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Which brain imaging technique measures changes in blood-oxygen levels

Published: 02.07.2022

which brain imaging technique measures changes in blood-oxygen levels

MRI perfusion (PMR), magnetic resonance perfusion, also known as hemodynamic magnetic resonance imaging, measures the flow, volume, and time that blood irrigates the brain parenyma total or regional.

In a more classical definition, perfusion refers to the delivery of oxygen and nutrients through the capillaries, which brain imaging technique measures changes in blood-oxygen levels. It is based on anges induced by intravascular magnetic susceptibility. These susceptibility teniques use extrinsic (gadolinium, Gd-DTPA), or intrinsic (deoxyhemoglobin) paramagnetic molecules.

Among the parameters that can be calculated, the best known are cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT). Other parameters that can be obtained are the signal intensity recovery percentage (PRS) and the peak height (Peak Height [PH]) through sime mathematical calculations.

There are three main teniques:

Weighted magnetic susceptibility image at T2.

T1-weighted dynamic perfusion

Arterial Spin Labeling Teniques

All these methods are based on the signal anges that accompany the passage of the tracer through the cerebrovascular system, whi can be endogenous (water) or exogenous (gadolinium elates).

The most widely used tenique is the T2-weighted magnetic susceptibility imaging.

The structures to be studied are distinguished by the high susceptibility of the paramagnetic molecules amid the low susceptibility of the adjacent tissue.

The higher magnetic susceptibility causes a greater loss of signal intensity.

This tenique will demonstrate isemic zones as areas with reduced regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV), as well as increased mean transit time of blood through the affected tissue. a hyperintense image.

Although it is still a little available procedure, it seems to have a high sensitivity and specificity in the early detection of cerebral isemia; these teniques may be able to differentiate transient isemic attacks from acute infarctions, as well as reliably detect areas at risk of isemia.

In brain gliomas, it correlates with the findings of tumor histological grade and vascular proliferation, although apparent diffusion coefficient measurements are better than perfusion resonance values ​​for distinguishing grades in gliomas. The combination of both improves the diagnostic accuracy of glioma classification (Hilario et al., 2011).

Dynamic contrast susceptibility-based T2-weighted imaging assesses cerebral hemodynamics at the MICRO-vascular level through relative blood volume.

In the future it could be used to predict the overall survival of patients independent of the molecular subclasses of glioblastoma multiforme, however, the Verhaak classification provides additional information, suggesting that molecular markers could be used in combination with hemodynamic imaging biomarkers in the future (Jain et al., 2012).

Bibliography

Hilario, A, A Ramos, A Perez-Nuñez, E Salvador, J M Millan, A Lagares, J M Sepulveda, P Gonzalez-Leon, A Hernandez-Lain, and J R Ricoy. 2011. “The Added Value of Apparent Diffusion Coefficient to Cerebral Blood Volume in the Preoperative Grading of Diffuse Gliomas.” AJNR. American Journal of Neuroradiology (December 29). doi:10.3174/ajnr.A2846. http://www.ncbi.nlm.nih.gov/pubmed/22207304.

Jain, Rajan, Laila Poisson, Jayant Narang, David Gutman, Lisa Scarpace, Scott N Hwang, Chad Holder, et al. 2012. “Genomic Mapping and Survival Prediction in Glioblastoma: Molecular Subclassification Strengthened by Hemodynamic Imaging Biomarkers.” Radiology (December 13). doi:10.1148/radiol.12120846.

Published: 02.07.2022 | Исправлено: 02.07.2022



Сагателов Магомед Егорович
02.07.2022 в 11:44
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