Bovine radiology pdf book generator#

There is always a rapid increase of temperature at the tissue-electrode interface, and this results in tissue desiccation and charring at the electrode tip.

This inherent limitation of monopolar RF ablation, in regards to the small dimension of coagulation necrosis, is attributed to resistive heating at a narrow rim of tissue that surrounds the electrode ( 1, 2, 10). However, current RF technology is limited in that only tissue 3.5- to 4.5 cm in diameter could be ablated with a single application of RF energy ( 5 - 9). Image-guided percutaneous radiofrequency (RF) ablation has become increasingly popular in recent years, and it has been accepted as an alternative to surgical resection for the treatment of primary and secondary hepatic malignancy in inoperable patients ( 1 - 4). The tissue temperature measured at 15 mm from the electrode was higher in groups C, D and E than other groups (p < 0.05): 53 В± 12в„ѓ in group A, 42 В± 2в„ѓ in group B, 93 В± 8в„ѓ in group C 79 В± 12в„ѓ in group D and 83 В± 8в„ѓ in group E. In addition, the volumes of RF-induced coagulation necrosis were greater in groups C and E than in group D, which was greater than in groups A and B than in group E (p < 0.05) 14.3 В± 3.0 cm 3 in group A 12.4 В± 3.8 cm 3 in group B 80.9 В± 9.9 cm 3 in group C 45.3 В± 11.3 cm 3 in group D and 81.6 В± 8.6 cm 3 in group E. As consequences, the mean current was higher for groups C, D, and E than for the other groups: 401 В± 145 mA in group A, 287 В± 32 mA in group B, 1907 В± 96 mA in group C, 1649 В± 514 mA in group D, and 1968 В± 108 mA in group E (p < 0.05). In group D, the impedance was well controlled in six of ten trials but it was increased in four trials (40%) 7 min after starting RF ablation. During RF ablation, the tissue impedance was well controlled in groups C and E, but it was often rapidly increased to more than 200 О© in groups A and B. With injection or infusion of NaCl solutions, the mean initial tissue impedance prior to RF ablation was significantly less in groups B, C, D, and E (43-75 О©) than for group A (80 О©) (p < 0.05).

The dimensions of the ablation zones and changes in impedance, current and liver temperature during RF ablation were then compared between the groups. During RF ablation, we measured the tissue temperature at 15 mm from the electrode. In groups C and E, infusion of the NaCl solutions was started 1 min before RF ablation and then maintained during RF ablation (wet RF ablation). After placing the perfused-cooled electrode in the explanted liver, 50 ablation zones were created with five different regimens: group A standard dry RF ablation, group B RF ablation with 11 mL of 5% NaCl solution preinjection, group C RF ablation with infusion of 11 mL of 5% NaCl solution at a rate of 1 mL/min, group D RFA with 6 mL of 36% NaCl solution preinjection, group E RF ablation with infusion of 6 mL of 36% NaCl solution at a rate of 0.5 mL/min.

Bovine radiology pdf book generator#

Radiofrequency was applied to excised bovine livers in a monopolar mode for 10 minutes using a 200 W generator and a perfused-cooled electrode with or without injection or slow infusion of NaCl solutions.