Nam C. Yu

Percutaneous radiofrequency ablation of hepatocellular carcinoma as a bridge to liver transplantation

Orthotopic liver transplantation (OLT) can be a definitive treatment for patients with hepatocellular carcinoma (HCC). Prolonged waiting times for cadaveric livers, however, may lead to dropout from the waiting list or worsened post‐OLT prognosis as a result of interval tumor progression. Percutaneous radiofrequency ablation (RFA) is widely used for local control of small unresectable HCC, but its pretransplant role remains unclear. We studied the outcome of 52 consecutive patients accepted for OLT bearing 87 HCC nodules and treated with percutaneous RFA. On initial staging, the tumor burden exceeded the Milan criteria in 10 patients. Complete tumor coagulation was observed in 74 of 87 (85.1%) nodules based on postablation imaging. After a mean of 12.7 months (range: 0.3‐43.5) on the waiting list, 3 of 52 patients (5.8%) had dropped out due to tumor progression. Forty‐one patients had undergone transplantation, with 1‐ and 3‐year post‐OLT survival rates of 85% and 76%, respectively. No patient developed HCC recurrence. There were three major complications in 76 RFA procedures (hepatic arterial hemorrhage, small bowel perforation, and liver decompensation salvaged by OLT), without resultant death or dropout. In conclusion, percutaneous RFA is an effective bridge to OLT for patients with compensated liver function and safely accessible tumors. Tumor‐related dropout rate and post‐OLT outcome compared favorably with published controls of patients with early‐stage disease. This can be attributed to the efficacy of RFA in producing local cure or curbing tumor progression during the waiting period. (HEPATOLOGY 2005;41:1130–1137.)

Microwave Liver Ablation : Influence of Hepatic Vein Size on Heat-sink Effect in a Porcine Model

PURPOSE To determine influence of hepatic vein size on perfusion-mediated attenuation in adjacent microwave thermal ablation. MATERIALS AND METHODS With approval of the institutional animal research committee, seven Yorkshire pigs underwent percutaneous (n = 2) or open (n = 5) microwave liver ablation under general anesthesia. In each, multiple ultrasound-guided, nonoverlapping thermal lesions were created within 1 cm of hepatic veins in a 5-10-minute ablation at 45 W. After euthanasia, the liver was harvested and sectioned at 0.5-cm intervals and the degree of perivascular coagulation attenuation was graded on histopathologic analysis. Correlation between venous size (small, < or =3 mm; medium, 3-6 mm; and large, >6 mm) and attenuation grade was performed with use of the Spearman rank test. RESULTS In 63 of 103 sections (61%)--29 of 37 (78%) small, 27 of 48 (56%) medium, and seven of 18 (39%) large veins--the thermal injury extended to the vein wall around the entire circumference of the coagulation front without distortion of the ablation margin. In 40 of 103 sections (38.9%), varying degrees of concave distortion of perivenous ablation margins were noted, with significant correlation between vein size and heat-sink extent (P < .01). However, thermal injury extended to the vascular wall in all sections without complete circumferential sparing of liver tissue. Around two thrombosed veins, thermal lesions encased the vessels, producing paradoxically convex ablation margins. CONCLUSIONS Although the heat-sink effect was significantly dependent on hepatic vein size, the majority of pathologic sections exhibited no or minimal effect. Further study is required to assess clinical implications.

CT and MRI Improve Detection of Hepatocellular Carcinoma, Compared With Ultrasound Alone, in Patients With Cirrhosis

BACKGROUND & AIMS In patients with cirrhosis, hepatocellular carcinoma (HCC) is detected by ultrasound (US), computed tomography (CT), or magnetic resonance imaging (MRI); US is recommended for screening and surveillance. We performed a retrospective analysis of the abilities of these cross-sectional imaging modalities to detect HCC. METHODS We analyzed data from 638 consecutive adult patients with cirrhosis who received liver transplants within 6 months of imaging at a tertiary care institution. Imaging reports and serum alpha-fetoprotein levels were compared with results from pathology analysis of explants as the reference standard. Sensitivities of US, CT, and MRI were calculated overall and in defined size categories. False-positive imaging results and patient-based specificities were evaluated. RESULTS Of the 638 patients, 225 (35%) had HCC, confirmed by pathology analysis of liver explants. In 23 cases, the lesions were infiltrative or extensively multifocal. In the remaining 202 explants (337 numerable, discrete nodules), respective lesion-based sensitivities of US, CT, and MRI were 46%, 65%, and 72% overall and 21%, 40%, and 47% for small (<2 cm) HCC. The sensitivity of US increased with the availability of CT or MRI data (P = .049); sensitivity values were 62% and 85% for lesions 2-4 and ≥ 4 cm, respectively. Patient-based specificities of US, CT, and MRI were 96%, 96%, and 87%, respectively. CONCLUSIONS US, CT, and MRI did not detect small HCC lesions with high levels of sensitivity, although CT and MRI provide substantial improvements over unenhanced US in patients with cirrhosis who received liver transplants.

Hepatocellular Carcinoma in Liver Transplantation Candidates : Detection with Gadobenate Dimeglumine-Enhanced MRI

OBJECTIVE The purpose of this study was to retrospectively evaluate the diagnostic performance of dynamic gadobenate dimeglumine-enhanced MRI with explant pathologic correlation in the detection of hepatocellular carcinoma (HCC) in patients undergoing liver transplantation. MATERIALS AND METHODS Forty-seven patients (28 men, 19 women; mean age, 49 years) underwent dynamic gadobenate dimeglumine-enhanced MRI within 3 months before primary liver transplantation. Dynamic imaging was performed before (unenhanced) and after (hepatic arterial, portal venous, equilibrium, and 1-hour delayed phases) IV bolus administration of gadobenate dimeglumine at 0.1 mmol/kg body weight. Retrospective image analysis to detect HCC nodules was performed independently by two abdominal radiologists who had no pathologic information. On a per-nodule basis, the sensitivity and positive predictive value were calculated for the two observers. Sensitivity and specificity in the diagnosis of HCC also were evaluated. Fishers exact test was performed to determine whether there was a detection difference between HCC nodules 1 cm in diameter or larger and nodules smaller than 1 cm and to evaluate the differences in causes of false-positive MRI findings based on lesion size (>or= 1 cm vs < 1 cm). RESULTS Twenty-seven patients had 41 HCCs. In HCC detection, gadobenate dimeglumine-enhanced MRI had a sensitivity of 85% (35 of 41 HCCs) and a positive predictive value of 66% (35 of 53 readings) for observer 1 and a sensitivity of 80% (33 of 41 HCCs) and a positive predictive value of 65% (34 of 52 readings) for observer 2. For both observers, sensitivity in the detection of HCCs 1 cm in diameter and larger (91-94%) was significantly different (p < 0.05) from that in detection of HCCs smaller than 1 cm (29-43%). Nonneoplastic arterial hypervascular lesions more often caused false-positive diagnoses of lesions smaller than 1 cm in diameter (80-86%) on MR images than of those 1 cm in diameter and larger (0-25%). The difference was statistically significant (p < 0.05) for both observers. In diagnosis, gadobenate dimeglumine-enhanced MRI had a sensitivity of 87% (20 of 23 patients) and a specificity of 79% (19 of 24 patients) for both observers. CONCLUSION Dynamic gadobenate dimeglumine-enhanced MRI has a sensitivity of 80-85% and a positive predictive value of 65-66% in the detection of HCC. The technique, however, is of limited value for detecting and characterizing lesions smaller than 1 cm in diameter.

Intraoperative Triple Antenna Hepatic Microwave Ablation

OBJECTIVE Microwave ablation is emerging as a new treatment option for patients with unresectable hepatic malignancies. This two-center study shows the results of a phase 1 clinical trial of patients with known hepatic masses who underwent synchronous triple antenna microwave ablation before elective hepatic resection. SUBJECTS AND METHODS Intraoperative microwave ablation was performed before hepatic resection. Hepatic lesions were targeted using real-time intraoperative sonography with three microwave antennas positioned in a triangular configuration. Microwave ablation was performed at 45 W for 10 minutes. Hepatic resection was then completed in the standard fashion. Gross specimens were sectioned and measured to determine tumor and ablation sizes. Representative areas were stained with H and E stain and vital histochemical nicotinamide adenine dinucleotide (NADH) stain. RESULTS Ten patients with a mean age of 64 years (range, 48-79 years) were treated. Tumor histology included colorectal carcinoma metastases and hepatocellular carcinoma. The mean maximal tumor diameter was 4.4 cm (range, 2.0-5.7 cm). The mean maximal ablation diameter was 5.5 cm (range, 5.0-6.5 cm), while the average ablation zone volume was 50.8 cm3 (range, 30.3-65.5 cm3). Gross and microscopic examinations of areas after microwave ablation showed clear coagulation necrosis, even surrounding large hepatic vessels (> 3 mm in diameter). A marked thermallike effect was observed with maximal intensity closest to the antenna sites. NADH staining confirmed the uniform absence of viable tumor in the ablation zone. CONCLUSION This study shows the feasibility of using multiple microwave antennas simultaneously in the treatment of liver tumors intraoperatively. Additional percutaneous studies are currently under way to investigate the safety and efficacy in treating nonsurgical candidates.

Targeted Sonography for Small Hepatocellular Carcinoma Discovered by CT or MRI: Factors Affecting Sonographic Detection

OBJECTIVE The purpose of this study was to evaluate the detection rate of targeted sonography for small (<or= 3 cm) hepatocellular carcinomas (HCCs) primarily discovered by CT or MRI and to assess factors affecting lesion visibility on targeted sonography. SUBJECTS AND METHODS Between October 2005 and April 2008, targeted sonography for small (<or= 3 cm) HCC was prospectively performed in cirrhotic patients. Targeted sonography was performed by a radiologist with knowledge of the size and location of the HCC. Invisible HCCs were compared with visible HCCs with regard to size, distance from the diaphragm, segmental location, subcapsular location, cause of liver cirrhosis, presence or absence of previous treatment, Child-Pugh class, and serum alpha-fetoprotein by using univariate and multivariate analyses. RESULTS A total of 93 consecutive patients (65 men and 28 women; mean age, 59 years) with 93 HCCs (mean size +/- SD, 1.8 +/- 0.6 cm) were enrolled in this study. Of those, 73 (78.5%) HCCs were visible on targeted sonography. The detection rate was 36.4% (4/11) for HCC <or= 1.0 cm, 77.6% (38/49) for HCC between 1.1 and 2.0 cm, and 93.9% (31/33) for HCC between 2.1 and 3.0 cm. In both univariate and multivariate analyses, the size of the tumor and distance between the tumor and the diaphragm were statistically significant factors affecting sonographic visibility. CONCLUSION The overall detection rate for small (<or= 3 cm) HCC on targeted sonography was 78.5%. Small size and subphrenic location of the tumor were two independent predictors of sonographic invisibility.

Radiofrequency Ablation of Hepatocellular Carcinoma: Can Subcapsular Tumors Be Safely Ablated?

OBJECTIVE Our purpose was to retrospectively evaluate percutaneous radiofrequency ablation of unifocal subcapsular hepatocellular carcinoma (HCC) in comparison with nonsubcapsular tumors with regard to the technical and clinical outcomes. MATERIALS AND METHODS A total of 42 patients (23 men and 18 women; age range, 22-83 years) with unifocal HCC underwent percutaneous radiofrequency ablation as their sole interventional treatment between May 1998 and August 2003. Subcapsular tumors were selected for ablation if there was no large exophytic component, and they were ablated through an indirect puncture, a gradual increase in radiofrequency power output, and needle track ablation. Technical effectiveness after single-session radiofrequency ablation, complications, local tumor progression, overall survival, and event-free survival rates were compared between the two groups. RESULTS There were 15 patients with subcapsular HCC and 27 patients with nonsubcapsular HCC. The technical effectiveness was 93% (14/15) in the subcapsular HCC group and 96% (26/27) in the nonsubcapsular group (p > 0.99), complication rates were 0% (0/15) and 7.4% (2/27) (p = 0.53), and rates of local tumor progression were 21% (3/14) and 15% (4/26) (p = 0.68), respectively. No needle track or peritoneal seeding was found in either group. No significant differences were found in overall survival (3 years: 60% vs 56%; p = 0.78) and event-free survival rates (3 years: 59% vs 48%; p > 0.99) between the two groups. CONCLUSION Radiofrequency ablation of subcapsular HCC can be comparable to that of nonsubcapsular HCC with regard to the technical and clinical outcomes when there is proper patient selection and an optimized technique is used.

Detection and Grading of Esophageal Varices on Liver CT: Comparison of Standard and Thin-Section Multiplanar Reconstructions in Diagnostic Accuracy

OBJECTIVE The objective of our study was to evaluate the performance of liver CT in the diagnosis of esophageal varices in patients with cirrhosis and to determine whether thin-section multiplanar reconstructions (MPRs) improve accuracy. MATERIALS AND METHODS We identified 109 patients with cirrhosis who underwent endoscopy within 10 weeks after dual-phase liver MDCT supplemented with thin-section axial and coronal portal venous phase reconstructions. Two blinded radiologists independently evaluated each CT examination for the presence and sizes of varices using standard 5-mm axial versus 1- to 3-mm multiplanar images in separate sessions. Sensitivity, specificity, and predictive value calculations and receiver operating characteristic analysis were performed using endoscopy as the reference standard. Interobserver variability and correlation of CT size to variceal grade were assessed. RESULTS Twenty-six cases of high-risk esophageal varices were identified; all except two were detected on CT by one of the readers on standard 5-mm images. For both readers, sensitivity and negative predictive value (NPV) for the discrimination of high-risk varices using a criterion of 2 mm or greater were nearly the same for the standard 5-mm images versus the 1- to 3-mm multiplanar images (sensitivity and NPV: reader 1, 96% and 98% vs 96% and 99%; reader 2, and 89% and 95% vs 89% and 96%, respectively). Standard 5-mm images yielded a lower specificity for high-risk esophageal varices than the thin-section multiplanar images, and this difference was statistically significant for reader 2. Substantial interobserver agreement was noted for both esophageal varices detection and size measurements. CONCLUSION Standard liver CT is sensitive for the detection of high-risk varices and deserves further investigation as a potential cost-effective screening tool for the evaluation of patients with cirrhosis. The addition of 1- to 3-mm MPRs may increase specificity for risk stratification based on size measurements.

MR-guided percutaneous ethanol injection for hepatocellular carcinoma in a 0.2T open MR system

The purpose of this work is to describe our experience with single‐session percutaneous ethanol injection (PEI) under the guidance of 0.2‐T open MRI for hepatocellular carcinomas (HCC) that were not suitable for ablation under ultrasound (US) or computed tomography (CT) guidance. None of the lesions (N = 7) were detectable on US. MRI was chosen over CT as the guidance modality because the nodules were located in the hepatic dome (N = 4) or were invisible on noncontrast CT (N = 3). All of the nodules were targeted successfully, and apparently complete tumor necrosis was achieved in six nodules (86%). During a follow‐up of one to 41 months, only one patient developed local recurrence four months after PEI. MR‐guided PEI is feasible and effective for treating HCC when other imaging guidance methods are not appropriate. J. Magn. Reson. Imaging 2005.

Diffuse gallbladder wall thickening on computed tomography in patients with liver cirrhosis: correlation with clinical and laboratory variables.

Objectives: The objective of the study was to retrospectively evaluate (a) which clinical/laboratory features are associated with the presence of diffuse gallbladder wall thickening (DGWT) in cirrhotic patients and (b) whether the degree of DGWT is correlated with such clinical/laboratory variables. Methods: After excluding patients with DGWT or laboratory test abnormalities from known causes unrelated to liver cirrhosis, a retrospective review of liver computed tomography obtained from 242 consecutive cirrhotic patients was performed by 2 radiologists in consensus to determine the presence of DGWT of greater than 3 mm in thickness and, if present, to measure the degree of DGWT defined as maximal thickness. Univariate and multivariate analysis were performed to evaluate association between presence/degree of DGWT and clinical/laboratory features. Results: Of 242 patients, 73 (30.2%) had DGWT. Diffuse gallbladder wall thickening was seen in 7.6% (12/157) of patients with Child-Pugh class A, 61.1% (33/54) of class B, and 90.3% (28/31) of class C (P < 0.001). The presence of ascites, lower platelet count, and lower albumin level were independently associated with the presence of DGWT (P < 0.01, P = 0.01, and P = 0.02, respectively). However, these factors did not show significant correlation with the degree of DGWT. Conclusions: The presence of DGWT in cirrhotic patients is associated with the presence of ascites, lower platelet count, and lower albumin level. The degree of DGWT is not correlated with such variables.