Source: Gurneet S. Sangha and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

Photoacoustic tomography (PAT) is an emerging biomedical imaging modality that utilizes light generated acoustic waves to obtain compositional information from tissue. PAT can be used to image blood and lipid components, which is useful for a wide variety of applications, including cardiovascular and tumor imaging. Currently used imaging techniques have inherent limitations that restrict their use with researchers and physicians. For example, long acquisition times, high costs, use of harmful contrast, and minimal to high invasiveness are all factors that limit the use of various modalities in the laboratory and clinic. Currently, the only comparable imaging techniques to PAT are emerging optical techniques. But these also have disadvantages, such as limited depth of penetration and the need for exogenous contrast agents. PAT provides meaningful information in a rapid, noninvasive, label-free manner. When coupled with ultrasound, PAT can be used to obtain structural, hemodynamic, and compositional information from tissue, thereby complementing currently used imaging techniques. The advantages of PAT illustrate its capabilities to make an impact in both the preclinical and clinical environment.

The following procedure describes the methods needed to set up VPAT for blood and lipid imaging of the infrarenal aorta in apolipoprotein-E deficient (apoE^-/-) mice.

1. Laser-ultrasound Coupling

1. Obtain a Nd:YAG pulsed optical parametric oscillator laser and an ultrasound system. Acquire a pulse generator, 1 BNC cable, and a D connector attached to two BNC cables.
2. Using the D connector set-up, attach the 'Fire' BNC cable to port A of the pul

Here, VPAT methods were used to perform lipid and blood specific imaging in vivo. By coupling a laser and ultrasound system, light was delivered to tissue and the resulting acoustic waves were detected. Ultrasound imaging allowed us to obtain structural information of the infrarenal aorta (Figure 1a) that can be used to better interpret VPAT compositional information. Specifically, a 1100 nm light was used to image blood within the aorta (