Quantitative blood flow as assessed by intravascular ultrasound

textabstractThe aim of the present study was to develop the correlation-based method for quantitative blood flow for intravascular ultrasound purposes. The feasibility of the technique was studied by means of computer simulations, in vitro and in animal measurements, and in patient validation. A general overview in IVUS flow is presented (Chapter 2). Computer simulations were implemented for the study of the decorrelation characteristics of the ultrasound beam from the lVUS array catheter. First, blood was mimicked as a collection of randomly located point scatterers as single red blood cells (Chapter 3). Second, strings of point scatterers were used as aggregates of red blood cell (Chapter 4). Different blood flow profiles were also studied by means of computer simulation (Chapter -5). In vitro measurements were performed to validate the results presented in Chapter 3, 4 and 5 (Chapter 6). In vitro measurements of the ultrasound beam of the IVUS array catheter were performed to calibrate the correlation-based method for quantitative blood flow method (Chapter 7). Noise in the radio frequency signals is of major importance in the correlation-based blood velocity method; therefore, a technique was needed to correct the correlation coefficients for noise. Numerical validation, and in vitro and in animal measurements were performed to validate the correlation-based method for blood velocity estimation and quantitative volume blood flow, and the new technique that corrects for noise (Chapter 8 and 9). Finally, a functional parameter such as coronary flow reserve ( CFR, ratio between high flow and low flow) of the heart was evaluated in patients (Chapter 9). In another series of patients CFR was compared with Geometric Measurements of Coronary Dimensions (Chapter 10)