Focus Ultrasound Based Microbubble Mediated Blood-Brain Barrier Opening: A Technique to Create Localized Transient Openings in Blood-Brain Barrier of Mouse by Sonoporation

For the administration of microbubbles for BBB opening, insert a 26 to 30 gauge tail vein catheter and flush the vein with a small volume of heparin solution. Secure the catheter with tissue tape to prevent detachment. If the catheterization is successful, fill the catheter with the heparin solution to avoid blood clotting.

Place the animal on the temperature-regulated stereotactic platform to avoid hypothermia. Fix the head of the animal using a bite bar and ear bars and tape the tail and catheter to the platform. Fix the body of the mouse with a strap.

Place the stereotactic platform with the mounted mouse in the imaging modality and take images of the animal. Determine whether the animal is correctly placed on the platform. Mark the position of the animal using the multi-modality fiducial markers in combination with the image processing pipeline according to the focus point of the transducer. Determine the target area by placing a brain outline over the acquired X-ray image, or by using BLI images to determine the center of the tumor.

Before positioning the transducer, protect the animal's nostrils and mouth with tape to prevent ultrasound gel from interfering with breathing. Apply ultrasound gel on top of the mouse's head for proper sound conduction. Record microbubble cavitation with the needle hydrophone, which is placed in the direct vicinity of the occipital bone.

Based on the calibration values, guide the transducer to the correct position above the animal. Apply pre-configured settings to all attached devices to target the brain region of interest. After the transducer is placed in the right position, dissolve and activate the microbubbles as described by the manufacturer.

Before microbubble injection, flush the tail vein catheter with saline to confirm tail vein access. Start the insonication trajectory and simultaneously inject the microbubbles. At the same time, the needle hydrophone will detect and verify microbubble cavitation in real-time. If desired, administer an intravascular contrast agent or drug after sonoporation. Monitor the animal until a predetermined time point.