High-speed X-ray imaging of needle-free jet injections

A custom-built high-speed X-ray imaging system with a maximum frame rate of 2,000 fps was used to visualize the flow of fluid injected using a 27 gauge needle and a needle-free jet injector. Two different needle injection techniques (injection after partial retraction of the needle, and injection after no needle retraction) were evaluated to demonstrate the different flow patterns. For needle-free jet injections, we demonstrate how a two-phase injection velocity profile affects tissue penetration and fluid delivery. We show that a high initial jet speed will first puncture the skin, deliver volume to the fat, and then puncture the muscle, and a slower following speed will deliver the remaining fluid to the muscle. In all cases, due to the inhomogeneous anisotropic nature of tissue, the injectate preferentially follows paths of least resistance.