Comparing Low Field vs. High Field MRI - Advantages and Disadvantages

A Breakdown of Differences Between Low Field and High Field MRI Systems

MRI systems depend on the power of their magnets to produce magnetic fields that are strong enough to capture high-quality diagnostic images. Because of their ability to generate such high-quality images, many hospitals invest in MRI systems. However, buying an MRI system can be a little overwhelming. This is because there are several different types of MRI systems  to choose from, including low field and high field MRIs.

Explore the differences between low field MRIs and high field MRIs and what they are used for to determine what type of MRI will best suit the needs of your medical facility. The following is a breakdown of the differences between low field and high field MRI systems to help you do just that.

Characterizing MRI’s By Their Field

The stronger the magnetic field that an MRI system can produce, the higher the resolution of the images produced. The magnetic field of an MRI magnet is measured by a unit of measure called the Tesla (T). The majority of MRI systems being used today are in the 1.5T range, although there are MRI systems that boast ultra-high fields (7T and above) that are mostly used for research purposes. Each Tesla is equal to 10,000 gauss, which is another unit of measure used with magnets. To get an idea of how strong the magnetic field an MRI produces is, the earth's magnetic field is only 0.5 gauss.

Low Field MRIs

MRIs that are considered to be low field tend to have a magnetic strength of 0.3T or below.  Low field MRI systems are generally open MRI systems, which means the patient won't be fully enclosed within the magnet. A lot of full-body MRI systems that are  0.3T and below tend to be less expensive. Low field MRIs also exist in the form of extremity MRIs, which are machines that are much smaller and typically only scan the extremities, one at a time. Essentially, the patient will sit beside the MRI or level to the MRI to insert their hand, wrist, arm, foot, ankle, or leg into the system.

High Field MRIs

High field MRI systems typically fall between the 1.0T and 3.0T range. They are available in both open and closed systems. 3T MRI systems are closed. This enables the patient to be completely surrounded by the magnet, allowing for more detailed and faster imaging. High field MRIs are the standard for most hospitals since the higher resolution images allow for more accurate diagnoses of difficult to identify symptoms or conditions.

Noticeable Differences For Practical Use

Although low field MRI systems may seem like they would be inferior in every way, they do have some advantages. For example, they can be used to provide motion studies of joints that are not possible in closed MRI systems (such as 3T MRIs). Extremity MRIs provide high accuracy when it comes to detecting and grading bone erosions, synovitis, and bone marrow oedema. In fact, studies have shown that the accuracy of the imaging for these conditions is just as high in low field MRIs as it is in high field MRIs.

However, high field MRIs can be used for much more. This is particularly true for neuro and orthopedic imaging. High field MRI systems are also much more dependable when viewing the organs, such as diagnosing or monitoring treatment for diseases of the liver or heart problems. The high field magnets are superconductive, and therefore allow for higher homogeneity and signal-to-noise, both of which affect the quality of the image, especially in large fields-of-view.

Lastly, high field MRI systems are more capable of detecting contrast agents, such as gadolinium. This means higher doses of contrast must be given to a patient to detect it in the image when scanned by a low field MRI system.

Advantages of Purchasing High Field MRI Systems

High field MRI systems will provide you with more flexibility and broader use categories compared to low field MRI systems. A high field MRI can perform advanced diagnostic imaging on a much wider range of patients and conditions due to the quality of the images produced through the use of a higher powered magnetic field.

Some of the conditions a high field MRI can be used to diagnose include traumatic brain injuries, brain tumors, spinal tumors, multiple sclerosis, stroke, infection, dementia, aneurysms, blood vessel blockages, artery diseases, pinched nerves, fractures, and more. Essentially, a high field MRI can do everything a low field MRI can and more. Beyond the superior image resolution, high field MRIs are also much faster.

Disadvantages of High Field MRI Systems

Although a high field MRI is capable of faster and better quality imaging than a low field MRI, it still has its disadvantages. Closed MRI systems, such as 3T MRIs, can be uncomfortable for patients who suffer from claustrophobia or anxiety. Even though high field MRIs are faster than low field MRIs, they still require patients to lie still for an extended period of time (usually around 30 minutes, although sometimes longer, depending on what they're being scanned for).

High field MRI systems are also much more expensive. This is in part due to their size, which requires a costly installation process. It's also due to the use of a superconducting magnet. Unlike low field MRIs, high field MRIs need liquid helium to keep their superconducting magnets cool. Liquid helium is a nonrenewable resource that experiences a lot of market volatility, which means it can be really expensive. It also typically needs to be refilled every two to three months,unless you invest in a model that has zero helium boil-off technology.

Choosing The Right Field Strength For Your Hospital

If your hospital is considering an investment in a new MRI system, be aware of these differences between a low field MRI and a high field MRI. Keep your hospital's budget in mind, but also consider the needs of your patients. If your practice does not call for MRI scans of the torso or head among your patients, a low field MRI system may suffice. However, a high field MRI will provide you with much more long-term flexibility in the event that you take on patients that do have certain musculoskeletal or neurological conditions.