Abstract
.Significance: Quantitative measures of blood flow and metabolism are essential for improved assessment of brain health and response to ischemic injury.Aim: We demonstrate a multimodal technique for measuring the cerebral metabolic rate of oxygen () in the rodent brain on an absolute scale ().Approach: We use laser speckle imaging at 809 nm and spatial frequency domain imaging at 655, 730, and 850 nm to obtain spatiotemporal maps of cerebral blood flow, tissue absorption (), and tissue scattering (). Knowledge of these three values enables calculation of a characteristic blood flow speed, which in turn is input to a mathematical model with a “zero-flow” boundary condition to calculate absolute . We apply this method to a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation. With this model, the zero-flow condition occurs during entry into CA.Results: The values calculated with our method are in good agreement with those measured with magnetic resonance and positron emission tomography by other groups.Conclusions: Our technique provides a quantitative metric of absolute cerebral metabolism that can potentially be used for comparison between animals and longitudinal monitoring of a single animal over multiple days. Though this report focuses on metabolism in a model of ischemia and reperfusion, this technique can potentially be applied to far broader types of acute brain injury and whole-body pathological occurrences.
Highlights
Assessing brain metabolism on a quantitative scale is critical for improved diagnosis, monitoring, and treatment of a wide variety of acute brain injury caused, for example, by ischemia, hemorrhage, and trauma
58.3 Æ 32.3 μM∕ min in an region of interest (ROI) selected over a large vein [Fig. 2(b)], but only 33.6 Æ 13.6 μM∕ min in an ROI selected over the parenchyma
Following the onset of ischemia, the CMRO2 rapidly decreased as the subject entered cardiac arrest (CA)
Summary
Assessing brain metabolism on a quantitative scale is critical for improved diagnosis, monitoring, and treatment of a wide variety of acute brain injury caused, for example, by ischemia, hemorrhage, and trauma. Numerous studies show abnormal brain metabolism in such Neurophotonics. In a clinical setting where patients present with an acute brain injury, there is often no way to obtain a baseline (preinjury) measurement, underscoring the need for translational research supporting absolute rather than relative measurements. Absolute CMRO2 measurements would enable quantitative comparisons between the values of different subjects at baseline and at subsequent time points in preclinical or clinical studies. These needs are currently unmet, as no existing technology directly and noninvasively measures absolute CMRO2 with both high spatial and temporal resolution using intrinsic signals
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