OR WAIT null SECS
Most 3T MR systems are sold to university hospitals and research facilities, and relatively few go to private practices.
Most 3T MR systems are sold to university hospitals and research facilities, and relatively few go to private practices. This is perhaps understandable. Choosing 3T over 1.5T means opting for a novel technology instead of a well-established solution. So why take the risk?
Private practices have to take many factors into account when considering whether to invest in 3T. Improved image quality continues to be the primary motivation for changing systems. The big promise of 3T is doubled signal compared with 1.5T. In reality, the signal-to-noise ratio varies depending on the type of examination performed and the tissues examined. An increase of 50% to 90% is common, and in certain applications, SNR may increase by only 30%. But this is still a significant advantage over 1.5T.
Most scientific 3T work to date has concentrated on using the increased signal to achieve higher resolution images. This ability has proven clinical advantages in several areas, such as the detection of small cartilage lesions in musculoskeletal examinations or visualization of epileptogenic foci on brain scans. It is easy to create striking, high-resolution images in many body regions with 3T. But is this enough to justify the acquisition of a much more expensive system? Hardly.
Increased signal, however, brings another important benefit: the possibility of reducing scanning time. Declining reimbursement poses great pressure upon private operators to optimize efficiency and throughput. Meanwhile, the demand for high-end imaging outside the hospital increases. In Europe, even complex examinations are increasingly being outsourced to private sites.
Balancing good image quality and high patient throughput is consequently of utmost importance to private sites. In our experience, 3T is able to achieve a better balance in this respect.
We started using 3T MRI at the Urania Diagnostic Center, a private imaging practice in Vienna, in October 2004. Our full set of dedicated coils allows us to examine every body region that we used to examine on our 1.5T system. Patient comfort in our short-bore scanner is identical to that for our 1.5T unit, and patient throughput is high. By June 2006, we had performed more than 20,000 routine clinical examinations at 3T, averaging 45 patients per day.
Parallel imaging is our essential tool for achieving an optimum balance between speed and quality. We can perform a high-quality knee MRI in six minutes, with excellent cartilage depiction. A complete temporal lobe epilepsy protocol with six sequences, including 1024 matrix high-resolution T2-weighted and inversion recovery sequences, takes just over 15 minutes. And our fat-saturated 3D sequence for shoulder arthrography-120 reformatable slices at 0.8 mm-is complete in just over four minutes.
The increased signal available at 3T offsets the major drawback of parallel imaging: decreased SNR. Parallel imaging also helps us to manage susceptibility artifacts and increased radiofrequency deposition, two inherent problems of high-field MRI.
The beauty of 3T MRI for us is that we can cover routine examinations quickly and produce high-quality images. But if the case requires that extra bit, then we have additional imaging power. We can bump up the resolution, do excellent MR angiography, and use more sophisticated techniques, such as diffusion tensor imaging and fiber tracking, real-time functional MRI, and spectroscopy. Many of these newer MR applications may open up further business opportunities, such as use of MR as a tool for presurgical planning. Being one of just a few sites to have the latest MR technology also leads to a competitive advantage.
Of course, 3T still has its weak points. I see little advantage in doing spinal imaging at 3T, for example. Sensitivity toward artifacts is also greater, especially in the upper abdomen.
I believe that most private sector MR imaging will be performed at 1.5T for a few more years yet. But if a private practice expects state-of-the-art quality, requires high patient throughput, has significant demand for complex examinations, and wants to keep within time constraints, it has to at least consider buying a 3T scanner.
Is it worth it, economically? Time will tell. It could be said that deciding between 1.5T and 3T is similar to choosing between a Volkswagen and a Mercedes and is thus a question of individual circumstances and personal taste. Many radiologists tend to choose the latter, don't they?
DR. DRAHANOWSKY is a senior radiologist and technical director at the Urania Diagnostic Center in Vienna.