Real-time optical imaging of experimental brain ischemia and hemorrhage inneonatal piglets

Our objective was to study the development of experimental brain ischemia a nd hemorrhage by real-time optical imaging. Optical imaging is based on the ability of near infrared light to non-invasively penetrate through the int act scalp and skull and measure brain concentrations of oxy- and deoxyhemog lobin, dominant brain absorbers. Optical imaging was performed in 7 anesthe tized, instrumented, and ventilated newborn piglets subjected to the inject ion of 0.3 cc of saline followed by 2 cc of blood into the left frontal sub cortical brain region via a needle inserted through the skull with stereota ctic guidance. The image-acquisition rate of 5.26 images per sec allowed fo r real-time imaging. The detection threshold of the imager at the estimated depth of 1-1.5 cm was similar to 70 mu L for saline and similar to 40 mu L for blood. The imager readily detected five subcortical hematomas and two large bilateral subarnchnoid hemorrhages. The imager detected a global decr ease in brain absorption associated with the volume-injection-related incre ase in intracranial pressure in the surrounding ipsilateral and contralater al brain. Any decrease in brain absorption is an equivalent to brain ischem ia. This study demonstrates the capability of optical imaging in detecting brain ischemia and hemorrhage in real-time with high temporal and spatial r esolution.