Imaging of Hepatic Fibrosis.

PURPOSE OF REVIEW: The purpose of this review is to discuss the current imaging techniques for non-invasive assessment of liver fibrosis (LF). RECENT FINDINGS: Elastography-based techniques are the most widely used imaging methods for the evaluation of LF. Currently, MR elastography (MRE) is the most accurate non-invasive method for detection and staging of LF. Ultrasound-based vibration-controlled transient elastography (VCTE) is the most widely used as it can be easily performed at the point of care but has technical limitations especially in the obese. Innovations and technical improvements continue to evolve in elastography for improving accuracy and avoiding misinterpretation from confounding factors. Other imaging methods including diffusion-weighted imaging (DWI), hepatocellular contrast-enhanced (HCE) MRI, T1 relaxometry, T1ρ imaging, textural analysis, liver surface nodularity, susceptibility-weighted imaging, and perfusion imaging are promising but need further evaluation and clinical validation. MRE is the most accurate imaging technique for assessment of LF.

Magnetic resonance elastography of abdomen.

Many diseases cause substantial changes in the mechanical properties of tissue, and this provides motivation for developing methods to noninvasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate noninvasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed.

Magnetic resonance elastography of liver: influence of intravenous gadolinium administration on measured liver stiffness.

PURPOSE: To evaluate the effect of intravenous gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) on estimation of liver stiffness using magnetic resonance elastography (MRE) for detection of liver fibrosis. MATERIALS AND METHODS: Liver MRI with MRE was performed in 210 subjects on a single 1.5 Tesla clinical MRI scanner. Liver MRE was performed before intravenous Gd-DTPA injection (NC-MRE) and 5 minutes post injection (PC-MRE) using a modified phase-contrast gradient-echo sequence (TR/TE=100/27 ms, FOV = 30-46 cm, 4 x 10 mm slices, gap 5 mm) which automatically generated stiffness maps. Two readers' blinded to clinical details independently performed liver stiffness measurements (LSM) by drawing 2 or more regions of interest (ROI) on the stiffness maps on each of the four slices of NC-MRE and PC-MRE obtained for each patient. The mean LSM in kilopascals (kPa) for NC-MRE and PC-MRE was calculated. The correlation between NC-MRE and PC-MRE LSM was evaluated with a paired t test and Pearson's correlation analysis, and the inter-observer correlation was evaluated using intra class coefficient (ICC) analysis. A receiver operating curve analysis (ROC) was performed to compare accuracies for detection and staging of liver fibrosis in a subgroup of 72 subjects with histological confirmation of liver fibrosis. RESULTS: There was an excellent correlation between NC-MRE and PC-MRE LSM (R(2)=0.98, p<0.001) with no significant differences. The interobserver agreement was also excellent (ICC, 0.94-0.99). There were no significant differences in the cut-off LSM value/accuracy/sensitivity/specificity for detection of significant liver fibrosis with NC-MRE and PC-MRE (2.98 kPa/98.5%/100%/88%, p<0.001 and 3.1 kPa/98.2%/98%/88%, p<0.001 respectively). CONCLUSION: Intravenous Gd-DTPA had no significant influence on LSM with MRE and does not significantly affect the diagnostic performance of MRE for fibrosis detection.

Magnetic resonance elastography for the detection and staging of liver fibrosis in chronic hepatitis B.

OBJECTIVES: We measured the accuracy of magnetic resonance elastography (MRE) for the detection and staging of liver fibrosis in chronic hepatitis B (CHB) and compared it with serum fibrosis markers. METHODS: Prospective comparison of MRE and routine serum fibrosis markers, namely serum alanine aminotransferase (ALT), serum aspartate aminotransferase (AST), ALT/AST ratio (AAR), AST to platelet ratio index (APRI) and prothrombin index (PI), was performed in 63 consecutive CHB patients who underwent MRE and histological confirmation of liver fibrosis within a 6-month interval. Diagnostic performance of MRE and serum markers for staging fibrosis (≥F1), significant fibrosis (≥F2), advanced fibrosis (≥F3) and cirrhosis (F4) was compared. RESULTS: The study group comprised 63 patients (19 female; mean age ± SD, 50 ± 11.9 years). MRE (ρ = 0.94, P < 0.0001), APRI (ρ = 0.42, P = 0.0006), PI (ρ = 0.42, P = 0.0006) and AST (ρ = 0.28, P = 0.028) results correlated significantly with fibrosis stage. MRE was significantly more accurate than serum fibrosis markers for the detection of significant fibrosis (0.99 vs. 0.55-0.73) and cirrhosis (0.98 vs. 0.53-0.77). Sensitivity, specificity, positive predictive and negative predictive values for MRE for significant fibrosis and cirrhosis were 97.4 %, 100 %, 100 % and 96 %, and 100 %, 95.2 %, 91.3 % and 100 %, respectively. CONCLUSION: MRE is an accurate non-invasive technique for the detection and staging of liver fibrosis in CHB. KEY POINTS: • Magnetic resonance elastography is accurate for liver fibrosis detection and staging. • MR elastography is more accurate than serum tests for staging liver fibrosis. • MR elastography can potentially replace liver biopsy in chronic hepatitis B.

Utility of non-contrast-enhanced CT for improved detection of arterial phase hyperenhancement in hepatocellular carcinoma.

PURPOSE: To determine the utility of non-contrast-enhanced CT (NC-CT) for improved detection of hyperenhancement in hepatocellular carcinomas (HCC). METHODS: We performed a retrospective analysis on CT studies of 104 consecutive patients with 124 HCCs between October 2006 and December 2012. The enhancement of HCC was evaluated on quadriphasic CT: non-contrast (NC), arterial phase (AP), portal-venous phase (PVP), and delayed phases (DP) were performed. For determination of enhancement, mean attenuation of the HCC and surrounding non-tumor bearing liver in the four phases were recorded. Hyperenhancement was defined by either HCC (AP-NC) representing absolute lesion enhancement or AP (HCC-liver), representing relative enhancement. An increase of ≥10 Hounsfield units (HU) was considered as enhancement. Two radiologists (R1 and R2) independently performed a conventional qualitative assessment for hyperenhancement of HCC. The accuracy of detection by proposed absolute lesion enhancement HCC (AP-NC) was compared to relative enhancement AP (HCC-liver) and qualitative assessment by readers with the McNemar test. RESULTS: The proposed criteria of absolute lesion enhancement, HCC (AP-NC) identified more hypervascular nodules compared to qualitative analysis (92% vs. 62% for R1 and 69% for R2), equating to an improvement of 23%-31%. In contrast, relative enhancement AP (HCC-liver) was found to be inferior to conventional qualitative analysis (50% vs. 62%-69% for readers). CONCLUSION: NC-CT is useful to improve the detection of hyperenhancement in HCCs for imaging diagnosis.

Imaging of fibropolycystic liver disease.

Fibropolycystic liver diseases (FLDs) make up a rare spectrum of heritable hepatobiliary diseases resulting from congenital ductal plate malformations (DPMs) due to the dysfunction of proteins expressed on the primary cilia of cholangiocytes. The embryonic development of the ductal plate is key to understanding this spectrum of diseases. In particular, DPMs can result in various degrees of intrahepatic duct involvement and a wide spectrum of cholangiopathies, including congenital hepatic fibrosis, Caroli disease, polycystic liver disease, and Von Meyenberg complexes. The most common clinical manifestations of FLDs are portal hypertension, cholestasis, cholangitis, and (in rare cases) cholangiocarcinoma. This article reviews recent updates in the pathophysiology, imaging, and clinical management of FLDs.

Spontaneous inferior epigastric artery pseudoaneurysm.

A case of spontaneous pseudoaneurysm of the inferior epigastric artery-diagnosed on Doppler sonography-is presented. A 19-year-old boy presented with a lump in the anterior abdominal wall. Clinically a smooth, nontender, and noncompressible mass was present above umbilicus to the right of midline. A bruit was heard over the swelling. Doppler sonography demonstrated an oval hypoechoic structure in the right rectus sheath with turbulent flow. The pseudoaneurysm could be traced to the inferior epigastric artery. Surgical excision of pseudoaneurysm was performed. Histopathology showed myxoid changes in the wall of the pseudoaneurysm with no inflammatory changes.

Advances in Magnetic Resonance Elastography of Liver.

Magnetic resonance elastography (MRE) is the most accurate noninvasive technique in diagnosing fibrosis and cirrhosis in patients with chronic liver disease (CLD). The accuracy of hepatic MRE in distinguishing the severity of disease has been validated in studies of patients with various CLDs. Advanced hepatic MRE is a reliable, comfortable, and inexpensive alternative to liver biopsy for disease diagnosing, progression monitoring, and clinical decision making in patients with CLDs. This article summarizes current knowledge of the technical advances and innovations in hepatic MRE, and the clinical applications in various hepatic diseases.

Abbreviated Magnetic Resonance Imaging Protocols in the Abdomen and Pelvis.

In recent decades, the clinical applications for which magnetic resonance (MR) imaging is routinely used have expanded exponentially. MR imaging protocols have become increasingly complex, adversely affecting image acquisition and interpretation times. The MR imaging workflow has become a prime target for process improvement initiatives. There has been growing interest in the cultivation of abbreviated MR imaging protocols that evaluate specific clinical questions while reducing cost and increasing access. The overarching goal is to streamline the MR imaging workflow and reduce the time needed to obtain and report examinations by eliminating duplicative or unnecessary sequences without sacrificing diagnostic accuracy.

CT of blunt pancreatic trauma: a pictorial essay.

Blunt trauma to pancreas is uncommon and clinical features are often non-specific and unreliable leading to possible delays in diagnosis and therefore increased morbidity. CT has been established as the imaging modality of choice for the diagnosis of abdominal solid-organ injury in the blunt trauma patient. The introduction of multidetector-row CT allows for high resolution scans and multiplanar reformations that improve diagnosis. Detection of pancreatic injuries on CT requires knowledge of the subtle changes produced by pancreatic injury. The CT appearance of pancreatic injury ranges from a normal initial appearance of the pancreas to active pancreatic bleeding. Knowledge of CT signs of pancreatic trauma and a high index of suspicion is required in diagnosing pancreatic injury.

Magnetic Resonance Elastography of Liver: Current Update.

The first clinical application of magnetic resonance elastography (MRE) was in the evaluation of chronic liver disease (CLD) for detection and staging of liver fibrosis. In the past 10 years, MRE has been incorporated seamlessly into a standard magnetic resonance imaging (MRI) liver protocol worldwide. Liver MRE is a robust technique for evaluation of liver stiffness and is currently the most accurate noninvasive imaging technology for evaluation of liver fibrosis. Newer MRE sequences including spin-echo MRE and 3 dimensional MRE have helped in reducing the technical limitations of clinical liver MRE that is performed with 2D gradient recalled echo (GRE) MRE. Advances in MRE technology have led to understanding of newer mechanical parameters such as dispersion, attenuation, and viscoelasticity that may be useful in evaluating pathological processes in CLD and may prove useful in their management.This review article will describe the changes in CLD that cause an increase in stiffness followed by principle and technique of liver MRE. In the later part of the review, we will briefly discuss the advances in liver MRE.

Liver vascular anatomy: a refresher.

To prevent and decrease procedural complications, it is important to identify variants of hepatic vascular anatomy before interventional radiologic procedures, surgery, and liver transplantation. Knowledge of the vascular variants helps in selecting patients and in exploring alternative management options. Non-invasive detailed demonstration of the hepatic vascular anatomy is possible with advanced multi-detector computed tomography (CT) and magnetic resonance (MR) imaging. The objective of this review is to provide a brief overview of clinically relevant hepatic vascular anatomy and important variants.

CT appearance of Varicella Zoster lesions in liver and spleen in an immunocompetent patient.

An adult patient presented with vesicular rash and abdominal pain of 5 days duration. His initial laboratory results showed elevated liver enzymes. A contrast enhanced CT scan demonstrated multiple small hypodense nodules in liver and spleen. His serum was reactive for Varicella Zoster IgM. Patient was treated with intravenous Acyclovir for 5 days and followed up with oral tablets for 2 weeks. At 3 weeks, CT scan showed resolution of hypodense nodules and his serum liver enzymes returned to normal at 6 weeks. Patient is on follow up and asymptomatic for 2 years. The CT appearances of nodules and their resolution following specific antiviral therapy are useful in diagnosis and in follow up of disseminated Varicella Zoster.

Magnetic Resonance Elastography and Other Magnetic Resonance Imaging Techniques in Chronic Liver Disease: Current Status and Future Directions.

Recent advances in the noninvasive imaging of chronic liver disease have led to improvements in diagnosis, particularly with magnetic resonance imaging (MRI). A comprehensive evaluation of the liver may be performed with the quantification of the degree of hepatic steatosis, liver iron concentration, and liver fibrosis. In addition, MRI of the liver may be used to identify complications of cirrhosis, including portal hypertension, ascites, and the development of hepatocellular carcinoma. In this review article, we discuss the state of the art techniques in liver MRI, namely, magnetic resonance elastography, hepatobiliary phase MRI, and liver fat and iron quantification MRI. The use of these advanced techniques in the management of chronic liver diseases, including nonalcoholic fatty liver disease, will be elaborated.

Magnetic resonance elastography of liver.

Magnetic resonance elastography (MRE) assesses tissue stiffness in vivo by imaging propagating shear waves through the tissues and processing the wave information. MRE is a robust technology with excellent technical success; is applicable in almost all patients and body habitus; and has excellent reproducibility, repeatability, and interobserver agreement for assessing liver stiffness. It is currently the most accurate noninvasive technique for detection and staging of liver fibrosis and has the potential to replace liver biopsy. This article describes the principles and technique of MRE, current clinical applications, and emerging clinical indications.

Imaging of malignancies of the biliary tract- an update.

Malignancies of the biliary tract include cholangiocarcinoma, gallbladder cancers and carcinoma of the ampulla of Vater. Biliary tract adenocarcinomas are the second most common primary hepatobiliary cancer. Due to their slow growing nature, non-specific and late symptomatology, these malignancies are often diagnosed in advanced stages with poor prognosis. Apart from incidental discovery of gall bladder carcinoma upon cholecystectomy, early stage biliary tract cancers are now detected with computed tomography (CT) and magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP). Accurate characterization and staging of these indolent cancers will determine outcome as majority of the patients' are inoperable at the time of presentation. Ultrasound is useful for initial evaluation of the biliary tract and gallbladder masses and in determining the next suitable modality for further evaluation. Multimodality imaging plays an integral role in the management of the biliary tract malignancies. The imaging techniques most useful are MRI with MRCP, endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasound (EUS) and positron emission tomography (PET). In this review we will discuss epidemiology and the role of imaging in detection, characterization and management of the biliary tract malignancies under the three broad categories of cholangiocarcinomas (intra- and extrahepatic), gallbladder cancers and ampullary carcinomas.