Some areas of the body are harder than others to image using traditional medical imaging procedures. However, this is sometimes due to incomplete information rather than location. In the case of liver and brain imaging, this could be especially true. In order to determine the extent of a disease and some of its changes, physicians may prefer less common scanning methods, such as magnetic resonance (MR) elastography.
What is MR elastography?
Magnetic resonance imaging (MRI) can be conducted using a variety of techniques to create different types of images. MRI works using a super-conducting magnet that changes the magnetic field around and inside of the scanner. The MR system then further changes the electromagnetic field through pulse sequences. These pulse sequences are designed to evoke signals from the patient's body. These signals are received by coils placed near the region of interest.
Magnetic resonance elastography is one of many techniques that can be used to produce images of the soft tissue structures and organs of a patient, though elastography can also be done for this reason using ultrasound.1 This scan is done using a traditional MR system and an additional piece of equipment.
A speaker-like object is placed near the patient. Then, this device directs painless, low-frequency vibrations into the body. The scanner, with the help of the host computer, measures the vibrations as they travel through the organ. This helps the radiologist to determine how much stiffness (or elasticity) the organ has.
MR elastography for the liver
MR elastography is most commonly done to assess the liver.1 Stiffness may be the result of liver disease. The scar tissue resultant of both alcoholic liver and fatty liver disease can lead to stiffness. People with these conditions may not experience symptoms, so liver assessment can be extremely important. Left untreated, the fibrosis (buildup of scar tissue) sometimes leads to another condition, which is called cirrhosis and can affect liver function to the point of death.
MR elastography for the brain
Research is being conducted to see if elastography may be of use in scanning different areas of the body, including the brain. MR can provide detailed images of the tissue structures in the brain, but scientists may want to develop a better understanding of the changes associated with diseases and age.
Lesions in the brain may appear different on MRI and MR elastography than normal brain tissue. This is because of the stiffness associated with these lesions, which can affect the ability to biopsy a specific lesion.2 A meningioma is typically benign but often stiffer than the average tissue. Stiff meningiomas would be considerably harder to biopsy than soft tumors.
Gliomas, the most common type of brain tumor in adults, is traditionally imaged using conventional MRI with a biopsy to follow.2 Because tumors have different levels of tissue stiffness, MR elastography may provide a way to determine the stiffness of a tumor prior to surgery. One goal of surgery on a tumor is to resect, or cut out, the cancerous tissue. The less stiff the tumor, the more likely it can be resected.
A recent study of patients ranging in age from 18-62 years old studied the stiffness of the white and gray matter in the brain.3 The goal of the study was to monitor changes in the brain over time. The patients showed a decrease in both anisotropic and isotropic stiffness in gray matter for both men and women. There was also a correlation between anisotropic and isotropic stiffness.
This could lead to a better understanding of the effects of aging on the brain. As a result of further research, scientists may be able to provide insight into the traditional longitudinal progression, which could help doctors recognize abnormalities sooner in patients with cognitive trouble.
MR elastography provides valuable information about the stiffness of tissue structures throughout the region of interest. This data could help to inform treatment decisions, surgical procedures and our understanding of how the brain ages. With the help of elastography, physicians may be able to determine whether a tumor is able to be resected. Elastography may, after being further researched, help doctors better understand the whole picture.
- Elastography. RadiologyInfo.org. https://www.radiologyinfo.org/en/info.cfm?pg=elastography. Last accessed September 3, 2019.
- Magnetic resonance elastography (MRE) in cancer: Technique, analysis, and applications. Prog Nucl Magn Reson Spectrosc. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4660259/. Last accessed September 6, 2019.
- Magnetic resonance elastography of brain: Comparison between anisotropic and isotropic stiffness and its correlation to age. Magnetic Resonance in Medicine. https://onlinelibrary.wiley.com/doi/abs/10.1002/mrm.27757. Last accessed September 6, 2019.