Iodine quantification and detectability thresholds among major dual-energy CT platforms.

OBJECTIVES: To estimate the minimum detectable iodine concentration on multiple dual-energy CT (DECT) platforms. METHODS AND MATERIALS: A phantom containing iodine concentrations ranging from 0 to 10 mg ml-1 was scanned with five dual-energy platforms (two rapid kilo volt switching (r-kVs), one dual source (DS), one sequential acquisition and one split-filter). Serial dilutions of 300 mg ml-1 iodinated contrast material were used to generate concentrations below 2 mg ml-1. Iodine density and virtual monoenergetic images were reviewed by three radiologists to determine the minimum visually detectable iodine concentration. Contrast-to-noise ratios (CNRs) were calculated. RESULTS: 1 mg mL-1 (~0.8 mg mL-1 corrected) was the minimum visually detectable concentration among the platforms and could be seen by all readers on the third-generation r-kVs and DS platforms. CONCLUSIONS: At low concentrations, CNR for monoenergetic images was highest on the DS platform and lowest in the sequential acquisition and split-filter platforms. ADVANCES IN KNOWLEDGE: The results of this study corroborate previous in vivo estimates of iodine detection limits at DECT and provide a comparison for the performance of different DECT platforms at low iodine concentrations in vitro.

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.

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.

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.

Sequential changes in echogenicity and conspicuity of small hepatocellular carcinoma on gray scale sonography after transcatheter arterial chemoembolization.

OBJECTIVE: The purpose of this study was to assess sequential changes in the echogenicity and conspicuity of small hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE). METHODS: Seventy patients with nodular HCC underwent 3 serial abdominal sonographic examinations before (t0), immediately after (t1), and 2 to 4 days after (t2) TACE. The echogenicity and conspicuity of the HCC nodules were prospectively graded using a 5-point scale. For all tumors, any changes in the echogenicity and conspicuity scores obtained at t0, t1, and t2 were evaluated. The degree of intratumoral uptake of iodized oil was categorized as compact or noncompact based on unenhanced computed tomographic images. Within each group, the sequential changes in the echogenicity and conspicuity were analyzed. Cross-sectional comparisons of the echogenicity and conspicuity at each time point between the two groups were also made. RESULTS: Overall, the lesion echogenicity and conspicuity at t1 increased compared with those at t0 (P < .05). Thereafter, both the echogenicity and conspicuity at t2 decreased compared with those at t1 (P < .05). There were 41 HCC nodules with compact iodized oil uptake and 29 with noncompact uptake. Significant sequential changes in the echogenicity (increase at t1 followed by decrease at t2) were noted in both groups, but only the compact group showed a significant change in conspicuity. In a cross-sectional comparison, the compact group showed higher scores for both echogenicity and conspicuity than the noncompact group at both t1 and t2 (P < .05). CONCLUSIONS: The echogenicity and conspicuity of HCC are increased immediately after TACE. These effects are significantly diminished 2 to 4 days after TACE.

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 (

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. Fisher's 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.

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.

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.

Esophageal varices in cirrhotic patients: evaluation with liver CT.

OBJECTIVE: The objective of this study was to evaluate the performance of routine helical liver CT in the detection and grading of esophageal varices in cirrhotic patients. MATERIALS AND METHODS: A total of 67 consecutive cirrhotic patients who underwent both upper endoscopy and helical liver CT within a 4-week interval were evaluated. The CT protocol included unenhanced, arterial, and portal phases with a collimation of 7-7.5 mm. Two blinded abdominal imagers (6 and 7 years' experience) retrospectively interpreted all CT images to detect the presence of esophageal varices on a 5-point confidence scale and measure the largest varix identified. Receiver operating characteristic (ROC) curve analysis was performed, and the correlation between CT measurements and endoscopic grading, the reference standard, was assessed. RESULTS: The variceal detection rates for the observers was 92% (11/12) and 92% (11/12) for large (i.e., clinically significant) varices, 53% (16/30) and 60% (18/30) for small varices, and 64% (27/42) and 69% (29/42) for all varices. The area under the ROC curve for the detection of esophageal varices of any size was 0.77 (observer 1) and 0.80 (observer 2). CT variceal grading showed a strong correlation with endoscopic grading for both observers (p < or = 0.001). Using a variceal diameter threshold of 3 mm on CT, sensitivity, specificity, and accuracy for distinguishing large esophageal varices from small or no varices were 92% (11/12), 84% (46/55), and 85% (57/67), respectively, for both observers. CONCLUSION: Liver CT is useful for the detection and grading of esophageal varices. A diameter of 3 mm may be an appropriate screening threshold for large clinically significant varices.

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.

Hepatocellular carcinoma: microwave ablation with multiple straight and loop antenna clusters--pilot comparison with pathologic findings.

The purpose of this study was to evaluate the clinical implementation of triangular and spherical designs for simultaneous multiple-antenna ablation of human hepatocellular carcinoma (HCC) with a recently engineered microwave coagulation system. Institutional review board approval and informed consent were obtained, and the study was compliant with HIPAA requirements. Nine patients (five men, four women; age range, 53-79 years; mean age, 66.2 years) with resectable HCC (diameter, 2.9-6.0 cm; mean, 4.2 cm) underwent intraoperative ultrasonography-guided tumor ablation followed by resection and pathologic examination. Standard single-straight (n = 2), triangular triple-straight (n = 4), and spherical triple-loop (n = 3) antenna configurations produced mean estimated coagulation volumes of 16.7, 51.7, and 54.3 cm(3), respectively, during a single concurrent 5-10-minute ablation cycle. The triple-loop configuration yielded the most uniformly round ablation shape. Simultaneous activation of multiple straight or loop antennae is a potentially promising technique for rapid and effective treatment of large HCCs.

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.

Pancreatic and peripancreatic diseases mimicking primary pancreatic neoplasia.

A variety of anatomic variants and pathologic conditions in and around the pancreas may simulate primary pancreatic neoplasia at routine abdominal cross-sectional imaging. An ambiguous lesion whose appearance suggests a pancreatic origin requires a broad differential diagnosis that can subsequently be narrowed on the basis of both clinical history and features at optimal computed tomography (CT) and magnetic resonance (MR) imaging. Pancreas-specific multidetector CT and MR imaging techniques with thin collimation, multiplanar and multiphasic scans, and newly introduced curved planar reformation may help avoid potential diagnostic pitfalls. These techniques can help identify and characterize a mass in multiple viewing planes, thereby helping distinguish a true pancreatic neoplasm from peripancreatic adenopathy or from a tumor of the adjacent duodenum or small bowel. They can also help determine the cause of a tumor. It is important that the radiologist be familiar with the wide spectrum of anatomic variants and disease entities that can mimic primary pancreatic neoplasia in order to initiate the appropriate lesion-specific work-up and treatment and avoid unnecessary tests or procedures, including surgery.

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.

Radiofrequency ablation of hepatocellular carcinoma: treatment success as defined by histologic examination of the explanted liver.

PURPOSE: To retrospectively evaluate the effectiveness of radiofrequency (RF) ablation of hepatocellular carcinoma (HCC) by using histologic examination of the explanted liver. MATERIALS AND METHODS: The study was approved by the medical center Institutional Review Board, with waiver of informed consent. Forty-seven HCC nodules in 24 patients (18 men, six women; age range, 33-71 years; mean age, 56 years) were treated with single or double RF ablation sessions prior to liver transplantation. Histologic data from hematoxylin-eosin staining of explanted liver specimens were retrospectively reviewed to determine treatment success, which was defined as the absence of residual or recurrent viable carcinoma cells at treatment site. Tumor size and the presence of large (> or =3 mm) abutting vessels that were observed during imaging were tested as potential predictors of treatment success or failure (Fisher exact test). In patients who underwent postablation computed tomographic (CT) or magnetic resonance (MR) imaging within 3 months prior to transplantation (21 patients with 44 tumors), imaging results were analyzed for sensitivity and specificity of residual or recurrent tumor by using histologic data as the reference standard. RESULTS: Thirty-five (74%) of 47 ablated tumors, including 29 (83%) of 35 tumors less than 3 cm, were found to be successfully treated on the basis of histologic findings after a mean interval of 7.5 months between RF ablation and transplantation. Nodules that were successfully treated had mean maximal diameter of 2.0 cm, and nodules that were unsuccessfully treated had mean maximal diameter of 3.1 cm (P=.014). Seven (47%) of 15 perivascular lesions were successfully treated whereas 28 (88%) of 32 nonperivascular lesions were successfully treated (P <.01). Imaging correlation showed 100% (33 of 33) specificity and 36% (four of 11) sensitivity of postablation CT and MR imaging for the depiction of residual or recurrent tumor. CONCLUSION: Histologic evidence directly validates RF ablation as an effective treatment of small (<3 cm) HCC.

Fistulas of the genitourinary tract: a radiologic review.

Fistulas of the genitourinary tract have diverse anatomic locations, causes, and clinical features. They can involve the upper urinary tract (kidney, ureter), the lower urinary tract (bladder, urethra), or the female reproductive tract (vagina, uterus). Causes include infection, inflammatory disease, neoplasms, congenital conditions, trauma, and iatrogenic injury. Diagnosis of genitourinary tract fistulas usually requires radiologic studies performed with fluoroscopic or cross-sectional modalities. Fistulography is the most direct means of visualizing a fistula and should be considered when feasible (eg, cutaneous fistulas). Intravenous urography and pyelography or ureterography are mainstays of investigation of the upper tract. Likewise, voiding cystourethrography and urethrography are central to study of the lower tract. Cross-sectional techniques, in particular computed tomography, are increasingly useful for diagnosis and are considered the primary test in some cases. Radiologists should be familiar with the radiologic features of genitourinary tract fistulas for accurate diagnosis and treatment planning. Management approaches depend on the type of fistula, the degree of morbidity, and the overall functional status of the patient and vary from conservative observation to aggressive surgical repair.