The Differences Between Open MRI vs Closed MRI Systems 

When it comes to MRI (magnetic resonance imaging) systems, there are two main types to choose from: closed MRI systems and open MRI systems. Although the closed MRI system is the most common type, you might be considering an open MRI system, which was designed to accommodate patients who may be too claustrophobic or too obese to undergo MRIs in closed MRI systems. However, the design of the system isn't the only difference between the two types. You should carefully evaluate the pros and cons of each before making your final decision.. 

Closed MRIs

The traditional closed MRI system consists of a cylindrical space through which the patient is conveyed. As a result, they end up laying on their backs in a mostly enclosed space other than the opening through which they were pushed. Typical MRI bore size is 60cm for a "standard" MRI and 70cm for a wide bore MRI.

The MRI system uses powerful magnetic fields and high-frequency radio waves in order to record detailed images of a specific area inside the patient's body for diagnostic purposes. These images are recorded by the MRI system by reading the energy that's produced by the water molecules within the body after they've re-aligned themselves following the pulse that's caused by the radio waves. The images that are produced tend to be very high quality due to the magnetic strength of a closed MRI, which is between 1.0T and 3.0T.

Unlike CT scans and X-rays, MRI scans take much longer to perform. Depending on the strength of the magnet being used as well as the images that are needed, MRI scans can take anywhere from 15 minutes to 90 minutes to complete.

Benefits of Using a Closed MRI

The major advantage of a closed MRI system is the ability to capture more detailed, higher-quality images due to the stronger magnetic field. While 1.5T is generally ideal for most imaging needs, a higher magnetic field of 3.0T allows for a more accurate identification of the following:
  • Anatomic structures in the wrist

  • Fibrocartilage lesions

  • Hepatic metastases

  • Lesions in multiple sclerosis

  • Nerve visibility for patients with brachial plexus

  • Single or multi-vessel diseases in patients with CAD

Essentially, a closed MRI can be used to help diagnose more issues than an open MRI. Due to the strength of the magnetic field, it's usually able to scan quicker as well, even if it can still take some time to do so depending on what part of the body needs to be scanned.

Drawbacks of the Closed MRI

While the image clarity of a closed MRI system is superior,  there are still some disadvantages, especially where patient comfort is concerned. The following are some of the common drawbacks of a closed MRI system:
  • Patients have to lie still - Patients have to lie as still as possible for the images to be clearly recorded. Some patients may have trouble not fidgeting, especially in such a confined space as a closed MRI system. If the images end up blurry as a result of the patient moving around, the patient will have to undergo the entire process again.

  • Patients can feel claustrophobic - It's not uncommon for patients to experience feelings of anxiety when forced to lie still in an enclosed space for a long period of time. Patients who are claustrophobic are going to have serious reservations about having an MRI done, while those who aren't may still find it challenging to lie inside a closed MRI system for more than 15 minutes. Fortunately, doctors can sedate patients who are claustrophobic or have anxiety problems to help patients lie still.

  • Closed MRI systems are loud - During the scanning process, a closed MRI system will make loud banging sounds. This can be incredibly disorienting for patients, especially for those who are claustrophobic or have anxiety issues. Patients can be provided with earplugs or headphones to help reduce any discomfort caused by noise.

  • Larger patients may not fit - Larger or obese patients may not fit comfortably in a closed MRI system -- or may not fit at all. Most closed MRI systems have an opening that's 60 cm (or roughly two feet) in diameter. However, there are some wide bore MRI systems that are designed with a larger bore of about 70 cm.

Open MRIs

Open MRI systems were designed specifically to help address the comfort of patients. Instead of a cylindrically shaped system that encloses the patient's entire body, an open MRI system is designed in a way that looks like a donut hovering above the patient, with the sides of the system open. The magnets are positioned above the patient and below the patient instead of all around them like in a closed MRI system.

Additionally, depending on what needs to be scanned, the patient doesn't have to be pushed completely underneath the top portion of the MRI system. For example, if it's the patient's legs that need to be scanned, the top half of the patient's body can remain outside the MRI system.

Pros of Using an Open MRI

The following are some of the benefits of using an open MRI system instead of a traditional closed MRI system:
  • Less enclosed - Open MRI systems won't cause the same levels of anxiety and claustrophobia as closed MRI systems since the patient won't be entirely enclosed by the system. This makes it much easier to accommodate patients of all sizes.

  • Quieter - Open MRI systems do not make nearly as much noise as closed MRI systems. The noises it does produce are less likely to affect patients adversely since they won't be in an enclosed space.

  • More child-friendly - Children don't do well in enclosed spaces by themselves. Open MRI systems make it easier to scan children, especially since a parent can accompany them by their sides.

  • Open MRI systems can be tilted - Many open MRI systems have weight-bearing features that allow the system to be tilted. This means that patients can be scanned in standing positions instead of having to lay flat. Such a tilting feature makes it easier to diagnose certain conditions, such as back pain or spinal injuries, with greater accuracy.

Cons of an Open MRI

Although an open MRI system tends to make the process much more comfortable for patients, it's not without its drawbacks. The following are some of the disadvantages of using an open MRI system:
  • Lower resolution scanning - The magnets used are not as strong in an open MRI system. Most open MRI systems range from 0.3T to 0.7T, although some systems are capable of 1.2T. This means that an open MRI will have more difficulty telling water and fat apart during the scanning process, resulting in lower resolution images where small body parts are concerned. 

  • Image scans can take longer - In a closed MRI, the patient is surrounded on all sides by higher powered magnets, which allows for faster scanning. Because the magnets in an open MRI system are only located above and below the patient and not on the sides, it will take longer to scan the targeted area. It also means it can't take full images.

Pros, Cons, and Cost Differences

When comparing closed MRI systems to open MRI systems, you'll find that closed MRI systems are more effective for diagnosing a wider range of issues due to the higher quality images it can produce as a result of its stronger magnetic field. However, open MRI systems are much more accommodating for patients, especially those who are larger or claustrophobic. 

It's important to consider the costs of each as well. Open MRI systems tend to cost less, both in terms of upfront costs and ongoing maintenance costs. This is mostly because open MRI systems use a cryogen-free design along with permanent magnets. As a result, less engineering manpower is needed for installation and service.

However, because of the reduced magnetic field, an open MRI system may not be capable of diagnosing certain issues, which means you need to balance the costs of the MRI system to the potential patient load. You may not be able to scan as many patients as you would with a closed system, which means you may not get as much use out of it. Additionally, even though closed MRI systems aren't as comfortable, there are ways to help improve the experience for patients, such as with the use of earplugs, specialized music or video entertainment centers and/or by sedating the patient.

Considerations To Take When Choosing the Right System

Patient comfort and lower maintenance costs may make an open MRI system seem like a good choice. However, a closed MRI system will give you the ability to produce  higher-quality scans in a shorter amount of time and allow you to use it on a larger number of patients. Getting more use out of your MRI system will most likely offset the money you would save on maintenance. 

As a result, it's important to keep in mind the type of patients you have. While some patients may struggle with claustrophobia or obesity, the number of patients needing high-quality image scanning to properly diagnose their conditions will far exceed those challenges. Choose the MRI system that’s best capable of handling the needs of the majority. There are plenty of ways to help make patients feel more comfortable during the scanning process in a closed MRI system.

Keeping this in mind, a closed MRI system tends to be the best option, even when patient comfort is taken into consideration.