Radio-frequency thermal ablation with NaCl solution injection: effect of electrical conductivity on tissue heating and coagulation-phantom and porcine liver study.
OBJECTIVE
To characterize the effects of NaCl concentration on tissue electrical conductivity, radio-frequency (RF) deposition, and heating in phantoms and optimize adjunctive NaCl solution injection for RF ablation in an in vivo model.


METHODS
RF was applied for 12-15 minutes with internally cooled electrodes. For phantom experiments (n = 51), the NaCl concentration in standardized 5% agar was varied (0%-25.0%). A nonlinear simplex optimization strategy was then used in normal porcine liver (n = 44) to determine optimal pre-RF NaCl solution injection parameters (concentration, 0%-38.5%; volume, 0-25 mL). NaCl concentration and tissue conductivity were correlated with RF energy deposition, tissue heating, and induced coagulation.


RESULTS
NaCl concentration had significant but nonlinear effects on electrical conductivity, RF deposition, and heating of agar phantoms (P<.01). Progressively greater heating was observed to 5.0% NaCl, with reduced temperatures at higher concentrations. For in vivo liver, NaCl solution volume and concentration significantly influenced both tissue heating and coagulation (P<.001). Maximum heating 20 mm from the electrode (102.9 degrees C +/- 4.3 [SD]) and coagulation (7.1 cm +/- 1.1) occurred with injection of 6 mL of 38.5% (saturated) NaCl solution.


CONCLUSIONS
Injection of NaCl solution before RF ablation can increase energy deposition, tissue heating, and induced coagulation, which will likely benefit clinical RF ablation. In normal well-perfused liver, maximum coagulation (7.0 cm) occurs with injection of small volumes of saturated NaCl solution.
Department of Radiology of Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215, USA.
S N
SN
Goldberg
M
M
Ahmed
G S
GS
Gazelle
J B
JB
Kruskal
J C
JC
Huertas
E F
EF
Halpern
B S
BS
Oliver
R E
RE
Lenkinski
D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005260:Female; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D008099:Liver / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D013552:Swine
D012462:Saline Solution, Hypertonic