Effect of Pulse Widths and Cycles on Invasive, Bipolar, and Gated Radiofrequency-Induced Thermal Reactions in ex vivo Bovine Liver Tissue

Figures & data

Table 1 Experimental Parameters for 1- and 2-MHz Invasive Bipolar Radiofrequency (RF) Treatment on ex vivo Bovine Liver Tissue

Number of pulse packs	Conduction time/pulse pack*	Off-time between pulse packs*	Total conduction time*	Total off time*	Total treatment time*
1	100	0	100	0	100
	200	0	200	0	200
	300	0	300	0	300
	400	0	400	0	400
	600	0	600	0	600
	800	0	800	0	800
2	100	50	200	50	250
	200	100	400	100	500
	300	150	600	150	750
	400	200	800	200	1000
	100	20	200	20	220
	200	40	400	40	440
	300	60	600	60	660
	400	80	800	80	880
3	100	20	300	40	340
	200	40	600	80	680
	100	50	300	100	400
	200	100	600	200	800
4	100	50	400	150	550
	200	100	800	300	1100
	100	20	400	60	460
	200	40	800	120	920
6	100	20	600	100	700
	100	50	600	250	850
	200	40	1200	200	1400
	200	100	1200	500	1700
8	100	20	800	140	940
	100	50	800	350	1150
	200	40	1600	280	1880
	200	100	1600	700	2300
10	100	20	1000	180	1180
	100	50	1000	450	1450
	200	40	2000	360	2360
	200	100	2000	900	2900

Note: *Conduction time and off time values are presented in msec.

Table 2 Factors Associated with Thermometric Values After 1- and 2-MHz Invasive Bipolar RF Treatments on ex vivo Bovine Liver Tissue in Univariate and Multivariate Linear Regression Analysis

	∆T1* = Timmediate – T baseline				∆T2* = T10s – T baseline
	Univariate		Multivariate		Univariate		Multivariate
	B (SE)	P value	B (SE)	P value	B (SE)	P value	B (SE)	P value
Frequency	2.819 (0.394)	< 0.0001	2.274 (0.307)	< 0.0001	0.885 (0.142)	< 0.0001	0.804 (0.115)	< 0.0001
Power	0.124 (0.054)	0.0238	0.105 (0.034)	0.0023	0.045 (0.019)	0.0167	0.040 (0.013)	0.0034
Number of pulse packs	−0.426 (0.078)	< 0.0001			−0.084 (0.029)	0.0052
Conduction time/pulse pack**	0.692 (0.127)	< 0.0001	0.550 (0.090)	< 0.0001	0.201 (0.046)	< 0.0001	0.174 (0.034)	< 0.0001
Off-time between pulse packs**	1.610 (0.462)	0.0007	2.133 (0.341)	< 0.0001	0.628 (0.157)	0.0001	0.634 (0.116)	< 0.0001
Total conduction time**	−0.066 (0.055)	0.2372			0.007 (0.019)	0.7041
Total off time**	−0.317 (0.131)	0.0174	−0.297 (0.100)	0.0038	−0.026 (0.046)	0.5806
Total treatment time**	−0.066 (0.041)	0.1098			0.002 (0.014)	0.9114

Note: *Where T is the surface temperature (°C) of ex vivo bovine liver tissue at specific time points, **per 100 msec.

Abbreviations: B, regression coefficient; SE, standard error.

Figure 1 Thermal imaging camera study. Images were captured at baseline, immediately, and 10s after bipolar radiofrequency (RF) treatment at a frequency of 1 MHz. The experimental settings were (A) a power of 4W, a conduction time/pulse pack of 200 msec, and a single pulse pack; (B) 12W, a conduction time/pulse pack of 200 msec, and a single pulse pack; (C) 12W, a conduction time/pulse pack of 600 msec, and a single pulse pack; (D) 12W, a conduction time/pulse pack of 100 msec, 2 pulse packs, an off-time between pulse packs of 50 msec, and a total conduction time of 200 msec; and (E) 12W, a conduction time/pulse pack of 100 msec, two pulse packs, an off-time between pulse packs of 20 msec, and a total conduction time of 200 msec. The thermometric values of baseline tissue were adjusted to 36°C.

Table 3 Factors Associated with Thermometric Values After 1-MHz Invasive Bipolar RF Treatment on ex vivo Bovine Liver Tissue in Univariate and Multivariate Linear Regression Analysis

	∆T1* = Timmediate – T baseline				∆T2* = T10s – T baseline
	Univariate		Multivariate		Univariate		Multivariate
	B (SE)	P value	B (SE)	P value	B (SE)	P value	B (SE)	P value
Power	0.155 (0.062)	0.0147	0.155 (0.046)	0.0012	0.056 (0.022)	0.0131	0.056 (0.019)	0.005
Number of pulse packs	−0.337 (0.075)	< 0.0001	−0.249 (0.068)	0.0005	−0.047 (0.030)	0.125
Conduction time/pulse pack**	0.707 (0.146)	< 0.0001	0.486 (0.134)	0.0006	0.186 (0.056)	0.0015	0.183 (0.051)	0.0006
Off-time between pulse packs**	1.280 (0.551)	0.0234	1.393 (0.408)	0.0011	0.506 (0.194)	0.0114	0.495 (0.171)	0.0051
Total conduction time**	−0.065 (0.053)	0.2273			0.010 (0.019)	0.6083
Total off time**	−0.244 (0.124)	0.0527			0.002 (0.045)	0.9709
Total treatment time**	−0.058 (0.039)	0.1376			0.005 (0.014)	0.6992

Note: *Where T is the surface temperature (°C) of ex vivo bovine liver tissue at specific time points, **Per 100 msec.

Figure 2 Thermal imaging camera study. Images were captured at baseline, immediately, and 10s after bipolar RF treatment at a frequency of 2 MHz. The experimental settings were (A) a power of 4W, a conduction time/pulse pack of 200 msec, and a single pulse pack; (B) 12W, a conduction time/pulse pack of 200 msec, and a single pulse pack; (C) 12W, a conduction time/pulse pack of 600 msec, and a single pulse pack; (D) 12W, a conduction time/pulse pack of 100 msec, two pulse packs, an off-time between pulse packs of 50 msec, and a total conduction time of 200 msec; and (E) 12W, a conduction time/pulse pack of 100 msec, two pulse packs, an off-time between pulse packs of 20 msec, and a total conduction time of 200 msec. The thermometric values of baseline tissue were adjusted to 36°C.

Table 4 Factors Associated with Thermometric Values After 2-MHz Invasive Bipolar RF Treatment on ex vivo Bovine Liver Tissue in Univariate and Multivariate Linear Regression Analysis

	∆T1* = Timmediate – T baseline				∆T2* = T10s – T baseline
	Univariate		Multivariate		Univariate		Multivariate
	B (SE)	P value	B (SE)	P value	B (SE)	P value	B (SE)	P value
Power	0.044 (0.064)	0.4913			0.019 (0.024)	0.4168
Number of pulse packs	0.604 (0.259)	0.0247			0.230 (0.095)	0.0199
Conduction time/pulse pack**	0.487 (0.147)	0.0019			0.160 (0.056)	0.0063
Off-time between pulse packs**	2.034 (0.463)	< 0.0001			0.782 (0.167)	< 0.0001
Total conduction time**	0.751 (0.059)	< 0.0001			0.269 (0.024)	< 0.0001
Total off time**	1.425 (0.295)	< 0.0001			0.546 (0.106)	< 0.0001
Total treatment time**	0.618 (0.047)	< 0.0001	0.618 (0.047)	< 0.0001	0.224 (0.018)	< 0.0001	0.224 (0.018)	< 0.0001

Note: *Where T is the surface temperature (°C) of ex vivo bovine liver tissue at specific time points, **per 100 msec.

Figure 3 Tissue reactions after 1-MHz bipolar RF treatment on ex vivo bovine liver tissue. The ex vivo bovine liver tissue was treated at experimental settings of (A and B) 12W, a conduction time/pulse pack of 100 msec, three pulse packs, an off-time between pulse packs of 50 msec, and a total conduction time of 300 msec and (C and D) 12W, a conduction time/pulse pack of 100 msec, three pulse packs, an off-time between pulse packs of 20 msec, and a total conduction time of 300 msec. The superficial (A and C) and deeper (B and D) parts of liver tissue specimens exhibit RF-induced tissue reactions at the proximal and distal parts of invasive microneedles, respectively. Hematoxylin & eosin stain. Original magnification x40.

Figure 4 Tissue reactions after 2-MHz bipolar RF treatment on ex vivo bovine liver tissue. The ex vivo bovine liver tissue was treated at experimental settings of (A) 12W, a conduction time/pulse pack of 300 msec, and a single pulse pack; (B) 12W, a conduction time/pulse pack of 400 msec, and a single pulse pack; (C) 12W, a conduction time/pulse pack of 100 msec, three pulse packs, an off-time between pulse packs of 50 msec, and a total conduction time of 300 msec; and (D) 12W, a conduction time/pulse pack of 100 msec, three pulse packs, an off-time between pulse packs of 20 msec, and a total conduction time of 300 msec. Hematoxylin & eosin stain. Original magnification x40.