Issue StoriesMoving Right Into the Futureby Wren Davis The ever-changing field of MRI continues to do just that.
"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 SeeMRI 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.
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.
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 ItMany 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 ItMany 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.
Wren Davis is a contributing writer for Medical Imaging. |
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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.
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