Comparison of the effects of 1MHz and 3MHz therapeutic ultrasound on endothelium-dependent vasodilation of humans: a randomised clinical trial

Abstract

Objective: To compare the effects of different waveforms of 1MHz and 3MHz therapeutic ultrasound on endothelial function in healthy subjects.

Design: Randomised placebo-controlled, crossover study with concealed allocation and assessor blinding.

Setting: Imaging Centre of the University Hospital.

Participants: Thirty volunteers aged between 18 and 35 years were divided into two homogeneous groups (1MHz and 3MHz).

Interventions: Continuous (CUT; 0.4W/cm^2SATA), pulsed (PUT; 20% duty cycle, 0.08W/cm^2SATA) and placebo waveforms (equipment off) of ultrasound (1MHz and 3MHz) were randomized and applied over the brachial artery for 5minutes.

Main outcome measures: Endothelial function was evaluated using the flow-mediated dilation (FMD) technique.

Results: Both 1MHz [CUT: mean difference 4%, 95% confidence interval (CI) 2 to 6%, P<0.001; PUT: mean difference 4%, 95% CI 2 to 6%, P<0.001] and 3MHz (CUT: mean difference 4%, 95% CI 2 to 6%, P<0.001; PUT: mean difference 4%, 95% CI 2 to 6%, P<0.001) of therapeutic ultrasound increased %FMD by approximately 4% compared with the placebo waveforms. The endothelium-dependent vasodilator responses were the same for both types of waves and frequencies. No differences in baseline diameter, hyperaemic flow, and nitroglycerin-mediated diameter and vasodilation were observed between groups.

Conclusion: Both CUT and PUT ultrasound waveforms improved endothelial function. The 1MHz and 3MHz frequencies of therapeutic ultrasound led to similar improvement in endothelial function in healthy volunteers. Clinical trial registration number RBR-4z5z3t.

Keywords: Endothelial function; Nitric oxide; Ultrasonic therapy; Ultrasound; Vascular endothelium.