Perfusion, cerebral, imaging studies

Fig. 9.3 Low rate of neuronal loss. A 72-year-old woman presented 13 h after stroke onset with left-sided weakness and neglect (NIHSS of 11). CT angiography revealed occlusion of the light middle cerebral artery. Diffusion and perfusion studies revealed a small diffusion abnormality (top left) and a very large perfusion abnormahty (bottom left). Repeat study performed 4 h after the initial imaging study showed very little growth in the size of the diffusion abnormality (top right), despite the persistence of a very large perfusion abnormality (bottom right)...

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. 

Liu, Y., et al.. Cerebral hemodynamics in human acute ischemic stroke a study with diffusion- and perfusion-weighted magnetic resonance imaging and SPECT. J Cereb Blood Flow Metab, 2000. 20(6) p. 910-20. 

The major challenge in using CTP for the assessment of the core infarct is the questionable reliability of dynamic perfusion imaging. CBV measurements are thought to be more robust than CBF and MTT measurements because the calculation of cerebral blood volume is relatively insensitive to bolus delay and dispersion [85, 86]. However, as a calculated parameter, it remains dependent on postprocessing (e.g., partial volume effects) and patient-specific issues (e.g., hematocrit levels) [87-89]. Additionally, as demonstrated in the DIAS-2 study [90], there is poor interrater agreement in assessing the CBV lesion. 

An exciting application of the HP xenon is the study of brain perfusion. Kilian and coworkers °° used a time series of Xe spectra after HP Xe inhalation to derive uptake in the brain. Two resonances detected at 196.5 and 193 ppm were assigned to HP Xe dissolved in gray and white matter, respectively. The Ti values are different, as well. Duhamel et al used an intra-carotid injection of HP Xe dissolved in intralipid, a xenon-soluble carrier, to measure cerebral blood flow. Rat brain xenon images were performed to enable regional blood flow measurements. 

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