Harmonic imaging at high frequencies for IVUS

The authors investigated the properties of harmonic fields at high frequencies. A 40 MHz focused broadband transducer was excited at 20 and 40 MHz. The response from 20 MHz was measured at 20 and 40 MHz. The response from 40 MHz was determined at 40 MHz. Hydrophone measurements revealed that the harmonic field was proportional to the square of the fundamental field. The harmonic field increased 10 dB over the focal zone with respect to the fundamental field at 40 MHz. Harmonic images of an excised human femoral artery gave significantly better resolution and more detail than the fundamental image. The fundamental at the double frequency gave similar resolution, but higher attenuation than the harmonic. Additional advantages of harmonic imaging are discussed