A simple approach for three‐dimensional mapping of baseline cerebrospinal fluid volume fraction

Abstract

A simple method of measuring baseline cerebrospinal fluid volume fraction (V CSF ) in three-dimensional is proposed that used the characteristic of cerebrospinal fluid with very long T 2 . It is based on the fitting of monoexponential decay of only cerebrospinal fluid signal, using a nonselective T 2 preparation scheme. Three-dimensional gradient-and spin-echo acquisition also improves signal-to-noise ratio efficiency and brain coverage. Both V CSF and T 2,CSF are fitted voxel by voxel and analyzed in different cortical areas across subjects. V CSF is largely regionally dependent (occipital: 8.9 6 1.7%, temporal: 11.4 6 2.4%, and frontal: 21.4 6 6.9%). Measured T 2,CSF was 1573 6 146 msec within cortical lobes as compared with 2062 6 37 msec from ventricle regions. Different parameter set were compared, and the robustness of the new method is demonstrated. Conversely, when comparing with the proposed approach, large overestimation of segmentation based method using T 1 -weighted images is found, and the underlying causes are suggested. Magn Reson Med 65:385-391, 2011. V C 2010 Wiley-Liss, Inc.Key words: CSF volume fraction; T 2 prep; GRASE Long considered as just a partial volume confounder in functional MRI, cerebrospinal fluid (CSF) volume fraction (V CSF ) is known to have large variations between different regions of a subject, especially for cortical gray matter and periventricular areas. As people age, CSF volume starts to increase, whereas brain volume steadily declines (1,2). Recently, a more active role in functional MRI contrast mechanism is being investigated for CSF: namely, redistribution in response to local blood volume changes during activation (3-6). As a consequence, mapping of V CSF at baseline will benefit from more quantitative interpretation of functional MRI results. Similarly, the knowledge of V CSF in each voxel is also important for determination of brain metabolite concentrations in proton MR spectroscopic imaging (7-11).One group of MRI methods to determine tissue composition is based on multicompartment T 2 decay fitting (7,12). This type of techniques need very high signal-tonoise ratio, which requires long time for both acquisition and analysis. A newly proposed promising method (13) acquired T 2 0 decay curves that were fitted with a sophisticated model for oxygen extraction fraction and other parameters including deoxygenated blood volume and CSF volume fraction. This method was recently employed for V CSF measurement (14). Another group of methods use segmentation of high-resolution threedimensional (3D) T 1 -weighted (8,15) or T 2 -weighted (9,16) images. Extracortical CSF (subarachnoid spaces) could not be distinguished from the skull in T 1 -weighted anatomical images because both appear dark (10). Even with high resolution, voxels could still contain CSF partial volume but are segmented as tissue and thus bring in errors for mapping V CSF .Jin and Kim (6) have recently measured both baseline and functional change of V CSF on an animal scanner with a surface receiving coil mo...

Blood oxygenation level‐dependent (BOLD)‐based techniques for the quantification of brain hemodynamic and metabolic properties – theoretical models and experimental approaches

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Point spread functions of the T2 decay in k-space trajectories with long echo train

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Velocity‐selective magnetization‐prepared non‐contrast‐enhanced cerebral MR angiography at 3 Tesla: Improved immunity to B0/B1 inhomogeneity

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