A specific branch of contrast-enhanced ultrasound,<unk>  is a minimally invasive and non-ionizing medical imaging technique used to visualize vasculature.<unk>  was first developed by the Dayton Laboratory at North Carolina State University and provides a safe, portable, and inexpensive alternative to the most common methods of<unk>  such as Magnetic Resonance<unk>  and Computed Tomography<unk> . Although ultrasound does not traditionally exhibit the high resolution of MRI or CT, high-frequency ultrasound (HFU) achieves relatively high resolution by sacrificing some penetration depth. HFU typically uses waves between 20-100 MHz and achieves resolution of 16-80μm at depths of 3-12mm. Although HFU has exhibited adequate resolution to monitor things like tumor growth in the skin layers, on its own it lacks the depth and contrast necessary for imaging blood vessels.<unk>  overcomes the weaknesses of HFU by combining contrast-enhanced ultrasound with the use of a dual-element ultrasound transducer to achieve high resolution visualization of blood vessels at relatively deep penetration levels.<unk>  is performed by first injecting specially designed microbubbles with a low resonant frequency into the vessels. Next, a low-frequency transducer element with good depth penetration is used to send ultrasound waves into the sample at the resonant frequency of the microbubbles. This will generate a response from the microbubbles consisting of subharmonic, fundamental, and super-harmonic frequencies, as well as a response from the surrounding tissue consisting of only the fundamental and second-harmonic frequencies. Finally, a high-frequency transducer with high resolution is used to measure the super-harmonic frequencies, effectively removing any background signal from the microbubble signal, and allowing the vessels to be visualized
Acoustic angiography
Narrow-band imaging
Laser Doppler imaging
Digital variance angiography
Terahertz tomography
Iatrochemistry
Microangiography
Laser speckle contrast imaging