Optimal timing for measuring cerebral blood flow after acetazolamide administration to detect preexisting cerebral hemodynamics and metabolism in patients with bilateral major cerebral artery steno-occlusive diseases: 15O positron emission tomography studies

Abstract

The present study determined the optimal timing of scanning for measurement of cerebral blood flow (CBF) after acetazolamide (ACZ) administration for detection of preexisting cerebral hemodynamics and metabolism in bilateral major cerebral artery steno-occlusive diseases. Thirty three patients underwent ¹⁵O gas positron emission tomography (PET) and each parameter was obtained in the bilateral middle cerebral artery (MCA) territories. CBF was also obtained using H₂ ¹⁵O PET scanning performed at baseline and at 5, 15, and 30 min after ACZ administration. Relative CBF at each time point after ACZ administration to baseline CBF was calculated. For MCA territories with normal cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO₂), CBF continued increasing until 15 min after ACZ administration. For MCA territories with abnormally increased CBV, CBF decreased 5 min after ACZ administration. After that, CBF continued increasing until 30 min after ACZ administration. For MCA territories with abnormally decreased CMRO₂, CBF did not change 5 min after ACZ administration. Ten min later, CBF increased. The accuracy to detect abnormally increased CBV was significantly greater for relative CBF₅ than for relative CBF₁₅. The accuracy to detect abnormally decreased CMRO₂ was significantly greater for relative CBF₅ or CBF₁₅ than for relative CBF₃₀. For detecting abnormally increased oxygen extraction fraction, the accuracy did not differ among each relative CBF. These findings suggested that CBF measurement at 5 min after ACZ administration is the optimal timing for detection of preexisting cerebral hemodynamics and metabolism in bilateral major cerebral artery steno-occlusive diseases.

Keywords: Atherosclerotic steno-occlusive disease; acetazolamide; cerebral blood flow; positron emission tomography; steal phenomenon.

Figure 1

Chronological changes in relative cerebral blood flow (CBF) after acetazolamide (ACZ) administration in each region of interest (ROI) subgroup with normal cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO₂), abnormally increased CBV, and abnormally decreased CMRO₂ in patients. * and ** denote P<0.05 and P<0.01, respectively.

Figure 2

Comparisons of relative cerebral blood flow (CBF) at 5 (CBF₅), 15 (CBF₁₅), and 30 (CBF₃₀) min after acetazolamide (ACZ) administration among each region of interest (ROI) subgroup with normal cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO₂), abnormally increased CBV, and abnormally decreased CMRO₂ in patients. Closed and open circles denote ROIs with and without abnormally increased oxygen extraction fraction (OEF), respectively. * and ** denote P<0.05 and P<0.01, respectively.

Figure 3

A 68-year-old man with transient ischemic attacks of right motor weakness due to left middle cerebral artery (MCA) occlusion and asymptomatic right MCA occlusion. In the symptomatic left MCA territory, baseline cerebral blood flow (CBF) was reduced, cerebral blood volume (CBV) and oxygen extraction fraction (OEF) were increased, and cerebral metabolic rate of oxygen (CMRO₂) was normal. In that territory, CBF was reduced at 5 min after ACZ administration when compared with baseline. Thereafter, CBF continued to increase until 30 min after acetazolamide (ACZ) administration. By contrast, in the asymptomatic right MCA territory, CBF continued to increase until 15 min after ACZ administration, and then decreased 15 min later.

Figure 4

A 65-year-old man with minor stroke of left motor weakness due to right middle cerebral artery (MCA) occlusion and asymptomatic left internal carotid artery stenosis. In the symptomatic right MCA territory, baseline cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO₂) were reduced and cerebral blood volume (CBV) and oxygen extraction fraction (OEF) were normal. In that territory, CBF continued to increase gradually until 30 min after acetazolamide (ACZ) administration. By contrast, in the asymptomatic left MCA territory, CBF was greatly increased at 5 min after ACZ administration and then slightly decreased 25 min later.