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Effect of Hyperbarism on Radiofrequency Ablation Outcome

Sandro Rossi1, Mario Gallati2, Laura Rosa1, Amedeo Marini3, Francesca Torello Viera1, Marcello Maestri4 and Paolo Dionigi4

1 VI Department of Internal Medicine, Policlinico San Matteo Foundation, IRCCS, Piazzale Golgi, no.1, 27100 Pavia, Italy.
2 Department of Hydraulics and Environmental Engineering, University of Pavia, Pavia, Italy.
3 Department of Physics and Chemistry, University of Pavia, Pavia, Italy.
4 Department of Surgical Sciences, Policlinico San Matteo Foundation, IRCCS, University of Pavia, Pavia, Italy.


Figure 1
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  		Fig. 1A —On graphs of effects of hyperbarism on radiofrequency thermal ablation procedures performed on explanted bovine liver specimens at power setting of 20 W, raw curves depict single point measured. Graphs show results of procedures performed at five different pressures (n = 7). Within pressure and temperature ranges used, enthalpy of vaporization and thermal and electrical conductivity of tissue fluids are not expected to undergo variations capable of influencing framework being established [22]. Graph shows time curves for maximum tissue temperatures (T) and impedance values (IV) recorded during radiofrequency thermal ablation procedures performed at following pressures: 101 (atmospheric, continuous line), 141 ({square}), 202({triangleup}), 273 ({circ}), and 364 (•) kPa.

 

Figure 2
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  		Fig. 1B —On graphs of effects of hyperbarism on radiofrequency thermal ablation procedures performed on explanted bovine liver specimens at power setting of 20 W, raw curves depict single point measured. Graphs show results of procedures performed at five different pressures (n = 7). Within pressure and temperature ranges used, enthalpy of vaporization and thermal and electrical conductivity of tissue fluids are not expected to undergo variations capable of influencing framework being established [22]. Graph shows effects of test pressures on boiling points of distilled water ({blacksquare}) [22] and liver tissue fluid ({square}). Tissue–fluid boiling point is reflected in graph by maximum tissue temperatures recorded by thermocouple just before impedance-related interruption of radiofrequency energy delivery. Small differences between boiling points of water and of tissue fluids are due to presence of salts and other biologic elements in tissue fluids and to temperature gradient between tissue and electrode tip that houses thermocouple. Agreement between experimental data and ideal water boiling points underlines importance of tissue water content on radiofrequency thermal ablation outcome. Same results were observed at power settings of 30, 40, and 50 W. SE = standard error

 

Figure 3
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  		Fig. 1C —On graphs of effects of hyperbarism on radiofrequency thermal ablation procedures performed on explanted bovine liver specimens at power setting of 20 W, raw curves depict single point measured. Graphs show results of procedures performed at five different pressures (n = 7). Within pressure and temperature ranges used, enthalpy of vaporization and thermal and electrical conductivity of tissue fluids are not expected to undergo variations capable of influencing framework being established [22]. Graph shows effect of hyperbarism on radiofrequency delivery time measured from initiation of power delivery to its abrupt impedance-related interruption. SE = standard error.

 

Figure 4
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  		Fig. 1D —On graphs of effects of hyperbarism on radiofrequency thermal ablation procedures performed on explanted bovine liver specimens at power setting of 20 W, raw curves depict single point measured. Graphs show results of procedures performed at five different pressures (n = 7). Within pressure and temperature ranges used, enthalpy of vaporization and thermal and electrical conductivity of tissue fluids are not expected to undergo variations capable of influencing framework being established [22]. Graph shows effect of hyperbarism on initial impedance values (IIV) and minimum impedance values (MIV) recorded during radiofrequency thermal ablation. SE = standard error.

 

Figure 5
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  		Fig. 2 —Effects of hyperbarism on size of thermal lesions created in explanted bovine liver with radiofrequency power setting of 20 W. Graph in bottom right corner shows relationship between thermal lesion volume and applied pressure; photographs show diameters (in centimeters) of representative thermal lesions produced at each pressure tested. SE = standard error.

 

Figure 6
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  		Fig. 3A —Graphs show effects of hyperbarism on radiofrequency thermal ablation performed in explanted bovine livers at constant power settings of 20 W ({square}), 30 W ({triangleup}), 40 W ({diamond}), and 50 W ({circ}). SE = standard error. Graph shows relationship between pressures and radiofrequency delivery time.

 

Figure 7
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  		Fig. 3B —Graphs show effects of hyperbarism on radiofrequency thermal ablation performed in explanted bovine livers at constant power settings of 20 W ({square}), 30 W ({triangleup}), 40 W ({diamond}), and 50 W ({circ}). SE = standard error. Graph shows relationship between pressures and thermal lesion volume.

 

Figure 8
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  		Fig. 3C —Graphs show effects of hyperbarism on radiofrequency thermal ablation performed in explanted bovine livers at constant power settings of 20 W ({square}), 30 W ({triangleup}), 40 W ({diamond}), and 50 W ({circ}). SE = standard error. Graph shows relationship between radiofrequency power setting, total amount of radiofrequency energy delivered to tissue, and thermal lesion size. For given amount of radiofrequency energy delivered, volumes of obtained thermal lesions with 20 W power setting ({diamond}) were larger than those with 50 W ({diamondsuit}).

 

Figure 9
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  		Fig. 4A —Effects of hepatic vein occlusion on radiofrequency thermal ablation procedures performed in livers of live pigs (n = 7). All thermal lesions were produced with constant power setting of 20 W. Graph shows maximum tissue temperatures recorded at end of radiofrequency thermal ablation procedures with ({square}) and without ({diamondsuit}) hepatic vein occlusion.

 

Figure 10
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  		Fig. 4B —Effects of hepatic vein occlusion on radiofrequency thermal ablation procedures performed in livers of live pigs (n = 7). All thermal lesions were produced with constant power setting of 20 W. Graph shows impedance values recorded during radiofrequency thermal ablation procedures with ({square}) and without ({diamondsuit}) hepatic vein occlusion.

 

Figure 11
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  		Fig. 4C —Effects of hepatic vein occlusion on radiofrequency thermal ablation procedures performed in livers of live pigs (n = 7). All thermal lesions were produced with constant power setting of 20 W. Representative photograph of thermal lesions created in liver of one of pigs with hepatic vein occlusion. Measurement units are centimeters.

 

Figure 12
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  		Fig. 4D —Effects of hepatic vein occlusion on radiofrequency thermal ablation procedures performed in livers of live pigs (n = 7). All thermal lesions were produced with constant power setting of 20 W. Representative photograph of control thermal lesion created in liver of same pig under normal flow condition. Measurement units are centimeters.

 

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