1.5T MRI: Friend to Physician and Patient Alike

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Utilization of magnetic resonance imaging is on the rise and 1.5T systems remain one of the strongest players in the marketplace. An estimated 24.2 million MRI procedures were performed in the United States in 2003 in facilities using fixed and mobile MRI systems - which shows a 10 percent+ jump from the 21.9 million procedures performed in 2002, according to IMV Medical Information Division Inc.'s 2004 MRI Market Summary Report. High-field 1.5T MRI systems accounted for more than two-thirds of MRI units installed in 2004, replacing older units in both hospitals and non-hospital settings, the report found.

MRI's strength in the diagnostic imaging community is attributed to a number of key elements, including its ability to acquire images without the use of ionizing radiation. MR imaging provides clinicians with unprecedented soft-tissue contrast, which is valuable in determining certain diseases and conditions.

Imaging at 1.5T has been done in for a number of years. "Because of its maturity, there has been more application development," says Vickey Hanson, America's 1.5T MR marketing manager for GE Healthcare. "There are larger surface coil portfolios. There are larger application portfolios - from very broad applications to very specific applications." These range from the bread-and-butter MRI applications, such as brain, spine and neck and musculoskeletal imaging, to emerging applications such as vascular, cardiac, breast and pediatric imaging, as well as functional MRI.

"There are more 1.5T scanners out there than any other [type of MR system]," says Edmond Knopp, MD, associate professor of radiology and neurosurgery, section chief of neuroradiology at New York University School of Medicine. "At the same time, they are capable of doing everything, whereas the low-field scanners are not capable of doing everything and their image resolution is very poor. Also, there are not many 3T systems [installed clinically] and they are somewhat more difficult to use."

The customer base for high-field 3T MRI systems has transitioned from research institutes to clinical settings as the technology touts increased signal to noise (SNR) ratio and faster scanning with higher resolution. However, 3T systems carry price tags of $700,000 to $1.2 million more than 1.5T systems. The 1.5T systems also are less sensitive to motion artifacts and do not have to deal with SAR (specific absorption rate) issues that plague 3T.

And patient friendly, too

Besides being workhorse scanners and accommodating a variety of emerging applications, the newer generation of 1.5T systems have designs that are more patient friendly. "The most prominent recent trend in the 1.5T market has been to introduce MRI scanners that are more patient focused," says Mark Totina, product manager for Toshiba America Medical Systems Inc. "If you were to analyze the latest MRI scanners released by the major vendors, you would find the common theme of shorter bores, wider apertures, quieter scanners and niche patient-focused features."

Toshiba's patient friendly applications for its Vantage 1.5T ultra-short MRI system include a noise reduction technology called Pianissimo. The technology decreases gradient acoustic noise up to 90 percent, which is equivalent to the noise reduction of being 40 meters away from a point source of noise.

Health Scan Imaging in Murrieta, Calif., recently installed Toshiba's Vantage 1.5T MR system. "MRI exams are noisy," says Bill Kelly, MD, neuroradiologist, founder and director of Health Scan Imaging. "This has become in many cases just as intimidating to the patient as the confinement [issues]. Now when patients come in for an exam and hear how quiet the magnet is, it's another factor that increases their likelihood of tolerating the exam."

Newer 1.5T designs also include shorter bores. Raleigh MRI in North Carolina utilizes Siemens Medical Solutions' Avanto 1.5T MRI scanner that has a compact 60-centimeter magnet (150 cm length). "You can actually stand next to the magnet and outstretch your arms and touch both ends," explains Margaret King, RT, director of MRI services at Raleigh MRI, an outpatient imaging center affiliated with Wake Radiology Diagnostic Imaging Inc. King says that lumbar spine exams are completed with some portion of the patient's head outside the bore.  

In August 2004, Siemens launched the open bore Magnetom Espree 1.5T MR system. The system's 70 cm bore (175 cm length) allows for 60 percent of exams to be completed with