Luke R. Wilkins

Real-time Monitoring of Radiofrequency Ablation and Postablation Assessment: Accuracy of Contrast-enhanced US in Experimental Rat Liver Model

PURPOSE To examine the accuracy of the unenhanced zone at contrast material-enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison. MATERIALS AND METHODS Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin-stained images were compared. The areas of DiI bubble-negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance. RESULTS The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble-negative zone on fluorescence images was noted at all time points. CONCLUSION The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment.

Key Concepts in Critical Limb Ischemia: Selected Proceedings from the 2015 Vascular Interventional Advances Meeting

Over 500,000 patients each year are diagnosed with critical limb ischemia (CLI), the most severe form of peripheral artery disease. CLI portends a grim prognosis; half the patients die from a cardiovascular cause within 5 years, a rate that is 5 times higher than a matched population without CLI. In 2014, the Centers for Medicare and Medicaid Services paid approximately

Chronic Mesenteric Ischemia

3.6 billion for claims submitted by hospitals for inpatient and outpatient care delivered to patients with CLI. Although significant advances in diagnosis, treatment, and follow-up of patients with CLI have been made, many challenges remain. In this article, we summarize selected presentations from the 2015 Vascular Interventional Advances Conference related to the modern demographics, diagnosis, and management of patients with CLI.

The Use of the Woodchuck as an Animal Model for Evaluation of Transarterial Embolization

Endovascular management and treatment of chronic mesenteric ischemia has taken on an increasing role in recent years. The safety, efficacy, and cost-effectiveness have been validated in several studies. The procedure is best performed by an operator with a complete understanding of the pertinent imaging findings; a thorough knowledge of the risks, benefits, limitations, and technical challenges of the procedure; and understanding of the importance and necessity of long-term clinical management. This article outlines a general approach to endovascular management of chronic mesenteric ischemia and discusses indications, potential complications, and technical aspects of the procedure.

Efficiency of combined blocking of aerobic and glycolytic metabolism pathways in treatment of N1-S1 hepatocellular carcinoma in a rat model

There are many shortcomings of current animal models as surrogates of hepatocellular carcinoma that handicap preclinical testing of embolization agents. The present study explores the feasibility of using the woodchuck (Marmota monax) as an animal model for the testing of novel embolization agents. Four woodchucks underwent magnetic resonance imaging, angiography, and left lobar hepatic artery particle embolization. Percutaneous access, arteriography, and lobar embolization were successful in all animals, with angiographic stasis obtained in the target vessel with minimal reflux of embolic material. These results support the feasibility of the woodchuck as an animal model for preclinical testing of embolization agents.

Selective toxicity of caffeic acid in hepatocellular carcinoma cells

Background/Aim: The aim of this study was to determine whether the addition of bumetanide (BU), a glycolytic metabolism pathway inhibitor, to arterial embolization improves tumor necrosis of N1-S1 hepatocellular carcinoma in a rat model. Materials and Methods: N1-S1 tumors were surgically implanted in the liver of 14 Sprague-Dawley rats. The rats were divided into three groups: In control group (n = 5), 1 ml of normal saline was injected intra-arterially. The tumor in the transarterial embolization group (TAE, n = 4) was embolized using 10 mg of 50–150 μ polyvinyl alcohol (PVA) particles and embolization plus BU group (TAE + BU, n = 5) were embolized with 10 mg of PVA plus 0.04 mg/kg of BU. Tumor volume was measured using two-dimensional ultrasound before intervention and twice a week afterward. Relative tumor volume after the intervention was calculated as the percentage of preinterventional tumor volume. After 4 weeks of observation, the rats were sacrificed for histopathological evaluation. Results: No statistically significant difference was detected in the preintervention tumor sizes between the three groups (P > 0.05). In the control group, the relative tumor volume increased to 142.5% larger than baseline measurements. In the TAE group, the tumor volume decreased by 18.2 ± 12.2%. The tumor volume in the TAE + BU group decrease by 90.4 ± 10.2%, which was 72.2% more than in TAE only group (P < 0.0001). Histopathological evaluation demonstrated no residual tumor in the TAE + BU group. Conclusion: Tumor necrosis significantly increased in N1-S1 tumor that received BU at the time of TAE when compared to TAE alone.

Strategies to Approaching Lower Limb Occlusions.

Caffeic acid is a natural phytochemical structurally similar to other cinnamic acids. In this study we found caffeic acid (CA) but not ferulic, sinapic or cinnamic acids inhibited proliferation of hepatocellular carcinoma cells (HCC) and reduced cell numbers by inducing apoptosis. Only transient exposure to CA was required for these lethal effects that are associated with disruption of mitochondrial membrane potential and induction of reactive oxygen species. By comparison, primary hepatocytes resisted CA toxicity for nearly 48 h, consistent with selective sensitivity of HCC to CA. These results support use of CA as an anti-tumor agent to inhibit HCC, especially if delivered by locoregional catheterization in an embolization procedure.

Rates of complication and embolic capture utilizing the NAV-6 embolic protection system during arterial interventions involving the lower extremity

Endovascular management of chronic total occlusions (CTO) can be challenging both from decision-making and technical perspectives. Successful treatment and management of a CTO requires the operator to have an understanding of the salient imaging findings, a thorough knowledge of the various technical challenges of the procedure, and comprehension of the importance and necessity of long-term clinical management. This article outlines a general approach to endovascular management of lower limb CTOs and discusses indications, techniques, potential complications, and therapeutic options of the procedure.

Cinnamic Acid Derivatives Enhance the Efficacy of Transarterial Embolization in a Rat Model of Hepatocellular Carcinoma

Effect of plantar arch integrity and number of crural vessel runoff on limb salvage rates Z. Tan, K. Tay, F. Irani, A. Gogna, S. Ramamurthy, R. Lo, A. Patel, S.X. Chan, C. Too, R. Jonathan, S.K. Sanamandra, B. Chua, S. Tan, S. Chng, S. Pasupathy, T. Chong, M. Pwint, B. Tan; Duke-NUS Graduate Medical School Singapore, Singapore, Singapore; Interventional Radiology Centre, Department of Diagnostic Radiology, Singapore General Hospital, Singapore, Singapore; Department of Vascular Surgery, Singapore General Hospital, Singapore, Singapore