Peter Noël, Nadav Shapira

Proceedings Volume 12031, 120311B (2022) https://doi.org/10.1117/12.2608743

KEYWORDS: Temperature metrology, Thermometry, Tissues, Computed tomography, Tumors, Safety, X-ray computed tomography

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Hepatocellular carcinoma, the fastest rising cause of cancer-related deaths, is commonly treated with percutaneous ablative therapies where tumor cells are destroyed once tissue temperatures reach a lethal threshold. However, high progression and recurrence rates post ablation suggest the need for intraprocedural temperature monitoring to ensure the lethal threshold (>60°C) is reached and a sufficient safety margin is obtained. A previously developed model generates physical density maps from spectral CT data. These spectral physical density quantifications enable thermometry by taking advantage of the thermal volumetric expansion equation that relates the change in temperature to physical density changes. To validate the physical density model, an ex vivo bovine muscle was weighed and scanned on a clinical spectral CT scanner with different scanning parameter combinations (collimation, dose, helical/axial scans). Calculated mass from physical density maps and volume demonstrated high accuracy with a maximum percent error of 0.34% (<1.1 grams for a345 gram sample) and minimal effects of scanning parameters. After validating the accuracy of the physical density maps, the muscle was subjected to heating and cooling while scanning to evaluate the relationship between physical density and temperature. Spectral results were continuously generated to calculate physical density maps at different temperatures. A linear relationship between change in temperature and change in physical density was established with strong correlation (R = 0.9781). The reflection of thermal volumetric expansion in physical density quantifications indicate its potential utility for providing real-time temperature feedback to interventional radiologists during ablative procedures for not only hepatocellular carcinoma, but also other types of malignancies.

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