Rigid, anatomy-specific coils have traditionally been used for MR exams, but in the last three to four years there has been growing interest in multi-purpose, flexible coils that fit any anatomical area. The days of trying to fit a rigid coil on a swollen knee are now in the past. Today, hospitals are trying to achieve better quality while reducing costs. Since flexible coils can serve a variety of different applications, they may help them do just that.

Hospitals that can afford the newer 3T MR systems are speeding up their exams and getting higher resolution images. However, 3T systems are not the only way to achieve that. New coils with more channels are able to achieve comparable signal-to-noise on 1.5T systems.

Whether or not these less-expensive, multi-purpose flexible coils will replace the standard, rigid, anatomy-specific coils remains to be seen. But as the industry searches for ways to cut costs, it seems more likely.

From rigid to flexible
Both the OEMs and third-party companies currently offer a range of flexible coils. GE Healthcare has its GEM Suite coils that are designed to be used with its Optima MR450W 1.5T MR. Toshiba America Medical Systems has 16-channel flexible coils for its Vantage Titan 1.5T and 3T systems. Siemens Healthcare also recently started offering 16-channel flexible coils.

The third-party company, MR Instruments, offers an 8-channel flexible coil with two paddles that is compatible with the GE 1.5T MR system as well as older systems. It comes in a 24-centimeter model and a 10-centimeter model.

One major benefit of flexible coils is that they can help save money. A hospital will usually purchase seven to 10 rigid coils at $30,000 to $40,000 each, but it would only need to purchase one flexible coil. In addition, a hospital can usually get a return on investment on a flexible coil in 12 to 18 months since it can be used to image patients who don’t fit in a rigid coil and can also be used for new applications. A few of those new applications include imaging the sternoclavicular joint at the top of the chest and the brachial plexus, which is the network of nerves that originates near the
neck and shoulder.

“With these types of exams, the doctors look for specific information, but really there wasn’t a specific coil to gather that data,” says Andrew Beck, vice president of sales and marketing at MR Instruments. “The technologist would have to try to figure out with the assorted coils he has, what would work best to cover that anatomical area.”

Outpatient and hospital-based facilities often use flexible coils to augment their legacy systems. They are able to keep those systems longer and bring in new referrals because they have a new coil that achieves better image quality and allows them to perform those new applications.

One new area of interest is noninvasive prostate imaging with 1.5T MR systems. Some facilities are using the flexible coils, instead of invasive, intracavity coils, and have experienced an increase in patient referrals. “The difficulty with an intracavity coil is that it is not a comfortable situation for the patient and they tend to gravitate away from an exam like that,” says Beck. “If you can come in with a noninvasive-type coil that is simple and you can get a good diagnostic study, then more of these exams may be ordered in the future.”

Some flexible coils on the market are torso-based coils and don’t have the resolution and signal-to noise ratio that is required for prostate imaging. But coils with a higher concentration of elements on the prostate area are able to perform good quality prostate imaging. DuoFLEX is able to achieve good image quality during those exams because it sits right upon the prostate without any space between the elements, which provides better signal-to-noise.

Goodbye endorectal coils?
Endorectal coils are used along with 1.5T MRs for prostate exams to provide greater spatial resolution, better quality images and a reduction in artifacts, but 3T systems can do all that without the use of a coil. “You don’t need the coil for 3T because the signal with the body array is already adequate or good enough, so you don’t need to enhance the signal,” says Ioannis Panagiotelis, chief marketing officer at GE.

The endorectal coils are uncomfortable for the patient and they also add time and cost to the exam. A great deal of research favors the use of the coils, but advances in multi-parametric MR with 3T systems are producing excellent quality exams with a high rate of spotting cancer, without the use of coils. 3T diffusion-weighted imaging (DWI) is also showing promise for this indication. A Swiss study published in March studied 111 men with prostate and/or bladder cancers who underwent 3T DWI and found that without an endorectal or contrast agent, 3T DWI has a “high probability” of detecting prostate cancer.

Larger coils for bariatric imaging
More than two-thirds of adults in the U.S. are considered to be overweight or obese, according to the National Institutes of Health. With obesity on the rise, radiology departments are faced with the challenge of improving clinical accuracy for bariatric imaging without compromising patient care.

“What do you do when the 500-pound patient shows up?” says Guy Poloni, director of the MR business unit at Toshiba. Often, a coil is too small to fit a bariatric patient, but Toshiba has developed an extra-large knee array coil for the Vantage Titan MR system. The company claims that it was the first diagnostic imaging vendor to offer an extra-large knee coil with a 22-centimeter interior diameter for MR imaging.

The coil can be used on most bariatric patients and also when imaging non-bariatric patients. Its wide diameter is optimal for imaging a flexed or bent knee, which is useful in cases when a patient cannot straighten their legs because of an injury or medical condition. The flexible coils can also be used for this purpose. Beck says that anatomy-specific coils are usually designed to cover 80 to 90 percent of the patient population, but that flexible coils can ,be used on 100 percent of the patient population for any type of anatomical area.

Because of that, facilities don’t lose any revenue since they don’t have to reschedule appointments or send the patients to another facility. A facility may be able to save two to three exams per week at $1,000 each, says Beck.

Whether flexible coils will replace rigid coils in the future remains to be seen, but the interest in these versatile solutions is continuing to grow. They are cutting costs, consolidating equipment, improving patient comfort, and accommodating larger patients, which is more important than ever in this new era of health care reform.