Collinear IVPA catheter probe.
(A) Main components of the collinear catheter before assembly. (B) Assembled IVPA catheter probe. (C) Zoom-in view of the catheter tip with illustration of collinear overlap between optical and ultrasonic waves. (D) Photograph of the fabricated catheter probe with a diameter of 1.6 mm and the detailed structure of the catheter tip (inset).