Background Blood flow in small vessels of synovial membrane in inflamed joints is characterized by slow-flow. The ability to detect this flow with Doppler ultrasound (US) is influenced by the quality of the US unit, Doppler modality and the Doppler settings. The standard Doppler settings provided by manufacturers of US units have previously been shown not to be optimal for the detection of this slow flow. However, significant improvement of Doppler sensitivity is possible.¹

Objectives The purpose of the study was to investigate how factory Doppler settings (FS) on a high-end US unit could be improved with respect to Doppler sensitivity by ultrasonographers who had just received lectures on optimizing Doppler settings. Secondly, how scoring and quantification of Doppler activity were affected by more sensitive Doppler settings.

Methods During an US course arranged as part of targeted ultrasound initiative (TUI) in Helsinki, participants were taught on Doppler settings and how to optimize these. The Doppler settings were adjusted by participants for increased Doppler sensitivity as suggested by Torp-Pedersen et al.² A General Electric LOGIQ-E9 ultrasound unit with a 6–15 MHz linear array transducer was used. Four rheumatoid arthritis (RA) patients with a clinically active wrist joint were examined with US by four groups of course participants. US was done using both the FS for superficial musculoskeletal US and the optimized setting (OS). Findings of each joint was scored semi-quantitatively (0–3) and for the maximum colour fraction (CF) using four seconds video clip. CF was calculated using the US unit's software for quantitative analysis based on a drawn region of interest (ROI).

Results All groups were capable of adjusting FS to a more sensitive Doppler setting as suggested in the preceding lectures. The median Doppler score for the four wrist joints were 1 (range: 0–2) on FS and 2 (1–2) on OS. In 12/16 evaluations the Doppler score increased by at least one point on OS compared to FS, and were unchanged in the remaining. In 5/16 evaluations (three patients) the score changed from 0 (normal) to a score of 1 or 2 using OS. The mean CF was 0.021 (range: 0–0.093) on FS and 0.082 (0.008–0.20) on OS (p=0.001; Wilcoxon signed rank test). No significant difference was observed in the area of the ROI (mean: 45 and 44 mm² on FS and OS, respectively).

Conclusions Optimization of Doppler settings for increased sensitivity for slow flow in synovial tissue of RA wrist joints is possible after proper instruction. An optimized Doppler setting led to significantly higher scores and CF in the examined wrist joints and in some patients synovial Doppler activity was observed only with an optimized setting. Consequently, using FS could result in active joint inflammation being missed or underestimated by the examiner. This small study demonstrates that knowledge on optimizing Doppler settings can be learned in workshops and highlights the importance of knowledge on how to improve Doppler sensitivity wherever US is used in clinical practice.

1. Torp-Pedersen S, et al. Arthritis Rheumatol. 2015;67:386–95

2. Torp-Pedersen S, Terslev L. Ann Rheum Dis. 2008;67:143–49

Disclosure of Interest None declared