Ultra-low-dose CT may offer alternative to MRI in suspected RA
medwireNews: Contrast-enhanced ultra-low-dose computed tomography (ULD-CT) may become a feasible alternative to magnetic resonance imaging (MRI) for the illustration of inflammatory soft-tissue changes in patients with rheumatoid arthritis (RA) of the hand, German research suggests.
For the study, 36 patients (mean age 60 years, 72% women) with RA of the hand or wrist underwent ULD-CT and MRI with weight-adapted intravenous contrast administration.
The estimated radiation exposure with ULD-CT was less than 0.01 mSv, which Torsten Diekhoff and co-researchers from Charité-Universitätsmedizin Berlin explain is comparable to the level of radiation received during an X-ray of the hands or feet.
All 36 patients showed synovitis, tenosynovitis or peritendonitis in the hand on MRI, compared with 69% on ULD-CT.
However, the investigators say that the sensitivity of ULD-CT could potentially “be improved by applying higher radiation to reduce image noise.”
And sensitivity was higher in patients with more severe inflammation, reaching 80% for those with a modified RA MRI Score (RAMRIS) of more than 1.
Diekhoff and team also grouped the joint scores according to location (wrist, metacarpophalangeal joints, proximal interphalangeal joints, extensor tendon and flexor tendons).
At the joint group level, the sensitivity of ULD-CT was 65% and the specificity was 88%.
Sensitivity was higher (71 vs 51%), but specificity lower (82 vs 96%), among the 24 patients who had a final diagnosis of RA, compared with the 12 who had a non-RA diagnosis, but the difference between the groups was not statistically significant.
In addition, the researchers found that the correlation between the modified RAMRIS sum scores for ULD-CT and MRI “was almost perfect”, with an r value of 0.94.
When the patients were asked about their experience of ULD-CT and MRI, the majority (85%) said they preferred ULD-CT examination due to the shorter examination time. They also reported greater levels of concern before the MRI examination, and more discomfort and anxiety during MRI than during ULD-CT.
Writing in the Annals of the Rheumatic Diseases, Diekhoff and co-authors say that their study “proves the feasibility of ULD-CT in suspected rheumatoid arthritis.”
They add: “In view of patient preference and recent concerns about gadolinium-based MRI contrast agents, CT may become a suitable alternative, especially for patients with contraindications to MRI or unable to tolerate the rather long examination times.”
The researchers conclude: “Future studies should compare the different techniques in larger patient populations and investigate how image quality can be improved.”
By Laura Cowen
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