Program Information
Evaluation of Microwave Ablation Zone Variance Based On Reported Changes in Thermal and Electrical Properties of Tissues
G Deshazer1*, P Prakash2 , M Hagmann3 , D Dupuy1 , D Merck1 ,(1) Rhode Island Hospital, Providence, RI , (2) Kansas State University, Manhattan, Kansas, (3) BSD Medical, Salt Lake City, Utah,
Presentations
SU-E-T-394 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:
Image-guided percutaneous ablation is an, effective, inexpensive, and accessible treatment for liver, lung, and kidney cancers. However, its relatively high recurrence rate makes it more palliative. We hypothesize that higher rates are due in part to inadequate margin estimation, resulting from over-simplified geometric planning. Better predictive planning is needed, however, this requires numerical model accounting for the physical characteristics of heterogeneous tissues around the target. Literature suggests that pathologies such as cirrhosis and malignant tissue have varying thermal and electrical properties when compared to normal tissue. The objective of this study is to employ a simulation based approach to determine the impact of heterogeneous tissue physical properties on treatment outcome.
Methods:
An electromagnetic-thermal finite-element model of the BSD Medical ST antenna was created. The antenna placed inside the center of a tumor that was immersed within liver tissue. The variance of ablation zone sizes with tissue physical properties was evaluated by assigning varying tissue dielectric and thermal properties to the tumor, consistent with data reported in the literature. 10-30 % variations in tissue effective electrical conductivity, and varying perfusion levels for tumor, normal, and cirrhotic liver (3-18 kg/m3/s) were considered. The CEM43 > 240 min threshold was used to estimate ablation zone extents.
Results:
Less than 4 mm variation in ablation zone extents was observed when considering 10-30 % differences in effective electrical conductivity between malignant and normal tissue. Perfusion variations showed the largest difference when compared to homogeneous simulation (~ 4.5 mm - 1.0 cm).
Conclusion:
The results suggest that dielectric inhomogeneities have limited impact on predicted ablation zone extents. However, variances in tumor and normal liver tissue blood perfusion, within the range of clinically measured values reported in the literature, significantly affects predicted ablation zone volumes. Further research investigating the impact of other tissue properties is warranted.
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