Tomosynthesis OK for Rheumatoid Arthritis Bone Erosion

Tomosynthesis is superior to radiography and almost comparable to MRI for the detection of bone erosion in patients with rheumatoid arthritis (RA), according to a study published in the AmericanJournal of Roentgenology.

Medical imaging is the standard method of assessing the level of bone erosion in RA and MRI has been effective in detecting erosion before it becomes apparent by radiography. Researchers from Japan undertook a small retrospective study of 20 patients with RA to compare the accuracy of tomosynthesis, which can also detect subtle fractures and the joint surface, with both radiography and MRI.

The 20 patients and five control patients underwent radiography, tomosynthesis, and MRI of the bilateral hand and wrist within one week. The mean total dose of radiography and tomosynthesis was 0.13 and 0.25 mGy, respectively. MRI evaluation was performed according to the Outcome Measures in Rheumatology Clinical Trials recommendations. Two radiologists reviewed the images for bone erosion, using a four-point scale (0: normal; 1: discrete erosion; 2: less than 50 percent of the joint surface; and 3: 50 percent or more of the joint surface). Twenty-five sites were reviewed for each subject (distal radius, distal ulna, eight carpal bones, first through fifth bases of metacarpal bones, and proximal and distal aspects of the first through fifth metacarpophalangeal joints.)

The results showed detection rates of bone erosion by radiography was 26.5 percent, by tomosynthesis was 36.1 percent, and by MRI 36.7 percent.

“Significantly more bone erosions were revealed with tomosynthesis and MRI than with radiography,” the authors noted.

Using MRI as a reference standard, the sensitivity was 68.1 percent, specificity was 97.5 percent, and accuracy was 86.7 percent for radiography. The sensitivity was 94.8 percent, specificity was 97.8 percent, and accuracy was 96.7 percent for tomosynthesis.

Interobserver agreement (kappa value) for bone erosion was good to excellent on tomosynthesis and MRI for all joints (0.65–1.00 and 0.68–1.00, respectively), whereas it was slight to fair on radiography for some carpal bones and bases of metacarpal bones (0.22–0.56).

The authors concluded that tomosynthesis is superior to radiography and almost comparable to MRI for the detection of bone erosion in patients with RA.