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SIR 2025

Interventional Oncology

Scientific Session

Session: AI, Machine Learning, Simulation, and Imaging 2

In Vivo Evaluation of Spectral CT Thermometry for Non-invasive, Real-time Temperature Monitoring of Thermal Ablation

Tuesday, April 1, 2025
3:27 PM – 3:36 PM CT
Location: Music City Center, 202 BC
Purpose: Non-invasive, real-time temperature monitoring for thermal ablation allows for visualization of the temperature distribution for the tumor and ablation margin, helping ensure complete ablation of both the tumor and margin to reduce local tumor recurrences. Spectral CT thermometry detects temperature by relating physical density to temperature through the principle of thermal volumetric expansion, which describes the decrease in physical density with increased temperature. It has demonstrated feasibility, reproducibility, and sufficient temperature sensitivity critical for its clinical translation in liver-mimicking phantoms. This study expands the evaluation of spectral CT thermometry in vivo to further assess its feasibility for temperature monitoring of thermal ablation.

Materials and Methods: Microwave ablation was performed on the liver of a Yorkshire pig at 65 W for 5 minutes. Optical fiber thermometers adjacent to the ablation probe measured “ground truth” temperature during the ablation. Dual-layer dual-energy CT was performed every 30 seconds during the ablation at a tube voltage of 120 kVp. Physical density maps at each time point were calculated using a previously developed spectral physical density model. Physical density was then measured in the liver tissue adjacent to each thermometer, avoiding metal artifacts and air bubbles. To relate physical density to temperature, thermal volumetric expansion was applied as a linear regression between the ratio of the initial physical density to the measured physical density and changes in temperature to evaluate the feasibility of spectral CT thermometry in vivo.

Results: During ablation, overall measured temperatures rose from 36.3 to 81.3 °C, corresponding to a decrease in physical density from 1.058 to 1.031 g/L. At a distance of 2.2 cm from the probe tip (farthest thermometer), the 3.2 °C increase in temperature to 40.1 C resulted in a minimal change in the physical density ratio from 0.999 to 0.997. Conversely, at the closest thermometer, which experienced a temperature increase of 44.8 °C, the physical density ratio increased from 1.008 to 1.025. Overall, the physical density ratio and change in temperature exhibited a strong linear relationship with a Pearson’s correlation coefficient of 0.8785, thus reflecting the principle of thermal volumetric expansion that is the basis of spectral CT thermometry.

Conclusion:

In vivo ablation of a porcine liver demonstrated the feasibility of spectral CT thermometry for non-invasive, real-time temperature monitoring for thermal ablation, spurring its clinical translation.