If patients ever have wondered if they have an impact on the development of medical imaging technology, open MRI may be the best example that they definitely do. Open MRI is one of the few pieces of medical equipment that has become popular almost entirely through patient demand.
“I think [patient demand] really has driven this marketplace,” says Tony Montagnolo, vice president of technology planning at healthcare technology assessment organization ECRI (Plymouth Meeting, Pa.).
Montagnolo recently had an MRI scan and was asked about claustrophobia before his exam. “It’s so imbedded now that the sites themselves are driving it,” he adds “because they are proactively asking you if you are claustrophobic to preferentially steer you to those sites.”
Some 3 to 4 percent of patients who are recommended for an MRI never follow through with their doctor’s orders because of claustrophobia.
Open MRI technology initially was developed about 10 years ago. The systems were designed with patient comfort in mind and to accommodate pediatric and large patients. They also are quieter than conventional MRI scanners, making the exam seem less frightening to patients. Today, medical imaging centers actively advertise and market their open MRI systems to the general public via radio and TV ads and highway billboards, trying to entice them to their facility for the patient-friendly exam.
Hitachi’s Airis II is a 0.3 Tesla permanent magnet system featuring high-performance gradients.
“Open MRI has certainly become mainstream MRI,” says Sheldon Schaffer, vice president and general manager of MR at Hitachi Medical Systems America Inc. (Twinsburg, Ohio). “Ten years ago, nobody actually knew about it, and those who knew about it had reservations. Nowadays, we see the MR sales activity being 50 percent open MR and 50 percent high-field MR.”
Most open MRI systems in medical imaging centers and hospitals are low- and mid-field systems used for typical “bread-and-butter” exams on the spine and joints, says Montagnolo. He adds that those units should not be confused with the latest open MRI technology now beginning to roll onto the market. The new generation of open scanners promise faster scan times (GE Medical Systems claims scan times three times faster than currently available units), boosts in applications thanks to a technology migration from higher field scanners, slightly larger field strengths, larger bores that accommodate larger patients as well as interventional procedures under MR guidance. In addition to the traditional MRI capabilities, such as knee, shoulder, ankle, spine and brain, the new units have potential applications in pediatric care, monitoring of stroke therapy, scanning trauma patients and providing guidance for minimally invasive procedures. Today, open MRI systems range from $600,000 to $1.5 million, with the new units occupying the higher price point.
GE Medical’s OpenSpeed MRI uses a 0.7 Tesla superconducting magnet.
GE Medical Systems (GEMS of Waukesha, Wis.) is the first vendor to roll out this new breed of open MRI scanner. The Signa OpenSpeed, which debuted in mid-November, was created for patientcomfort and to enhance image quality for interventional procedures, says Dennis Cooke, general manager of global MR.
It took GEMS some 18 months to develop Signa OpenSpeed at a cost of some $30 million. The system — which has a list price of $1.5 million — received FDA 510(k) clearance in November 1999. The first installment was at St. Luke’s Medical Center (Milwaukee). GEMS is targeting sales of 100 Signa OpenSpeed systems worldwide by the end of this year.
The higher-field, open system uses a 0.7-Tesla, superconducting magnet, rather than a permanent magnet and employs the same Sigma LX platform used on GEMS’ high-field MRI scanners.
Robert Breger, M.D., St. Luke’s director of MRI, says the “safe, non-invasive nature of MRI makes it very popular with patients, and the open MRI systems provide a less confining feel than traditional MRI systems.”
Siemens Medical Systems Inc. (Iselin, N.J.) was the next vendor to debut its concept for a new open scanner, although it is still more than a year away from commercialization (expected summer 2001). The works-in-progress 1.0-Tesla open MRI system will have the highest field strength on an open MRI, designed to accommodate new whole-body applications, such as spectral fat saturation, diffusion for stroke imaging, perfusion, contrast-enhanced MR angiography (MRA) and blood oxygenated level dependent (BOLD) imaging. Additionally, the system will be accompanied by a set of integrated panoramic array coils for the head, neck, spine and body, and other CP multi-purpose coils.
Siemens has two commercially available open MRIs, the 0.2 Tesla Magnetom Open Viva and the 0.2 Tesla Magnetom Open Jazz. The Open Viva is a C-shaped permanent magnet for whole body scanning, while the Open Jazz is a dedicated orthopedic unit.
“The trend is to make more powerful and more open magnets,” says Anne Deery-Sheehan, MR product manager. “This has always been the goal, but it hasn’t been very easy to accomplish.”
Jonathan Lewin, M.D., director of MRI and vice chairman of research and academic affairs at University Hospital of Cleveland (UHC), uses the Magnetom Open and the Open Viva 0.2 Tesla. The Magnetom Open was installed in 1995 and used as a shared system with the radiology department for diagnostic and interventional MRI. The hospital began to use the system for intraoperative procedures and purchased an Open Viva in 1998. That unit is housed in a dedicated operating room and is used primarily for neurosurgical procedures.
“It doesn’t replace another method [of diagnosis], but it’s a new method for visualization for us, as most places are doing this,” Lewin says. Once surgery has been completed, the doctor scans the patient to make sure the entire tumor has been removed. Lewin says the open MRI eliminates the guesswork by irrefutably distinguishing between a tumor and normal brain tissue.
Philips Medical Systems North America (Shelton, Conn.) is the most recent entry to the new-generation open MRI market with the roll-out of its Gyroscan Panorama in March. Philips also debuted the Gyroscan Intera.
Picker’s Outlook ProView 0.23 Tesla MRI
The Gyroscan Panorama — introduced at the meeting of the European Congress of Radiology in March — features 0.23 Tesla field strength and a side entrance into the magnet. A unique table design lets the technician move the patient left and right once inside the magnet, as well as from head to feet. It has a wide array of coils and comes standard with Philips’ synergy technology, or phased array technology. The unit, which is being built by Finland-based Picker Nordstar, a subsidiary of Marconi Medical Systems (Highland Heights, Ohio), has been installed in Europe and Japan, and Philips currently is working on the Panorama’s first installation in the United States. The Gyroscan Panorama, thus, shares many characteristics of Marconi’s Outlook ProView open MRI scanner.
The Gyroscan Panorama, which has been cleared by the FDA, is expected to be available by mid-summer. It is expected to sell for less than $1 million.
The new Gyroscan Intera is available in field strengths of 0.5, 1.0 and 1.5 Tesla, and has a single platform that is suitable for all applications, including cardiac and research capabilities. There is a RapidView reconstructor that permits scanning at 256 matrix and reconstruction at up to 196 images per second. A new in-room, ceiling-mounted LCD display can show images or physiology information, or a technician can run the system from inside the exam room, which is beneficial for interventional and surgical procedures, or to lend comfort to the patient. An interactive scanning option lets the technician change field of view, angulation and other scan parameters while scanning is taking place.
Marconi debuted its Outlook ProView open MRI in May 1998. The Outlook ProView has a 46-cm patient gap, which is one of the widest openings of any C-arm or permanent open MRI system.
The unit’s design also features side-first patient entry and a detachable patient couch. An optional second table with vertical motion may be added to the Outlook ProView, allowing the operator to prepare the patient and position the RF coil before a patient enters the exam room.
The Outlook ProView accommodates pediatric, elderly and critically ill patients, as well as large patients and those who require kinematic studies.
Phased array RF coils are standard on the Outlook ProView. Because the system receives and reconstructs signals from each channel separately, the highest possible signal-to-noise from each coil is utilized throughout the imaging volume for greater image quality than with non-phased array quadrature RF coils.
Toshiba America Medical Systems (Tustin, Calif.) features a 0.35-Tesla cryogenless open magnet MRI called Opart, which competes in the $800,000 to $900,000 market. The open design allows four-side access to the patient, with 100cm-by-50cm openings. There are currently 250 Opart systems installed worldwide, with half that amount located in the U.S., the biggest market for open scanners, according to Scott Eaton, director of Toshiba’s MRI business unit.
Toshiba recently introduced several enhancements to the system. Since their debut at RSNA ’99, two works-in-progress have received FDA approval: an array head coil and the Version 3.0 software package, which allows for faster scan times. Toshiba also is expanding the number of coils available to make peripheral angiography possible on an open MRI.
Diffusion-weighted imaging is a new territory for open MRI systems, because it is susceptible to motion of fluid in the brain. It can be used to stage and detect stroke. Toshiba started doing these types of images two years ago and found them unacceptable for diagnosis. The company since has developed the technology to an acceptable level and it is part of the Version 3.0 software.
Another application for the next generation of open MRIs is the ability to do water-fat separation. This capability allows for the diagnosis bone conditions and ligament damage, viewing the optic nerve and imaging of joints in muscular skeletal applications. The technique was never possible on open systems before, because a low-field MRI cannot distinguish between fat and water, says Eaton.
Mark Winkler, M.D., director of MRI at Steinburg Diagnostics (Las Vegas), has six Toshiba MRI units installed at his clinic, including two 0.35T Opart systems.
“Our main reason [for getting an open MRI] was that our patients really wanted it,” he says. “There’s a tremendous patient-driven demand for MR systems that are more friendly … For 99 percent of our procedures, it’s as good as or better than a high-field or conventional MR.”
By adding the open MRI scanners, Winkler says that the center preserved its client base which it was losing to other new facilities that had only open MRIs. Winkler also needed the open system to compete for managed-care contracts in Nevada.
Hitachi’s open MRIs — the Airis and Airis II — can be upgraded with new high-performance capabilities that were introduced at RSNA ‘99. Hitachi counts 250 Airis II systems and 850 other open MRIs in the U.S. and 2,000 open MRI systems installed worldwide.
The Airis II is a 0.3-Tesla permanent magnet system, featuring high-performance gradients. This capability allows for the use of multiple array coils to increase scanning coverage.
Schaffer says the company soon will introduce a phased-array CTL (cervical thoracic lumbar) coil to image a longer area of the spine, rather than take separate images for each section of the spine. A 64-bit RISC-based computer system will support technology, such as echo planar diffusion-weighted imaging and water-fat separation. Schaffer expects these new applications to become realities on Hitachi MRI systems within the year.
When Open MRI of Cherry Hill (Cherry Hill, N.J.) decided to replaced an older MRI unit, it chose an Airis II.
“Image quality on this scanner is pretty exceptional considering that it is only a 0.3 [Tesla] magnet,” says Charlene Sims, a technologist board-certified in MRI.
Another reason for Cherry Hill’s choice was the fast MIP (maximum intensity projecting) time, the post-processing of an MRA. The mipping process takes two to three minutes on the Airis II, according to Sims, so patients need wait approximately 10 minutes for their films to be ready to take back to their doctors. Studies are done every 30 minutes, compared with every hour with the facility’s old scanner. With the new open scanner, the clinic now has the capability of cardiac gating, something that was never a possibility with the previous system. Sims says Cherry Hill also is attracting more patients because of the openness of the Airis II.
The future of open MRI
“We’re seeing an application explosion in MR,” says GEMS’ Cooke. “It seems like every time we turn around, somebody is doing something new and exciting, whether it be cardiac MR or functional MRI for neuro.”
The technology has brought about high-field capability to open MRI units, cardiac MR systems, and functional MRI for surgical planning. Cooke believes that product introductions are much more rapid now because of customer demand and agrees that patients are driving the open MRI market.
Toshiba also chose the superconducting route for its open MRI.
“Many times, when we develop things for Opart and we go beyond what it can do today, we know we’re competing with a high-field system,” says Eaton. “Radiologists don’t want to make that compromise from a high-field [MRI] to an open [MRI] just for the sake of patient convenience. They have at stake a proper diagnosis. Our challenge is to do whatever we can do to the equipment so we’re not forcing them to make that compromise.”
Eaton says Toshiba has found acceptance of Opart’s image quality for diagnosis among muscular skeletal radiologists, but there remains some doubts from neuroradiologists.
Interventional medicine has become more commonplace using an open MRI scanner. There is no ionizing radiation involved, according to Eaton, which makes it safer for radiologists. Easy access to the patient in the MRI also contributes to its increased usage.
Joint motion studies cannot be done on a closed-bore MRI. This technique is useful for injuries where the doctor needs to see how the bone and ligaments move with a joint when in different positions. Another advantage is that since open MRIs have a lower field-strength, they are not subject to susceptibility artifacts.
“One of the big advances that medicine is going to make is along the lines of minimally invasive therapy and the role that MRI can play — and currently it is open MRI primarily — in the development of minimally invasive therapeutic strategies,” says UHC’s Lewin. “From an economic or societal perspective, it costs probably a fifth to a 10th of the expense of doing conventional surgery. I think the minimally invasive therapy side is really much bigger than simply the improvements in open MRI technology. MRI technology has been essential to the development of these MRI-guided procedures.”
Schaffer foresees using open MRIs in orthopedic and neuro applications, such as diffusion-weighted imaging for further evaluation of stroke patients. “I think there are a lot of activities that are forthcoming in both breast MR and cardiac MR that we look forward to seeing the potential adaptation of those applications in open MR as well,” he says.
Many doctors and technicians who are using open MRI believe it is best to have both an open and a closed-bore system in a hospital or clinic.
“If you don’t have both conventional and open MR services, then you probably won’t be able to win a managed-care contract,” says Steinberg’s Winkler. That is the case in southern Nevada. He theorizes that open and conventional MRIs will eventually merge and become indistinct, as open MRIs are upgraded to greater field strength and conventional MRIs become more open in design and quieter. 
