A Single-Scan, Rapid Whole-Brain Protocol for Quantitative Water Content Mapping With Neurobiological Implications

Abstract

Water concentration is tightly regulated in the healthy human brain and changes only slightly with age and gender in healthy subjects. Consequently, changes in water content are important for the characterization of disease. MRI can be used to measure changes in brain water content, but as these changes are usually in the low percentage range, highly accurate and precise methods are required for detection. The method proposed here is based on a long-TR (10 s) multiple-echo gradient-echo measurement with an acquisition time of 7:21 min. Using such a long TR ensures that there is no T 1 weighting, meaning that the image intensity at zero echo time is only proportional to the water content, the transmit field, and to the receive field. The receive and transmit corrections, which are increasingly large at higher field strengths and for highly segmented coil arrays, are multiplicative and can be approached heuristically using a bias field correction. The method was tested on 21 healthy volunteers at 3T field strength. Calibration using cerebral-spinal fluid values (∼100% water content) resulted in mean values and standard deviations of the water content distribution in white matter and gray matter of 69.1% (1.7%) and 83.7% (1.2%), respectively. Measured distributions were coil-independent, as seen by using either a 12-channel receiver coil or a 32-channel receiver coil. In a test-retest investigation using 12 scans on one volunteer, the variation in the mean value of water content for different tissue types was ∼0.3% and the mean voxel variability was ∼1%. Robustness against reduced SNR was assessed by comparing results for 5 additional volunteers at 1.5T and 3T. Furthermore, water content distribution in gray matter is investigated and regional contrast reported for the first time. Clinical applicability is illustrated with data from one stroke patient and one brain tumor patient. It is anticipated that this fast, stable, easyto-use, high-quality mapping method will facilitate routine quantitative MR imaging of water content.

Whole‐Brain Water Content Mapping Using Super‐Resolution Reconstruction with MRI Acquisition in 3 Orthogonal Orientations

“…• as in Ref., 10 becomes negligible for all tissues except CSF. The value of SF is more than 0.993 for T 1 < 2 s (the upper limit of T 1 in healthy brain tissue at 3 T 34 ).…”

“…Consequently, measuring brain water content is relevant to understanding numerous conditions, including ischemia, brain injuries, hypoxia, brain tumors, multiple sclerosis, and hepatic encephalopathy. [3][4][5][6] MRI-based methods offer a way to measure water content, [7][8][9][10][11][12][13][14][15][16][17][18] thus enabling the detection of changes in tissue integrity noninvasively and quantitatively.…”

“…Oros-Peusquens et al described a technique for water content mapping where additional corrections for T 1 weighting are no longer necessary, eliminating the need for additional scans. 10 This is achieved with a 2D interleaved multi-slice multi-echo gradient recalled echo (mGRE) acquisition with a long TR, reducing the acquisition time for water content mapping to within a clinically feasible time. The sequence is usually included in the manufacturer's software on clinical scanners, making this a fast and easy-to-access quantitative method for clinical applications.…”

A Minireview on Brain Models Simulating Geometrical, Physical, and Biochemical Properties of the Human Brain

“…The main chemical components of the brain, water, lipids ( O’Brien and Sampson, 1965 ; Dawson, 2015 ), other molecules such amino-acids and amides ( Daković et al, 2013 ), and elements such as iron, copper and zinc ( Grochowski et al, 2019 ), are well-known. The water content (g water/g tissue or %) ranges from 67 to 72 in WM and 80 to 87 in GM ( Alexander and Looney, 1938 ; Whittall et al, 1997 ; Tofts, 2004 ; Oros-Peusquens et al, 2019 ). The proton density (percentage; water = 100) ranges from 69 to 77 in WM and 78 to 86 in GM ( Tofts, 2004 ).…”

Matching Quantitative MRI Parameters with Histological Features of Treatment-Naïve IDH Wild-Type Glioma

“…Quantitative MRI values reflect physical tissue properties, thus indicating physiological and pathological changes of the brain microstructure [3]. T1 values increase both with the intracellular water content (e.g., in the case of cytotoxic edema) and the extracellular water content (e.g., in vasogenic edema and upon loss of solid mass, for example as a consequence of demyelination) [30]. T2 values depend likewise on tissue water environments and vary among different brain structures.…”