Biomedical Engineering Reference
In-Depth Information
1000
800
RF
4 mm
Phantom
Animal
600
400
200
0
0
10
20
30
40
Power (W)
50
60
70
80
1000
800
RF 8
mm
Phantom
Animal
600
400
200
0
0
10
20
30
40
Power (W)
(d)
50
60
70
80
FIGURE 6.15
(
d
) Comparison of lesion volumes obtained with phantom and with
canine left ventricular models for RF catheters [90].
6.5.2
Dose-Response Curve
The relationship between delivered power and tip temperature was evaluated
for a 4-mm and an 8-mm RF catheter as well as for a microwave catheter (with
a 12-mm helical antenna). There was a linear relationship between power and
change in surface temperature (Fig. 6.15
b
). The correlation coefficient (
r
) was
0.998 for the 4-mm electrode, 0.997 for the 8-mm electrode, and 0.997 for the
microwave catheter. More power was required to achieve the same change
in temperature with an 8-mm electrode than with a 4-mm catheter. The
power density required to achieve a similar surface temperature was 2.59 times
higher for an 8-mm RF catheter. The microwave catheter required still higher
power in order to achieve the same changes in temperature.
6.5.3
Depth and Rate of Heating
The time course of heating at various depths was analyzed by plotting the
change in temperature as a function of time. The change in temperature was
expressed as the percent of the maximal surface temperature achieved during
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