Figure 2.

Acoustic characterization of customized stacked-type intravascular ultrasound transducer. (A) Measured beam profiles of planar- (A1) and concave-aperture (A2) prototypes; the red arrows indicate the radiation direction, and the red contour lines denote the mechanical index of 0.3 with voltage input of 80 V_pp which implies the approximated threshold of inertial cavitation of microbubbles. −6 dB beam diameters of planar- and concave-aperture prototypes are 3.1 mm and 1.3 mm, respectively. (B) Measured pressure output (1 mm away from the aperture) with voltage inputs of 10–80 V_pp (n = 2). The concave aperture prototype exhibits approximately 2.5-fold increase in peak-to-peak pressure (PTP) and 2.3-fold increased peak-negative-pressure (PNP) relative to the planar aperture prototype. (*P < 0.05).