Ultrasonic arterial imaging with an intraluminal catheter array.

A method of real-time arterial color flow imaging using an FIR filter bank to estimate relative blood speed is presented. These measurements are clinically valuable, however realizing the full clinical potential of blood flow imaging requires quantitative speed and volume measurements in real time. Unfortunately, the rate of RF echo to echo decorrelation is not directly related to scatterer speed because the elevational extent of the imaging slice varies with r. Consequently, flow imaging methods that use any type of decorrelation processing to estimate blood speed without accounting for spatial variation of the radiation pattern will have estimation errors prohibiting accurate comparison of velocity estimates from different depths. The FIR filter bank takes a frequency domain approach to decorrelation processing by measuring the rate of change in the echoes by estimating the spectrum of the slow time signal. A filter bank of N band pass filters is applied in parallel to estimate of the N point DFT. A derivation of the relationship between the slow-time spectrum, aperture diffraction pattern and scatterer speed for a simplified target is presented. Since the ultimate goal of this work is to make quantitative velocity estimates using the FIR filter bank method, a method to map slow time spectral characteristics to a numerical velocity is derived. Results of the velocity estimator are shown for simulated and experimental data. Since adding a forward-looking capability to conventional side-looking arrays would aid catheter deployment by imaging directly in front of the catheter and allow Doppler processing to improve blood velocity estimation, a modified weighting method is derived that allows near full-aperture imaging performance with an forward-looking annular array appropriate for intravascular applications.Ph.D.Applied SciencesBiomedical engineeringElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123510/2/3079562.pd