Liver examinations without needles

How is your liver doing? Decades of research into the use of magnet resonance imaging is now being put to work to gain information about patients’ livers – without needles.
“Today I can refer patients with questions that were in the realm of fiction 25 years ago”, says Mattias Ekstedt, researcher and physician.

Demonstration of MR elastography.To measure scarring in a patient’s liver with magnet resonance imaging, a vibrator is affixed above the liver. The vibrator causes compression waves in the liver, which can be observed in the images. The more scarring, the faster the wave motion. Photo credit Thor BalkhedTaking the lift two floors up from the Gastroenterology Clinic at Linköping University Hospital brings patients to the Center for Medical Image Science and Visualization (CMIV). For the past year, it has been possible to carry out advanced investigations of the liver using the magnet resonance equipment here.

“A tissue sample is central to discovering and diagnosing diseases in the liver, and this requires inserting a needle into the liver and taking a liver biopsy. But few people welcome having a needle stuck into them, and the procedure is associated with a certain risk of bleeding. The idea behind using a non-invasive liver biopsy is that we can capture everything we could normally see in a liver biopsy by magnetic resonance imaging instead”, says Mattias Ekstedt, consultant and associate professor in the Department of Health, Medicine and Caring Sciences (HMV) at LiU.

Diagnostic imaging has long been a strong suit in Linköping. It was natural for researchers here to be among the pioneers in looking at how liver disease can be investigated using magnetic resonance tomography, also known as magnetic resonance imaging (MRI). The idea originally arose around 25 years ago, and researchers have made steady progress since then. The methods developed are now in clinical use.

Fatty liver increasingly common

The first advance was to measure the amount of fat in the liver. It’s generally known that fat can be stored in the liver as a consequence of, for example, excessive alcohol consumption. But a fatty liver can also be caused by other factors that have become widespread, such as a sedentary lifestyle and overweight. Fatty liver has become a lifestyle disease. It has been estimated that around 20% of people in Sweden have fatty liver, but most of them do not experience any symptoms and do not become seriously ill. But some develop other conditions as a consequence, and it’s important for physicians to detect these at an early stage. It is particularly dangerous when the excess fat in the liver causes inflammation and scarring, also known as fibrosis, in the liver.Mattias Ekstedt.Mattias Ekstedt, consultant and associate professor. Photo credit Thor Balkhed

“We have established a clinical method to measure fat, iron and scarring in a single test. MRI is currently the best method to measure the amounts of fat and iron in the liver”, says Mattias Ekstedt.

Magnetic resonance imaging gives very accurate measurements, but is expensive. It is used in more complicated cases, where ultrasound of the liver and analysis of blood samples do not give sufficiently clear answers.

“For the patients, it means that their diagnosis is more accurate. One of the most important things a doctor can do is to let people know that they are healthy. Better diagnosis also makes it easier for us to identify the patients who run a higher risk of complications.”

Scarring makes the liver stiffer

To measure the degree of scarring in the liver, the researchers use a technique known as MR elastography (MRE) that measures how elastic the liver is. The more connective tissue present, the stiffer the liver tissue. During MRE, the liver is shaken, and the way in which wavelike compressions propagate through the liver is observed. CMIV is one of few centres in the world that can use MRE, and is a global leader in the field.Mattias Ekstedt, Nils Dahlström, Peter Lundberg, Bengt Norén and Patrik Nasr.A healthy liver is elastic. Using a technique that shakes the liver, researchers can measure how hard the liver is, and thus the degree of scarring. Red and yellow regions in the left image are the least elastic. The liver is the dark grey region in the right image. From left: Mattias Ekstedt, Nils Dahlström, Peter Lundberg, Bengt Norén and Patrik Nasr. Photo credit Thor Balkhed

The researchers would dearly love to be able to measure inflammation using magnet resonance imaging. This is important, since inflammation occurs in nearly all liver diseases, and promotes the formation of scar tissue. The phenomenon is, however, elusive, and difficult to capture in an image.

“It’s a matter of very small changes that do not show up as major changes in the liver tissue. Our research is now focussed on developing a method to measure inflammation”, says Mattias Ekstedt.

The research is carried out in collaboration with physicians in the gastroenterology clinic, engineers, specialist physicists in technology, and doctors specialised in diagnostic imaging (radiologists). One important question is how these new diagnostic techniques can be brought into clinical use. In one part of the research project, physicians and health economists are analysing how best to design the chain of care, such that the right patients are investigated with the right technology at the right time.

“CMIV is hugely important and makes this type of research possible. Not only do we have the technology available here, but also an environment in which interdisciplinary collaboration thrives.”

Translated by George Farrants

This article has been published in LiU Magazine 3/2012.

Three quick comments on magnet resonance imaging

What’s the magnet used for?
The magnetic resonance machine consists in principle of a large tunnel-shaped electromagnet in which the patient is placed. The strong magnetic field is the key to the technology that images tissues in the body.

How is the image formed?
All hydrogen atoms in the body, such as those in water and fat, are affected by the magnetic field, acting as small magnets. During the imaging, the magnetic field is changed, which causes the atomic nuclei (the protons) to emit a very faint but fully detectable signal. The signals are measured and converted in a computer to detailed images of the body’s internal organs. The technology images soft tissues that contain water and/or fat very well, and can be used to see differences in these tissues.

Is it dangerous?
The magnetic field does not involve any known health risks. It is, however, extremely important that no metal items get into the magnetic field, since they may become projectiles that can injure people and damage the equipment. Heavy items, such as hospital beds, are also attracted to the magnet resonance machine.

The technical content of the text has been reviewed by Peter Lundberg, adjunct professor in magnetic resonance physics at LiU.

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