Bilirubin-biliverdin concentration measurement using photoacoustic spectroscopic analysis for determining hemorrhage age.

The onset of intracerebral hemorrhage and its progression toward acute brain injury have been correlated with the concentration of unconjugated bilirubin (BR). In addition, BR has been considered a novel predictor of outcome from intracranial hemorrhage. Since the existing invasive approach for determining localized BR and biliverdin (BV) concentration within the hemorrhagic brain lesion is not feasible, the predictive capability of BR in terms of determining the onset of hemorrhage and understanding the consequences of its progression (age) is unknown. In this study, we have demonstrated a photoacoustic (PA) approach to the noninvasive measurement of BR-BV ratio that can be utilized longitudinally to approximate the onset of the hemorrhage. The PA imaging-based measurements of BV and BR in tissues and fluids can potentially be used to determine hemorrhage "age," quantitatively evaluate the hemorrhage resorption or detect a rebleeding, and assess responses to therapy and prognosis.