Multifunction MRI: The 1.5T Workhorse

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More open magnet design, new coil technology, faster sequences and high-quality images are helping to maintain 1.5T MRI as a standard of care—clearly a clinical workhorse. Patient-friendly designs add to the marketability of 1.5T systems for hospitals and imaging centers to both patients and physicians. 1.5T breast MRI also is making its clinical mark—increasing flexibility and improving—and speeding—breast cancer diagnosis.

Seattle Radiologists, a full-service outpatient diagnostic imaging center in Seattle, Wash., has been a long-time user of 1.5T MRI systems. Currently, the facility utilizes a variety of scanners, including two GE Healthcare Signa 1.5T and one GE Signa 3T MR scanners. The workout the 1.5T magnets get come largely from body scans, thanks to the performance of their sophisticated coils. For example, one coil can scan an abdomen and pelvis at one time. The 12-channel coil has a 48 cm field of view, says Kirby Souther, RT(R)(MR)(CT), lead technologist at Seattle Radiologists. Orthopedic studies also are done on the 1.5T system because the center does not yet have the necessary coils to do these studies on the 3T magnet. Breast biopsies also are always done on the 1.5T scanner.

Determining which patient will be triaged to which MR scanner at Seattle Radiologists is sometimes driven by the physician ordering the study. Souther explains that in order to increase referrals and become competitive in the marketplace, many free-standing imaging centers are adding 3T scanners to their portfolios. However, hospital-based physicians who are largely keeping referrals in-house may continue to rely on the proven imaging strength of 1.5T. While 3T is steadily growing, 1.5T systems still account for the majority of MR installations worldwide. (In the 2007 Health Imaging & IT Top Trends Survey last October, respondents estimated that 1.5T is the system of choice 49 percent of the time vs. 37 percent for 3T.)

“The 1.5T MR system has been the workhorse of the industry for a very long time. The protocols have really been developed on this system because it has been around for many years,” says Souther. He has worked with 1.5T magnets for 18 years, and has seen the modality develop into the robust technology it is today.

Setting the standards

The MR suite at Saint Barnabas Ambulatory Care Center in Livingston, N.J., scans about 60 to 70 patients daily. The center utilizes numerous Philips Medical Systems’ MR systems including an Achieva 1.5T system, an Achieva 3T, a Panorama high-field open system and the Achieva 1.5T XR that is rampable to 3T. “We have a very diverse referral base,” says MRI supervisor Robert Smith, BS, RT(R)(MR)(CT). “We are big into everything from breast MRI to oncology, body imaging, orthopedics, brain imaging and diffusion and perfusion scanning.”

The 1.5T system—what Smith calls the gold standard in MR imaging today—plays a steadfast role in patient care at the center. Even though 3T systems can scan faster or at higher resolution than their 1.5T counterparts, the proven, reliable imaging strength and quality of 1.5T systems is what everybody compares everything else to, says Smith. “The 1.5T is the standard in the sense that the majority of the protocols and coils have been developed for that field strength,” he explains.

In addition to cost, there are a number of reasons 1.5T maintains its strong foothold. One challenge of higher strength magnets is interaction with certain implants such as stents, clips and shunts. “It is very well established at 1.5T which devices are compatible and which ones are not,” says Smith.

Opening up

1.5T magnet design has continued to improve as have the openness of the system bores, allowing access and comfort for a more wide-spread patient base. High-field, open-bore MRI is growing rapidly, promising faster scan times and improved patient comfort. Siemens Medical Systems’ Magnetom Espree 1.5T MR system is one example of the next-generation 1.5T systems, with a 70-cm bore and magnet size of approximately 125cm long. This allows more than 70 percent of exams to be completed with the patient’s head outside of the bore.

New York’s Zwanger Pesiri Radiology Group, a state-of-the-art radiology group serving central Long Island, provides the latest imaging technologies the field has to offer, including digital x-ray, digital mammography, 64-slice CT, PET/CT and SPECT. The group uses a combination of MRI systems: eight 1.5T and four 3T scanners. An equal amount of studies