The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a longitudinal multisite observational study of healthy elders, mild cognitive impairment (MCI), and Alzheimer's disease. Magnetic resonance imaging (MRI), (18F)-fluorodeoxyglucose positron emission tomography (FDG PET), urine serum, and cerebrospinal fluid (CSF) biomarkers, as well as clinical/psychometric assessments are acquiredat multiple time points. All data will be cross-linked and made available to the general scientific community. The purpose of this report is to describe the MRI methods employed in ADNI. The ADNI MRI core established specifications thatguided protocol development. A major effort was

The large spatial inhomogeneity in transmit B 1 field (B 1 + ) observable in human MR images at high static magnetic fields (B 0 ) severely impairs image quality. To overcome this effect in brain T 1 -weighted images, the MPRAGE sequence was modified to generate two different images at different inversion times, MP2RAGE. By combining the two images in a novel fashion, it was possible to create T 1 -weigthed images where the result image was free of proton density contrast, T 2 ⁎ contrast, reception bias field, and, to first order, transmit field inhomogeneity. MP2RAGE sequence parameters were optimized using Bloch equations to maximize contrast-to-noise ratio per unit of time between brain tissues and minimize the effect of B 1 + variations through space. Images of high anatomical quality and excellent brain tissue differentiation suitable for applications such as segmentation and voxel-based morphometry were obtained at 3 and 7 T. From such T 1 -weighted images, acquired within 12 min, high-resolution 3D T 1 maps were routinely calculated at 7 T with sub-millimeter voxel resolution (0.65-0.85 mm isotropic). T 1 maps were validated in phantom experiments. In humans, the T 1 values obtained at 7 T were 1.15 ± 0.06 s for white matter (WM) and 1.92 ± 0.16 s for grey matter (GM), in good agreement with literature values obtained at lower spatial resolution. At 3 T, where whole-brain acquisitions with 1 mm isotropic voxels were acquired in 8 min, the T 1 values obtained (0.81 ± 0.03 s for WM and 1.35 ± 0.05 for GM) were once again found to be in very good agreement with values in the literature. © 2009 Elsevier Inc. All rights reserved. IntroductionIn the past decade, the magnetization-prepared rapid gradient echo, MPRAGE (Mugler and Brookeman, 1990), sequence has become one of the most commonly used sequences to obtain T 1 -weighted anatomical images of the human brain, in particular at high magnetic field. MPRAGE images are routinely used as anatomical reference for fMRI or for brain tissue classification in voxel-based morphometry (Ashburner and Friston, 2000). However, at high static magnetic fields (≥ 3 T), the increased inhomogeneity of the transmit B 1 + and receive B 1 − fields creates intensity variations throughout the image (bias field). Bias fields not only render segmentation and quantitative analysis difficult but also severely affect image quality at ultra-high fields (≥7 T). The use of adiabatic pulses to perform the inversion in the MPRAGE is only partially able to mitigate the effects of inhomogeneous B 1 . A number of strategies have been proposed to minimize or to correct bias fields generated by the inhomogeneity of the B 1 fields. Most correction strategies aim at correcting the combined (transmit and receive) bias field via post-processing techniques. This can be done either by low-pass filtering (Cohen et al., 2000;Wald et al., 1995) or by fitting slowly varying functions such as Gaussians or low order polynomials (Styner et al., 2000). The result from these low pass filters or fits is then su...

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Recently, the spin-echo full-intensity acquired localized (SPE-CIAL) spectroscopy technique was proposed to unite the advantages of short TEs on the order of milliseconds (ms) with full sensitivity and applied to in vivo rat brain. In the present study, SPECIAL was adapted and optimized for use on a clinical platform at 3T and 7T by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and improved shimming using FASTMAP. High-quality single voxel spectra of human brain were acquired at TEs below or equal to 6 ms on a clinical 3T and 7T system for six volunteers. Narrow linewidths (6.6 ؎ 0.6 Hz at 3T and 12.1 ؎ 1.0 Hz at 7T for water) and the high signal-to-noise ratio ( Stimulated-echo acquisition mode (STEAM) (1) or pointresolved spectroscopy (PRESS) (2) are the major methods used for localized proton magnetic resonance spectroscopy (MRS). As STEAM suffers a two-fold signal loss compared to PRESS, but allows shorter echo times (TEs), it is highly desirable to combine the short TE achievable with STEAM with the full signal intensity provided by PRESS. In general, short echo times below 20 ms offer the benefits of reduced signal decay due to T 2 relaxation and J-evolution of coupled spin systems. This in turn allows a more precise quantification of metabolites including those with short T 2 relaxation times. In addition, signal contributions from macromolecules that generally exhibit short T 2 s can be analyzed in short TE spectra to provide insight into specific diseases (3). Short echo times are more easily achievable with STEAM because of the lower peak radiofrequency (RF) pulse power requirements for 90°com-pared to 180°pulses. This is especially important for studies in humans, where the available peak RF power is limited. The STEAM technique was extensively used in previous studies to acquire human brain spectra at field strengths of 1.5T, 3T, 4T, and 7T using TE ϭ 5 ms (4) and 6 ms (5), 6.8 ms (6), 4 ms (7), and 6 ms (8), respectively.On the other hand, it is advantageous to acquire the signal of the full magnetization using spin-echo (SE)-based methods, such as PRESS. For the aforementioned reasons, only few studies report results acquired at short TE. Reducing crusher gradients and using short RF pulses in one approach, or utilizing a dedicated transmit/receive head coil at 3T in pediatric patients in another approach, enabled PRESS acquisitions of in vivo human single-voxel spectroscopy (SVS) data at TE Ϸ 10 ms (9,10). Using the proton echo-planar spectroscopic imaging technique, a TE of 15 ms was reported in MR spectroscopic imaging (MRSI) at 3T and 4T (11).The advantages of short TEs on the order of milliseconds (ms) were recently combined with full signal intensity achieved with SE-based scans using the SE full intensity acquired localized (SPECIAL) spectroscopy technique and applied to in vivo rat brain (12). The sequence benefits from RF coils producing strong B 1 fields and combines interleaved water suppression (WS) and outer volume saturation...