Paradoxical reduction of cerebral blood flow after acetazolamide loading: a hemodynamic and metabolic study with 15O PET

Abstract

Paradoxical reduction of cerebral blood flow (CBF) after administration of the vasodilator acetazolamide is the most severe stage of cerebrovascular reactivity failure and is often associated with an increased oxygen extraction fraction (OEF). In this study, we aimed to reveal the mechanism underlying this phenomenon by focusing on the ratio of CBF to cerebral blood volume (CBV) as a marker of regional cerebral perfusion pressure (CPP). In 37 patients with unilateral internal carotid or middle cerebral arterial (MCA) steno-occlusive disease and 8 normal controls, the baseline CBF (CBF b ), CBV, OEF, cerebral oxygen metabolic rate (CMRO 2 ), and CBF after acetazolamide loading in the anterior and posterior MCA territories were measured by 15 O positron emission tomography. Paradoxical CBF reduction was found in 28 of 74 regions (18 of 37 patients) in the ipsilateral hemisphere. High CBF b (>47.6 mL/100 mL/min, n = 7) was associated with normal CBF b /CBV, increased CBV, decreased OEF, and normal CMRO 2 . Low CBF b (<31.8 mL/100 mL/min, n = 9) was associated with decreased CBF b /CBV, increased CBV, increased OEF, and decreased CMRO 2 . These fi ndings demonstrated that paradoxical CBF reduction is not always associated with reduction of CPP, but partly includes high-CBF b regions with normal CPP, which has not been described in previous studies.

Sequential PET estimation of cerebral oxygen metabolism with spontaneous respiration of 15O-gas in mice with bilateral common carotid artery stenosis

“…PET data were reconstructed using Fourier rebinning 19 and a filtered back projection algorithm with a 1 min frame duration, 128 Â 128 Â 95 matrix size, and 0.43 Â 0.43 Â 0.80 mm 3 voxel size, which included corrections for random and deadtimes without corrections for scatter and attenuation. Figure 3 shows representative volumes of interest (VOIs) drawn in the whole brain and the heart on summed images of 15 3 , respectively (the shapes and volumes of the heart VOIs were identical for all measurements, and only the location was adjusted for a series of PET scans of each animal taken on a single day).…”

“…Since oxygen is a fundamental energy source for brain activity, use of Positron emission tomography (PET) for in vivo quantitative measurements of parameters related to cerebral oxygen metabolism such as cerebral blood flow (CBF), cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ) in the presence of 15 O labeled gases ( 15 O-O 2 , 15 O-CO 2 , and 15 O-CO) is of great importance both in clinical [1][2][3][4] and basic settings. [5][6][7] Given the importance of small animal models such as mice and rats to many research fields, the development of noninvasive measurement methods to assess oxygen metabolism in small animals is needed.…”

X-ray angiography perfusion imaging with an intra-arterial injection: comparative study with15O-gas/water positron emission tomography

“…PET images were obtained using a SET-3000 GCT/X scanner (Shimadzu Corp, Kyoto, Japan) with arterial blood sampling 15. For cerebral blood volume (CBV) measurement, a static 4 min scan was started 3 min after 1 min of C 15 O gas inhalation (3.0 GBq/min).…”

Evaluation of Functional Connectivity in the Brain Using Positron Emission Tomography: A Mini-Review

“…Regional CBF and CMRO 2 can be quantitatively evaluated via 15 O-labeled gas and water PET (Hatazawa et al, 1996; Watabe et al, 2014). Our group recently reported that functional correlations in the DMN can be estimated using quantitative 15 O-PET (Aoe et al, 2018).…”