Nanorod-based flow estimation using a high-frame-rate photoacoustic imaging system.
A quantitative flow measurement method that utilizes a sequence of photoacoustic images is described. The method is based on the use of gold nanorods as a contrast agent for photoacoustic imaging. The peak optical absorption wavelength of a gold nanorod depends on its aspect ratio, which can be altered by laser irradiation (we establish a wash-in flow estimation method of this process). The concentration of nanorods with a particular aspect ratio inside a region of interest is affected by both laser-induced shape changes and replenishment of nanorods at a rate determined by the flow velocity. In this study, the concentration is monitored using a custom-designed, high-frame-rate photoacoustic imaging system. This imaging system consists of fiber bundles for wide area laser irradiation, a laser ultrasonic transducer array, and an ultrasound front-end subsystem that allows acoustic data to be acquired simultaneously from 64 transducer elements. Currently, the frame rate of this system is limited by the pulse-repetition frequency of the laser (i.e., 15 Hz). With this system, experimental results from a chicken breast tissue show that flow velocities from 0.125 to 2 mms can be measured with an average error of 31.3%.
Liao
Chao-Kang
CK
National Taiwan University, Department of Electrical Engineering, Taipei 106, Taiwan.
Huang
Sheng-Wen
SW
Wei
Chen-Wei
CW
Li
Pai-Chi
PC
D000162:Acoustics / Q000295:instrumentation*; D000818:Animals; D001783:Blood Flow Velocity; D002645:Chickens; D006046:Gold; D018056:Hemorheology / Q000295:instrumentation* / Q000706:statistics & numerical data; D053768:Metal Nanoparticles; D018482:Muscle, Skeletal / Q000098:blood supply; D043942:Nanotubes; D055095:Optics and Photonics / Q000295:instrumentation*; D019047:Phantoms, Imaging
D006046:Gold