MAGNETIC RESONANCE IMAGING

Once a week, a gleaming white semitrailer backs up to Bigfork Valley Hospital.

But it is not delivering anything. In fact, its vertical loading ramp is used for people coming into the trailer. They have an appointment for a Magnetic Resonance Imaging scan – or MRI – which can provide a unique look at soft tissues and muscles inside the body as well as the body’s bone structure.

We think of X-ray pictures as a recording of something solid, like a bone, that blocks an X-ray passing through the body. But MRI actually records energies that are produced by hydrogen atoms inside the body. And because hydrogen is part of the water molecule that makes up much of our soft tissues and muscles, the result is a fascinating and detailed picture of those areas that lie in the dark spaces on the traditional X-ray films.

To do it, first the hydrogen atoms in the body are lined up with a strong magnetic field. Then a focused radio signal of a specific frequency is passed through the body. Some of the hydrogen atoms absorb this frequency, changing their spin. When the radio signal is turned off, the hydrogen relaxes to its normal alignment and releases the energy absorbed. Antennae pick up these energy signals and send the data to a computer to be converted into a number of images.

What happens when you stand on the ramp and are brought into the trailer? The first half hour or so, explained Steve Solien, MRI Technologist with DMS Imaging, is devoted to an interview on patient background. It is especially important for him to know if there is any metal in the patient’s body; particularly ferrous metals or wires which might be affected by the magnetic field. The field could create a current in a pacemaker, for instance, or a neurostimulator. Aneurism clips could heat up. Dentures or jewelry must be removed. In fact, Solien recommends coming in sweat clothes to eliminate metal clips on clothing.

The patient is then positioned on a bed that will move into a 4 foot tunnel running through the center of the magnet. Although 4 feet may not seem like a long distance, Solien said there are those who find it claustrophobic. To counter this feeling, the color scheme was selected from about 250 choices by psychologists to be the most soothing, and a picture of waves on a beach covers a wall. Patients have the option of music in headphones to soften the loud staccato noise made by the machine.

The scan itself takes about 20 minutes, said Solien, and the patient must lie still. However, the MRI is extremely flexible, and while the patient stays in one place, the MRI can pinpoint a particular area. The images are produced as films which are then sent to a radiologist for interpretation.

Although the technology itself is less than 30 years old, it is always improving. In fact, a new machine that can display a cardiac image was delivered for use in July, although it replaced one just a year old, said Solien.

DMS Imaging is based in Fargo and offers a number of mobile diagnostic services throughout the country.