Radiologist Questions Mri

Open MRI

Is an open MRI as accurate as a standard MRI? If it is why aren't all MRIs open?

11 Answers

Open MRIs are becoming extinct. I read an article that less than 30 were sold in US last year. They are much less powerful and therefore suffer from poor contrast resolution. I used to read an open 0.5 T MRI and it could not perform chemical fat suppression which is extremely helpful on all MSK studies particularly if IV contrast is given.

Closed MRIs come in 1.5 and 3T. They are narrow but offer great resolution and less motion artifact especially with good technologists. 3T is necessary for many body imaging e ams such as multiparametric prostate MRIs to avoid using an endorectal coil.

Recently, a third option has become available called wide short bore MRI. These scanners have a shorter wider bore the patient enters. They still offer 1.5 and 3T capabilities as the narrow bore magnets and can accommodate larger patients and those with claustrophobia. Most hospitals are replacing their scanners with this newer generation. They are more expensive so many imaging centers are holding off on purchasing new equipment until their scanners are end of life.

Bottom line, the best quality scanner is closed MRI and the wide bore is more tolerable for patients.
No. Open MRI does not produce the same quality images. The images may be adequate to diagnose some pathology but generally the images are not as good as a standard MR. Magnetic Field inhomogeneities are greater with open MRI, degrading image quality. You’d have to study and understand the physics of magnetic resonance to understand why you’d want to reduce field inhomogeneities. Suffice it to say the fewer the better. A standard bore (donut) magnet reduces field inhomogeneities

There are different levels of image quality. You may not need the best to identify disc bulges which are easy to see. However, if you are looking for subtle nerve abnormalities you are going to want to generate the finest quality images with the ability to see great detail. Open MRs generate the lowest quality images. A 1.5 T (“T” stands for “Tesla” which is a unit of measurement that identifies the strength of the magnet) is better . A 3T magnet generates better quality images than a 1.5 T and a 7T magnet - usually only available in research facilities -gives even better image quality. 3T is the best commonly available. Open MR is designed for the claustrophobic- not best image quality though.
NO. Open MRI systems have magnetic field strengths ranging from 0.2 Tesla to 1.2 Tesla. Routine MRIs range from 1.5 Tesla to 3 Tesla. This increased field strength provides increased signal/noise ratio which allows for thinner sections and more detailed images. In addition, most new routine MRI scanners are short, wide bore systems which help with claustrophobia. They can also accommodate patients weighing up to 550 lbs.
As a general rule, no. However, there are a couple of open systems that are exceptional. The technology is changing all the time. The key is the radiologist reading...fellowship training is key.

All the best.
Open MRIs are lower field magnets resulting in lower spatial resolution. They are inferior to closed MRI systems in this regard. However, they are great for dealing with claustrophobic patients and in situations where dynamic or kinematic imaging or upright imaging is required.

Hope this helps.

Hi there. Thank you for your question. Believe me, a very important one! Both Open and closed MRI units are magnets and work in a very similar way to construct an image of our body parts and tissues. However, Open MRI units work with low strength magnetic fields. This strenght is measured in units called Teslas (T). For example, Open MRI units strength range from 0.23T to 0.5T as opposed to closed MRI units that go from 1.0 to 3T or above. Rule of thumb: the greater the magnetic field, the better will be the signal acquired from the tissues to obtain better sensitivity of disease processes, better anatomic detail, and better tissue contrast. Unfortunately, due to the magnet size and strength, we still do not have the capability to build it in an open enclosure. Open MRI units are still useful in claustrophobic patients or bigger patients that cannot fit in a regular closed unit. In general, both you and your doctor can benefit more from the detail from a closed High Field strength unit.

Dennis Perez MD FACR
In many cases, an open MRI does not provide comparable images when compared to a closed MRI, which results in diminished diagnostic accuracy.
Open MRI scanners tend to have weaker field strength magnets. This means there is less signal to noise to generate images of your body. You can use the analogy of the cell phone camera on a flip phone compared to the latest one on an Iphone X. If you want to have the best anatomic detail of your brain, spine, or body, a higher field strength magnet will provide higher quality images.
Open and closed MRIs have different capabilities. This partially depends on the manufacture. Open MRIs can of course be used with people who are terribly claustrophobic. Closed MRIs tend to give better imaging. They are somewhat more versatile and cover a larger range of imaging well.
Open MRI have less resolution due to weaker magnetic field. In general closed MRI are better unless you are claustrophobic. Closed MR may be OK if high resolution not needed.
Older open mri's are low field, 0.3 Tesla. Closed MRI is 1.5T or 3T. Open mri got their bad repuatations with .3T strength. There are newer open MRI machines that are 0.7T or 1.2T, I would shop around for an open 1.2T magnet, we have one in Racine.