Abstract
.Significance: The cerebral metabolic rate of oxygen () is an important indicator of brain function and pathology. Knowledge about its magnitude is also required for proper interpretation of the blood oxygenation level-dependent (BOLD) signal measured with functional MRI. Despite the need for estimating , no gold standard exists. Traditionally, the estimation of has been pursued with somewhat indirect approaches combining several different types of measurements with mathematical modeling of the underlying physiological processes. The recent ability to measure the level of oxygen () in cortex with two-photon resolution in in vivo conditions has provided a more direct way for estimating , but has so far only been used to estimate the average close to cortical penetrating arterioles in rats.Aim: The aim of this study was to propose a method to provide spatial maps of based on two-photon measurements.Approach: The method has two key steps. First, the maps are spatially smoothed to reduce the effects of noise in the measurements. Next, the Laplace operator (a double spatial derivative) in two spatial dimensions is applied on the smoothed maps to obtain spatially resolved estimates.Result: The smoothing introduces a bias, and a balance must be found where the effects of the noise are sufficiently reduced without introducing too much bias. In this model-based study, we explored this balance using synthetic model-based data, that is, data where the spatial maps of were preset and thus known. The corresponding maps were found by solving the Poisson equation, which relates and . MATLAB code for using the method is provided.Conclusion: Through this model-based study, we propose a method for estimating with high spatial resolution based on measurements of in cerebral cortex.
Highlights
The level of consumption of oxygen by metabolic processes, that is, the cerebral metabolic rate of oxygen (CMRO2), is an important indicator of brain function and pathology
Knowledge about the magnitude of the CMRO2 is required for a proper interpretation of the blood oxygenation level-dependent (BOLD) signal measured in functional MRI studies.[1]
We assume the spatial map of pO2 to follow the Krogh–Erlang formula in Eq (16), mimicking the situation where a single arteriole is the source of the oxygen, and the oxygen consumption M is constant around the arteriole
Summary
The level of consumption of oxygen by metabolic processes, that is, the cerebral metabolic rate of oxygen (CMRO2), is an important indicator of brain function and pathology. The possibility to optically measure the partial pressure of oxygen (pO2) around cortical diving arterioles with two-photon resolution in vivo[3] has provided a more direct way to estimate the CMRO2. We (Sakadžic, Devor, and collaborators) used measured pO2 gradients around diving arterioles in rats to estimate the average CMRO2 in the vessel’s vicinity, that is, within a radius of ∼100 μm.[4] We based our estimates on the Krogh–Erlang formula relating the pO2 to the CMRO2 in a cylinder section around an arteriole providing the brain tissue with oxygen.[5,6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
