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