While 3T MRI fits the bill as the latest and greatest technology to be introduced to the MR imaging community, not everybody is welcoming the magnet with open arms — cost and complexity remain important factors as to why some physicians and healthcare facilities are on the fence. However, clinical users of 3T are very impressed with the technology’s imaging capabilities, reporting better imaging of brain, musculoskeletal (MSK) and angiography cases with 3T versus its lower-Tesla cousins. While the decision to install a 3T MRI system is not a straightforward one, users suggest a careful evaluation of one’s imaging services is key. And if the time is right, some advice from the trenches may help ensure a more successful and less painful install.
Sometime in the next two years, Steven Braff, MD, interim radiology chair, department of radiology at Fletcher Allen Healthcare in Burlington, Vt., foresees that 3T will become the new 1.5T standard. “You can’t beat that extra signal,” he says, “signal is the currency of MRI.”
Users gain a lot of extra signal with 3T as compared with lower Tesla magnets, such as 1.5T. Braff says the radiologists at Fletcher Allen, a 500-bed teaching hospital in Burlington that is affiliated with the University of Vermont School of Medicine, are benefiting from the extra signal to noise when reading brain and musculoskeletal images. Neurology applications have proven to be better at 3T and MSK work is rapidly gaining acceptance as a result of the availability of higher channel coils.
One of the primary benefits of imaging with a 3T magnet is that it allows users to either acquire images faster, by using less signal to obtain a diagnostic image, or to go to higher spatial resolution and acquire finer detailed images. But the technology does come at a much higher cost than its lower-Tesla counterparts, and not everybody is convinced the time is right for 3T.
“There is the cost and complexity factors of 3T that are challenges,” says Braff. Coupled with the economics that amount to about $1 million per Tesla, clinical limitations such as increased specific absorption rate (SAR) and prolonged T1 relaxation times, some physicians are still weighing their options — buying a high-end 1.5T system or making the leap to 3T.
“In terms of being able to market it and in terms of getting better images, I think 3T is worth it if you are in a place that is doing enough cases,” says Braff. “If you’re not doing it, your competitor around the block is.”
As hardware and software developments have allowed manufacturers to release a more mature breed of 3T systems, and coil technology continues to improve, 3T is becoming broadly applicable to a large range of clinical applications. It is no longer an experimental modality that serves only niche populations. An increasing number of smaller hospitals and outpatient facilities are adopting 3T today, as opposed to academic hospitals and research facilities — the primary users of 3T just a few years ago.
“If the costs were the same for 1.5T and 3T, then I would say that 3T is the only choice you have to make,” says Larry Tanenbaum, MD, FACR, section chief MRI, CT and neuroradiology at Edison Imaging - NJ Neuroscience Institute, Seton Hall School of Graduate Medical Education in New Jersey. “But they are not the same. What I tell people is that you must consider 3T.”
Just better at 3T
The healthcare facilities that have considered 3T are now using the scanner routinely in clinical practice are impressed with the results, especially in brain and musculoskeletal imaging and MR angiography. Applications clinicians say are improving at 3T but may not be ready for prime time just quite yet include spine, cardiac and breast work.
A 3T magnet fills the role of mainstream MR imaging at Edison. “We have been working with 3T MRI for about six years, and with a short-bore generation system [GE Healthcare’s Signa HDx 3T] for about three years,” says Tanenbaum. “The newer generations of systems are similar to 1.5T in form factor because they have a shorter bore and the same bore circumference [as 1.5T]. They also have high-performance gradients.”
Competitive pressures were important factors as to why Edison started imaging routinely with 3T. “There are a number of orthopedic groups that work with me that insist on 3T, and they refer to me solely because we have this magnet,” says Tanenbaum. “If you have a high-end practice in MSK or neuro, you might be encouraged by your doctors to put in a higher level of technology.”
Neuroskeletal Imaging Institutes in Florida has imaged more than 35,000 patients on its 3T systems since purchasing its first magnet in 2003. In addition to the initial installation at NII’s Winter Park location, the imaging group has installed GE’s Signa HDx 3T MR system at each of its three other south Florida outpatient imaging centers.
“We use it for everything,” says Mark Shapiro, MD, chief of neuroimaging at NII. “We do between 25 and 35 cases a day on each of the 3T scanners. We choose not to scan faster, but to do more detailed imaging. We do a lot of brain tumor imaging and we do perfusion imaging and spectroscopy on every patient who has a brain tumor.”
Fletcher Allen’s 3T MRI system, a Philips Medical Systems’ Intera Achieva, is primarily used for neuro and MSK cases. “We look at white matter tracks and advanced neuro imaging for things like surgical planning,” says Braff. “We have improved functional imaging at 3T for BOLD [blood oxygen-level dependent imaging]. Our MR angiography is done faster and at a higher resolution. We are really approaching or equaling the quality of digital subtraction angiography. In MSK, we are able to do cartilage imaging that is exquisite. There are very small structures in the wrist, such as the triangular fibro-cartilage, and we can see it more exquisitely at 3T than 1.5T. We can go to 1024 matrix imaging. Typically the time and signal to do that at 1.5T was not there. We can now do that routinely which gives us much higher resolution and smaller voxel sizes.
“The other area you can use 3T is in handling patient motion,” he continues. “Instead of doing conventional T2-weighted imaging of the brain, we can do something called single shot fast spin echo imaging. We use this all the time for our uncooperative patients. Each image is 100 milliseconds and we can virtually freeze patient motion. Spectroscopy is another signal starved application. We can now do 56 second spectroscopy examinations of the brain, which would take six minutes at 1.5T. We can do turbo spectroscopy and that is reintroducing the technique more than we were in the last couple of years.”
Is 3T for me?
“I think that everyone is asking that question because 3T is so much more expensive,” says Tim Mosher, MD, vice chair of clinical radiology research, chief of MSK imaging and MRI at the Penn State Hershey Medical Center (PSHMC) in Hershey, Pa. “So people are considering ‘what is this system going to do for me and for my practice?’”
At PSHMC, a Philips’ 3T Intera MRI system is being used clinically for MSK and neuro cases. The center has had experience with 3T on the research side since 1991 and started imaging clinically with the high-field magnet two years ago. “Once clinicians understood the improved image quality with 3T, they started requesting that their patients be scanned on the system,” says Mosher.
The utilization of 3T at PSHMC has heightened the diagnostic confidence levels of its radiologists to diagnose certain diseases and medical conditions, explains Mosher. “In the articular cartilage, for example, one thing we have found is that when we made the diagnosis of a cartilage legion [with 3T versus 1.5T], we were more often correct so we had fewer false positives,” he says. “I think overall our diagnostic confidence in our ability to diagnose those lesions was higher at 3T than 1.5T.”
So what kinds of imaging are better due to the doubled signal strength? “MSK is the one that really stands out where we see a clear added value from 3T,” says Mosher. “The other thing would be MRA in certain body applications, especially in peripheral MRA or in neurovascular MRA. The higher signal to noise is a benefit when you are looking at smaller vessels. Other areas limited by low SNR where 3T has a distinct advantage include MR spectroscopy and functional MRI.”
Although 3T is being used more for bread-and-butter routine imaging in clinical settings, the high field magnet continues to benefit various areas of research, such as breast MRI. Linda Moy, MD, assistant professor at New York University Medical Center, specializes in breast MRI and is currently researching the advantages of breast imaging at 3T.
“It’s not that 3T is going to help detect breast cancer earlier,” says Moy “We are hoping that 3T will show finer, more morphologic detail which may be able to help us radiologists be more confident in describing and detecting lesions that are benign or suspicious.”
In 2005, NYU Medical Center was the first facility to install Siemens Medical Solutions’ Magnetom Trio 3T system. The hospital now has two of these scanners, and both are used for clinical and research purposes.
In the realm of breast MRI, Moy and her colleagues have been researching whether or not certain applications can be done better at 3T than 1.5T. “We can do MR spectroscopy better on a 3T system than on a 1.5T system,” she says. “With 3T, we can do spectroscopy routinely on lesions that are 1 cm, whereas at 1.5T we can only perform spectroscopy on lesions that are 2 cm. In terms of running the sequences, we are actually able to perform spectroscopy faster on the 3T compared with a 1.5T.
“When we are performing breast MRIs, there always is a trade off with spatial and temporal resolution,” continues Moy. “One of the challenges of breast MRI is that you have to take a very long image in order to get a very sharp image. If you take a long image, you could be loosing information on how the contrast is washing in and out of the breast. With 3T, the spatial and temporal resolution tradeoff will be less of an issue because there is more signal to go around.”
The right time to buy
While increased cost and learning curves immediately come to mind as challenges to 3T’s adoption, Fletcher Allen’s Braff says to keep in mind that healthcare facilities grow their business by effective marketing, especially to sub-specialists. “Sophisticated sub-specialists are going to want the better imaging when they know what it can offer,” he says.
Inpatient facilities are more likely considering if they only want the one magnet, or if the system is going to be added to their current capabilities. “I think the doctors who come from university hospitals who already have four magnets are all going to want to do 3T,” says Braff. “A high throughput imaging center with 2 magnets also will want a 3T scanner.”
However, an outpatient facility will most likely choose its magnet dependant on the market it serves or wants to serve. Do you want to address neurology or overall imaging? Are you targeting a niche, or attempting to become a center of excellence? Also, 3T users say it is critical that the smaller imaging centers that want to do 3T must be in touch with their referral base.
And of course, the healthcare facility needs to carefully evaluate their clinical application needs as well as understand their market. “If you are doing a lot of spine imaging and abdominal imaging, I would shy away from 3T,” says Mosher. “If you are doing a lot of MSK, brain and sports imaging, I would probably say 3T has potential application in your practice.
“The next thing would be referral base,” he continues. “Are the physicians sending you questions that you can not answer with a 1.5T magnet? For example, our physicians were very interested in articular cartilage pathology and they wanted us to be able to reliably give them an assessment of the cartilage. We did not feel like we could do that at 1.5T and we are learning how to do that at 3T. If you are interested in doing spectroscopy or functional imaging, these are techniques for your particular practice that may be a real benefit in going to 3T. Practices that should shy away from 3T, for example, may be a standalone practice where physicians are not on site. I would not recommend it as a single instrument for an outpatient site that does not have people there who are able to optimize its capabilities.”
A stitch in time…
As the old proverb suggests, a number of steps can and should be taken to ensure the success of a 3T install. Penn State’s Moser says first-time users should use a graduated approach as to how the modality is brought online and introduced into clinical practice. “By that I mean trying to focus on one particular body part or clinical exam,” he explains. “For example, you may start with the brain. Try to really optimize the field strength for that application and doing it in a systematic fashion. I think that some people plummet in and try to do everything all at once. You really need to be somewhat patient with 3T. It really does require a little more input from referring physicians and people who have some knowledge on how to optimize protocols and techniques.
“A lot of people are going to take what they typically do at 1.5T and are going to plug it into 3T and just expect beautiful images,” Mosher continues. “That is not always the case. MSK is one of the areas where that approach works fairly well. But there are other areas in the brain and the spine — because of differences in the physics and the contrast that you get — where people are going to be disappointed. It is really going to require somebody who is going to invest some time in it to really take advantage of the additional quality and flexibility that you have at 3T. Also, you really need to purchase additional educational time, or have additional on site application. There is a learning curve and you really want to plan up front for that.
Mosher also suggests that users get to know the system before utilizing it routinely in practice. “When you are first getting your 3T system installed, you may want to look at increasing the time you have per appointment,” says Mosher. “You may want to try some additional sequences that you were not able to do at 1.5T as part of the optimization program.”
Here are some more recommendations:
- Set standards: “Take your best technologists and send them to a site that does tech training so they will understand what they are getting into,” says Fletcher Allen’s Braff. “I think that is very important. Secondly, when you go on a site visit, you should go to a place that allows you to see a whole month or two worth of images on a PACS. You should take the good cases that have the image quality you like and have those put on a CD. That should be a template for how good your images should look.”
- Market, market, market: “If you are going to buy a 3T scanner, I would advise sites to aggressively market their services,” says Edison’s Tanenbaum. “Let everyone in the community know that you have stepped up and acquired the finest technology and that you know how to use it. That will reward itself. Neurologists and neurosurgeons respond almost within a day to the higher field technology. Once you start to get other specialists interested, such as vascular and orthopedists, then it starts to become a real positive proposition.”
As a more mature breed of 3T MRI systems and surface coils continue to hit the market, the high-field system is no longer intended for multi-site, university-based healthcare institutions and research facilities. As costs drop and the clinical applications of 3T expand, mid-sized and community hospitals and outpatient imaging centers are installing the systems so that they too can benefit from what 3T has to offer: doubled magnetic field strength. And anybody considering 3T for their next modality purchase must carefully evaluate their institution’s clinical application needs — as well as understand their market — to decide if 3T is right for them.