Portable MRI for
in-office use can be an invaluable tool to the diagnosis
and management of patients with inflammatory arthropathies
and should therefore be readily available as an important
diagnostic modality.
Background
Magnetic Resonance Imaging (MRI) has been shown to be
superior to conventional radiography for detection of
marginal erosions in inflammatory arthropathies and can
be a diagnostic tool to predict subsequent radiographic
damage.1-3 Early detection and staging of rheumatoid arthritis
appears to have significant prognostic implications on
disease progression4-5 and can more accurately help guide
therapy in the individual patient. Until recently, the
routine use of MRI in evaluating inflammatory arthropathies
has been limited by the relative high cost, the difficulty
in positioning disabled patients and the inability to
image several joints simultaneously. However, there are
now available lower-cost, portable, in-office MRI units
which can be used without special room preparation and
shielding. These smaller unit scan protocols are tailored
for optimal visualization of erosions in the hands, wrist,
and feet. We believe this technology is an important advance
in the evaluation and treatment of patients with arthritis
and offer these additional facts as support.
1) A peripheral MRI is small and
can be incorporated into a specialty office practice
in a comfortable and convenient setting for patients.
2) Compared with traditional MRI technology this is
relatively inexpensive.
3) Portable low field MRI systems image small areas
in a nonuniform magnetic field, which contributes to
lower installation and operational costs than standard
MRI which are built around a uniform magnetic field.
3) The images are created at a much higher spatial resolution
than traditional machines allowing more detail of erosions,
which are critical to guiding rheumatology decision
making. The cuts are 1x1x1 millimeter as opposed to
standard MRI, 3 mm cuts with 0.5mm spaces between cuts.
Since bony erosions are often 2 to 3 mm the standard
machines can miss entire erosions.
4) Traditional MRI machines require patients to lie
immobile with their arms extended above their heads
to image the hands or wrists and this is difficult or
impossible for many patients with disabling arthritis.
Portable low field units allow patients to sit or lay
back in a standard reclining chair and place the hand
or foot into the open machine for imaging.
5) Early disease detection and proper identification
of early structural changes in arthritis patients with
aggressive disease can help guide therapeutic interventions
and improve outcomes.
Bibliography
1. Crus J, Shellock F, Dardashti s, et al. Identification
of wrist and MCP joint erosions using a portable-MR
system compared to conventional x-ray. J Rheumatol 2004;31:676-85.
2. Backhaus M, Burmester GR, Sandrock D, et al. Prospective
two year follow up study comparing novel and conventional
imaging procedures in patients with arthritic finger
joints. Ann Rheum Dis 2002;61:895-904.
3. McQueen F, Benton N, Perry D, et al. Bone edema scored
on magnetic resonance imaging scans of the dominant
carpus at presentation predicts radiographic joint damage
of the hands and feet six years later in patients with
rheumatoid arthritis. Arthritis & Rheumatism 2003;48(7):1814-1827.
4. Emery P. Evidence supporting the benefit of early
intervention in rheumatoid arthritis. Journal of Rheumatol
2002;29:3-8.
5. Irvine S, Munro R, Porter D. Early referral, diagnosis,
and treatment of rheumatoid: evidence for changing medical
practice. Ann Rheum Dis 1999;58:510-513.
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