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Comparative Study
. 2009 Dec;16(12):1539-48.
doi: 10.1016/j.acra.2009.06.016.

Thermal ablation a comparison of thermal dose required for radiofrequency-, microwave-, and laser-induced coagulation in an ex vivo bovine liver model

Pawel Mertyna  1 , Wallace Goldberg, Wei Yang, S Nahum Goldberg
Affiliations
Comparative Study

Thermal ablation a comparison of thermal dose required for radiofrequency-, microwave-, and laser-induced coagulation in an ex vivo bovine liver model

Pawel Mertyna et al. Acad Radiol. 2009 Dec.

Abstract

Rationale and objectives: To compare thermal dosimetry metrics for specified diameters of coagulation achieved using three different ablation energy sources.

Materials and methods: 204 ablations measuring 20, 30, or 40 +/- 2 mm were created in an ex-vivo bovine liver model using 1) 2.5 cm cluster RF electrodes (n = 114), 2) 3 cm microwave antennas (n = 45), and 3) 3 cm laser diffusing fibers (n = 45). Continuous temperature monitoring was performed 5-20 mm from the applicators to calculate: a) the area under the curve (AUC), b) cumulative equivalent minutes at 43 degrees C (CEM43), and c) Arrhenius damage integral (Omega) for the critical ablation margin (DOC), with results compared by multivariate analysis of variance and regression analysis.

Results: The end temperatures at the margin of coagulation varied, and was lowest for the RF cluster electrode (33-58 degrees C), higher for laser (52-72 degrees C), and covered the widest range for microwave (42-95 degrees C). These end temperatures correlated with applied energy, as linear functions (r(2) = 0.74-0.96). The total heat needed to achieve ablation (AUC) varied with applied energy and coagulation diameter as negative exponential (RF and laser) or negative power (microwave) functions (r(2) = 0.82-0.98). Similarly, CEM43 values varied exponentially with energy and distance (r(2) = 0.52-0.76) over a wide range of values (10(12)). Likewise, Omega varied not only based upon energy source and DOC, but also as a positive linear correlation to applied energy and with sigmoid correlation to duration of ablation (r(2) = 0.85-0.97).

Conclusion: Our study demonstrates that the thermal dosimetry of ablation is not based solely on a fixed end temperature at the margin of the coagulation zone. Thermal dosimetry is not constant, but dependent on the type and amount of energy applied and distance suggesting the need to take into account the rate of heat transfer for ablation dosimetry.

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Figures

Figure1
Figure1
(a). Overview of the experimental design . An internally cooled 2.5cm cluster RF electrode (white arrow) has been inserted into a sample of bovine liver placed in a 0.9% saline bath. The RF generator (lower black arrow) and a temperature measurement device (upper black arrow) can be seen in the background. (b). RF cluster electrode, (c) Microwave 3cm antenna and (d). Laser 3cm externally cooled diffusing fiber, are noted by arrows. For all energy applicators thermocouple probes (arrowheads) were placed at defined distances (5,10, 15, and 20mm diameter) from the device, which enabled precise measurement of temperature over time over the course of the ablation.
Figure1
Figure1
(a). Overview of the experimental design . An internally cooled 2.5cm cluster RF electrode (white arrow) has been inserted into a sample of bovine liver placed in a 0.9% saline bath. The RF generator (lower black arrow) and a temperature measurement device (upper black arrow) can be seen in the background. (b). RF cluster electrode, (c) Microwave 3cm antenna and (d). Laser 3cm externally cooled diffusing fiber, are noted by arrows. For all energy applicators thermocouple probes (arrowheads) were placed at defined distances (5,10, 15, and 20mm diameter) from the device, which enabled precise measurement of temperature over time over the course of the ablation.
Figure1
Figure1
(a). Overview of the experimental design . An internally cooled 2.5cm cluster RF electrode (white arrow) has been inserted into a sample of bovine liver placed in a 0.9% saline bath. The RF generator (lower black arrow) and a temperature measurement device (upper black arrow) can be seen in the background. (b). RF cluster electrode, (c) Microwave 3cm antenna and (d). Laser 3cm externally cooled diffusing fiber, are noted by arrows. For all energy applicators thermocouple probes (arrowheads) were placed at defined distances (5,10, 15, and 20mm diameter) from the device, which enabled precise measurement of temperature over time over the course of the ablation.
Figure1
Figure1
(a). Overview of the experimental design . An internally cooled 2.5cm cluster RF electrode (white arrow) has been inserted into a sample of bovine liver placed in a 0.9% saline bath. The RF generator (lower black arrow) and a temperature measurement device (upper black arrow) can be seen in the background. (b). RF cluster electrode, (c) Microwave 3cm antenna and (d). Laser 3cm externally cooled diffusing fiber, are noted by arrows. For all energy applicators thermocouple probes (arrowheads) were placed at defined distances (5,10, 15, and 20mm diameter) from the device, which enabled precise measurement of temperature over time over the course of the ablation.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 2
Figure 2
Relationships of analyzed parameters for RF cluster electrode (a) CEM43 versus current (b) End temperature versus current (c) AUC versus current, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration. For this and all subsequent figures each trial of the experiments run in triplicate are represented as a data point.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 3
Figure 3
Relationships of analyzed parameters for MW antenna (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
Figure 4
Figure 4
Relationships of analyzed parameters for laser (a) CEM43 versus power (b) End temperature versus power (c) AUC versus power, (d) AUC versus duration, (e) Arrhenius damage integral (Ω) versus current and (f) Ω versus duration.
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