MRI: Keeping Your Options Open

Necessity may be the mother of invention as Plato suggested, but providing high-quality patient care for difficult-to-image patients trumps all other considerations when it comes to open magnetic resonance imaging systems.

The original open MR scanners were designed to meet the needs of two groups of patients: those who were terrified by the enclosure of tube-shaped scanners, and those whose size precluded their ability to fit into a closed bore system. Prior to the availability of open systems, patients who suffered from severe claustrophobia were imaged only if they were sedated heavily, and those who were too large to fit in standard closed-bore systems went un-scanned.

As a matter of physics, traditional open scanners were designed with lower field strength magnets - resulting in longer scan times and reduced image quality. But that's all changed, of course, with today's open MR scanners packing more punch in terms of magnet strength, clinical applications and coil variety. Popularity with patients and the continued marketing draw have kept up, too.


Making a difference

"The 'opens' can handle 95 to 98 percent of the studies," observes Ken R. Dunwoody who spent five years as an owner of freestanding imaging centers and currently serves as director of operations for SERI (an internet-based educational site) out of Dallas, Texas. "Open [MRI] had lots of resistance a decade ago, but since then the systems have evolved and many companies have developed new enhancements."

Dunwoody recently has been involved in building two freestanding centers and was the first to install the 0.35 tesla small footprint Siemens Magnetom C! in the United States. Radiologists are quite enthusiastic about its capabilities, he says, and given the evolution of technology and the addition of coils to enhance image quality, it performs the majority of MR studies well. Some side-by-side image comparisons of the system vs. the facility's 1.5T closed unit even stumped some of their dozen radiologists.

He notes that coil arrays make a vast difference because they intensify the image and add more power to enhance image quality. That coupled with the improved software throughout the system, namely in post-processing, provides sharp images.

The facility also makes good use of the Hitachi Airis II 0.3 tesla permanent magnet, self-shielded scanner - with similarly high-quality images.

Victoria Bedel, BS, RT(R)(CT), FAHRA, national director of clinical operations for Radiologix, Inc. in Dallas agrees that the major MRI vendors have been working hard to re-design software and improve coil technology and thus boost image quality in the open realm.

"The signal-to-noise ratio is better [than previous-generation scanners], and they can image more and collect more data in less time," she says. Additionally, she notes that the coil technology has evolved to become much more efficient from a workflow perspective. Historically, patients had to be re-positioned and different coils had to be changed out for different body parts. Today in their true open scanners, they complete many routine scans and non-enhanced brain scans. Yet, for serving truly claustrophobic patients, Bedel does not believe that the new short-bore scanners, promoted as open machines, truly address the needs. "If you have a patient who has been scanned in a true open system, when they see the short bores, they're still frightened," Bedel notes.

Two other groups of individuals benefit from true open MR scanner design: pediatric patients and large athletic patients.

Carmen Arango, MD, DABR, medical director and owner of Arango Imaging Center in El Paso, Texas, describes their very busy practice as including a number of different oncology diagnoses and many pediatric patients, including musculoskeletal and head and neck work. They installed a Toshiba Ultra 0.35 tesla open scanner in September 2001, but prior to that scanner, they used the Toshiba Opart.

She explains that the Ultra is an upgrade because it features high gradients that provide higher image resolution. The motorized table and the CTL (Cervical/Thoracic/Lumbar) coil array for the spine means that they can produce spinal exams more easily.

Where this system excels is in "the new gradients," Arango says, "the resolution is better, speed is greater and the fat suppressor technique is elegant which is important when you're doing musculoskeletal images. I use it for MR myelograms when I do spines. For older neurosurgeons who want traditional myelograms, with this new technique we can provide that."

Besides placing the scanner in a room decorated with a beach mural on the walls and the ceiling painted with the sky as seen through palm trees to provide a visualization of a pleasant environment, Arango also has developed an innovative technique for imaging pediatric patients. She has a number of MR-compatible toys that she asks her tiny patients if they'd like to take into the scanner with them. She described one five-year-old girl, who was asked to help a Barbie doll that was ill and needed the youngster's help to be scanned. After the child held tightly to the doll throughout the exam, she asked if Barbie was OK at the end. Of course.


What matters

Maurice Poplausky, MD, director of diagnostic imaging at the Hudson Valley Hospital Center in Courtlandt Manor, N.Y., is using a Toshiba Ultra open scanner for pediatric cases as well. With the open design, a parent can sit beside their child with full visualization and contact designed to reduce the child's - and parent's - stress.

Poplausky notes that gaining experience is key to gaining clinical confidence in reading open MR studies. "With a closed magnet, you're spoiled because you see everything. When you go onto an open, although it's very good, it's not what you're used to seeing and you may begin to doubt yourself," he says. "The physician has to develop a comfort level to realize these are good studies and good images."

Besides use in pediatrics, Hudson Valley Hospital Center utilizes the system to perform all types of neurologic exams, as well as shoulder and knee studies. He explains that for certain diseases such as multiple sclerosis, where they are looking for very fine white matter plaques, the open scanner would not be used either for an initial diagnosis or if the patient is having a flare up or active disease. They would, however, use the open scanner for patients with stable disease.

Poplausky says scanning time is somewhat longer on their open system. And for a center with very high throughput, he recommends an open scanner not be their only MR option.

Dunwoody stresses the importance of establishing appropriate protocols once an open MR system is installed.

"Both Siemens and Hitachi provide great support systems where we could go in via [remote access] and review similar studies and see the protocols they used," he says.  "You can have a great machine and poor protocols and not get as good a picture." The scanners are sent from the factory after being calibrated there, but following shipping and installation, they require further adjustment. Most radiologists set the protocols that will be used in their center.

Irwin Grossman, MD, medical director of Grossman Imaging Centers in Oxnard, Calif., has been using a GE Signa Ovation 0.35 tesla scanner since May 2001. He stresses the importance of making sure the software you are using is updated frequently.

In 2004, their scanner was upgraded with Excite technology, which he explains as increasing the signal to noise significantly. The Excite upgrade took five days to completely revamp both hardware and software. And since then, he describes the images as beautiful, such as shoulder scans, where they need T1 images with fat saturation.

"People think of open MRI the way it was 7 or 8 years ago, which was low gradients, low field, poor image quality," says Grossman. "There are several things that go into producing an image and field strength is only one of them." However, he says that when he compares images from the Ovation with those on high-field scanners, he cannot tell which scanner was used. "The neurologists, orthopods, neurosurgeons and other clinicians who originally were reluctant [to use open MR], and told us not to do their patients on the open scanner, now actively refer patients for scans here. Any patient who is the least bit claustrophobic, or has any hesitation, they send them in. So it's been a tremendous boon to our practice."

Besides improving patient care, Grossman says that the Ovation is their busiest scanner, and from a financial standpoint, he describes it as the best investment he's made with any scanner.

Vincent Disabella, DO, FAOASM, who serves as team physician for the University of Delaware in Newark, is responsible for the healthcare of 750 athletes - including those who play on 23 varsity teams as well as international figure skaters. He uses three imaging centers, two with open systems and one with a short-bore system for necessary MR scans. Because he often must decide quickly which athlete can return to play within days, he needs a fast turnaround time for studies.  

"We use MRI for many injuries, whether they are knee, shoulder, wrist, hip, ankle or lower back. There are two companies in the area with small magnet traditional opens, one being a 0.35 tesla system, and one with 11 imaging centers here in Delaware that has a 0.6 tesla scanner. They're the true open MRIs."

One advantage Disabella has over many colleagues is that since most of their teams are digitally videoed, he can actually review the images to see how the injury occurred.  He also appreciates the collaboration with the radiologists from the imaging centers in discussing images together.

"Any sports medicine doctor or orthopedic surgeon is going to be reviewing his or her own images," he says. "Since we look at those distinct images daily, we do have the advantage of examining the patient which is something the radiologist seldom has the luxury of doing. If we look at these films while examining the patient in the room, we can correlate the information."

In addition, he notes that providing adequate information to the radiologist and technologist about what specifically he needs to see, he obtains better results. Their referral form provides as much information as possible about the injury and notes from the physical exam.


Counterpoint

Anthony J. Scuderi, MD, chairman of Laurel Highlands Advanced Imaging in Johnstown, Pa., offers an opposing view in the traditional open versus short-bore debate. He uses a Siemens Magnetom Espree 1.5 Tesla open-bore MRI scanner rather than a traditional open system.

As far as the clamshell design, he notes that the opening is only 40 to 47 centimeters. The Espree offers a 70 cm wide gantry that is 125 cm in length, which he describes as almost an identical footprint to their CT scanner.

"The reason I bring up those distances is that claustrophobia is not only a function of small space but also the amount of time a person has to spend in it. With a low field strength 0.2 to a 0.35 T magnet, it takes a longer time to image to obtain adequate signal to noise and adequate resolution," he says. "If someone is claustrophobic, and doesn't want to spend 30 to 45 minutes in the magnet, we can scan them faster in the short bore…within 15 minutes with the higher field strength."

Scuderi says that he believes one of the issues involves the fact that the public has seen photos of the traditional open scanners and therefore do not recognize short bore scanners as "open system" scanners.

He does note that the low-field scanners are less expensive, and given that reimbursement is based on the study and not the type of equipment used, economic certainly play a role in deciding which scanner to purchase.


Conclusion

Traditional open MRI systems have undergone a metamorphosis over the past few years, with improvements designed to enhance image quality, decrease scan times and improve patient care for specific groups of patients. Many facilities have found open systems to be valuable additions to their imaging suite.