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

Our objective was to study the development of experimental brain ischemia and hemorrhage by real-time optical imaging. Optical imaging is based on the ability of near infrared light to non-invasively penetrate through the intact scalp and skull and measure brain concentrations of oxy- and deoxyhemoglobin, dominant brain absorbers. Optical imaging was performed in 7 anesthetized, instrumented, and ventilated newborn piglets subjected to the injection of 0.3 cc of saline followed by 2 cc of blood into the left frontal subcortical brain region via a needle inserted through the skull with stereotactic guidance. The image-acquisition rate of 5.26 images per sec allowed for real-time imaging. The detection threshold of the imager at the estimated depth of 1-1.5 cm was approximately 70 microL for saline and approximately 40 microL for blood. The imager readily detected five subcortical hematomas and two large bilateral subarachnoid hemorrhages. The imager detected a global decrease in brain absorption associated with the volume-injection-related increase in intracranial pressure in the surrounding ipsilateral and contralateral brain. Any decrease in brain absorption is an equivalent to brain ischemia. This study demonstrates the capability of optical imaging in detecting brain ischemia and hemorrhage in real-time with high temporal and spatial resolution.