John J. Park

Thermometry based on computed tomography images during microwave ablation: Trials on ex vivo porcine liver

Temperature knowledge may be beneficial to improve the outcomes of thermal treatments for tumor ablation. Among several thermometric methods, contactless approaches based on diagnostic imaging techniques are attractive for this field. Computed Tomography (CT) images are sensitive to temperature, so some groups of research are working to assess the feasibility of CT-based thermometry for monitoring the effects of thermal treatments. The aim of this study is to assess the feasibility of CT-thermometry during Microwave ablation (MWA) in ex vivo animal model. Healthy porcine livers were heated with two 2.45 GHz cooled-shaft MW antennas for four minutes at 65 W for each probe. Livers were scanned before heating and 16 times during the ablation (each 15 s). Liver temperature was measured in two points by two thermocouples. The relationship between the CT number (Hounsfield Unit, HU) and tissue temperature was investigated by using a linear regression analysis; thermal sensitivity of the CT number was estimated as the slope of the best fitting line. Results showed that CT number in liver tissue decreases during heating. The relationship between CT number and temperature is well described by a linear model (R2=0.91), and the thermal sensitivity is −0.52±0.02 HU∙°C-1. CT-based thermometry is feasible during MWA in ex vivo porcine livers. This technique is particularly attractive due to its non-invasiveness nature and can be used to monitor three-dimensional temperature distributions in heated tissues. Therefore, it may provide a powerful new tool during MWA or other thermal ablation procedures.

Outcomes of Salvage Percutaneous Biliary Drainage after Occlusion of Endoscopic Stents

PURPOSE To describe outcomes of patients with malignant biliary obstruction who undergo salvage percutaneous biliary drainage after occlusion of endoscopic biliary stents. MATERIALS AND METHODS A single-center retrospective review was performed of 47 patients (25 men, 22 women) who underwent percutaneous biliary drainage for recurrent obstruction after endoscopic stent placement between 2005 and 2015. Primary malignancies were bile duct (n = 13), colorectal (n = 11), gallbladder (n = 7), pancreas (n = 5), hepatocellular (n = 4), and other (n = 7). Indication for salvage drain placement was infection (n = 19) and jaundice or need to decrease bilirubin (n = 28). Kaplan-Meier and Cox regression methods were used for survival analysis. Logistic and multivariate regressions were employed to identify factors associated with survival. RESULTS Median survival after salvage biliary drain placement was 1.8 months (95% confidence interval [CI], 1.3-2.7). Elevated international normalized ratio (INR) ≥ 1.5 before drainage was associated with poorer survival after drainage (median survival 0.7 months vs 2.4 months, P < .01). Median survival was shorter in 28 patients (64%) with bilirubin ≤ 2 mg/dL (34.2 µmol/L) after drainage (1.2 months vs 5.4 months, P < .001). Left-sided drain placement, elevated bilirubin, and elevated INR correlated with decreased likelihood of achieving bilirubin ≤ 2 mg/dL (34.2 µmol/L) (odds ratio [OR] 0.13, 95% CI, 0.02-0.71, P = .02; OR 0.18, 95% CI, 0.05-0.69, P = .01; OR 0.10, 95% CI, 0.01-0.90, P = .04). CONCLUSIONS Survival is limited for most patients who undergo salvage percutaneous biliary drainage. Elevated bilirubin and INR before drainage portend a poor prognosis.