Abraham Rijbroek

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

PurposeWe assessed test–retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2), and oxygen extraction fraction (OEF) measurements derived from dynamic 15O positron emission tomography (PET) scans.ProceduresIn seven healthy volunteers, complete test–retest 15O PET studies were obtained; test–retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO2 in arterial flow territories were calculated.ResultsWhole-brain test–retest coefficients of variation for CBF, CBV, CMRO2, 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, CMRO2, and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively.ConclusionsThe test–retest variability of CMRO2 measurements derived from dynamic 15O PET scans is comparable to within-session test–retest variability derived from steady-state 15O PET scans. Excellent regional test–retest variability was observed for CBF, CMRO2, and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF.

Asymptomatic carotid artery stenosis: Past, present and future : How to improve patient selection?

Background: The role of carotid endarterectomy (CEA) for asymptomatic carotid artery stenosis (aCAS) remains a matter of debate. It seems that not only the degree of stenosis, but also other factors have to be taken in account to improve patient selection and increase the benefit of CEA for aCAS. Methods and Results: The literature pertaining aCAS was reviewed in order to describe the natural history, risk of stroke and benefit of CEA for patients with aCAS in regard to several factors. Conclusion: The benefit of CEA for aCAS is low. Current factors influencing the indication for CEA are severity of stenosis, age, contralateral disease, stenosis progression to >80%, gender, concomitant operations and life expectancy. To improve patient selection investigations will concentrate on plaque characteristics and instability and cerebral hemodynamics and metabolism.

Comparison of transcranial Doppler ultrasonography and positron emission tomography using a three-dimensional template of the middle cerebral artery

Abstract Objective: Transcranial Doppler (TCD) measures blood flow velocities (BFV) and is an indirect method of assessing cerebral blood flow (CBF). Positron emission tomography (PET) is a direct method to measure CBF. This study evaluates the correlations between TCD and PET findings Methods: Nine patients with a symptomatic carotid artery stenosis, who underwent CEA, were studied pre- and post-operatively on the ipsi- and contralateral sides. Measurements of the BFV, CO2 reactivity, CBF, cerebral blood volume (CBV) and mean vascular transit time (MVTT) were performed using a three-dimensional volume of interest (VOI) for the middle cerebral artery (MCA). Results: CBF in the MCA region, as measured with PET, shows a good correlation with BFV, as measured with TCD, with similar pattern for total, gray and white matter MCA territory (Pearsons correlation coefficients: 0.751, 0.748 and 0.748, respectively). This correlation was found in the pre-operative as well as the post-operative state. No association could be demonstrated between CO2 reactivity and CBV or (Pearsons correlation coefficients: 0.051 and 0.166, respectively). Conclusion: With PET, it is possible to create three-dimensional VOI of arterial territories. CBF measured in these VOI seems to correlate with BFV before and after CEA on ipsi- and contralateral sides, while CBV shows no association with pre-operative CO2 reactivity.

Hemodynamic changes in ipsi- and contralateral cerebral arterial territories after carotid endarterectomy using positron emission tomography

BACKGROUND The purpose of this study was to characterize ipsi- and contralateral cerebral hemodynamics before and after CEA. METHODS Cerebral blood flow, CBV, and MVTT were measured in 10 patients before and after CEA using PET. Absolute and relative values of these parameters were calculated bilaterally for the entire arterial territories and hemispheres. RESULTS For all territories in both hemispheres, the mean absolute postoperative CBF was significantly increased compared with preoperative CBF (P < .05). Only in MCA was this increase higher in the ipsilateral than in the contralateral hemisphere (P = .02). Cerebral blood volume was unaffected, whereas MVTT decreased in ipsilateral MCA (P = .05). CONCLUSIONS The present findings suggest that, on the first day after CEA, absolute CBF is increased in all arterial territories on both ipsi- and contralateral sides, but that there are only minor changes in the relative distribution, whereas the CBV was unaffected.

Peroperative Neuromonitoring during Carotid Endarterectomy in Relation to Preoperative Positron Emission Tomography Findings

OBJECTIVES To compare stump pressure (SP), transcranial Doppler (TCD), electroencephalography (EEG) and selective shunting during carotid endarterectomy (CEA) with preoperative positron emission tomography (PET) parameters. MATERIALS AND METHODS Preoperative PET measurements and peroperative neuromonitoring were performed in ten patients undergoing CEA for symptomatic carotid artery disease. PET parameters measured were cerebral blood flow (CBF), oxygen extraction fraction (OEF), cerebral oxygen metabolism (CMRO(2)), cerebral blood volume (CBV), mean vascular transit time (MVTT) and cerebral perfusion pressure (CPP). Results of these measurements in ipsilateral medial cerebral artery (MCA), ipsilateral hemisphere and total cerebrum were compared with absolute mean SP, mean SP<40mmHg, TCD, EEG changes and selective shunting. RESULTS None of the PET parameters showed any significant correlations with peroperative neuromonitoring findings. There were only trends for correlations of CBF and MVTT with TCD changes and of CPP and CMRO(2) with selective shunting. CONCLUSIONS Preoperative PET examinations are not useful for predicting the need for shunting during CEA.

Aortic arch thrombus caused by nitrous oxide abuse

Nitrous oxide is a recreational drug gaining in popularity for its deemed innocence. However, side effects have recently been reported. In this case, a patient suffered major aortic arch thrombus resulting in arterial occlusion of his arm and temporary cerebral infarction and later deep venous thrombosis and pulmonary embolism. No common causes for thrombus in this high-flow vessel were identified. The authors state that the patients chronic nitrous oxide abuse might have led to this thrombus, although it has never been described previously. This hypothesis is supported with laboratory tests at several presentations.

Treatment of Abdominal Aortic Endograft Infolding

Aortic endograft infolding is considered a rare endograft related complication and is mostly reported after deployment in the thoracic aorta. We report a case of early abdominal endograft infolding with luminal obliteration and acute bilateral limb ischemia after endovascular treatment of a common iliac aneurysm. Even though completion Computed Tomography (CT) angiography, three days prior, revealed no apparent mismatch of the stent graft to the aortic wall. This report aims to describe an overview of the different treatment modalities and focuses on the endovascular techniques for inducing re-expansion of the infolded graft and allowing for improved sealing of the endograft.