Evaluation of Temperature Distribution Around the Probe in Cryoablation of Lipiodol-Mixed-Tissue Phantom
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LABORATORY INVESTIGATION
NON-VASCULAR INTERVENTIONS
Evaluation of Temperature Distribution Around the Probe in Cryoablation of Lipiodol-Mixed-Tissue Phantom Masanori Yamashita1 • Hiroshi Miura1 • Yu Ohara1 • Tatsuya Yoshikawa1 • Tatsuya Hirota1 • Takanobu Fukunaga2 • Hiroshi Takamatsu2 • Takuji Yamagami3 Kei Yamada1
•
Received: 7 July 2020 / Accepted: 3 November 2020 Springer Science+Business Media, LLC, part of Springer Nature and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) 2020
Abstract Purpose To determine whether lipiodol, which has low thermal conductivity, influences ice ball formation during cryoablation of a lipiodol-mixed-tissue phantom. Materials and Methods Lipiodol-mixed-tissue phantoms were created by injecting lipiodol (4–6 ml) into the renal arteries of ex vivo porcine kidneys (lipiodol group). A TM cryoprobe (CryoHit Needle S) with a holder that was set with thermocouples at various positions around the cryoprobe was inserted. After freezing for 300 s, the followings were evaluated: ice ball size on CT, temperature distribution around the cryoprobe, and calculated distances at 0 C and - 20 C. Each variable was compared between lipiodol group (n = 6) those obtained in a control group without lipiodol injection (n = 6). Results Mean ice ball diameter (width/length) on CT was 22.1 ± 2.3/22.9 ± 2.3 mm in the lipiodol group and 21.6 ± 0.7/22.2 ± 1.3 mm in the control group. Mean cryoprobe temperature was - 118 ± 3.0 C in the lipiodol group and - 117 ± 2.6 C in the control group. In both groups, temperature at the 3 mm thermocouple reached approximately - 50 C and was \ 0 C within * 10 mm of the cryoprobe. Temperature of 0/- 20 C occurred at a & Masanori Yamashita [email protected] 1
Department of Radiology, Kyoto Prefectural University of Medicine, 465, Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan
2
Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
3
Department of Radiology, Kochi Medical School University, 185-1 Kohasu, Oko-cho, , Nankoku-shi, Kochi 783-8505, Japan
mean distance from the cryoprobe of 11.1 ± 0.5/ 6.9 ± 0.4 mm in the lipiodol group and 11.0 ± 0.2/ 6.9 ± 0.2 mm in the control group. There was no significant difference in any variable between the groups. Conclusion The inclusion of lipiodol in a tissue phantom had no negative effects on ice ball formation that were related to thermal conductivity. Keywords Cryoablation Renal Lipiodol
Introduction CT-guided cryoablation is less invasive than surgical resection for treating small renal cell carcinomas [1, 2]. The frozen region (i.e., ice ball) can be visualized directly on CT as an area of hypodensity [3, 4]. However, it is difficult to distinguish the boundary between the tumor and the renal parenchyma during non-enhanced CT-guided cryoablation [5]. Preoperative transcatheter arterial marking using lipiodol (i.e., lipiodol marking) has been reported as a useful method for tumor visualization [5, 6]. In addition, lipiodol mark
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