Background The accurate assessment of joint inflammation and sensitive monitoring of the disease activity in rheumatoid arthritis (RA) patients are vital to assess the disease outcome and treatment response.In the past decade, musculoskeletal ultrasonography (US) has become an established imaging technique for the diagnosis and follow-up of RA patients. US is considered highly operator-dependent.
Objectives We compared three-dimensional (3D) power Doppler (PD) US and 2D PDUS of synovial vascularity in finger joints of RA patients to study the reliability and possible advantages of 3D PDUS.
Methods We randomly selected 43 patients who met the 2010 ACR/EULAR criteria, were randomly selected for this study (33 women, 10 men, mean age: 56.9±12.2 (range: 30-84) years). The mean disease duration was 6.7±1.1 (range: 1-30) years. At each clinical examination, 28 joints were assessed for tenderness and swelling. The tender joint count, swollen joint count, and visual analog scale were recorded to assess the patient’s overall functional status. The 28-joint Disease Activity Score (DAS28) was used to assess disease activity. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) tests were performed on the same day as the clinical and US examinations. A 6.0–14.0 MHz linear probe and a 7.0–14.0 MHz linear 3D volumetric probe were used for US. Eight joints were assessed using 2D and 3D PDUS: bilateral second/third metacarpophalangeal (MP) joints and second/third proximal interphalangeal (PIP). In all, 344 joints (172 MP and 172 PIP) were evaluated in the 43 subjects. After B-mode examination, the 2D PDUS was performed. A separate PDUS subjective score was recorded per joint. The 2D PDUS index is the sum of the PDUS scores of all 8. The 3D volume was activated to a 3D box from the same finger joints, and the PD signal was obtained. Each volumetric sweeping scan was performed automatically in a single sweep. The both 2D and 3D PD images were stored as “Digital Imaging and Communication in Medicine (DICOM)” files and transferred to a personal computer for further analysis using quantitative software, based on the region-growing method, developed in-house. The 2D PDUS pixel counts represents the number of vascular flow pixels in the articular cavity, and the 3D PDUS voxel counts presents the sum of the pixel signals, consisting of approximately 30 single slices of each joint.
Results The 2D PDUS index and 3D PDUS voxel counts showed significant positive correlation (r =0.820, p<0.0001). The 3D PDUS voxel counts were significantly correlated with DAS28-ESR (r =0.427, p<0.003) and DAS28-CRP (r =0.350, p<0.02). The 3D voxel counts and 2D pixel counts were significantly correlated (r =0.924, p<0.0001). The 3D voxel counts of 2D PDUS scores 0-3 were (median, mean ± SD, range); score 0: 0, 19±112, 0-1046 (n=270): 703, 1230±1423, 0-6716 (n=58): 6599, 7711±4059, 1363-15330 (n=14): and 26838, 26838±209, 26690-26985 (n=2), respectively.
Conclusions Thus, 3D PDUS can objectively assess joint synovitis without knowledge of anatomic landmarks or correct probe placement. Our results suggest that quantitative measurement of finger joint vascularization by 3D PDUS is more sensitive for evaluating synovial vascularity than semi-quantitative assessment.
Disclosure of Interest None Declared