If you are currently the proud owner of a low-field open MRI, right about now you may be wondering whether it is time to put the old .23 Tesla out to pasture. After all, the latest generation of 1.5Ts and even the 3Ts have arrived, and with RSNA occurring recently, now may be a good time to go shopping and invest in the future. Then again, you may be asking yourself, do I really need to upgrade? Will a new high-field deliver significantly better, faster results than I have now? Can I afford to upgrade? Can I afford not to? Playing the fields in MRI can be tricky these days. The right answers to those questions may depend not only on clinical considerations, but also on your particular market and appetite for risk.

Keeping It on the Down Low Field

When low-field MRs first became popular in the 1990s, they were a coup not only for the rapidly expanding outpatient imaging center markets, but also for the patients who were avoiding MR scans because of anxiousness and claustrophobia.

The trade-off, of course, was that the image quality was not as sharp when compared to higher-field magnets that were also available, albeit with a narrow aperture and a closed gantry.

Ten years later, equipment manufacturers’ latest generation of 1T and 1.5T MRs tout their ultrashort bores along with larger-aperture diameters—not to mention their new coils, software, and imaging techniques. For patients and physicians who still want high field with a truly open platform, there are products such as the Panorama 1.0T Open MR by Philips Medical Systems, Andover, Mass, which positions the patient on an open table under the canopy overhead.

Another patient-friendly feature, which is now being offered by Tustin, Calif-based Toshiba America Medical Systems’ Vantage MR line, is a proprietary technology that reduces the chug-chug-chug of intimidating high-field gradient noise.

With these new high-field products largely having the same advantages as its low-field predecessors, manufacturers have seen the writing on the view box and have largely discontinued production of their open low-field models. So why not trade in the old low-field MR for a supercharged 1.5T? Three letters: DRA.

DRA and the Low Field Advantage

The repercussions of the Deficit Reduction Act of 2005 and its MRI fee-reduction schedule are reason enough for many imaging operators to stay with their low fields for now.

Economically, many centers have completely paid off their low-field magnets. Even with a $10,000 per month service contract and a shorter list of procedures compared with 1.5T systems, the additional revenue is a welcome, steady income that can offset DRA’s lower reimbursements.

Clinically, one can argue that having a great diagnostician is more important to patients and their referring physicians than a shiny new 3T magnet that will give the same diagnosis. After all, low-field MRIs have been successfully used by radiologists for more than a decade.

Bill Kelly, MD, founder and medical director of Health Scan Imaging in Palm Desert, Calif, and a neuroradiologist, saw the development of high-field and low-field MRIs while doing his neuroradiology fellowship at the University of San Francisco in the early 1980s. Today, with 23 years of imaging experience at academic institutions, hospitals, and imaging centers, he appreciates the capabilities of the latest generation of MRs and uses them in several of his eight imaging centers. At the same time, Kelly is torn about the prospect of retiring his .23T open magnets at two of his imaging centers, especially considering DRA’s cuts.

Kelly said, “I’m a very firm believer that the majority of diagnoses can be made effectively and adequately on low-field-strength exams, particularly if there are allowances made for increased imaging time, improving the signal-to-noise ratio, appropriate coil usage, and judicious selection of pulse sequences. It’s not simply field strength, obviously. The determines of signal quality are definitely multifactorial.”

Kelly also believes that errors and shortfalls in exam outcomes are more often due to perceptual diagnostic errors than the image quality of the MR equipment. Consequently, it is more important to have a highly skilled radiologist interpreting the exam than to own the latest and greatest magnet. Moreover, there are many types of MR procedures where better technology will not consistently yield a better or more accurate diagnosis.

“What is needed to diagnose a meniscus tear? An ACL rupture? Chondro-malacia of the knees? Certainly, that can be done adequately on low-field magnets,” Kelly said. “When you look at the more esoteric diagnoses or whole-body MRA, or small parts imaging, certainly there are compelling advantages of the high-field-strength, multichannel, better-configured systems.”

Jumping into the High-Field Life

DRA and confidence in one’s diagnostic abilities may be two good reasons not to move up to a high field, but that has not stopped 1.5Ts from dominating MR sales for those who are ready to make the move.

According to John Hipple, product manager for MR, Toshiba America Medical Systems Inc, Tustin, Calif, sales of 1.5Ts make up 70% to 80% of the sales right now.

The main advantage of 1.5T is the better signal-to-noise ratio, which can improve anatomic and/or temporal resolution and reduce scan time while maintaining image quality. The new software and new coils that come with these 1.5Ts also allow hospitals and imaging centers to provide a larger menu of services, such as:

  • Perfusion/diffusion studies of the brain for early stroke detection;
  • Breast MR for implants and cancer screenings;
  • Cerebrospinal fluid (CSF) flow data studies; and
  • MR angiography.

These are but a few of the MR procedures that are possible or significantly enhanced with a high-field 1.5T magnet.

Economically, however, one must still consider what extra whistles and bells make sense for a particular imaging center. While the coils and software packages selected with a new or even refurbished 1.5T system can enable an imaging center to offer more exams, one must still be selective according to one’s referral base and business plan.

For example, breast MRI may be performed extremely well with a 1.5T’s 3D dynamic imaging. But having a 1.5T does not necessarily mean that physicians will refer their patients to your facility. Referring physicians are more likely to continue referring patients to a facility that is previously known for women’s health imaging services, such as plain-film mammography, ultrasound, and MR-guided breast biopsy mammography.

On the other hand, DRA has barely affected breast MR reimbursement levels, which may be justification enough for an established women’s center to invest in a 1.5T—in addition to offering neurological, orthopedic, MRA, etc, services.

Another economic consideration in favor of upgrading to 1.5Ts is that they have been on the market long enough now to allow budget-strapped imaging operators to buy refurbished systems for as little as $500,000. A brand new, basic, 1.5T scanner is almost twice as much—generally around $900,000.

The downside is that the refurbished systems are less likely to have the ultra-short bores and wider apertures as the latest-generation 1.5Ts. For those operators concerned about losing patients who are anxious or claustrophobic, an assisted conscious sedation program may be implemented and discussed with referring physicians. Highlighting the benefits of the 1.5T and explaining the minimal risks involved with sedating the patient may be all that is necessary to maintain the same referral base.

Go 3T? Not So Fast

Despite the newest generation of 1.5Ts, hospitals and imaging centers must also consider their capital budgets and rapidly obsolete imaging equipment. Some may believe that today’s 1.5Ts are going to have to be replaced by yet another generation, so one might as well spend the extra money for a 3T system and gain market advantage over competitors.

However, Kelly believes that 1.5Ts are already near their maximum potential. While previous 1.5T generations had the raw field-strength power, Kelly believes that vendors had not matched that power with the proper coils with maximum sensitivity, the full array of sequences, and multichannel imaging—along with experienced radiologists who could use these advanced systems. But now he believes that with the latest 1.5T generation, this category of technology has begun to plateau.

“Aside from further shortening of bore length coupled with integrated dynamic table motion and multichannel coil technology, I think we are approaching the point where we’re getting diminishing marginal returns from any future generational changes of 1.5 Tesla field-strength imaging,” he said.

If that is true, then the next consideration for clinicians and operators is whether to skip 1.5T and invest capital dollars into the new crop of 3T scanners that have recently come onto the market. But Hipple notes that Toshiba has delayed introducing its commercially available 3T system because of lack of demand due to DRA. Instead, while the market is cool, Toshiba has decided to fine-tune its 3T product.

“Given the recent slowdown as far as reimbursements go, we’re just continuing to work on the 3T to make sure that when it does become commercially available, it will have the same patient-friendly features as the 1.5,” Hipple said.

Clinically, there is no question that 3T has better image quality over 1.5T, especially for neuroimaging applications, such as functional MRI and MR spectroscopy. The question remains: Will the extra cost spent for image quality translate into significantly better diagnostic results? One study, published in Acta Radiol in 2005, conducted with MR at 3T followed a series of 20 patients with intracranial tumors. Functional MRI using 3T affected the surgeon’s view of lesion operability in nine cases, altered the surgical approach in 13, and led to changes in the planned extent of resection in 12.

But Hipple points out that the latest generation of 1.5T systems performs neurological applications quite well. He said, “We do spectroscopy [at 1.5]. We do functional MR at 1.5 and all the neuron applications. The 3T just does them slightly better.” (For more on 3T’s clinical advantages and disadvantages over 1.5T, go online to www.medicalimagingmag.com/issues/articles/2006-08_01.asp)

Hipple added that while the scanner may indeed be faster, that does not necessarily translate into increased patient volume or better workflow. He said, “It’s not as if you buy a 3T scanner and automatically do twice as good and twice as many patients. You don’t do them twice as fast because you’re still dealing with that limitation of about a half an hour for that patient to be taken in and out of that scanner. Depending on the number of sequences, you may only image 15 minutes for that half hour.”

Buying the $2.2 Million Sledgehammer

Another deciding factor is that while a new 3T can cost around $2.2 million, 3T owners will not receive any additional insurance reimbursement for a 3T. Meanwhile, the cost of a new 1.5T package is anywhere from $900,000 to around $1.6 million.

Kelly said that in most cases, using a 3T at this point is using a sledgehammer when a 1.5T framing hammer would do just fine. However, as the owner of eight outpatient imaging centers in an extremely competitive Southern California market, he also understands that many physicians and patients are attracted to the notion of being scanned by the best university-level magnet, regardless of the experience of the radiologist.

He asks rhetorically, “What’s on the short list of priorities for the clinician who chooses an imaging center for patient referrals? You can look at reality, and you can look at what it should be. That list should be ordered:

  1. Diagnostic accuracy
  2. Image quality
  3. Service

In reality, that list is upside-down.”

It is this jumbled list of priorities that may compel competing radiology groups in densely populated areas to adopt a 3T magnet—eventually. But most people see high-field 3Ts being purchased primarily by university hospitals, research institutions, and urban medical centers within the next 3 to 5 years.

As to his own choice of fields, Kelly has decided to retain his two low-field open MRIs in the mix with seven 1.5T systems throughout his Southern California network.

Tor Valenza is a staff writer for Medical Imaging. For more information, contact .