Preliminary studies into high velocity transverse blood flow measurement

The design, fabrication and operation of a 4.5-MHz dual-beam probe capable of high-velocity blood flow measurement with a good lateral resolution is described. The authors describe an aluminum lens which is used to generate two adjacent focal spots at a focal length in the range of 30 mm to 80 mm, making it suitable for in vivo blood velocity measurements. The limits on the maximum velocity detectable with this system are dependent on the separation of the two spots and the pulse repetition frequency (PRF). A comparison between simulated PRFs and the measured lens characteristics at different focal lengths is discussed. A possible extension of the technique to three-dimensional velocity measurements is discussed. >