Evaluation of Cerebral Perfusion Reserve in Patients With Carotid-Artery Occlusion

In moyamoya disease (MMD), surgical revascularization may be complicated with postoperative hyperperfusion. We analyzed cerebral perfusion and metabolism using positron emission tomography (PET) or single-photon emission computed tomography (SPECT) before and after bypass surgery on 42 sides of 34 adult patients with MMD. In seven cases (16.7%) with symptomatic hyperperfusion, diagnosed by qualitative 123 I-iodoamphetamine (IMP) SPECT, a subsequent PET study during postoperative subacute stages revealed significantly increased cerebral blood flow (CBF) from 34.1 ± 8.2 to 74.3 ± 12.8 mL/100 g per minute (P < 0.01), a persistent increase in cerebral blood volume (CBV) from 5.77±1.67 to 7.01±1.44 mL/100 g and a significant decrease in oxygen extraction fraction (OEF) from 0.61 ± 0.09 to 0.40 ± 0.08 (P < 0.01). Mean absolute CBF values during symptomatic hyperperfusion were more than the normal control + 2 standard deviations, the predefined criteria of PET. Interestingly, two patients with markedly increased cerebral metabolic rate of oxygen (CMRO 2 ) at hyperperfusion were complicated with postoperative seizure. Among preoperative PET parameters, increased OEF was the only significant risk factor for symptomatic hyperperfusion (P < 0.05). This study revealed that symptomatic hyperperfusion in MMD is characterized by temporary increases in CBF > 100% over preoperative values caused by prolonged recovery of increased CBV.

Section: Risk Of Symptomatic Hyperperfusionmentioning

confidence: 99%

Cerebral Blood Flow and Metabolism of Hyperperfusion after Cerebral Revascularization in Patients with Moyamoya Disease

Kaku

Iihara

Nakajima

et al. 2012

“…Measurement of CBV in conjunction with CBF and CMR02 has been shown to be of value in the in vivo assessment of cerebral circulation Gibbs et al, 1984;Powers et aI., 1984Powers et aI., , 1985. In particular, CBV data provide insights into the de gree of the autoregulatory response in patients with impaired cerebral perfusion pressure secondary to extraparenchymal cerebral vascular disorders .…”

Section: Fig 3 Topmentioning

confidence: 99%

Cerebral Blood Volume Measured with Inhaled C¹⁵O and Positron Emission Tomography

Martin

Powers

Raichle

1987

152

Summary: Local cerebral blood volume (CBV) has been measured previously with inhaled llCO and positron emission tomography (PET). The model used assumes that equilibrium in tracer concentration has occurred be tween arterial and systemic venous blood before the PET measurement is made. To verify that this model may be used with the much shorter half-lived CISO, we have si multaneously measured arterial and venous blood radio activity following CISO inhalation. Equilibrium occurred 95 ± 39 s after inhalation (n = 7). If the PET measure-The in vivo measurement of regional cerebral blood volume (rCBV) with positron emission to mography (PET) is useful for two reasons. First, assessment of rCBV in conjunction with regional CBP (rCBF) is important to fully assess cerebral hemodynamics . Second, an independent rCBV measurement must be performed to correct for intravascular ISO ac tivity when the regional CMROz (rCMR02) is mea sured with PET (Lammertsma et ai., 1983; Mintun et ai., 1984).Estimation of rCBV requires the administration of a labeled tracer compound that remains limited to the intravascular space of the brain during the PET study. The first tomographic measurement of rCBV reported fulfilled this requirement with 99mTc-labeled red blood cells (Kuhl et ai., 1975). An alternative approach is to use radiolabeled carbon Abbreviations used: FW HM, full width at half-maximum; PET, positron emission tomography; rCBF, regional CBF; rCBV , regional cerebral blood volume; rCMR02, regional CMR02· 421 ment is commenced prior to arteriovenous equilibrium, significant errors occur in calculated CBY. These data in dicate that CISO may be used as a tracer for CBV mea surement provided that emission data collection com mences at � 120 s after inhalation. Strict quality control measures must be maintained to minimize the contamina tion of administered CISO with ISO-labeled CO2, Key Words: Cerebral blood volume-IsO-labeled carbon monoxide-Positron emission tomography.monoxide, which, when inhaled in tracer quan tities, becomes tightly bound to hemoglobin in vivo forming carboxyhemoglobin, hence selectively la beling the red cell mass and fulfilling this require ment. In the past we have performed this measure ment by having the subject inhale "C-Iabeled carbon monoxide (t1/2 = 20.3 min) as first described by Grubb et ai. (1978). However, in patients under going three separate physiologic measurements (i.e., rCMR02, rCBF, and rCBV) , each requiring the administration of a different labeled compound, we felt it desirable to investigate the use of ISO-la beled carbon monoxide (t'l2 = 2.07 min) for three very practical reasons. First, the use of ISO rather than "c reduces the radiation dose to the patient (Kearfott, 1982). Second, our measurements could be completed more rapidly and accurately because prolonged, residual, in vivo background activity from ISO-labeled carbon monoxide is almost non existent, whereas it is appreciable after the admin istration of "C-Iabeled carbon monoxide. Finally, our technique for the measurement...

“…Thus, unlike CBF, the MTT (1) is almost uniformly distributed across the gray and white matter (Bristow et al, 2005;Ito et al, 2003;Sette et al, 1989) and (2) monotonously increases in proportion to cerebral perfusion pressure decreases (Gibbs et al, 1984;Schumann et al, 1998;Sette et al, 1989). As a result, it quickly returns to normal or even abnormally short values with reperfusion (Kidwell et al, 2001), presumably even in the above situation of partially reperfused core.…”

Section: Introductionmentioning

confidence: 99%

The Vascular Mean Transit Time: A Surrogate for the Penumbra Flow Threshold?

Carrera

Jones

Iglesias

et al. 2010

Depicting the salvageable tissue is increasingly used in the clinical setting following stroke. As absolute cerebral blood flow (CBF) is difficult to measure using perfusion magnetic resonance or computed tomography and has limitations as a penumbral marker, time-based variables, particularly the mean transit time (MTT), are routinely used as surrogates. However, a direct validation of MTT as a predictor of the penumbra threshold using gold-standard positron emission tomography (PET) is lacking. Using 15 O-PET data sets obtained from two independent acute stroke samples (N = 7 and N = 30, respectively), we derived areas under the curve (AUCs), optimal thresholds (OTs), and 90%-specificity thresholds (90%-Ts) from receiver operating characteristic curves for absolute MTT, MTT delay, and MTT ratio to predict three penumbra thresholds ('classic': CBF < 20 mL/100 g per min; 'normalized': CBF ratio < 0.5; and 'stringent': both CBF < 20 mL/100 g per min and oxygen extraction fraction > 0.55). In sample 1, AUCs ranged from 0.79 to 0.92, indicating good validity; OTs ranged from 7.8 to 8.3 seconds, 2.8 to 4.7 seconds, and 151% to 267% for absolute MTT, MTT delay, and MTT ratio, respectively, while as expected, 90%-Ts were longer. There was no significant difference between sample 1 and sample 2 for any of the above measurements, save for a single MTT parameter with a single penumbra threshold. These consistent findings from gold-standard PET obtained in two independent cohorts document that MTT is a very good surrogate to CBF for depicting the penumbra threshold.