E³ 318 - Chronic liver disease: guidelines for the radiologist
E³ 318 - Chronic liver disease: guidelines for the radiologistWednesday, March 1, 14:00 - 15:30 Room: M 4 Session Type: E³ - ECR Academies: Tips and Tricks in Liver, Bile Ducts and Pancreas Imaging Topics: Imaging Methods, Abdominal Viscera Moderator: B. J. Op de Beeck (Anwerp/BE) Add session to my schedule In your schedule (remove)
Chronic liver disease is a substantial worldwide problem. Its major consequence is increasing deposition of fat, iron and fibrous tissue within the liver, leading to the development of cirrhosis with its consequences, portal hypertension, hepatic insufficiency and HCC. During this session, the question “how accurate are we in measuring fat and iron with MRI” will be answered. The goal is to become familiar with the different acquisition techniques, to understand the correspondence between MRI evaluation and histological scores and to learn about the limitations of the method. A second problem will be discussed concerning the question “can we reliably identify and quantify liver fibrosis and cirrhosis”. It is important to understand the basic principles of fibrosis evaluation with US and MRI, how these methods could be implemented in daily practice, and how to make a radiological report. Fibrosis is independently associated with the viscoelastic parameters and is less associated with the diffusion parameters than is steatosis. There is a need for non-invasive detection and follow-up of these chronic liver diseases. Elastographic techniques are rapidly becoming the method of choice for the assessment of liver fibrosis, replacing liver biopsy for diagnosis, evaluation of disease progression and treatment monitoring. Finally, the problem of a small liver nodule in a patient with chronic liver disease will be discussed with the focus on characterisation and the international guidelines presenting diagnostic and follow-up strategy. Not only HCC presents as a hypervascular nodule, but also FNH, FNH-like lesions, adenoma, capillary haemangioma and nodular regenerative hyperplasia.
1. To become familiar with the different acquisition techniques allowing measurement of fat and iron with MRI.
2. To understand the correspondence between MRI evaluation and histological scores.
3. To learn about the limitations of the method.
Liver steatosis is the hallmark of non-alcoholic fatty liver disease (NAFLD) but is also commonly found in different diffuse liver diseases. Iron overload is found not only in genetic haemochromatosis, transfusional haemosiderosis and iron loading anaemias, but also in chronic liver diseases. Because liver biopsy has several limitations, magnetic resonance (MR) imaging biomarkers have been developed for fat and iron quantification. Liver fat quantification can be accurately performed by MR spectroscopy or using multi-echo chemical shift encoded (MECSE) MR sequences. For precise quantification of proton density fat fraction (PDFF), MECSE MR sequences must be corrected for T1 bias, T2* decay effect, noise and fat spectral complexity. Nowadays, PDFF is being considered as the best imaging biomarker of liver steatosis. Quantification of liver iron using MR imaging can be performed with signal intensity ratio (SIR) methods as well as R2 and R2* relaxometry techniques. As MR imaging does not depict iron itself, but the effect of iron in nearby protons, all these different MR methods require calibration against liver biopsies, to generate empirical calibration curves. Both R2 and R2* values are increasingly being used for quantification of liver iron concentration, either for diagnosis or treatment monitoring, but they must be performed with validated acquisition and analysis protocols. MECSE-MR sequences have the advantage of simultaneously quantifying steatosis and siderosis and are promising as fast non-invasive biomarkers of liver fat and iron, also providing spatial coverage of all liver parenchyma.
1. To understand the basic principles of fibrosis evaluation (US and MRI), how these methods could be implemented in daily practice, and how to make a radiological report.
2. To learn about the correlation between imaging tools and other methods and to understand the clinical strategy.
3. To become familiar with the necessity for non-invasive detection and follow-up of chronic liver disease.
Diagnosis of cirrhosis on imaging is not difficult as there are striking features, the most common being surface nodularity and morphologic changes of the liver (atrophy of segment 4 and hypertrophy of the caudate lobe). Diagnosis and staging of fibrosis was done on pathologic examination of the liver for years but quantitative imaging has changed the paradigm. First, diffusion-weighted MR has enabled to assess liver fibrosis as the ADC decreases with increasing fibrosis stage. More recently, imaging-based elastography (using ultrasound or MR imaging) has shown high diagnostic performance to stage fibrosis. The principle of these two methods is to measure the speed of shear waves propagating in the organ. The shear-wave speed is related to tissue stiffness and, therefore, to the fibrosis. The first technique that has been extensively validated is the fibroscan (transient elastography). More recently ultrasound-based techniques such as ARFI and shear-wave elastography have shown comparable or even better performance over fibroscan. They are nowadays performed in clinical practice. Some limitations are patient overweight and increased intercostal thickness. There are confounding factors that should be known. MR-based elastography is a very accurate technique that has been recently validated in multicentric studies. Its advantages is the 3D assessment of the liver and the ability to go deeper in tissue characteristics (elasticity and viscosity). MR elastography is performed in many centres nowadays but still more in research than for daily use. Both approaches compare favourably with liver biopsy and are particularly helpful for monitoring patients.
1. To become familiar with the problem of characterisation of liver nodule on cirrhosis/fibrosis.
2. To understand the imaging strategy.
3. To learn about the international guidelines presenting diagnostic and follow-up strategy.
The enrolment of patients with chronic liver disease into surveillance programs has determined a steady increase in the number of small hepatic masses being detected. In addition, technological advances have improved the spatial, contrast and temporal resolution of imaging modalities allowing for higher rates of detection. However, detection and characterization of a lesion in a cirrhotic liver is oftentimes a challenging task, due to the intrinsic features of a fibrotic/cirrhotic organ and to a different epidemiology in comparison to the noncirrhotic population. While most lesions in a cirrhotic liver are hepatocellular, a wide array of other observations can be encountered, such as haemangioma, nodule-like arterial phase hyperenhancement, focal fibrosis, cholangiocarcinoma and metastases. Moreover, small HCC frequently present with atypical findings, such as lack of enhancement, lack of washout or no capsule. Furthermore, HCC <1cm grows very slowly; therefore, stability (i.e. lack of growth) over a few months does not entirely rule out malignancy, and a negative biopsy is not helpful due to the high false-negative sampling rate. In these instances, two possible options are 1) further imaging with a different technique or 2) imaging follow-up.