Progress generally comes in two varieties: extensive or incremental. The cardiac magnetic resonance (MR) market this year is probably best characterized as the latter, but if you’re one of those the-glass-is-half-full people, you might disagree.
Whatever your take on the progress, there’s no denying that cardiac MR proponents these days exude a palpable enthusiasm for the increased interest and improved atmosphere the modality is earning. Accomplishments have appeared in the form of technological tweaking and increased clinical acceptance for cardiac MR, both for dedicated cardiac MR units and software (with the former edging out the field of late). Turf issues are slowly giving way to more collaboration between radiologists and cardiologists at some institutions, and increasing education and training are creating more highly trained users.
Growing availability of the modality that images perfusion, function and viability is evident. However, compensation issues, questions about 3 Tesla magnets and needed improvement in imaging coronary arteries require more attention. And as vendors and researchers continue to reach for answers through software redesigns, further validation of applications, and more robust solutions, lobbying continues for CPT codes for cardiac MR applications.
Organizations such as the Society for Cardiovascular Magnetic Resonance (SCMR of Mt. Royal, N.J.) are ratcheting up certification offerings and spreading the word and work of cardiac MR as centers are answering the call to train more users. Zahi Fayad, M.D., director of cardiovascular imaging research and associate professor of radiology and medicine at Mt. Sinai School of Medicine (New York, N.Y.) serves on the SCMR’s Board of Directors and says the society continues to see exponential growth.
“Our task and the society’s goal is to [stress] the educational aspect,” Fayad says. “The society is hosting meetings attracting about 800 or 900 people and helping a lot with education … co-sponsoring meetings and [doing] satellite meetings.” Through the SCMR’s efforts, more courses are being offered in the field.
Duke University Medical Center’s Cardiovascular Magnetic Resonance Center (DCMRC of Durham, N.C.) became the first facility in the nation devoted solely to cardiovascular MRI. The center is a result of a strategic research and development and educational agreement between Duke and Siemens Medical Solutions USA Inc. (Malvern, Pa.) to jointly foster wider clinical application of cardiovascular MR technology.
The Heart Group, PLLC (Nashville, Tenn.), a practice of 24 physicians serving middle Tennessee, northern Alabama and southern Kentucky, opened The Nashville Cardiovascular Magnetic Resonance Institute last month. The practice has a large heart failure program and expanding peripheral vascular program. Travis Wood, CEO of The Heart Group, sees this type of focused facility approach as one to watch.
“I think you will see this trend develop among large cardiology practices,” Wood says. “I believe this will be the growth market of cardiovascular MRI.” A few private practices currently have this capability, but it is clearly in its infancy, according to Wood.
Dipan J. Shah, M.D., a cardiologist involved with the development of Duke’s MR center will head up the program at the Nashville center. Two additional cardiologists from The Heart Group will be trained to support Shah.
At William Beaumont Hospital (Royal Oak, Mich.), cardiac MR equipment is located in the cath lab (serving as an adjunct to procedures there) near where the cardiologists work, a somewhat unusual approach. The cardiac MR program at William Beaumont is under the co-directorship of Gilbert Raff, M.D., a cardiologist and director of cardiac research, and Kostakis Bis, M.D., a radiologist who shares responsibilities.
“One of the reasons this program is successful here, in my opinion, is that we have close coordination between myself and Dr. Bis,” Raff says. “Our facility is jointly directed by radiology and cardiology. And I can tell you flat out, there’s no way it would be half as good if we didn’t have both. I think the most exciting facilities around the country are ones where somehow those two specialties can come together. It’s very important, and it’s a source of distress to me many places are polarized.”
Cardiac MRI at Beaumont includes essentially two kinds of imaging situations. “One is in ischemic heart disease, coronary artery disease, and the other is the full range of other heart diseases, including valvular heart diseases, other similar acquired heart diseases and congenital heart disease,” Raff says.
In the area of coronary artery disease, Raff and his colleagues are doing a special study of acute myocardial infarction to determine how early they can decide when a part of the heart is still viable after having a heart attack. “We want to apply our knowledge to try to improve therapy by using steps beyond angioplasty,” Raff says.
Two patients can present with heart attacks in the same artery. Both of them can get identical therapy, such as angioplasty to open the artery and are given anticoagulants. Both patients have the same amount of heart muscle that is not moving well afterwards. “Even if something is going to recover, it doesn’t recover that very minute, so at that point, both of these patients by any other imaging technique look identical,” Raff says. “They have an area that’s not moving. They have an artery that’s not opened, and you cannot say with other techniques if that muscle is eventually going to recover three months later, if it’s going to be normal again or it is not going to recover.”
Philips Medical Systems’ Intera 1.5T MRI system acquired the cardiac images (above) with Philips’ cardiac coil.
The answer depends on the microscopic vessels, the microvasculature below the artery level, which may or may not be able to carry blood, sometimes because clots go down stream and break up and are filtered out. Other reasons may have to do with the breakdown of the capillaries. They themselves get ischemic and cannot carry blood.
“The hospital is doing a lot of that kind of research [with cardiac MR] into the early therapy after angioplasty,” Raff says. “You don’t want to do that on everybody. It’s expensive, time consuming and would be a waste if you did it on a person who is going to recover anyway. So you need to have a new tool that can distinguish between one type of situation and another that currently cannot be diagnosed.”
In addition to the more routine work in coronary artery disease, looking at perfusion of the heart, function to examine movement and viability to determine potentially recoverable areas through bypass or angioplasty, cardiac MR work at the hospital also includes finding flow problems through the valves. “That also is effective in looking at congenital heart disease, where you have [inborn] abnormal connections around the heart, as well as muscle abnormalities, such as hypertrophic cardiomyopathy that is excessively thick because of genetic disorders,” Raff says.
Investigational work with cardiac MR also includes procedures for atrial septal defect (ASD) and ventricular septal defect (VSD). With ASD and VSD, two sides of the heart are separated by a hole, causing a dangerous mix of oxygenated and deoxygenated blood. Cardiac MR allows measurement of the hole and the flow on both sides of the heart. “That can give a very good handle on how big the shunting is from one side to the other,” Raff says. “If the shunt is two times what it should be, then maybe you should consider closing that. There is a new procedure where you can … put in a closure device by a catheter so you don’t need surgery. It’s investigational, but it’s being done more and more, and we’re doing it here.” One of the roles of cardiac MR is to give very fine detail to the doctor who is going to correct the ASD or VSD, providing exact anatomy, size of the hole and a view of the surrounding structure.
Elsewhere, pediatric cardiologists are now commonly replacing heart catheterizations with cardiac MR in small children. “If you put flow and structure together, very often you can tell as much as you get in a heart catheterization,” Raff says.
William Beaumont Hospital performs approximately 10 cardiac MR procedures per week, but based on two other major research projects they have accepted, Raff expects to increase that number in the near future. They use a dedicated Siemens Sonata system.
Mt. Sinai’s Fayad uses Siemens’ Sonata cardiac MR technology to study plaque, the build-up of fat in the carotid and in the aorta. “We have shown really for the first time that we can take patients who have had some disease, either advanced or some stage of the disease, and have them undergo MRI to look at plaque,” Fayad says. “We can give them lipid-lowering drugs [statins] and follow after treatment what is happening to the plaque in terms of changes in the composition and in size. So for the first time we can show the benefit of these drugs. That’s a really powerful concept because that’s where imaging now is going to play the role in terms of monitoring and interventions.” The center performs more than 20 cardiac MR scans per week.
Cardiac image is from Beth Isreal Deaconess Medical Center, taken with a Philips’ Intera 1/5T MRI system.
Plaque imaging is important because now doctors know that atherosclerosis is a disease that develops because of injury or inflammation inside of the vessel wall in the blood. Patients with coronary artery disease end up having a build-up of plaque inside the artery, but not necessarily obstructing the flow of the blood. Once a certain type of event is triggered, the fat or plaque breaks up and creates a blood clot that can be fatal.
“MRI is really the most promising noninvasive technique to [image plaque],” Fayad says. “CT will probably most likely become the method of choice in terms of looking at coronary arteries, and it may pinpoint the area of trouble. It may not be very strong in finding the area of characterization of plaque, the high-risk plaque. So CT may find the area of trouble, and then we can zoom into it with MRI to find exactly where it is.”
The SCMR has made a recommendation that cardiology fellows have a month exposure to being on an MR cardiology service. That’s based on the society’s desire to have a basic Level I certification. “There is a more formal structure than there was just a few years ago. …” Raff says. He himself had a difficult time finding a place where he could get a commitment for cardiac MR training. “I really sympathize with cardiologists who are trying to get involved,” Raff says. “They are going to need places to train and, likewise, radiologists are going to need exposure to a cardiac dedicated facility, because cardiology is quite different than radiology.”
Issues in the cardiac MR field remain, and the modality’s future undoubtedly will depend on how well these are addressed. “Unfortunately, many of the procedures that cardiac MR is doing are not well accepted by third-party payers,” Raff says. “Because [the procedures are] so new, people aren’t used to seeing charges for a cardiac MRI machine, and they just reject them off hand.” Cardiac MR perfusion lacks an approved FDA imaging agent. “Gadolinium is approved for imaging everything, and it always passes through the heart, but if you take a picture of it, you can’t get paid for it.”
The high cost of the machines and software upgrades also inhibits people who want to get involved. And the elusive improvement to enable coronary artery imaging remains a major limitation. “There are studies that show very promising results, but as a practitioner I am not ready to say patients should be sent to me for that purpose,” Raff says. “I think it needs to get better. I believe all the imaging companies are well aware of this and they’re striving hard to work on it. That’s sort of the Holy Grail at this point.”
MR spectroscopy remains an area of promise. Measuring chemical constituents in tissue and directly sampling the products of ischemia — such as downstream chemicals that are produced when the heart isn’t getting enough blood — holds great interest for cardiologists. “The potential for measuring ions and other chemicals directly is very far away, according to my best assessment, but five years from now, we may be doing those very commonly,” Raff says.
Most of the focus of Siemens’ work today relating to cardiac MR is on how to take the existing techniques and make them clinically robust, according to Jeffrey Bundy, Ph.D., cardiac business development manager for the MR Division. “We had some technology, for example, in the delayed enhancement imaging. …” Bundy says. “We haven’t necessarily changed the physics technique, but we changed essentially the way that is acquired. So we’re trying to remove dependency on the technologist.”
One example is a technique that eliminates the need to set parameters manually by a knowledgeable technologist or radiologist. The computer does it for them. “We spend a lot of time working on making the clinical routine, the clinical workflow more efficient, eliminat[ing] as much repetitive operator activity as we can,” Bundy says. “Within our product we have software techniques, our inline technology, across the MR products which do that.”
Essentially, when a task is understood enough and repetitive enough, it is taken out of the hands of the technologist and put into an automatic routine. Siemens also did a redesign of its software interface for cardiac MR examination. Bundy sees Siemens Phoenix feature impacting MR in general and in the cardiac area. Phoenix allows taking an expert user’s protocol for coronary imaging, for example, and saving the data on a DICOM compact disk for any user to load on his or her scanner and reproducing the protocol from the expert user. It eliminates figuring out the protocol and typing in numbers to change parameters to acquire images. The exact protocol is provided. Phoenix images also are available on the Siemens web site (www.siemens.com) and downloadable there.
Siemens introduced its self-gating technology at the SCMR meeting in February. Lack of accurate ECG gating or synchronization can be an obstacle in getting a good cardiac MR study. “We acquire our data over several heart beats and put the data back together at the end of the study,” Bundy says. “The self-gating technique enables you to [get accurate synchronization with the heart beat] … without the use of any kind of ECG or pulse wires required. That has an advantage in that in the MR environment because of hemodynamics in the magnetic field …, it’s difficult to get a reliable ECG signal. We have ways of solving that and making it better.”
Toshiba America Medical Systems’ (TAMS of Tustin, Calif.) Excelart system is moving to a new platform that has increased speed and patient improvements. The company has released its coil technology called Speeder, its version of parallel imaging. “The coil and the receiver we use are quite high quality from the point of view that if you can increase your signal to noise in MR, you can use that in many ways, including faster scanning, higher temporal resolution, higher spatial resolution and all the things you like to do with cardiac imaging, particularly when you’re starting to shoot for the coronaries,” Joseph Fritz, Ph.D., senior manager of clinical development for TAMS.
With its focus on the more affordable 1.5T technology, TAMS has implemented cardiac capabilities on its 1.5T Excelart products. The new configuration has a much shorter bore. The company is answering patient comfort needs, recognizing that larger patients tend to have cardiovascular disease.
“We wanted to go for continuing with the patient comfort aspect and make it as open as possible at 1.5T,” Fritz says. “So we’ve gone to what will be the shortest MR gantry on the market, using a 1.4 meter magnet and maintaining a 65 centimeter bore opening. One of the aspects is speed [with] the parallel imaging implementation, and the second is development of the configuration of the magnet itself that allows for greater patient comfort.”
Additional development in the area of 3D techniques, particularly without using contrast, has also progressed using TAMS TrueSSFP (steady state free precession), allowing very rapid scanning, building up the signal and ending with a very high contrast, very good signal to noise, even though scan times are extremely short, the company says.
“The ability to do coronary imaging without contrast, allowing the patient to breathe freely as opposed to doing a breath-hold to get high-resolution 3D acquisition that allows you to use post-processing to view the right direction and to lay out the vessel in different display ways, is an important improvement that we’ve seen in the last year,” Fritz says.
Philips Medical Systems’ (Bothell, Wash.) cardiac MR offering is the Intera CV dedicated system and associated packages. The company says it has made a “significant refinement” of its balanced TFE (turbo field echo) techniques, giving blood and tissue contrast at high speed of acquisition. “We refined our navigator technology that allows us to do respiratory compensation,” Paul Gallagher, MR field marketing manager.
In addition to the advancement of contrast agents, Gallagher sees the potential of blood pool agents as a plus for cardiac MR. “Blood pool agents being developed remain in the blood pool for a longer period of time,” Gallagher says. “One dosage gives you vascular information, and there’s also really intriguing work going on in molecular imaging. There’s an interesting application of the technology that I normally associate with neuro work, fiber tracking, and I’ve seen research work with Philips where that’s being used for the myocardium, looking for disruption of the fiber myocites [muscle cells] when you are looking for infarcted tissue.”
Myocardial viability remains at the top of many people’s lists of cardiac MR needs. A report published in The Lancet last year showed the study of viability with MRI to be superior to SPECT imaging. Higher spatial resolution in MRI can detect smaller areas within the whole myocardium on the endocardial or epicardial sides.
When it comes to 3T, some vendors are in active pursuit, while others are taking a wait-and-see approach. 3T’s higher signal to noise ratio should translate into faster imaging, better contrast and more resolution and detail.
“Those are things that should allow us to do better coronary artery imaging,” Gallagher says. “However, there are also limitations [including] more artifacts, unacceptably high patient SAR [specific absorption rate] levels where you’re inputting too much RF energy into a patient and causing tissue heating. I’ve seen some tantalizing images done with prototype coils on a research basis for cardiac using parallel imaging, what Philips calls Sense (sensitivity encoding).”
Siemens considers the higher magnet strength a focus for the company and its research partners. “It’s not the state of the market where your average customer is buying 3T, but a number of our collaborative partners are buying 3T to look at its potential in the body and in cardiac imaging,” Bundy says. “1.5T does a very good job. We may see areas at 3T where the biggest potential for advantage would be in the cardiac perfusion imaging and coronary imaging. The other areas there may be some advantages that will take a little bit longer to pull out.”
TAMS says it will not be introducing the 3T version until more of the issues have been addressed, including reimbursement, and when there is actually an opportunity for people to be making money to overcome extra costs associated with 3T. “I think eventually you’ll see where 3T is going to become very popular, but as of today, the expense and some of the drawbacks are limiting its growth,” Fritz says. “Toshiba tends to introduce products once the market is ready for them … so you won’t see Toshiba introducing the 3T version until we are really comfortable that a lot of these technical and pricing issues are addressed.”
While 3T research continues, 1.5T maintains its place as the burgeoning cardiac MR workhorse. Fayad says cardiac MR is now becoming “very simple to do if you are well trained and have good accreditation. It’s really become very straightforward.” His message: “It’s ready to be used. Don’t be intimidated. I really believe it should be integrated into your day-to-day clinical service and assessment of the patient.”