Cerebral blood volume is the

blood volume Blood volume (volemia) is the volume of blood (blood cells and plasma) in the circulatory system of any individual. Humans A typical adult has a blood volume of approximately 5 liters, with females and males having approximately the same blood pe ...

in a given amount of brain tissue.

Pathophysiology

The typical human adult's skull contains approximately 1500 grams of the brain (including gray matter and white matter), 100-130 milliliters of blood, and 75 milliliters of

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

. About 15% of the blood volume is present in the

arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...

, 40% in the veins, and 45% in the nerve tissue and capillaries. There is a difference between the cerebral blood volume of gray and

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distributi ...

. The cerebral blood volume value of gray matter is about 3.5 +/- 0.4 ml/100g, and the white matter is about 1.7 +/- 0.4 ml/100g. The

gray matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingui ...

is nearly twice that of white matter. In both white and gray matter, cerebral blood volume decreases by about 0.50% per year with increasing age. Intracranial hematoma and

Intracerebral hemorrhage Intracerebral hemorrhage (ICH), also known as cerebral bleed, intraparenchymal bleed, and hemorrhagic stroke, or haemorrhagic stroke, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleed ...

(ICH) will cause an increase in cerebral blood volume.

Ischemic stroke Stroke (also known as a cerebrovascular accident (CVA) or brain attack) is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, ...

will cause a substantial reduction in cerebral blood volume.

Measurement methods

Magnetic resonance imaging

The cerebral blood volume maps can be calculated by dynamic

magnetic resonance image Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio w ...

set obtained by echo planar imaging after intravenous injection of thiol

contrast agent A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radio ...

. Planar imaging techniques or single high-speed shots provide the necessary resolution for contrast agents to display rapid brain blood movements. These magnetic resonance cerebral blood volume imaging methods can be applied to academic research of normal human brain activities and clinical studies of patients with brain tumors. Ct scan cone beam

Emission computed tomography

In vivo studies using emission computed tomography gave coefficients of variation for regional cerebral blood volume and cross-sectional cerebral blood volume over 80 minutes. A clear tomographic depiction of cerebral blood volume distribution in human subjects can achieve by using

emission computed tomography Emission computed tomography (ECT) is a type of tomography involving radioactive emissions. Types include positron emission tomography (PET) and Single-photon emission computed tomography (SPECT). The imaging agent used in SPECT emits gamma ra ...

, which provides real-time measurements of the cerebral

hemodynamic Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously ...

parameters. Carbon monoxide administered by a single inhalation is a reliable and accurate blood tracer for measuring cerebral blood volume with emission computed tomography.

Synchrotron radiation computed tomography

Synchrotron Radiation Computed Tomography uses a monochromatic and parallel

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

beam to measure the value of cerebral blood volume. It allows the sample to be placed away from the detector, thereby avoiding scattering effects. This technique measures absolute contrast concentration with relatively high precision and spatial resolution. Cerebral blood volume measurements are based on methods used in dynamic computed tomography. After a large dose of iodinated contrast agent was injected into the brain tissue, the temporal change in iodine concentration was compared to changes in cerebral arterial input. It is a new method for studying hemodynamic changes in brain

pathophysiology Pathophysiology ( physiopathology) – a convergence of pathology with physiology – is the study of the disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury. Pathology is t ...

, including clinical studies of cerebrovascular diseases or brain tumors.

CT perfusion

Cerebral blood volume is one of the parameters that is assessed with CT perfusion, often as part of

evaluation.

Cerebral blood flow

Cerebral blood volume has a close and positive correlation with cerebral blood flow. Both cerebral blood volume and cerebral blood flow depend on several important parameters, including cerebrovascular resistance, intracranial pressure, and mean arterial pressure. The ratio between cerebral blood flow and cerebral blood volume can be an accurate predictor of decreased cerebral perfusion pressure, thereby predicting cerebral circulation.

References

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