Fick principle for CMRO2 quantif

2019-05-28 本文已影响0人要努力的人儿

Definition

CMRO2为脑氧代谢率(cerebral metabolic rate of oxygen)，假定组织从血液中所摄取的所有氧气都用于ATP的产生，则CMRO2可借由Fick原理量化确定如下：

$CMRO_{2} = C_{a} * CBF * (Y_{a}-Y_{v})$

$Y_{a}$ : arterial oxygen saturation in %HbO2

$Y_{v}$ : venous oxygen saturation in %HbO2

$CBF$ : cerebral blood flow in μmol per minute per 100g of brain tissue

$C_{a}$ : arterial oxygen content of fully saturated arterial blood (i.e. blood with $Y_{a}$ =100% HbO2) in μmol of O2 per mL blood, giving CMRO2 in μmol per minute per 100g of brain tissue. $C_{a}$ is a Hb-dependent constant:

$C_{a}=0.620559*Hb$

Hb is in g/dL and the scaling factor is calculated based on a hemoglobin molar mass of 64,458g/mol

$Y_{a}-Y_{v}$ : arteriovenous oxygen diﬀerence (AVO2D), AVO2D is very similar to OEF for Ya in the normal physiologic range and are sometimes used interchangeably

$OEF = AVO_{2}D/Y_{a}$

Measurement

$CBF$ : measured by phase-contrast MRI (PC-MRI) in large cerebral vessels or mapped on a voxel-wise basis with arterial spin labeling (ASL)

$Y_{a}$ : measured continuously with a digital pulse oximeter or assumed to be near 98% HbO2 in normal conditions

$Y_{v}$ : MR-based quantifying through para-magnetism of dHb. These methods can be categorized based on the tissue compartment in which the eﬀects of dHb are modeled (extravascular vs. intravascular) and the MR contrast method used to quantify these eﬀects ( $T_{2}^*$ , $T_2$ ', $T_2$ ,or susceptibility).

Measurement of

Y_{v}

Fick principle for CMRO2 quantif

Definition

Measurement

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