Figure 1

Illustration of IVPA imaging and fabricated catheter. (a) Implementation of IVPA imaging. Optical pulses from the excitation laser are coupled to the imaging catheter through a multimode fiber and a rotary joint, and directed to the arterial wall for PA excitation. The generated sound wave from optical absorption by lipid is collected by a transducer installed in the catheter tip. Simultaneously, a delayed ultrasonic pulse is delivered and its echo is received by the same transducer to produce a co-registered US image. The rotational and pullback stages are used to constantly rotate and linearly pull back the IVPA catheter inside a protective sheath for 3D imaging. The reconstructed PA and US images are displayed on a monitor in real time. 3D images of the artery are reconstructed from the cross-sectional image stacks in a pullback. (b) Photograph of quasi-collinear IVPA catheter with a complete sheath. The unit scale of the ruler in the left inset of b is 1 mm.