As low-cost “open” MRI systems have become more numerous, patient choice of an MRI center is often steered by advertising and perceived comfort, rather than which MRI center may provide the best diagnosis. Thus, it is important for physicians to help their patients make informed decisions in choosing the appropriate MRI center for their studies.

It is true that some patients are truly too large or too claustrophobic to tolerate being within a tubular magnet. But this is a small minority. Most patients can tolerate the 30 minute examination without sedation, or with only mild sedation or mild analgesia.

All MRI systems (both tubular and “open”) not only require the primary magnetic field but also coils that closely wrap around the body part of interest to pick up the signal emitted by the body. The coil is analogous to a car radio antenna. You could be driving by a large radio tower, but without the antenna – no music. These coils must be close to the body because of the minute signal emitted by the body. For example, a head coil closely wraps around the head and this can be the most confining part of the examination in either a tubular or “open” magnet.

The primary factor in MRI image quality is magnet strength. The signal (and hence the signal-to-noise ratio) is directly proportional to magnet strength. This is a fact of Physics. Clinical MRI systems vary in magnet strength from 0.23 Tesla to 3.0 Tesla. Because signal is directly proportional to magnet strength, a 1.5 Tesla magnet (such as we have at Lexington Clinic) has 6 times more signal than a low field 0.23 T “open” magnet. The most advanced “open” magnet in the Lexington area has a magnetic field strength of 0.6 T, and hence, only 40% of the signal of a 1.5 T system (remember, signal=information, otherwise you are looking at white noise). There are techniques that may be used to compensate for the lower signal to noise ratio of the lower field systems, but these techniques are also available on the higher magnetic field strength systems. The Physics remains unchanged. Moreover, these techniques compromise the image quality in other ways. For one example, you can increase signal by increasing voxel size, but this will then lower spatial resolution.