Portable MRI system improves early detection of wrist, hand joint erosions in RA

[Guest guest]

Apr 12, 2004

Portable MRI system improves early detection of wrist, hand joint erosions

in RA

Melbourne, Australia, and Los Angeles, CA - Research groups in Australia and

the US report in the April 2004 Journal of Rheumatology that magnetic

resonance imaging (MRI) is better than either conventional radiography or

sonography at detecting bone erosions of the hands and wrists in patients

with early rheumatoid arthritis (RA) [1,2]. One of these groups used a

portable MRI system designed for office use and suggests that it might be a

practical tool for clinicians assessing and monitoring RA joint status.

" While MRI is a relatively expensive procedure, its use in RA may prove

cost-efficient if it can reduce unnecessary treatment of patients with

costly biological therapies. "

An accompanying editorial by Dr G Petterfy (Synarc Inc, San

Francisco) notes, " While MRI is a relatively expensive procedure, its use in

RA may prove cost-efficient if it can reduce unnecessary treatment of

patients with costly biological therapies. This may apply to more than 30%

of RA patients on initial presentation " [3].

MRI much more sensitive than radiography or ultrasound for detecting early

erosions

Dr Jan Lucus Hoving (Monash University, Melbourne) compared MRI, sonography,

and radiography of the hand in 46 patients with newly diagnosed RA (onset

within 2 years). He found that for detecting bone erosions, MRI had more

than twice the sensitivity of radiography or sonography. At baseline, Hoving

observed one or more bony erosions in 39 patients with MRI, 17 with

radiography, and 14 with sonography. Six months later, the number of

patients with detectable bony erosions had increased to 42 with MRI, 22 with

radiography, and 19 with ultrasound.

MRI and sonography were equivalent for detecting synovitis, but sonography

was more sensitive than MRI for detecting joint effusions (28 versus 2

patients at baseline, 38 versus 6 patients after 6 months).

Only one patient had erosions on plain radiograph not detected by MRI (1 out

of 17, 5.9%), and one had erosions on ultrasound not detected by MRI (1 out

of 14, 7.1%).

" MRI was the most sensitive imaging modality for detection of bony erosions,

identifying more than twice as many erosions as sonography and radiography. "

Hoving concludes, " MRI was the most sensitive imaging modality for detection

of bony erosions, identifying more than twice as many erosions as sonography

and radiography. Sonography was the least sensitive method for damage

assessment, detecting slightly fewer erosions than radiography. MRI was more

sensitive for detecting synovial disease than sonography and the only

modality able to detect bone edema. Sonography was more sensitive to joint

effusion and tendon sheath inflammation compared to MRI. "

Portable MRI for extremities more accurate than radiographs

Moving this into the clinic is likely to require something cheaper, faster,

and less claustrophobic than the usual whole-body MRI scanner. Dr V

Crues (University of Southern California, Los Angeles) reports that the new

portable MRI systems designed for imaging the extremities are promising[2].

Crues and colleagues compared MR imaging and radiographs of wrists (n=227)

and second and third metacarpophalangeal joints (n=188) of 132 patients with

inflammatory arthritis. The equipment (MagneVu 1000, MagneVu, Carlsbad, CA)

is designed solely to image feet, hands, or wrists. It includes a

self-shielded, low-field (0.2 Tesla) scanner, operates on standard 110V

power, doesn't need special air conditioning, and comprises two components

on wheels that occupy about 4 square meters and can be easily moved.

Crues reports that technically acceptable MR images were obtained for 97% of

body locations or 95% of patients and that motion artifact problems occurred

in only 2 examinations.

" We found that MR imaging using this scanner detected erosions in 125

patients (315 body locations, p<0.05), whereas radiographs identified

erosions in only 78 patients (156 body locations). Thus, in this study

population, MR imaging had superior sensitivity to bone destruction,

suggesting that use of the portable MR system is extremely promising in the

assessments of patients with inflammatory arthropathies, " Crues writes.

Interpretations had " moderate reliability " comparing first reading to second

reading of the same observer (kappa statistic of K=0.564) and also comparing

MR imaging interpretations of two readers (K=0.429). Crues points out that

this is considered acceptable agreement, and that readers were reliable in

84% of intraobserver interpretations and in 79% of interobserver

comparisons.

" If the presence of erosions on MR imaging prompts clinicians to more

aggressively treat patients with RA with newer disease-modifying

antirheumatic drugs, then the cost of MR imaging and accessibility to this

diagnostic procedure becomes important. In the clinical setting,

office-based portable MR systems may permit treating physicians to make

decisions in a timelier manner. Further, these decisions may be more

appropriate because of the increased sensitivity of MR imaging for

identifying abnormal joint findings associated with RA, " Crues concludes.

Janis

Sources

1. Hoving JL, Buchbinder R, Hall S et al. A comparison of magnetic resonance

imaging, sonography, and radiography of the hand in patients with early

rheumatoid arthritis. J Rheumatol 2004; 31:663-675.

2. Crues JV, Shellock FG, Dardashti S et al. Identification of wrist and

metacarpophalangeal joint erosions using a portable magnetic resonance

imaging system compared to conventional radiographs. J Rheumatol 2004;

31:676-685.

3. fy CG. Is there a role for extremity magnetic resonance imaging in

routine clinical management of rheumatoid arthritis? J Rheumatol 2004;

31:640-644.