Measurement and Analysis of Tissue Temperature During Microwave Liver Ablation

Abstract

We measured tissue temperature changes during ex vivo microwave ablation (MWA) procedures for bovine liver tissue. Tissue temperature increased rapidly at the beginning of the MW power application. It came to a plateau at 100 degrees C to 104 degrees C before it increased again. We split the changes of tissue temperature versus time into four phases. This suggests that tissue temperature changes may be directly related to tissue water related phenomena during MWA, including evaporation, diffusion, condensation and tissue water composition. An additional analysis indicated the lesion boundary at approximately 50 degres C to 60 degrees C temperature. We also measured the water content of ablated tissue lesions and examined the relationship of tissue water content and tissue temperature by mapping temperature to remaining tissue water after ablation. The results demonstrate significant tissue water content changes and lead to a better understanding of tissue water movement.

Quantifying local stiffness variations in radiofrequency ablations with dynamic indentation

“…It was present in all ablations and corresponded to the region where vaporized water condensed after being driven from the ablation center [26][27][28]. Profiles were not extended to the ablation center, but the most critical region of the ablation to investigate was the region of low modulus contrast, i.e.…”

“…Rather, each profile was drawn perpendicular between the outer transition zone boundary in the indented, unstained image and the outer edge of the stained "ring" within the white zone of the ablation in the registered, stained image. The ring corresponded to the boundary where water condensed after being driven from the dehydrated ablation core and will be referred to as the condensation boundary [26][27][28]. The profile distance was normalized for all samples to show average changes between these landmarks.…”

Microwave Ablation (MWA): Basics, Technique and Results in Primary and Metastatic Liver Neoplasms – Review Article

“…This illustrates the volume heating effect that can be seen in MWA. Microwaves spread from the ▶ [12]. Since the electromagnetic energy requires no direct current flow, it overcomes the limitations of RFA regarding carbonization and evaporation of the tissue.…”

Exploiting Microwave Imaging Methods for Real-Time Monitoring of Thermal Ablation

“…These changes proved to be nonreversible and can be associated at temperatures close to 60 ∘ C-80 ∘ C with proteins denaturation [10]. At temperatures close to 90 ∘ C-100 ∘ C the rapid drop of both dielectric properties can be linked to loss of water due to the vaporization phenomenon and to diffusion of the generated water vapor towards the lower-temperature surrounding tissues [11].…”