| Popis: |
The radial position and tilt of an ultrasound catheter can vary widely in a great vessel because of the large vessel lumen. Position and tilt are important in both wall imaging and blood flow measurement. In order to identity some of the dimensional parameters for an intravascular ultrasound system, aorta and pulmonary artery (PA) diameters and lengths were measured in 50 humans, 11 pigs, and 2 calves. When these results were combined with further in vivo inspection they indicated that the calf provides the best anatomical model for the human PA while the swine, although suitable, is the best for aorta anatomical modelling. Angular backscattering was measured from excised canine pulmonary arteries at 12 and 20 MHz. Attenuation coefficients of blood were measured at 10, 15, 20 and 26 MHz. Using interpolation as well as the anatomical information the magnitude of wall echo signals were calculated for various ultrasound positions in the pulmonary artery at 12 and 20 MHz. Signal loss ranged from -47 to -100 dB and -53 to -104 dB for these frequencies. In this manuscript we have outlined the value of a mechanical catheter centring device in the vessels, and we have suggested two techniques. |
