Mobile MRI—Imaging on Wheels
The seminal discovery—that atomic nuclei in a strong magnetic field rotate with a frequency that is dependent on the strength of the magnetic field and that their energy increase when radio waves with the same frequency or resonance are absorbed—was made early in the 20th century. This discovery was later followed with another in which the possibility would exist to create a two dimensional picture by introducing gradients in the magnetic field. There were several key scientists, including Paul Lauterbur, Peter Mansfield, and Raymond Damadian, that were instrumental in MRI as we know it today.
All seem to have played an important and controversial role in the development of what we recognize today as being MR imaging. Physicists had already been using nuclear magnetic resonance (NMR), first reported in 1938, to study various materials, but it was Damadian who postulated that hydrogen in water could prove responsive within the cells of living tissue. Moreover, he thought that abnormal cells such as cancer cells, might respond differently than normal healthy cells. Subsequent research has shown that relaxation times cannot reliably differentiate between cancer and normal tissue. He eventually built his prototype scanner in 1977 called “Indomitable,” and which now is located and preserved in the Smithsonian Institute.1 His scanner would flood the body with intense, but seemingly harmless magnetic fields combined with radio waves to cause hydrogen nuclei within the body’s molecules to vibrate and emit radio-frequency (RF) energy. The MRI scanner detects the RF energy emissions and transforms them into a viewable image. Even minor changes in tissue resonance, perhaps caused by pathology, can affect the rate at which energy is emitted and, consequently, will affect the final image produced. MR imaging is now considered to be safe; emitting no ionizing radiation and, in many cases, is the gold standard diagnostic imaging test of choice for many applications.
“MR imaging is now considered to be safe; emitting no ionizing radiation and, in many cases, is the gold standard diagnostic imaging test of choice for many applications.”
Mobile MRI-A Function of Efficiencies
In 2001 (the most recent year for which data were available), the average number of MRI procedures in hospitals with fixed MRI units was 3,300. Facilities with more than one MRI unit were performing an even greater number of procedures — approximately 5,390 per unit. Based on 2001 data, there were approximately 5,550 sites in the U.S. performing MRI procedures, including 4,000 sites with a fixed MRI scanner onsite, and 1,685 sites utilizing mobile technology. At that time, the majority of mobile MRI users were small (less than 200 beds) hospitals (81%), while 9% of the mobile users were 200-399 bed hospitals. The remainder were non-hospital (private, corporate owned) sites. Although the total number of facilities (hospitals, private clinics, etc) that now own MRI scanners has increased considerably since 2001, there is growing evidence that the mobile MRI sector is growing at an even faster pace due primarily to two reasons: the high cost of owning a fixed MRI scanner combined with a growing demand for MRI scans across the board. Utilization data derived from Medicare seems to support an approximate 8% total radiology workload increase per year, with CT and MRI procedures being ordered at the highest rate.2 With the added demand for MRI services, fixed unit providers are under pressure to be able to service the growing demand, but they do so with aging technology.
MRI scanners can cost millions of dollars, with hospitals and health care systems in general, being reluctant to swap out the older generation MRI scanners for new ones due to obvious economic reasons. Rapidly evolving software advances and upgrades can only compensate for hardware obsolescence to a certain degree. MRI technology is rapidly advancing and MRI provider competition in many regions is tight, partly due to state restrictions on MRI ownership expansions. Some states require a certificate of need (CON) to be issued prior to opening an MRI center, often a formidable task for prospective investors. Other trends such as shrinking payor reimbursement, an aging baby boomer population demanding more diagnostic precision, and greater workload demands on existing radiologists are some of the factors that have helped to drive the need for faster (more efficient), more accurate, and more accessible MRI services.3 Mobile MRI is evolving at a rapid pace for all these reasons and it can make good sense in the current cost-constrained health care environment.
While MRI systems are among the most expensive imaging devices in terms of unit and operating costs even though, like most technology, relative costs have decreased over time. Some have predicted that there are three powerful trends that will shape the future of MRI, those being;
- the requisite of improved image quality or resolution,
- the need for faster patient processing, and
- a significantly increased demand for MRI examinations, but at a lower reimbursement rate across the payor mix.
Not everyone agrees, but this may lead one to speculate that the higher field 3T units would be those devices in line to replace the older, low and mid field units currently being used in hospitals and outpatient clinics.4 Even if this is true, however, replacing existing high field units might not be enough to maintain sales projections for new MRI units, according to some industry leaders. Some observers are suggesting that users of high field units such as research centers, large hospitals and teaching hospitals already have high field units. These facilities are more likely to purchase or rent a mobile MRI unit than to incur the cost of building expansion and/or purchase another MRI system.