Laser ultrasound for investigation of arteriosclerotic arterial tissue

Angioplasty has become a common procedure for reducing the effects of constrictions in human arteries caused by the build up of fatty deposits, thrombosis and calcification (arteriosclerosis). An intraluminal laser ultrasound probe has been designed and constructed. The probe allows the use of a small pulsed laser to generate ultrasound on the tissue surface and to determine the nature of the tissue to be treated. Its design is also compatible with that required for a therapeutic laser beam to be delivered to the same site. The results obtained at both 532 nm and over the range of wavelengths covered by the optical parametric oscillator show that variations in the optical absorption characteristics within a tissue sample caused significant differences in the detected acoustic signal. This suggests that the acoustic signal obtained by optical absorption within the tissue can be used to gain information on the structure of the tissue sample. As the wavelength of the laser used was increased, waveforms suggested that the optical absorption of tissue decreased, leading to an increase in the amplitude of the signals from within the tissue if absorption centres were present. The results suggest that laser ultrasound can be used to determine the nature of arterial tissue samples and to distinguish between healthy and diseased arterial tissue