Background Digital tomosynthesis (DT), relatively a new tool, is superior to convetional radiography (CR) in detecting erosions1. High resolution ultrasound (HRUS) is an established tool in the evaluation of rheumatoid arthritis (RA). DT is significantly cheaper and quicker compared to MRI and HRUS, and does not need intravenous contrast administration.
Objectives To compare the DT and HRUS in the detection of erosions in wrists and hands in estalished RA.
To compare the benefits of DT and HRUS in the evaluation of hands and wrists in RA.
Methods 13 estalished RA patients underwent both DT and HRUS evaluation of hands on the same day. HRUS was performed and DT images were read by the same experienced musculoskeletal radiologist. Wrists and hands were scanned on DT and van der Heijde Modified Sharp Score2 was used for image interpretation. Wrists, index finger MCP joint (MCP2), PIP joint (PIP2) and middle finger MCP joint (MCP3), PIP joint (PIP3) were scanned on HRUS. These images were interpreted using German US7 score3. Non parametric tests were used to analyse the data using the software SPSSv.21. Mann-Whitney test was used to compare the erosion scoring between the two modalities.
Results See Table 1.
HRUS was unable to pick up any erosion at wrist but DT detected 18 erosions in 8 joints. Detection of erosions was statistically significant on DT (p 0.007). At MCP and PIP joints numerically HRUS detected more erosions, but this was not statistically significant.
We also found that strength of DT was in identifying joint space narrowing and ability to grade the severity of erosions. Whereas HRUS gave additional informations such as synovitis and activity of erosions.
Conclusions 1. DT is superior to HRUS in detecting erosions in a larger joint like wrist compared to smaller joints like MCP/PIP where HRUS seems superior.
2. DT and HRUS have their own strengths and short comings. Combining both modalities would give greater understanding of disease burden in RA.
3. Both modalities are cheaper and less time intensive compared to Magnetic Resonance Imaging (MRI) with gadolinium contrast.
4. A study to compare all three modalities to will help to understand the clinical utility and the most useful imaging technique/s.
Canella C et al. Use of Tomosynthesis for Erosion Evaluation in Rheumatoid Arthritic Hands and Wrists. Radiology 2011; 258(1): 199-205
van der Heijde D et al. How to read radiograph according to the Sharp/van der Heijde method. J Rheumatol 1999; 26: 743-5
Backhaus M et al. Evaluation of a Novel 7-joint ultrasound score in daily rheumatologic practice: a pilot project. Arhritis Rheum 2009; 61(9): 1194-201
Acknowledgements Patients who took part in the study and radiographers performing the DT.
Disclosure of Interest None declared