A subcutaneous transport pathway in humans has been previously visualised by injection of a paramagnetic tracer into the specific region of skin.In the current study,we further investigated the behaviours of imaging tracers in the transport pathways using imaging techniques.Three types of imaging tracers,including Gd-DTPA,iodised oil,and fluorescein sodium,were hypodermically injected into different acupuncture points of healthy volunteers to visualise the transport pathways by magnetic resonance imaging(MRI),X-ray,CT,and a digital fluorescein camera.Several longitudinal transport pathways in the arms and feet,which represent venous vessels and subcutaneous transport pathways(STPs) without well-defined boundaries,were visualised by MRI.Among the visualised veins,the partial walls of a few veins were enhanced by Gd-DTPA.The fluorescent images further indicated that STPs likely represent boundless pathways.The findings in this study suggested that specific anatomical structures within the subcutaneous tissues or the partial walls of certain veins werenot vascular conduits but rather represented unique transport pathways in humans that warrant extensive future studies.
