A practical approach to measuring an intravascular ultrasonographic imaging system beam pattern.

Characterizing beam patterns of miniature (1 to 3 mm diameter) catheter sonographic systems operating at 15 to 50 MHz is difficult and such information is often not provided by manufacturers. For investigators in the field, quantitative information describing catheters and their systems is important to properly understand measurements and images. A practical means of characterizing the system is described that can be assembled in most laboratories and used with existing catheter systems. The ultrasonic beam pattern from an intravascular sonographic transducer is characterized in three dimensions using images generated from a 150 microns diameter spherical target. Experiments are described in which the point spread function or beam pattern is mapped throughout the imaging system field-of-view. Using this approach, the beam pattern and resolutions for a commercial 1.18 mm diameter, 20 MHz intravascular catheter were measured.