Burnout among Radiologists in Korea: Prevalence, Risk Factors, and Remedies

Burnout among radiologists has recently emerged as an issue that poses a threat to patient safety. Burnout adversely effects the quality of patient care and may lead to health problems in physicians. Approximately 84% of board-certified radiologists working in large hospitals in Korea responded that they had experienced burnout at least once. To overcome this, the standardization of physicians’ workloads, as well as improvements in the professional workflow are necessary to ensure a healthy lifestyle balance.

Severity of hyperechoic pancreas on ultrasonography as a risk factor for glycemic progression

Purpose@#The aim of this study was to evaluate the association between the severity of hyperechoic pancreas (HP) on ultrasonography (US) and glycemic progression. @*Methods@#In total, 1,386 participants who underwent abdominal US as part of health examinations between December 2008 and May 2014 were included in this retrospective study. We classified pancreatic echogenicity on a 4-point scale, and compared it using two distinct criteria: fatty pancreas (FP) 1 criterion (normal vs. ≥mild HP) and FP2 criterion (normal/mild HP vs. ≥moderate HP). According to the presence of nonalcoholic fatty liver disease (NAFLD), participants were subdivided into four groups: non-NAFLD and non-HP, isolated NAFLD, isolated HP, and HP with NAFLD. Glycemic progression was defined as progression from normoglycemia to prediabetes or diabetes or progression from prediabetes to diabetes. @*Results@#During the follow-up (median, 5.9 years), 262 of the 1,386 participants developed glycemic progression. Using FP2, the probability of glycemic progression across the four subgroups showed cumulative aggravation for NAFLD and HP (all P<0.05). Isolated HP showed a higher probability of glycemic progression than isolated NAFLD according to FP2 (P<0.001). The highest probability of glycemic progression was observed in patients with both NAFLD and HP (P<0.001). The hazard ratio for glycemic progression increased with the severity of HP. @*Conclusion@#Increasing severity of HP on US was found to be significantly correlated with glycemic progression. Moreover, isolated HP of moderate or greater severity predicted glycemic progression independent of NAFLD.

Two-Dimensional-Shear Wave Elastography with a Propagation Map: Prospective Evaluation of Liver Fibrosis Using Histopathology as the Reference Standard

Objective@#The aim of this study was to prospectively evaluate whether liver stiffness (LS) assessments, obtained by twodimensional (2D)-shear wave elastography (SWE) with a propagation map, can evaluate liver fibrosis stage using histopathology as the reference standard. @*Materials and Methods@#We prospectively enrolled 123 patients who had undergone percutaneous liver biopsy from two tertiary referral hospitals. All patients underwent 2D-SWE examination prior to biopsy, and LS values (kilopascal [kPa]) were obtained. On histopathologic examination, fibrosis stage (F0–F4) and necroinflammatory activity grade (A0–A4) were assessed. Multivariate linear regression analysis was performed to determine the significant factors affecting the LS value.The diagnostic performance of the LS value for staging fibrosis was assessed using receiver operating characteristic (ROC) analysis, and the optimal cut-off value was determined by the Youden index. @*Results@#Reliable measurements of LS values were obtained in 114 patients (92.7%, 114/123). LS values obtained from 2D-SWE with the propagation map positively correlated with the progression of liver fibrosis reported from histopathology (p < 0.001). According to the multivariate linear regression analysis, fibrosis stage was the only factor significantly associated with LS (p < 0.001). The area under the ROC curve of LS from 2D-SWE with the propagation map was 0.773, 0.865, 0.946, and 0.950 for detecting F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The optimal cut-off LS values were 5.4, 7.8, 9.4, and 12.2 kPa for F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The corresponding sensitivity and specificity of the LS value for detecting cirrhosis were 90.9% and 88.4%, respectively. @*Conclusion@#The LS value obtained from 2D-SWE with a propagation map provides excellent diagnostic performance in evaluating liver fibrosis stage, determined by histopathology.

Two-Dimensional-Shear Wave Elastography with a Propagation Map: Prospective Evaluation of Liver Fibrosis Using Histopathology as the Reference Standard

Objective@#The aim of this study was to prospectively evaluate whether liver stiffness (LS) assessments, obtained by twodimensional (2D)-shear wave elastography (SWE) with a propagation map, can evaluate liver fibrosis stage using histopathology as the reference standard. @*Materials and Methods@#We prospectively enrolled 123 patients who had undergone percutaneous liver biopsy from two tertiary referral hospitals. All patients underwent 2D-SWE examination prior to biopsy, and LS values (kilopascal [kPa]) were obtained. On histopathologic examination, fibrosis stage (F0–F4) and necroinflammatory activity grade (A0–A4) were assessed. Multivariate linear regression analysis was performed to determine the significant factors affecting the LS value.The diagnostic performance of the LS value for staging fibrosis was assessed using receiver operating characteristic (ROC) analysis, and the optimal cut-off value was determined by the Youden index. @*Results@#Reliable measurements of LS values were obtained in 114 patients (92.7%, 114/123). LS values obtained from 2D-SWE with the propagation map positively correlated with the progression of liver fibrosis reported from histopathology (p < 0.001). According to the multivariate linear regression analysis, fibrosis stage was the only factor significantly associated with LS (p < 0.001). The area under the ROC curve of LS from 2D-SWE with the propagation map was 0.773, 0.865, 0.946, and 0.950 for detecting F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The optimal cut-off LS values were 5.4, 7.8, 9.4, and 12.2 kPa for F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The corresponding sensitivity and specificity of the LS value for detecting cirrhosis were 90.9% and 88.4%, respectively. @*Conclusion@#The LS value obtained from 2D-SWE with a propagation map provides excellent diagnostic performance in evaluating liver fibrosis stage, determined by histopathology.

Added value of 2D shear wave imaging of the gallbladder bed of the liver for acute cholecystitis

Purpose@#The purpose of this study was to evaluate whether shear wave elastography (SWE) and the shear wave dispersion slope (SWD) obtained from 2-dimensional shear wave imaging (2D-SWI) of the gallbladder (GB) bed of the liver could be helpful in the diagnosis of acute cholecystitis. @*Methods@#We included 44 patients referred for abdominal ultrasonography (US) under the impression of acute cholecystitis from April 2018 to March 2019. Patients with chronic liver disease were excluded from this study. In addition to routine upper abdominal US, we performed 2D-SWI including liver stiffness measurements by SWE and SWD, which reflects tissue viscosity. 2D-SWI was performed at the GB bed of the liver through the right intercostal approach at least 3 times with different frames. We assessed typical US findings and the added value of 2D-SWI in diagnosing acute cholecystitis. Histopathologic results of surgical specimens were used as the standard of reference. If a surgical specimen was unavailable, a bile fluid test or clinical followup for more than 3 months served as the reference standard. @*Results@#The optimal cutoff values for SWE and SWD were 8 kPa and 10.9 (m/sec)/kHz, respectively. In the univariate analysis, SWE, GB distension, and sludge were predictive factors of acute cholecystitis. In the multivariate analysis, categorized SWE was the only significant predictor (P<0.01). By using 2D-SWI, the diagnostic performance of two readers did not significantly increase, although the inter-reader agreement improved (k=0.654-0.778). @*Conclusion@#2D-SWI of the GB bed of the liver could be helpful for diagnosing acute cholecystitis.

The AFSUMB Consensus Statements and Recommendations for the Clinical Practice of Contrast-Enhanced Ultrasound using Sonazoid

The first edition of the guidelines for the use of ultrasound contrast agents was published in 2004, dealing with liver applications. The second edition of the guidelines in 2008 reflected changes in the available contrast agents and updated the guidelines for the liver, as well as implementing some nonliver applications. The third edition of the contrast-enhanced ultrasound (CEUS) guidelines was the joint World Federation for Ultrasound in Medicine and Biology-European Federation of Societies for Ultrasound in Medicine and Biology (WFUMB-EFSUMB) venture in conjunction with other regional US societies such as Asian Federation of Societies for Ultrasound in Medicine and Biology, resulting in a simultaneous duplicate on liver CEUS in the official journals of both WFUMB and EFSUMB in 2013. However, no guidelines were described mainly for Sonazoid due to limited clinical experience only in Japan and Korea. The new proposed consensus statements and recommendations provide general advice on the use of Sonazoid and are intended to create standard protocols for the use and administration of Sonazoid in hepatic and pancreatobiliary applications in Asian patients and to improve patient management.

History of the Asian Society of Abdominal Radiology

A Rare Case of Zinner's Syndrome with Ectopic Prostate and Triorchidism

Zinner's syndrome is a rare congenital abnormality of the mesonephric duct. Unilateral renal agenesis, ipsilateral seminal vesicle cyst, and ipsilateral ejaculatory duct obstruction are the triad of maldevelopment of the mesonephric duct which comprises Zinner's syndrome. It is an extremely rare case, in that approximately 100 cases only have been reported worldwide. We discovered a rare developmental anomaly with other mesonephric duct-associated abnormalities, Zinner's syndrome with a presumed ectopic prostate and triorchidism and do report here.

Arteriovenous Malformation of the Distal Ileum in a 14-Year-Old Girl with Recurrent Abdominal Pain: A Case Report

Arteriovenous malformation (AVM) is a lesion involving a high-flow vascular malformation, which is one of the causes of massive gastrointestinal bleeding. In the pediatric population, AVM is quite rare in the gastrointestinal tract, and the most common primary site is the colon. A small bowel is a rare primary site of AVM, and only 1 case has been reported in Korea. Here, we report on a case of AVM found in the distal ileum of a 14-year-old girl who complained about recurrent lower abdominal pain only without a gastrointestinal hemorrhage. In the previous research literature, a small bowel AVM can be diagnosed through detecting the existence of an enhancing nidus of the intestinal wall at the arterial phase, accompanied by an early draining vein as it appeared on a dynamic contrast-enhanced abdominal computed tomography. In our case, the pathologically confirmed AVM of the distal ileum showed a dot-like enhancement within the thick low-attenuating submucosal layer of the terminal ileum.

Ultrasonography: current status, challenges, and future directions

No abstract available.

Radiologic Findings in Extrapancreatic Solid Pseudopapillary Tumor with Aggressive Behavior: a Case Report

Solid pseudopapillary tumor (SPT) is a low grade malignant tumor in the pancreas, and extrapancreatic SPT is extremely rare. We report a case of a 61-year-old woman who complained abdominal pain with diffuse tenderness. She was diagnosed with extrapancreatic SPT with extensive peritoneal dissemination and hepatic metastases. Although a few cases have reported imaging findings of extrapancreatic SPT, there have been no reports of extrapancreatic SPT with aggressive tumor behavior and dismal prognosis. Although imaging features closely resembled those of classical pancreatic SPTs, malignant transformation of extrapancreatic SPT should be considered when focal discontinuity of the tumor capsule with ill-defined margin and invasion of adjacent structures were identified.

Therapeutic Effects of Microbubbles Added to Combined High-Intensity Focused Ultrasound and Chemotherapy in a Pancreatic Cancer Xenograft Model

OBJECTIVE: To investigate whether high-intensity focused ultrasound (HIFU) combined with microbubbles enhances the therapeutic effects of chemotherapy. MATERIALS AND METHODS: A pancreatic cancer xenograft model was established using BALB/c nude mice and luciferase-expressing human pancreatic cancer cells. Mice were randomly assigned to five groups according to treatment: control (n = 10), gemcitabine alone (GEM; n = 12), HIFU with microbubbles (HIFU + MB, n = 11), combined HIFU and gemcitabine (HIGEM; n = 12), and HIGEM + MB (n = 13). After three weekly treatments, apoptosis rates were evaluated using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay in two mice per group. Tumor volume and bioluminescence were monitored using high-resolution 3D ultrasound imaging and in vivo bioluminescence imaging for eight weeks in the remaining mice. RESULTS: The HIGEM + MB group showed significantly higher apoptosis rates than the other groups (p < 0.05) and exhibited the slowest tumor growth. From week 5, the tumor-volume-ratio relative to the baseline tumor volume was significantly lower in the HIGEM + MB group than in the control, GEM, and HIFU + MB groups (p < 0.05). Despite visible distinction, the HIGEM and HIGEM + MB groups showed no significant differences. CONCLUSION: High-intensity focused ultrasound combined with microbubbles enhances the therapeutic effects of gemcitabine chemotherapy in a pancreatic cancer xenograft model.

Comparison of Multidetector CT and Gadobutrol-Enhanced MR Imaging for Evaluation of Small, Solid Pancreatic Lesions

OBJECTIVE: To compare multidetector computed tomography (MDCT) and MRI for lesion conspicuity, as well as the detection and characterization of small solid pancreatic lesions (SPLs). MATERIALS AND METHODS: 193 patients with small SPLs ( 0.05). The accuracies of CT and MRI for making a specific diagnosis were as follows: 85.7% (210/245) vs. 86.9% (213/245), respectively, for reviewer 1 (p = 0.736), and 91.8% (225/245) vs. 93.5% (229/245), respectively, for reviewer 2 (p = 0.454). CONCLUSION: MRI showed better lesion conspicuity than MDCT, but did not show significantly different diagnostic performance compared with MDCT for detecting and characterizing small SPLs.

Dynamic Contrast-Enhanced MRI Using a Macromolecular MR Contrast Agent (P792): Evaluation of Antivascular Drug Effect in a Rabbit VX2 Liver Tumor Model

OBJECTIVE: To evaluate the utility of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using macromolecular contrast agent (P792) for assessment of vascular disrupting drug effect in rabbit VX2 liver tumor models. MATERIALS AND METHODS: This study was approved by our Institutional Animal Care and Use Committee. DCE-MRI was performed with 3-T scanner in 13 VX2 liver tumor-bearing rabbits, before, 4 hours after, and 24 hours after administration of vascular disrupting agent (VDA), using gadomelitol (P792, n = 7) or low molecular weight contrast agent (gadoterate meglumine [Gd-DOTA], n = 6). P792 was injected at a of dose 0.05 mmol/kg, while that of Gd-DOTA was 0.2 mmol/kg. DCE-MRI parameters including volume transfer coefficient (K(trans)) and initial area under the gadolinium concentration-time curve until 60 seconds (iAUC) of tumors were compared between the 2 groups at each time point. DCE-MRI parameters were correlated with tumor histopathology. Reproducibility in measurement of DCE-MRI parameters and image quality of source MR were compared between groups. RESULTS: P792 group showed a more prominent decrease in K(trans) and iAUC at 4 hours and 24 hours, as compared to the Gd-DOTA group. Changes in DCE-MRI parameters showed a weak correlation with histologic parameters (necrotic fraction and microvessel density) in both groups. Reproducibility of DCE-MRI parameters and overall image quality was not significantly better in the P792 group, as compared to the Gd-DOTA group. CONCLUSION: Dynamic contrast-enhanced magnetic resonance imaging using a macromolecular contrast agent shows changes of hepatic perfusion more clearly after administration of the VDA. Gadolinium was required at smaller doses than a low molecular contrast agent.

Reduced Field-of-View Diffusion-Weighted Magnetic Resonance Imaging of the Pancreas: Comparison with Conventional Single-Shot Echo-Planar Imaging

OBJECTIVE: To investigate the image quality (IQ) and apparent diffusion coefficient (ADC) of reduced field-of-view (FOV) di-ffusion-weighted imaging (DWI) of pancreas in comparison with full FOV DWI. MATERIALS AND METHODS: In this retrospective study, 2 readers independently performed qualitative analysis of full FOV DWI (FOV, 38 × 38 cm; b-value, 0 and 500 s/mm²) and reduced FOV DWI (FOV, 28 × 8.5 cm; b-value, 0 and 400 s/mm²). Both procedures were conducted with a two-dimensional spatially selective radiofrequency excitation pulse, in 102 patients with benign or malignant pancreatic diseases (mean size, 27.5 ± 14.4 mm). The study parameters included 1) anatomic structure visualization, 2) lesion conspicuity, 3) artifacts, 4) IQ score, and 5) subjective clinical utility for confirming or excluding initially considered differential diagnosis on conventional imaging. Another reader performed quantitative ADC measurements of focal pancreatic lesions and parenchyma. Wilcoxon signed-rank test was used to compare qualitative scores and ADCs between DWI sequences. Mann Whitney U-test was used to compare ADCs between the lesions and parenchyma. RESULTS: On qualitative analysis, reduced FOV DWI showed better anatomic structure visualization (2.76 ± 0.79 at b = 0 s/mm² and 2.81 ± 0.64 at b = 400 s/mm²), lesion conspicuity (3.11 ± 0.99 at b = 0 s/mm² and 3.15 ± 0.79 at b = 400 s/mm²), IQ score (8.51 ± 2.05 at b = 0 s/mm² and 8.79 ± 1.60 at b = 400 s/mm²), and higher clinical utility (3.41 ± 0.64), as compared to full FOV DWI (anatomic structure, 2.18 ± 0.59 at b = 0 s/mm² and 2.56 ± 0.47 at b = 500 s/mm²; lesion conspicuity, 2.55 ± 1.07 at b = 0 s/mm² and 2.89 ± 0.86 at b = 500 s/mm²; IQ score, 7.13 ± 1.83 at b = 0 s/mm² and 8.17 ± 1.31 at b = 500 s/mm²; clinical utility, 3.14 ± 0.70) (p 0.05). ADCs of adenocarcinomas (1.061 × 10⁻³ mm²/s ± 0.133 at reduced FOV and 1.079 × 10⁻³ mm²/s ± 0.135 at full FOV) and neuroendocrine tumors (0.983 × 10⁻³ mm²/s ± 0.152 at reduced FOV and 1.004 × 10⁻³ mm²/s ± 0.153 at full FOV) were significantly lower than those of parenchyma (1.191 × 10⁻³ mm²/s ± 0.125 at reduced FOV and 1.218 × 10⁻³ mm²/s ± 0.103 at full FOV) (p < 0.05). CONCLUSION: Reduced FOV DWI of the pancreas provides better overall IQ including better anatomic detail, lesion conspicuity and subjective clinical utility.

UltraFast Doppler ultrasonography for hepatic vessels of liver recipients: preliminary experiences

PURPOSE: The purpose of this study was to investigate the value of UltraFast Doppler ultrasonography (US) for evaluating hepatic vessels in liver recipients. METHODS: Thirty-nine liver Doppler US sessions were conducted in 20 liver recipients. Each session consisted of UltraFast and conventional liver Doppler US in a random order. We compared the velocities and phasicities of the hepatic vessels, duration of each Doppler study, occurrence of technical failures, and differences in clinical decisions. RESULTS: The velocities and resistive index values of hepatic vessels showed a strong positive correlation between the two Doppler studies (mean R=0.806; range, 0.710 to 0.924). The phasicities of the hepatic vessels were the same in both Doppler US exams. With respect to the duration of the Doppler US exam, there was no significant difference between the UltraFast (251+/-99 seconds) and conventional (231+/-117 seconds) Doppler studies (P=0.306). In five poor breath-holders, in whom the duration of conventional Doppler US was longer, UltraFast Doppler US (272+/-157 seconds) required a shorter time than conventional Doppler US (381+/-133 seconds; P=0.005). There was no difference between the two techniques with respect to technical failures and clinical decisions. CONCLUSION: UltraFast Doppler US is clinically equivalent to conventional Doppler US with advantages for poor breath-holders during the post-liver transplantation work-up.

Adaptive Iterative Dose Reduction Algorithm in CT: Effect on Image Quality Compared with Filtered Back Projection in Body Phantoms of Different Sizes

OBJECTIVE: To evaluate the impact of the adaptive iterative dose reduction (AIDR) three-dimensional (3D) algorithm in CT on noise reduction and the image quality compared to the filtered back projection (FBP) algorithm and to compare the effectiveness of AIDR 3D on noise reduction according to the body habitus using phantoms with different sizes. MATERIALS AND METHODS: Three different-sized phantoms with diameters of 24 cm, 30 cm, and 40 cm were built up using the American College of Radiology CT accreditation phantom and layers of pork belly fat. Each phantom was scanned eight times using different mAs. Images were reconstructed using the FBP and three different strengths of the AIDR 3D. The image noise, the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) of the phantom were assessed. Two radiologists assessed the image quality of the 4 image sets in consensus. The effectiveness of AIDR 3D on noise reduction compared with FBP were also compared according to the phantom sizes. RESULTS: Adaptive iterative dose reduction 3D significantly reduced the image noise compared with FBP and enhanced the SNR and CNR (p < 0.05) with improved image quality (p < 0.05). When a stronger reconstruction algorithm was used, greater increase of SNR and CNR as well as noise reduction was achieved (p < 0.05). The noise reduction effect of AIDR 3D was significantly greater in the 40-cm phantom than in the 24-cm or 30-cm phantoms (p < 0.05). CONCLUSION: The AIDR 3D algorithm is effective to reduce the image noise as well as to improve the image-quality parameters compared by FBP algorithm, and its effectiveness may increase as the phantom size increases.

Noninvasive Assessment of Hepatic Fibrosis in Patients with Chronic Hepatitis B Viral Infection Using Magnetic Resonance Elastography

OBJECTIVE: To evaluate the diagnostic performance of magnetic resonance elastography (MRE) for staging hepatic fibrosis in patients with chronic hepatitis B virus (HBV) infection. MATERIALS AND METHODS: Patients with chronic HBV infection who were suspected of having focal or diffuse liver diseases (n = 195) and living donor candidates (n = 166) underwent MRE as part of the routine liver MRI examination. We measured liver stiffness (LS) values on quantitative shear stiffness maps. The technical success rate of MRE was then determined. Liver cell necroinflammatory activity and fibrosis were assessed using histopathologic examinations as the reference. Areas under the receiver operating characteristic curve (Az) were calculated in order to predict the liver fibrosis stage. RESULTS: The technical success rate of MRE was 92.5% (334/361). The causes of technical failure were poor wave propagation (n = 12), severe respiratory motion (n = 3), or the presence of iron deposits in the liver (n = 12). The mean LS values, as measured by MRE, increased significantly along with an increase in the fibrosis stage (r = 0.901, p or = F1, > or = F2, > or = F3, and F4 were 2.45 kPa, 2.69 kPa, 3.0 kPa, and 3.94 kPa, respectively, and with Az values of 0.987-0.988. CONCLUSION: MRE has a high technical success rate and excellent diagnostic accuracy for staging hepatic fibrosis in patients with chronic HBV infection.

Differentiating between Adenomyomatosis and Gallbladder Cancer: Revisiting a Comparative Study of High-Resolution Ultrasound, Multidetector CT, and MR Imaging

OBJECTIVE: To compare the diagnostic performance of high-resolution ultrasound (HRUS) with contrast-enhanced CT and contrast-enhanced magnetic resonance imaging (MRI) with MR cholangiopancreatography (MRCP) to differentiate between adenomyomatosis (ADM) and gallbladder cancer (GBCA). MATERIALS AND METHODS: Forty patients with surgically proven ADM (n = 13) or GBCA at stage T2 or lower (n = 27) who previously underwent preoperative HRUS, contrast-enhanced CT, and contrast-enhanced MRI with MRCP were retrospectively included in this study. According to the well-known diagnostic criteria, two reviewers independently analyzed the images from each modality separately with a five-point confidence scale. The interobserver agreement was calculated using weighted kappa statistics. A receiver operating characteristic curve analysis was performed and the sensitivity, specificity, and accuracy were calculated for each modality when scores of 1 or 2 indicated ADM. RESULTS: The interobserver agreement between the two reviewers was good to excellent. The mean Az values for HRUS, multidetector CT (MDCT), and MRI were 0.959, 0.898, and 0.935, respectively, without any statistically significant differences between any of the modalities (p > 0.05). The mean sensitivity of MRI with MRCP (80.8%) was significantly higher than that of MDCT (50.0%) (p = 0.0215). However, the mean sensitivity of MRI with MRCP (80.8%) was not significantly different from that of HRUS (73.1%) (p > 0.05). The mean specificities and accuracies among the three modalities were not significantly different (p > 0.05). CONCLUSION: High-resolution ultrasound and MRI with MRCP have comparable sensitivity and accuracy and MDCT has the lowest sensitivity and accuracy for the differentiation of ADM and GBCA.

Monopolar Radiofrequency Ablation Using a Dual-Switching System and a Separable Clustered Electrode: Evaluation of the In Vivo Efficiency

OBJECTIVE: To determine the in vivo efficiency of monopolar radiofrequency ablation (RFA) using a dual-switching (DS) system and a separable clustered (SC) electrode to create coagulation in swine liver. MATERIALS AND METHODS: Thirty-three ablation zones were created in nine pigs using a DS system and an SC electrode in the switching monopolar mode. The pigs were divided into two groups for two experiments: 1) preliminary experiments (n = 3) to identify the optimal inter-electrode distances (IEDs) for dual-switching monopolar (DSM)-RFA, and 2) main experiments (n = 6) to compare the in vivo efficiency of DSM-RFA with that of a single-switching monopolar (SSM)-RFA. RF energy was alternatively applied to one of the three electrodes (SSM-RFA) or concurrently applied to a pair of electrodes (DSM-RFA) for 12 minutes in in vivo porcine livers. The delivered RFA energy and the shapes and dimensions of the coagulation areas were compared between the two groups. RESULTS: No pig died during RFA. The ideal IEDs for creating round or oval coagulation area using the DSM-RFA were 2.0 and 2.5 cm. DSM-RFA allowed more efficient RF energy delivery than SSM-RFA at the given time (23.0 +/- 4.0 kcal vs. 16.92 +/- 2.0 kcal, respectively; p = 0.0005). DSM-RFA created a significantly larger coagulation volume than SSM-RFA (40.4 +/- 16.4 cm3 vs. 20.8 +/- 10.7 cm3; p < 0.001). Both groups showed similar circularity of the ablation zones (p = 0.29). CONCLUSION: Dual-switching monopolar-radiofrequency ablation using an SC electrode is feasible and can create larger ablation zones than SSM-RFA as it allows more RF energy delivery at a given time.