Photoacoustic Tomography to Image Blood and Lipids in the Infrarenal Aorta

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 pulse generator, and 'Q-switch' to port B of the pulse generator. Finally, attach a BNC cable from port C to 'trigger in' on the back of the ultrasound system.
3. Align the fiber optic cable with the laser and attach the fiber ends to the sides of the 40 MHz ultrasound transducer.
4. Adjust the delay of ports A, B, and C to the values listed here (Port A: 0.00000000, Port B: 0.00021440, Port C: 0.00000910). Set ports A and B to inverted signal and port C to normal signal.

2. Animal Preparation and Image Acquisition

1. Anesthetize an apoE^-/- mouse using 3% isoflurane in an anesthesia induction chamber. Once the animal is anesthetized move the mouse to a nose cone to deliver 1-2% isoflurane.
2. Apply eye lubricate to the animals eyes to prevent corneal desiccation. Tape the mouse's paws to electrodes built into the heated stage to monitor animal's respiration and heart rate. Finally, insert rectal probe to monitor body temperature.
3. Apply depilatory cream to remove hair from the animal's abdomen. Wipe off after 30 s with a gauze pad.
4. Place the ultrasound transducer on the animal's abdomen and locate the infrarenal aorta. The left renal vein and the aortic trifurcation into the tail artery are two landmarks that will help the user locate this area.
5. Run the laser to output 1100 nm light to target blood followed by 1210 nm light to target lipid. Use appropriate laser safety goggles when the laser is in use.