The electrical conductivity of in vivo human uterine fibroids

Figures & data

Figure 1. RF Ablation System.

Figure 2. Applicator Detail.

Table I.  Human uterus.

Parameter	Symbol	Value	Units	Reference
Electrical conductivity	σ	To be determined	S/m	–
Density	ρ	1052	kg/m^3	[32], p. 139]
Thermal conductivity	k@37°C	0.512^a	W/K-m	–
Heat capacity	C	3600^b	J/kg-K	–
Blood density	ρb	1055	kg/m^3	[32], p. 138]
Blood heat capacity	Cb	3840	J/kg-K	[32], p. 28]
Blood temperature	Tb	37	°C	–
Perfusion coefficient	ω	0.0064	1/sec	^c

^aThis value is within the range reported in [32], pp. 14–15 for human muscle and human liver.

^bTaken to be the same as human liver reported in [32], p 28. This value is also approximately the same as that reported [32], p 28 for human muscle. As discussed later, the exact value for tissue heat capacity has a negligible effect on the calculated power.

^cA wide range of blood perfusion rates are reported for tissue. As discussed later, the value for perfusion has a negligible effect on the calculated power for the conditions of this study.

Table II.  Catheter (PEEK – Victrex 381 G).

Parameter	Value	Reference
ρ	1300	33
k	0.25	33
C	2160	33

Table III.  Trocar (304 Stainless Steel).

Parameter	Value	Reference
ρ	8000	33
k	16.2	33
C	500	33

Figure 3. Side view of trocar showing line locations for tissue temperature profiles.

Figure 4. Measured applied voltage for Procedures 503, 504, and 505.

Figure 5. Side view of trocarshowing mesh for a simulation utilizing approximately 100,000 elements.

Figure 6. Results from simulation of Clinical Ablation 503 showing measured power dissipation and computed power dissipation with a 37°C tissue electrical conductivity of 0.305 S/m and a tissue electrical conductivity temperature coefficient of 0.2%/°C. Electrodes completely retracted.

Figure 7. Results from simulation of Clinical Ablation 504 showing measured power dissipation and computed power dissipation with a 37°C tissue electrical conductivity of 0.300 S/m and a tissue electrical conductivity temperature coefficient of 0.2%/°C. Electrodes completely retracted.

Figure 8. Results from simulation of Clinical Ablation 505 showing measured power dissipation and computed power dissipation with a 37°C tissue electrical conductivity of 0.310 S/m and a tissue electrical conductivity temperature coefficient of 0.2%/°C. Electrodes completely retracted.

Figure 9. Results from simulation of Clinical Ablation 504 showing measured power dissipation and computed power dissipation with a 37°C tissue electrical conductivity of 0.300 S/m and a tissue electrical conductivity temperature coefficient of 0.2%/°C (baseline conditions). Electrodes completely retracted. Four additional simulations shown with tissue thermal conductivity increased by 20%, tissue heat capacity increased by 20%, trocar thermal capacity increased by 5%, and perfusion coefficient changed from 0 to 6.4e-3 1/s.

Figure 10. Results from simulation of Clinical Ablation 504 showing measured power dissipation and computed power dissipation with a 37°C tissue electrical conductivity of 0.300 S/m and a tissue electrical conductivity temperature coefficient of 0.2%/°C (baseline conditions). Electrodes completely retracted. Two additional simulations shown with tissue electrical conductivity at 37°C increased by 20% and tissue electrical conductivity temperature coefficient reduced by 50%.

Figure 11. Computed tissue temperatures outward on a radius from the trocar surface at a distance of 4.1 mm from the trocar tip. The temperature profiles are shown at durations of 8 seconds, 12 seconds, and 16 seconds. Profiles are shown with the nominal value for tissue thermal conductivity and the nominal value increased by 20%.

Figure 12. Computed tissue temperatures outward on a radius from the trocar surface at a distance of 5.8 mm from the trocar tip. The temperature profiles are shown at durations of 8 seconds, 12 seconds, and 16 seconds. Profiles are shown with the nominal value for tissue thermal conductivity and the nominal value increased by 20%.

Duck F. Physical Properties of Tissue: A Comprehensive Reference Book. Academic Press, New York 1990; 14, 28, 138, 139

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