Magnetic Resonance Elastography of Liver: Technique, Analysis and Clinical Applications

 

applications mre

Status of a Visa Application → Click here for information about Types of Visa. NOTE: There is no need for a visa if the traveler arrives in Brazil on a flight, remains in the international transit area, without passing through immigration control, and departs on another flight from the same airport. The application of MRE in the brain is an area of significant research and clinical interest due to the potential of altered mechanical properties of brain tissue in a variety of pathologies including cancer, Alzheimer’s disease, hydrocephalus, and multiple sclerosis [].Cited by: Abstract. MRE is performed by using a vibration source to generate low frequency mechanical waves in tissue, imaging the propagating waves using a phase contrast MRI technique, and then processing the wave information to generate quantitative images showing mechanical properties such as tissue marimapomess.gq by:


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Magnetic resonance elastography MRE has been successfully implemented in the assessment of diffuse liver diseases. Currently, MRE is the most accurate noninvasive technique for detection and staging of liver fibrosis with a potential to replace liver biopsy. Magnetic resonance elastography is able to differentiate isolated fatty liver disease from steatohepatitis with or without fibrosis.

Potential clinical applications include the differentiation of benign and malignant focal liver masses and the assessment of treatment response in diffuse liver diseases. For hundreds of years, palpation has been a simple technique for assessing tissue stiffness during physical examination. With palpation, physicians are usually able to differentiate soft normal tissues from pathological tissues that are typically stiffer or harder. However, applications mre, this clinical method is most suitable for superficial structures and organs.

Deep-seated organs, like liver, applications mre, and lesions within them, are difficult to palpate entirely except at surgery, applications mre. It is well known to surgeons that normal liver is soft, like abdominal fat, whereas cirrhotic liver and malignant applications mre tumors are stiffer or hard, applications mre. Elastography techniques that assess mechanical properties of tissues are now available and can provide stiffness information of deep-seated tissues including the liver.

The techniques currently available for use in assessment of chronic liver diseases include ultrasound-based transient elastography, acoustic radiation force impulse imaging, and magnetic resonance elastography MRE. Chronic liver diseases, irrespective of etiology, lead to liver fibrosis, and continued damage to the liver progresses to cirrhosis with its associated complications.

Traditionally, liver biopsy has been the gold standard for assessment of chronic liver diseases, applications mre. However, its invasive nature, risk of complications, sampling errors, and interobserver variability limit the use of liver biopsy for assessment of liver fibrosis and cirrhosis. Magnetic resonance elastography, 8 a magnetic resonance imaging MRI —based technique, can evaluate mechanical properties of tissues in vivo, applications mre.

The most successful clinical application of MRE has been in the evaluation of chronic liver diseases. Magnetic resonance elastography is now available at several leading medical centers and is an integral part of noninvasive assessment of chronic liver disorders at some centers, applications mre.

In this review, we will briefly describe the technique of MRE of liver and the clinical applications of MRE in liver diseases. Magnetic resonance elastography can be easily incorporated into a routine liver MRI protocol with only a few minutes added to the total scan time, applications mre.

Magnetic resonance elastography of the liver essentially involves 3 steps: 1 generating applications mre shear waves within the liver; 2 imaging the propagating shear waves in the liver using a special MRI sequence with motion-encoding gradients; and 3 processing the information in the wave images with an inversion algorithm to generate quantitative maps of mechanical properties, applications mre.

The MRE setup needs additional hardware: 1 an active acoustic driver, 2 a 7. The passive pneumatic driver is a cm plastic disc with a drum membrane that is placed against the right lower chest wall and upper abdominal wall, with its center at the level of xiphisternum Fig.

This location is chosen so that the applications mre part of the liver is directly under the passive driver. The passive driver is held in place with an elastic strap to ensure continued contact with body wall and prevent migration of the driver.

The passive driver can be easily placed between the patient and the surface receiver coils used for liver imaging. The active driver is synced to the MRE sequence from the scanner as previously described. Setup for clinical liver MRE examination. The active driver is placed outside the scanner room. The active driver is connected via a long plastic tube to the passive driver placed over the liver. Schematic diagram showing the placement of the passive driver for liver MRE.

The driver is positioned at the level of xiphisternum, applications mre. A continuous Hz acoustic vibration is used for MRE of the liver. The vibrations produced in the tissues with MRE are very low energy and well tolerated, applications mre.

The amplitude of vibrations is maintained within European Union directive limits. The wave images are processed automatically by an inversion algorithm 11 that is installed on the scanner, applications mre. The inversion algorithm reports a confidence map based on the correlation coefficients of polynomial fits, applications mre, and a threshold value of 0.

The Applications mre sequence typically produces a set of images Fig. The stiffness maps depict shear stiffness in units of kilopascals. Regions of interest ROI are applications mre on the stiffness maps to obtain stiffness values. The ROI can be oval, circular, or geographical and should avoid liver edges, vessels greater than 3 mm, fissures, and areas of pulsation artifacts and wave interference.

Generally, the left lobe is avoided because it is subject to motion caused by cardiac pulsations. To ensure a larger volume of liver being sampled, geographical ROIs are preferred. In our clinical practice, we report a mean stiffness value obtained by averaging the stiffness values from 4 slices. Larger volumes of liver may be assessed with 3-dimensional MRE, and this is currently under evaluation, applications mre.

Mean stiffness of livers can also be calculated using an automated segmentation algorithm. Magnetic resonance elastography of the liver in a patient with NASH.

Processed images from the inversion algorithm includes a gray-scale stiffness map Ccolor stiffness map with a 0- to applications mre scale Dconfidence map E with hatched out areas representing less valid areas for measurement, applications mre, and a color wave image F. The mean stiffness of the liver was 4. Studies have demonstrated that MRE of the liver has excellent reproducibility 13 — 15 and repeatability, 16 — 18 with high interobserver agreement.

Liver MRE is performed in a supine position. To reproduce the slice positions consistently, MRE is usually performed in end-expiration; however, applications mre, it can also be obtained in inspiration in applications mre who are unable to hold their breath well in end-expiration.

Liver MRE can be performed in most patients, applications mre, with the exception of contraindications to an MRI study like a cardiac pacemaker and severe claustrophobia. MRE of the liver has been successfully performed in pediatric subjects, 20 obese patients, patients with ascites and anatomical variants, 9 and posttransplant recipients.

The normal liver is soft, and the mean stiffness values reported in the literature ranges from applications mre. Studies on normal healthy volunteer populations to date do not report any correlation with age, sex, and body mass index. The liver stiffness measured with MRE is not affected by the presence of isolated fatty change only.

Inflammation of the portal tracts and necroinflammatory activity are the predominant abnormalities in the early stages of chronic liver diseases, and fibrosis follows as a healing response. In advanced fibrosis, islands of regenerative parenchyma are surrounded by bands of fibrosis of variable thickness, giving rise to the typical nodular appearance of cirrhosis. The degree of fibrosis is variable in chronic liver diseases from different etiologies.

This histopathological staging system applications mre architectural applications mre and provides a semiquantitative assessment of fibrosis. Briefly, fibrosis is staged as follows: F0, no fibrosis; F1, portal fibrosis without septa; F2, portal fibrosis with rare septa; F3, numerous septa without cirrhosis; F4, cirrhosis.

Fibrosis staging systems are limited by sampling errors and interobserver variability. Applications mre physical examination and liver function tests were normal in both patients. T2-weighted and postcontrast MRI images do not show any significant abnormalities to suggest chronic liver disease. Magnetic resonance elastography revealed a normal liver stiffness of 2. Several studies have established MRE as an accurate technique for diagnosis of hepatic fibrosis and for differentiating applications mre livers from normal livers.

Similarly, applications mre, acute flare episodes in chronic viral hepatitis may result in a higher liver stiffness. Follow-up MRE studies after normalization of serum liver enzyme levels may be useful for confirmation of liver fibrosis. Preliminary studies with single etiologies like chronic hepatitis B, 19 chronic hepatitis C, 37 nonalcoholic steatohepatitis NASH38 alcohol, 39 and Gaucher disease 40 are now available, and the reported cutoff values may be useful for application in those specific etiologies.

Some conditions not associated with liver fibrosis can cause increased liver stiffness. These include acute hepatitis from any cause, acute biliary obstruction, and passive congestion caused by congestive cardiac failure or raised central venous pressure. These conditions often can be diagnosed with clinical features and laboratory tests, applications mre, and MRE is rarely required in the evaluation of these applications mre. However, MRE of the liver can be performed when the acute conditions have resolved and an underlying chronic liver disease is suspected.

Knowledge of the presence of confounding conditions is useful in the interpretation of MRE in patients without any chronic liver diseases. The stage of liver fibrosis influences the management of chronic liver diseases. Liver stiffness measured with MRE increases systematically with increasing stages of fibrosis Fig.

The cutoff values reported in these studies range from 2. Overall, MRE has a high positive predictive value for ruling in significant fibrosis and a high negative predictive value for ruling out cirrhosis that is useful in clinical decision making. Representative MRE images from different patients with chronic hepatitis C and biopsy-proven fibrosis stages F0 through F4. Each column represents different patients, applications mre.

The top row images are magnitude images, with corresponding wave images middle row and color stiffness maps bottom row. The color scale for shear stiffness in kilopascals is on the right. Nonalcoholic fatty liver disease spectrum consists of diffuse fatty change or isolated fatty liver IFL only, steatohepatitis, and steatohepatitis with fibrosis.

Isolated fatty liver does not affect liver stiffness. The use of MRE in this particular chronic liver disease will have a significant role as obesity-related chronic liver disease is a major health burden in Western countries and an emerging health care problem in lesser-developed countries.

Examples of steatosis only, steatohepatitis, and steatohepatitis with fibrosis. Magnetic resonance elastography magnitude images top row and stiffness maps bottom row in patients with biopsy-proven steatosis only first columnapplications mre, steatohepatitis second columnapplications mre, and steatohepatitis with grade 1 fibrosis third column, applications mre.

The mean liver stiffness was 2. Spleen stiffness correlates applications mre liver stiffness and, in patients with liver fibrosis, spleen stiffness increases in parallel with increasing liver stiffness. A splenic stiffness greater than Results from these preliminary studies provide motivation for future studies on the applications mre of assessment of splenic stiffness with MRE in chronic liver diseases and portal hypertension.

Contrast-enhanced T1-weighted image B and stiffness map B in chronic hepatitis C. The mean liver stiffness was 6.

The liver is nodular with an enlarged left lobe. Focal liver lesions Fig. Malignant tumors tend to have a higher stiffness as compared with benign tumors and normal tissues. Preliminary studies have shown that malignant liver tumors are stiffer than benign liver tumors and normal liver.

Magnetic resonance elastography of focal liver lesions. Non—contrast-enhanced top row and contrast-enhanced middle row T1-weighted images and stiffness maps bottom row of hepatic adenoma first columnapplications mre, focal nodular hyperplasia second columnhepatocellular carcinoma applications mre columnand intrahepatic cholangiocarcinoma fourth column.

 

‎ULINK MRE on the App Store

 

applications mre

 

Texas A&M has the best MRE programs in the country. Find all the information you need to know about getting your master's here. Jul 27,  · ‎Read reviews, compare customer ratings, see screenshots, and learn more about ULINK MRE. Download ULINK MRE and enjoy it on your iPhone, iPad, and iPod touch. ‎ULink, la nouvelle application mobile de Umnia Bank, vous permet d’ouvrir votre compte bancaire où que vous soyez dans le monde 24h/24 7j//5(3). Magnetic resonance elastography (MRE) is a non-invasive medical imaging technique that measures the stiffness of soft tissues by generating shear waves in tissue, imaging their propagation using MRI, and processing the images to generate a stiffness map (elastogram). It is one of the most commonly used elastography marimapomess.gqe: measures the mechanical properties of soft tissues.