If it can be imagined, it can be achieved. This notion has inspired countless inventors, scientists, and futurists, emboldened by the continuous advancement of technology. They believe that time ushers in new possibilities. Many cite as proof the fact that “far-fetched” ideas plotted in the novels of Jules Verne?submarines and spaceships, for example?have actually come to pass. Others look to medicine for instances?and they don’t have to look too hard. MRI has evolved from antiquated grainy images into a sophisticated tool that captures not only bones and muscle, but also brain function and blood flow.
“The technology has finally caught up to the idea,” says Bob Giegerich, director of the MR business unit at Toshiba America Medical Systems Inc (TAMS of Tustin, Calif). MRI is now used to look at nearly every part of the body, including the breast and the vascular system, as well as different functions, such as brain metabolism. MRI has become invaluable to diagnostics and key to certain interventional procedures.
New technologies improve these capabilities, leading to new techniques, which, in turn, expand the modality’s applications. Slowly, higher field strengths are creeping into facilities and the market, bringing improvements in images and acquisition that will push possibilities even further. What we cannot image today, we could be able to image tomorrow. And what we imaged yesterday, we can see more clearly than ever before.
What We Can See
MRI is used primarily to view the brain, the spine, and the extremities/orthopedics, according to Steve Mitchell, director of product marketing for Philips Medical Systems (Andover, Mass). “MR spans a broad mix of customer types, from entrepreneurial or mainstream clinical hospitals to high-end research centers, with growth seen in imaging centers. Procedural volumes are divided into 27 percent brain, 26 percent spine, 19 percent extremities, 10 percent body, 9 percent vascular, and 2 percent cardiac,” says Mitchell, sharing some utilization stats from IMV Ltd (Des Plaines, Ill). He notes that body and cardiac imaging are showing the most growth.
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| GE Healthcare responded to a physician’s request for better imaging of the foot (above) by increasing coil sensitivity to show greater detail. |
According to Michael Wood, manager of MR research at GE Healthcare (Waukesha, Wis), “A vascular radiologist once counseled me that if we had serious aspirations of substituting MRI for the more risky X-ray angiography in the leg, manufacturers would have to do a better job of imaging the foot. Vascular physicians need to know about blood flow in the foot, particularly in diabetes patients, and MR did not image the tiny vessels well. But about a year ago, we developed a coil with ten times more sensitivity. Now, physicians can see these smaller structures.”
MR angiography (MRA) provides detailed images of blood vessels and blood flow, often without using contrast material, although its use in a special form can make the images clearer. The technology is not new, but the ability to view blood flow with such clarity is.
“MRA evaluates blood vessels noninvasively and essentially with no risk to the patient. It can provide details of the vascular system, including intracranial blood vessels, the carotid arteries in the neck, and peripheral vascular structures,” says Jeffrey Weinreb, MD, professor of radiology with Yale University School of Medicine (New Haven, Conn) and chief of MRI at Yale/New Haven Hospital.
Since it does not require contrast, the MRA exam is easier. “With a contrast injection, the radiologist has to be on-site in case the patient has a negative reaction. With no injection, the radiologist doesn’t have to be at the facility?a benefit to physicians covering more than one site and arranging their schedule around injections,” says TAMS’ Giegerich.
The advances are giving the technology a mainstream boost, unlike fMRI, which receives a lot more press than clinical use. “fMRI has a small role in the current marketplace. It’s a highly intellectual pursuit that shows a lot of interesting things, but no one knows yet how to use that information. It will expand eventually, but it could take a while,” Giegerich notes.
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Clinically, fMRI is used to map the brain prior to surgery. By identifying the areas related to function, the surgeon can avoid them, protecting such abilities as speech and movement. GE Healthcare’s Wood also points to the use of diffusion tensor tractography to show nerve tracks in the brain’s white matter. The information can be used in surgical planning and prognosis.
As a research tool, fMRI is being used to map brain function?for instance, looking at affects related to addiction, physiological response, aging, criminality, and even, according to Giegerich, reactions to colors used in advertising. However, none of this use is reimbursable. “Expansion of fMRI into clinical use will occur once it gets a repayment code,” says Philips Medical’s Mitchell.
Breast MRI has a repayment code; however, some would argue it should be higher. Although it is not recommended as a screening tool for the general population, its use in high-risk patients has increased. “Breast MRI is not new. The first ones were performed more than 20 years ago,” says Yale’s Weinreb. “What is new is that in the past couple of years, there’s been enough scientific data to convince the community of its value.”
What We Will See
“Breast technology is constantly evolving. As patients and physicians demand it, companies will spend more time and money in that area,” Giegerich says. Dedicated breast coils, specific MR sequences, and automated processing packages have advanced breast MR.
These techniques, and many others, can be refined and used in new applications, Weinreb notes. Higher-quality images acquired in less time produce less artifact and clearer pictures. Technologies?for example, 3-D volume acquisitions, diffusion tensor imaging, arterial spin labeling, fat suppression, parallel imaging, and multi-channel systems?improve images even more.
Also, advances in contrast agents are expanding applications and increasing safety. New contrast agents are in development, and some technologies create alternatives. “WET [water excitation technology] uses water as a contrast, and produces beautiful carotids?better than anything ever seen. But it also allows us to get away from gadolinium, which is more expensive and used off-label,” Giegerich says.
Bound and unbound water molecules can be used to predict inflammatory diseases, which include cancer and Krohn’s disease, Giegerich adds. Cardiac techniques will be employed in the study of angiogenesis, an area that Weinreb believes is worth watching. Advances will grow MRI’s role in noninvasive therapies as well as cancer diagnosis and treatment. And in the distant future, Wood expects molecular imaging to gather information about cellular and molecular processes through MRI.
How We Will See It
Many of these technologies, both mainstream and developing, produce better images at a higher field strength, particularly those that benefit from the resulting higher signal to noise. They range from MRA to PET and spectroscopy to body imaging.
“Most of what I’m familiar with in MR benefits from 3T, even if it just means the image is captured more quickly,” says GE Healthcare’s Wood, whose company recently released a new 3T MRI unit. (See “MRI Marketplace” below for a list of current product offerings.)
“It’s important that everyone consider a higher field magnet,” says Lawrence Neil Tanenbaum, MD, FACR, president of the Clinical Magnetic Resonance Society (CMRS of Tampa, Fla). He acknowledges that might not be right for everyone, but he says there should be a good reason for not making the purchase. “The clinical feasibility of 3T is a hot topic. It’s not held back by the expense as much as technology issues. The higher field strength deposits RF [radio frequency] waves into the patient four times faster, which [used to] limit the aggressiveness of the scan technique. But surface coil technology changed, and now they show better efficiency.”
Currently, 3T represents about a quarter of the installed market, including many high-end research centers and educational institutes. Although no one expects the technology to dominate anytime soon, they anticipate 3T to grab a larger share of the market.
And though some question the viability of the product, for others, the issue could be about money. “Higher field strength systems require more expensive subsystems, especially for the magnet and the RF-related components, so 3T costs more,” says Philips Medical’s Mitchell.
But, reimbursement is the same. “Whether an exam is run on a 1.5T or 3T system, it gets the same reimbursement. So there is no financial incentive to buy one over the other,” says Charlie Collins, director of product marketing for the radiology segment at Siemens Medical Solutions (Malvern, Pa).
In addition, most techniques have been refined for use at 1.5T, notes Giegerich of TAMS, which has a 3T machine in development. “The software [for all companies] needs to be rewritten,” he says, adding that in 5 years, he believes 3T will be an industry staple.
Why Will We See It
Many MRI applications will expand with advanced technology. “Those expected to benefit are intrinsically signal-poor or require special techniques, such as detailed brain images, diffusion, and spectroscopy. The biggest beneficiary might be the body, which must be done rapidly to avoid problems with motion,” says Yale’s Weinreb.
But even at 1.5T, MRI has become critical to care. “The healthcare industry itself has come to depend on the diagnostic capabilities of MR systems. Physicians require it for diagnosing conditions across the board,” Collins says.
Tanenbaum concurs. “Virtually every medical specialty uses MR,” he says, citing neurology, oncology, and vascular surgery as some of the most common. “In general, it reduces invasiveness, the need for repetition, and the cost of care.” In addition, it adds no risk. Everyone can relate to the lack of ionizing radiation.
“MRI has become a very powerful and versatile tool. The applications have expanded rapidly and include every part of the body. Virtually everyone in medicine uses the technology, and its use is driven in part by the fact that it’s so good,” Weinreb says. Perhaps the early MRI researchers never expected that their discoveries would lead to such praise. But then again, maybe they did imagine it.
MRI MARKETPLACEAccording to The Basics of MRI, written by Joseph P. Hornak, PhD, the market hosts approximately six major clinical MRI original equipment manufacturers (OEMs), two major experimental MRI OEMs, and a number of other MRI-related subsystem manufacturers that produce RF coils, contrast agents, compatible devices, RF amps, and magnets.1 The clinical MRI OEMs include:1
Medical Imaging spoke with five of these vendors* about their products. All offer a portfolio of equipment designed to appeal to every market. How to choose? Buyers should consider the usual vendor factors, including reputation, time in the market, product reliability, features, and cost. In deciding between products, Steve Mitchell of Philips Medical narrows the choice down to field strength versus openness versus price. He suggests augmenting existing systems. “If the hospital already has a cylindrical system, and business is suffering, you might augment it with an open system. If you already have low field strength, you might want to expand to higher fields. Fundamentally, it’s a choice of field strength, patient comfort, and price,” Mitchell says, adding that such factors as throughput and use should influence the decision as well. Magnet field strengths range from 0.2T to 3T, the latter of which is beginning to penetrate the market. As the field strength increases, the image resolution and acquisition time improve. However, the machines also grow longer and louder, becoming difficult for patients with claustrophobic issues. Also, the open systems tend to have lower field strengths, which could limit their application. To help aid in your decision-making process, we’ve compiled a brief product overview: FonarThe Fonar Upright MRI is the world’s only whole-body MRI that performs Position imaging (pMRI) and scans patients in numerous weight-bearing positions, including standing, sitting, in flexion, extension, and the conventional lie-down position. Approximately 85% of patients are scanned sitting while they watch a 42-inch flat-screen TV. Currently, an installation of the Fonar 360?a room-size MRI?is under way in Oxford, England, where it will be used in clinical trials to develop image-guided surgical procedures known as intraoperative MR imaging.
GE HealthcareGE Healthcare’s MRI family includes eight product offerings. First are the low-gradient open systems, which feature Excite technology: the Signa Profile 0.2T, the Signa Ovation 0.35T, and the Signa OpenSpeed 0.7T. Next are the higher-gradient systems, all of which feature HD technology: Signa HD 1.5T, Signa HDe 1.5T, Signa HDx 1.5T, Signa HD 3T, and Signa HDx 3T. The HDx offerings incorporate the second generation of HD technology. “HD MR is high-definition MR,” says Michael Wood of GE Healthcare. Higher definition translates to greater resolution, improved depiction of moving objects, and alternatives to minimizing artifacts. Philips Medical SystemsPhilips Medical’s product portfolio has two segments: its Panorama line and its Achieva line. The Panorama machines are vertical-field open systems available at 0.23T, 0.6T, and the new 1.0T. “The applications on a 1.0T system are similar to 1.5T, but offer greater patient comfort,” Mitchell says. The Achieva cylindrical systems also are available in three strengths: 1.5T, 3T, and a new 7.0T, the latter of which is available for research only.
Siemens Medical SolutionsSiemens Medical’s Magnetom family includes six products: Magnetom Avanto, a high-end 1.5T system; Magnetom Espree, which offers a 70-cm bore and a 125-cm magnet length, at 1.5T to offer high-field strength in a less-claustrophobic atmosphere; Magnetom Symphony, a 1.5T system designed for clinical and research use; Magnetom Trio, a Tim (Total imaging matrix) system offering 3T field strength; Magnetom C!, a 0.35T open system with a small footprint; and Magnetom Concerto, a 0.2T open system.
“Espree, our open-bore MRI, was introduced last year. Our latest product is the Magnetom Trio with Tim technology, which is featured on all of our 1.5T and 3T products now,” says Charlie Collins of Siemens Medical. Tim technology uses 32 independent RF channels and up to 102 Matrix coils to allow faster patient setup, parallel imaging, and high-quality image acquisition. TAMSTAMS also offers products in mid- and high-field strength, including the Vantage. This closed system features 1.5T; however, it also features an ultra-short and ultra-wide bore. “This is useful for claustrophobic patients as well as larger patients,” says Bob Giegerich of TAMS. The products feature TAMS’ unique MRI gradient field technology as well as its Pianissimo, which reduces noise by up to 90%. The company has a 3T machine in development. |
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*Not all vendors were available for comment. |
Wren Davis is a contributing writer for Medical Imaging.
