Purpose: To evaluate reproducibility of total cerebral blood flow (CBF) measurements with phase contrast magnetic resonance imaging (pcMRI). Materials and Methods:We repeated total CBF measurements in 15 healthy volunteers with and without cardiac triggering, and with and without repositioning. In eight volunteers measurements were performed at two different occasions. In addition, measurement of flow in a phantom was performed to validate MR measurements. Results:A difference of 40.4 ml/minute was found between CBF measurements performed with and without triggering (P Ͻ 0.05). For repeated triggered measurements, the coefficient of variation (CV) was 7.1%, and for nontriggered measurements 10.3%. For repeated measurements with repositioning, the CV was 7.1% with and 11.2% without triggering. Repeated measurements at different occasions showed a CV of 8.8%. Comparing measured with real flow in the phantom, the triggered differed 4.9% and the nontriggered 8.3%. Conclusion:The findings of this study demonstrate that pcMRI is a reliable method to measure total CBF in terms of both accuracy and reproducibility. METHODS THAT CURRENTLY ARE USED to assess total cerebral blood flow (CBF) can be divided into two groups based on the underlying concepts. On the one hand, total CBF can be estimated based on information generated by flow in the capillaries; on the other hand, total CBF can be assessed by measuring flow in the supplying vessels of the brain. Methods that are based on measurements of flow in the capillaries are single positron emission computed tomography (SPECT), xenon-computed tomography (Xe-CT), and perfusion magnetic resonance imaging (MRI). Blood flow in the supplying vessels of the brain can be measured using Doppler ultrasound and phase contrast MRI (pcMRI). Advantages of both Doppler ultrasound and pcMRI are no need for using ionizing irradiation or administration of intravenous agents, and the possibility of repeated measurements on a short-term basis. However, limitations of Doppler ultrasound are its operator dependency and overestimation of total blood flow in a given vessel due to the fact that only the highest flow in the center of the vessel is assessed (1). Using pcMRI, total CBF can be assessed by simultaneously measuring flow in the internal carotid arteries and the basilar artery. As compared to Doppler ultrasound, pcMRI has the advantage of being operator independent and involving straightforward flow quantification. In addition, pcMRI can be added to morphologic MRI sequences, offering the option to correlate flow to morphology based on data generated during one examination.In vitro and in vivo studies have demonstrated that pcMRI provides reliable flow data (2-4). However, data on short-term and long-term reproducibility are scarce. Furthermore, there is an ongoing discussion whether total CBF should be measured using a cardiac-triggered or a nontriggered pcMRI technique (4 -6). Finally, using pc-MRI, considerable differences in total CBF have been found between healthy volunteers (7,8). ...

No abstract

on behalf of the PROSPER Study GroupBackground and Purpose-Low wall shear stress (WSS) is an early marker in the development of vascular lesions. The present study aims to assess the relationship between diastolic and systolic WSS in the internal carotid artery and periventricular (PWML), deep white matter lesions, and cerebral infarcts (CI). Methods-Early, mid, and late diastolic and peak systolic WSS were derived from shear rate obtained by gradient echo phase contrast magnetic resonance sequences multiplied by individually modeled viscosity. PWML, deep white matter lesions, and CI were derived from proton density (PD), T2, and fluid attenuated inversion recovery (FLAIR) MRI in 329 participants (70 -82 years; PROSPER baseline

Blood flow in magnetic resonance images of small vessels can be assessed accurately, rapidly, and fully automatically using model-based postprocessing by fitting a first approximation of the velocity profile to the actual flow data.

Purpose:To verify whether wall shear stress (WSS) can be assessed in a reproducible manner using automatic modelbased segmentation of phase-contrast MR images by determination of flow volume and maximum flow velocity (Vmax) in cross-sections of these vessels. Materials and Methods:The approach is based on fitting a 3D paraboloid to the actual velocity profiles and on determining Vmax. WSS was measured in the internal carotid arteries of two groups of healthy young volunteers. The reproducibility of rescanning and repositioning was studied in the first group. In the second group a 1-week and a 1-month interval was investigated. Reproducibility was calculated by the intraclass correlation (ICC). Results:The flow volume, Vmax, and WSS averaged over the cardiac cycle were found to be 287.8 Ϯ 29.7 mL/min, 37.0 Ϯ 4.6 cm/s, and 1.13 Ϯ 0.16 Pa, respectively. The diastolic WSS varied between 1.00 Ϯ 0.21 Pa without averaging to 0.88 Ϯ 0.16 Pa with temporal and spatial averaging. Systolic WSS was 1.67 Ϯ 0.33 Pa without averaging and 1.67 Ϯ 0.25 Pa with averaging. ICC varied between 0.58 and 0.87 without averaging and between 0.75 and 0.90 with averaging for WSS. Conclusion:WSS in MR images of the internal carotid artery can be assessed semiautomatically with good to excellent reproducibility without inter-or intraobserver variability using model-based postprocessing.