Fundamental Evaluation of Thermophysical Properties of Lipiodol Associated with Cryoablation: Freezing Experiments Using Lipiodol Phantom.

PURPOSE: To elucidate the basic thermophysical properties at low temperatures of lipiodol, which is used as a marker by transarterial injection before CT-guided cryoablation for solid tumors, by fundamental experiments with pure lipiodol phantom. MATERIALS AND METHODS: The freezing point of lipiodol was measured using differential scanning calorimeter (DSC) by detecting differences in the heating rate during heating from - 30 °C. Freezing experiments were conducted using pure lipiodol and a tissue phantom, which were prepared in an acrylic container at 37 °C. The growth of the frozen region was observed for 10 min. Temperatures were monitored at the cryoprobe surface and designated positions around the cryoprobe. RESULTS: The DSC experiment showed that freezing was observed between - 5 and - 30 °C, which indicated that the freezing point was approximately - 5 °C. Freezing experiments revealed that the diameter of frozen region in the lipiodol was smaller than that in the tissue phantom (5 mm vs 24 mm) after 10-min freezing. The temperature at the probe surface was - 130 °C in lipiodol, which was 25 °C lower than that in the tissue phantom. There was a larger temperature gradient near the cryoprobe in lipiodol due to lower thermal conductivity. CONCLUSIONS: The present results suggest that an extremely high concentration of lipiodol (close to pure lipiodol) potentially reduces frozen region because of its lower freezing point and smaller thermal conductivity. However, since lipiodol concentrations in clinical cases differ from the current model, further studies using models that are close to clinical conditions are required. LEVEL OF EVIDENCE: No level of evidence, laboratory investigation.

Is the Cessation of Blood Flow Faster than the Polymerization of an n-Butyl Cyanoacrylate-Lipiodol Mixture? An In Vitro Phantom Study.

PURPOSE: To compare the polymerization time of n-butyl cyanoacrylate (NBCA) and lipiodol mixture in a static model and a pulsating flow model simulating embolization procedure of small caliber arteries. MATERIALS AND METHODS: The polymerization time of NBCA-lipiodol mixture was measured by the morphological changes of a glue droplet in a petri dish. For the flow model, we used a 2-mm-inner-diameter polyvinyl alcohol tube connected to a pulsation pump. Bovine serum was supplied from the pump and circulated into the system at 30 ml/min and 60 bpm. A 0.64-mm-inner-diameter silicon microcatheter was inserted into this system, and then, 0.5 ml of glue was injected into the tube. The flow cessation time was defined as the time it took to stop the serum draining from the end of the tube. Six samples of 100, 66, 50, 40, 33, and 20 vol% NBCA were assessed. RESULTS: The median polymerization times for each concentration were 0.12, 3.72, 12.30, 27.41, 57.68, and 63.67 s, respectively. The median flow cessation times were 0.28, 0.78, 1.43, 3.75, 4.50, and 9.29 s, respectively. The flow cessation time was significantly shorter than the polymerization time for all samples except for 100 vol% cyanoacrylate (p < 0.05). CONCLUSION: The flow cessation time of cyanoacrylate glue was significantly shorter than the polymerization time in an in vitro experiment. The injected glue possibly stops the blood flow before the completion of polymerization in the vascular system.

Transcatheter arterial embolization with N-butyl cyanoacrylate for acute life-threatening gastroduodenal bleeding uncontrolled by endoscopic hemostasis.

PURPOSE: To investigate the feasibility, efficacy, and safety of transcatheter arterial embolization with N-butyl cyanoacrylate (NBCA) for gastroduodenal nonvariceal bleeding uncontrolled by endoscopic hemostasis. MATERIALS AND METHODS: Between January 2006 and December 2011, a total of 317 patients underwent emergent endoscopic therapy for nonvariceal gastroduodenal bleeding, but hemostasis was not achieved in 20 cases. Emergent surgery was performed immediately following endoscopy in two patients. Arteriography was performed in the remaining 18 patients, and embolization with NBCA was performed in 15 patients (mean age, 71.3 y) in whom the bleeding site was detected on arteriography. For embolization, NBCA was mixed with iodized oil at a ratio of 1:1.5-1:4, and no other embolic material was used in the procedure. Technical and clinical success rates, recurrent bleeding, procedural time, complications, and clinical outcomes were determined for each procedure. RESULTS: Embolization with NBCA was technically and clinically successful in all procedures, without major complications. No patient receiving embolization with NBCA experienced recurrent bleeding or required further treatment after the one-session procedure. All patients were discharged after clinical improvement. The time between puncture of the femoral artery and completion of embolization ranged from 25 to 240 minutes (mean, 66 min), and the time between the microcatheter reaching the ultimate catheter location selected for embolization and hemostasis ranged from 142 to 550 seconds (mean, 322s). CONCLUSIONS: In this limited series, embolization with NBCA was found to be a safe, feasible, and effective treatment for gastroduodenal arterial bleeding when endoscopic hemostasis had failed.

A new flow control technique using diluted epinephrine in the N-butyl-2-cyanoacrylate embolization of visceral artery pseudoaneurysms secondary to chronic pancreatitis.

Although n-butyl-2-cyanoacrylate (NBCA) has been used as an effective liquid embolization material, its indication for pseudoaneurysms has seemingly been limited because of the technical difficulties of using NBCA, such as reflux to the parent artery and causing significant infarction. Thus, considerable skill in using NBCA or a device to control blood flow during its polymerization is required to achieve embolization without severe complications. We report our new technique for controlling blood flow using diluted epinephrine in transcatheter arterial NBCA embolization of five pseudoaneurysms in four cases secondary to hemosuccus pancreaticus.