Cerebral perfusion reserve

It follows from the above that the ratio of cerebral blood flow to cerebral blood volume is a measure of cerebral perfusion reserve (Schumann et al. 1998). Below a ratio of approximately 6.0, even if cerebral blood flow is still normal, vasodilatation and cerebral blood volume are maximal and the reserve is exhausted, as shown by a rising oxygen extraction fraction on PET. 

Long-term angiotensin-converting enzyme inhibitor perindopril therapy improves cerebral perfusion reserve in... 

Knowledge of cerebral blood flow regulation, and the relationship between cerebral blood flow and cerebral metabolism, has had a major influence on the understanding of the pathophysiology of impaired perfusion reserve and acute ischemic stroke (Frackowiak 1986 Marchal et al. 1996 Baron 2001 Rutgers et al. 2004). 

Chronically impaired perfusion reserve tends to occur when one or both internal carotid arteries are stenosed by at least 50% of the luminal diameter (Brice et al. 1964 DeWeese et al. 1970 Schroeder 1988), or are occluded, and the collateral circulation is inadequate (Powers et al. 1987 Kluytmans et al. 1999). In this situation, the brain is vulnerable to any fiirtber fall in cerebral perfusion pressure and cerebral metabolism is begiiming to become impaired, with the appearance of structural abnormalities on MRI (van der Grond et aL 1996 Isaka et al. 1997 Derdeyn et al. 1999). 

Technetium ( Tcj Bicisate Injection. A sterile colorless solution of bicisate is complexed with Tc-99m pertech-neuite after reduction with a stannous salt. The precise structure of the technetium complex is fN,N -ethylene-di-L-cy.steinato(3-) oxo "Tc]technetium(V) diethyl ester. This radiopharmaceutical is a neutral and lipophilic complex that crosses the blotxl-brain barrier and is selectively retained in the brain. Therefore, this radiotracer is used as a brain-perfusion imaging agent. After intravenous injection of 20 mCi (740 MBq) of Tc-99m bicisate, about 5% of the injected dose is localized within the brain cells 5 minutes after injection and demonstrates rapid renal excretion (74% in 24 hours). This radiotracer is used clinically to evaluate dementia, stroke, lack of brain perfusion ("brain death"), cerebral vascular reserve, or risk of stroke (acetazolamide challenge. study) and to localize a seizure focus for surgical removal. 

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