Ultrasonic integrated backscatter coefficient profiling of human coronary arteries in vitro

A theoretical formulation for the profile of the integrated backscatter coe fficient (IBC) is derived. This new formulation is based on a theoretical t reatment by Chen et al. [1]. It includes correction for the diffraction of the ultrasonic beam and correction for the non-ideal nature of the referenc e signal. The inclusion of these correction factors permits accurate quanti tative profiling of the IBC over the transducer focal zone. Experimental me asurements are first performed on well-calibrated vessel-equivalent phantom materials and subsequently on human coronary arteries in vitro. A spherica lly focused 50.0 MHz f/1.83 transducer is used. IBC profiles are shown for three samples that are representative of early, mid, and advanced atheroscl erotic coronary disease. The IBC profiles clearly differentiate the arteria l tissues. However, Variation between samples with histologically confirmed intimal thickening (N = 24) was large. The mean IBC (+/-1 standard deviati on), in (Sr.mm)(-1), for media, adventitia, and thickened intima were 3.86 X 10(-3), 1.53 X 10(-2) and 2.24 X 10(-2), respectively. The mean IBC of th ickened intima is larger than previous measurements obtained from femoral a rteries, and the mean IBC for media and adventitia layers are lower, reflec ting differences in tissue composition between coronary and femoral vessels .