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

Abstract

ObjectiveTo compare the effects of different waveforms of 1MHz and 3MHz therapeutic ultrasound on endothelial function in healthy subjects. DesignRandomised placebo-controlled, crossover study with concealed allocation and assessor blinding. SettingImaging Centre of the University Hospital. ParticipantsThirty volunteers aged between 18 and 35 years were divided into two homogeneous groups (1MHz and 3MHz). InterventionsContinuous (CUT; 0.4W/cm2SATA), pulsed (PUT; 20% duty cycle, 0.08W/cm2SATA) and placebo waveforms (equipment off) of ultrasound (1MHz and 3MHz) were randomized and applied over the brachial artery for 5minutes. Main outcome measuresEndothelial function was evaluated using the flow-mediated dilation (FMD) technique. ResultsBoth 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. ConclusionBoth 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.