Evaluation of a thermoprotective gel for hydrodissection during percutaneous microwave ablation: in vivo results.
OBJECTIVE
To evaluate whether thermoreversible poloxamer 407 15.4 % in water (P407) can protect non-target tissues adjacent to microwave (MW) ablation zones in a porcine model.


METHODS
MW ablation antennas were placed percutaneously into peripheral liver, spleen, or kidney (target tissues) under US and CT guidance in five swine such that the expected ablation zones would extend into adjacent diaphragm, body wall, or bowel (non-target tissues). For experimental ablations, P407 (a hydrogel that transitions from liquid at room temperature to semi-solid at body temperature) was injected into the potential space between target and non-target tissues, and the presence of a gel barrier was verified on CT. No barrier was used for controls. MW ablation was performed at 65 W for 5 min. Thermal damage to target and non-target tissues was evaluated at dissection.


RESULTS
Antennas were placed 7 ± 3 mm from the organ surface for both control and gel-protected ablations (p = 0.95). The volume of gel deployed was 49 ± 27 mL, resulting in a barrier thickness of 0.8 ± 0.5 cm. Ablations extended into non-target tissues in 12/14 control ablations (mean surface area = 3.8 cm(2)) but only 4/14 gel-protected ablations (mean surface area = 0.2 cm(2); p = 0.0005). The gel barrier remained stable at the injection site throughout power delivery.


CONCLUSIONS
When used as a hydrodissection material, P407 protected non-targeted tissues and was successfully maintained at the injection site for the duration of power application. Continued investigations to aid clinical translation appear warranted.
Department of Radiology, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA, ajmoreland@gmail.com.
Anna J
AJ
Moreland
Meghan G
MG
Lubner
Timothy J
TJ
Ziemlewicz
Douglas R
DR
Kitchin
J Louis
JL
Hinshaw
Alexander D
AD
Johnson
Fred T
FT
Lee
Christopher L
CL
Brace
D000818:Animals; D017115:Catheter Ablation / Q000009:adverse effects*; D004210:Dissection; D005782:Gels / Q000494:pharmacology*; D006358:Hot Temperature / Q000009:adverse effects*; D007668:Kidney / Q000000981:diagnostic imaging / Q000601:surgery; D008099:Liver / Q000000981:diagnostic imaging / Q000601:surgery; D008872:Microwaves / Q000009:adverse effects; D023421:Models, Animal; D020442:Poloxamer / Q000494:pharmacology*; D015641:Radiography, Interventional; D013154:Spleen / Q000000981:diagnostic imaging / Q000601:surgery; D013552:Swine; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional; D014867:Water
D005782:Gels; D014867:Water; D020442:Poloxamer