Comparison of oxygen-15 PET and transcranial Doppler CO2-reactivity measurements in identifying haemodynamic compromise in patients with symptomatic occlusion of the internal carotid artery

BACKGROUND: Transcranial Doppler (TCD) CO(2)-reactivity and oxygen-15 positron emission tomography (PET) have both been used to measure the cerebral haemodynamic state in patients who may have a compromised blood flow. Our purpose was to investigate whether PET and TCD identify the same patients with an impaired flow state of the brain in patients with internal carotid artery (ICA) occlusion. METHODS: Patients with recent transient ischaemic attack or minor ischaemic stroke associated with ICA occlusion underwent TCD with measurement of CO(2)-reactivity and oxygen-15 PET within a median time interval of 6 days. RESULTS: We included 24 patients (mean age 64 ± 10 years). Seventeen (71%) patients had impaired CO(2)-reactivity (≤20%), of whom six had absent reactivity (0%) or steal (<0%) in the hemisphere ipsilateral to the ICA occlusion. PET of the perfusion state of the hemisphere ipsilateral to the ICA occlusion demonstrated stage 1 haemodynamic compromise (decreased cerebral blood flow (CBF) or increased cerebral blood volume (CBV) without increased oxygen extraction fraction (OEF)) in 13 patients and stage 2 (increased OEF) in 2 patients. In 12 patients (50%), there was agreement between TCD and PET, indicating haemodynamic compromise in 10 and a normal flow state of the brain in 2 patients. There was no significant correlation between CO(2)-reactivity and CBF ipsilateral/contralateral hemispheric ratio (r = 0.168, p value = 0.432), OEF ratio (r = −0.242, p value = 0.255), or CBV/CBF ratio (r = −0.368, p value = 0.077). CONCLUSIONS: In patients with symptomatic ICA occlusion, identification of an impaired flow state of the brain by PET and TCD CO(2)-reactivity shows concordance in only half of the patients

Day-to-Day Test–Retest Variability of CBF, CMRO2, and OEF Measurements Using Dynamic 15O PET Studies

Contains fulltext : 169592.pdf (publisher's version ) (Open Access)PURPOSE: We assessed test-retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF) measurements derived from dynamic (15)O positron emission tomography (PET) scans. PROCEDURES: In seven healthy volunteers, complete test-retest (15)O PET studies were obtained; test-retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO(2) in arterial flow territories were calculated. RESULTS: Whole-brain test-retest coefficients of variation for CBF, CBV, CMRO(2), and OEF were 8.8%, 13.8%, 5.3%, and 9.3%, respectively. Test-retest variability of CBV left-to-right ratios was <7.4% across all territories. Corresponding values for CBF, CMRO(2), and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively. CONCLUSIONS: The test-retest variability of CMRO(2) measurements derived from dynamic (15)O PET scans is comparable to within-session test-retest variability derived from steady-state (15)O PET scans. Excellent regional test-retest variability was observed for CBF, CMRO(2), and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF

Transcranial Doppler Ultrasonography CO&lt;sub&gt;2&lt;/sub&gt; Reactivity Does Not Predict Recurrent Ischaemic Stroke in Patients with Symptomatic Carotid Artery Occlusion

&lt;b&gt;&lt;i&gt;Background:&lt;/i&gt;&lt;/b&gt; Patients with transient ischaemic attacks (TIAs) or minor disabling ischaemic stroke associated with an internal carotid artery (ICA) occlusion have a high risk of recurrent stroke in case of compromised cerebral blood flow. Recent studies showed that increased oxygen extraction fraction measured by positron emission tomography (PET) is still an independent predictor of subsequent stroke under current medical treatment, but PET facilities are not widely available. Transcranial Doppler (TCD) ultrasonography CO&lt;sub&gt;2&lt;/sub&gt; reactivity is a cheap and non-invasive alternative to measure haemodynamic compromise. The aim of our study was to investigate whether TCD CO&lt;sub&gt;2&lt;/sub&gt; reactivity is an independent predictor of recurrent ischaemic stroke in a large cohort of patients with symptomatic ICA occlusion in a time where rigorous control of vascular risk factors has been widely implemented in clinical practice. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; Between July 1995 and December 2009, we included consecutive patients with TIAs or minor disabling ischaemic stroke (modified Rankin Scale ≤3) associated with ICA occlusion who were referred to the University Medical Centre Utrecht, The Netherlands. All patients were treated with antiplatelet therapy and received rigorous control of vascular risk factors, including statins, treatment for diabetes and hypertension and lifestyle advices. CO&lt;sub&gt;2&lt;/sub&gt; reactivity was measured with TCD within 3 months after presentation. We determined the predictive value of TCD CO&lt;sub&gt;2&lt;/sub&gt; reactivity for recurrent ischaemic stroke using Cox proportional hazard analysis. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; We included 201 patients with a median follow-up time of 7.1 years. Mean CO&lt;sub&gt;2&lt;/sub&gt; reactivity was 15% (±20 standard deviation). The annual rate for ipsilateral ischaemic stroke was 2.2% [95% confidence interval (CI) 1.4-3.2] and for any recurrent stroke 3.2% (95% CI 2.3-4.4). We did not find a significant relationship between CO&lt;sub&gt;2&lt;/sub&gt; reactivity and the risk of ipsilateral [hazard ratio (HR) for every increase in percentage point 1.01, 95% CI 0.99-1.02] or any recurrent ischaemic stroke (HR 1.01, 95% CI 0.998-1.02). Multivariable analysis showed a significant relationship with history of stroke (HR 4.0, 95% CI 1.8-9.0) for ipsilateral recurrent stroke, and age (HR for increase per year 1.05, 95% CI 1.01-1.09) and a history of stroke (HR 3.4, 95% CI 1.7-6.6) for any recurrent stroke. &lt;b&gt;&lt;i&gt;Conclusions:&lt;/i&gt;&lt;/b&gt; In patients with TIAs or non-disabling stroke associated with occlusion of the carotid artery, the long-term annual risk of stroke is generally low with careful control of vascular risk factors. Impaired CO&lt;sub&gt;2&lt;/sub&gt; reactivity measured within 3 months after presentation does not identify the subgroup of patients at high risk of recurrent ischaemic stroke.</jats:p

Prognostic Value of A Qualitative Brain MRI Scoring System After Cardiac Arrest

BACKGROUND AND PURPOSETo develop a qualitative brain magnetic resonance imaging (MRI) scoring system for comatose cardiac arrest patients that can be used in clinical practice. METHODSConsecutive comatose postcardiac arrest patients were prospectively enrolled. Routine MR brain sequences were scored by two independent blinded experts. Predefined brain regions were qualitatively scored on the fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences according to the severity of the abnormality on a scale from 0 to 4. The mean score of the raters was used. Poor outcome was defined as death or vegetative state at 6 months. RESULTSSixty-eight patients with 88 brain MRI scans were included. Median time from the arrest to the initial MRI was 77 hours (IQR 58-144 hours). At 100% specificity, the cortex score performed best in predicting unfavorable outcome with a sensitivity of 55%-60% (95% CI 41-74) depending on time window selection. When comparing the cortex score with historically used predictors for poor outcome, MRI improved the sensitivity for poor outcome over conventional predictors by 27% at 100% specificity. CONCLUSIONSA qualitative MRI scoring system helps assess hypoxic-ischemic brain injury severity following cardiac arrest and may provide useful prognostic information in comatose cardiac arrest patient