Real-Time Contrast-Enhanced Ultrasound (Rt-Ceu) For The Determination Of Flowmotion Within Skeletal Muscle

Flowmotion within skeletal muscle in vivo is difficult to determine and has depended upon invasive studies with implanted Laser Doppler flow (LDF) probes. This study reports the novel use of RT‐CEU to determine flowmotion in rat muscle in vivo . Anaesthetised rats were infused with Definity® microbubbles and the microvascular flow monitored by an US transducer (L9‐3) on the upper thigh. Contrast imaging was performed with a iU22 US machine and analysis of regions of interest by QLab (Philips) Wavelet analysis was used to determine the contribution by endothelial (0.006–0.02Hz), neurogenic (0.02–0.06Hz) and myogenic (0.06–0.3Hz) vasomotion. RT‐CEU data was compared to simultaneous subcutaneous data made with LDF surface probes (Moor Instruments). Both RT‐CEU and LDF data demonstrated that muscle and subcutaneous tissues displayed flowmotion with a strong neurogenic rhythmical variation. Phentolamine treatment abolished the neurogenic flowmotion and lead to a recruitment of microvascular flow to the same extent as muscle contraction. RT‐CEU provides a new technique that can be used to determine in vivo flowmotion within skeletal muscle of experimental animals and humans. This technique has the potential to provide novel information about defects in the vascular regulation in pathological conditions (insulin resistance, sepsis) that are associated with poor nutrient delivery. Funded by NHMRC(Aust).