This article details a method for imaging the brain of an anesthetized rat using photoacoustic signals. The procedure involves securing the animal, preparing the scalp, and utilizing ultrasound technology to capture brain images.
Secure an anesthetized rat on an imaging bed with its nose and mouth fitted into a mask that delivers an anesthetic agent.
Attach a pulse oximeter to monitor physiological parameters.
Apply ultrasound gel to the scalp, then position the bed under the scanner with the scalp centered under the imaging window.
Raise the bed until the gel contacts the window.
Acquire test images and adjust the bed height to align the brain's cross-sectional plane with the ultrasonic transducer's focus.
Set the imaging parameters and begin scanning.
The imaging system's pulsed-laser diode emits nanosecond light pulses that penetrate the scalp and interact with chromophores, such as hemoglobin.
The absorbed light induces localized heating, generating transient pressure waves called photoacoustic signals.
These signals are captured from multiple angles by the rotating ultrasound transducer.
Using software, process the signals to reconstruct a 2D cross-sectional brain image, highlighting vascular structures.
To begin the imaging procedure, obtain a healthy female rat. Following anesthesia, trim the fur on the scalp with a hair clipper. Gently apply depilatory cream to the trimmed area. After four to five minutes, remove the cream with a cotton swab.
Apply sterile ocular ointment to the rat's eyes to prevent dryness and to block scattered laser beams. Fix a custom-made imaging bed equipped with a breathing mask on a lab jack with surgical tape. Place the animal in a prone position on the imaging bed with its nose and mouth in the mask. Secure the animal in the imaging bed with surgical tape.
Position the imaging bed assembly on the optical table. Connect the breathing mask to an anesthesia machine. And begin delivering the inhaled anesthetic. Affix a pulse oximeter to the animal's tail or hind paw to monitor its physiological condition throughout the procedure.
Apply a colorless ultrasound gel to the scalp of the animal. Ensure that the imaging bed assembly is securely positioned under the scanner, with the animal's scalp centered under the imaging window. Carefully raise the imaging bed until the ultrasound gel contacts the imaging window, taking care to minimize the pressure against the animal's head.
Acquire test images, and adjust the vertical position of the bed until the imaging cross-sectional plane of the brain is at the focus point of the ultrasonic transducer. Then set the parameters for the experiment and start the scan. Monitor the animal during the imaging period. Use reconstruction software to obtain the cross-sectional brain image.
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