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Background-Neuroimaging in mild cognitive impairment (MCI) and Alzheimer disease (AD) generally shows medial temporal lobe atrophy and diminished glucose metabolism and cerebral blood flow in the posterior cingulate gyrus. However, it is unclear whether these abnormalities also impact the cingulum fibers, which connect the medial temporal lobe and the posterior cingulate regions.

In functional magnetic resonance imaging (fMRI) head motion can corrupt the signal changes induced by brain activation. This paper describes a novel technique called Prospective Acquisition CorrEction (PACE) for reducing motion‐induced effects on magnetization history. Full three‐dimensional rigid body estimation of head movement is obtained by image‐based motion detection to a high level of accuracy. Adjustment of slice position and orientation, as well as regridding of residual volume to volume motion, is performed in real‐time during data acquisition. Phantom experiments demonstrate a high level of consistency (translation < 40μm; rotation < 0.05°) for detected motion parameters. In vivo experiments were carried out and they showed a significant decrease of variance between successively acquired datasets compared to retrospective correction algorithms. Magn Reson Med 44:457–465, 2000. © 2000 Wiley‐Liss, Inc.

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Automatic recognition of different tissue types in histological images is an essential part in the digital pathology toolbox. Texture analysis is commonly used to address this problem; mainly in the context of estimating the tumour/stroma ratio on histological samples. However, although histological images typically contain more than two tissue types, only few studies have addressed the multi-class problem. For colorectal cancer, one of the most prevalent tumour types, there are in fact no published results on multiclass texture separation. In this paper we present a new dataset of 5,000 histological images of human colorectal cancer including eight different types of tissue. We used this set to assess the classification performance of a wide range of texture descriptors and classifiers. As a result, we found an optimal classification strategy that markedly outperformed traditional methods, improving the state of the art for tumour-stroma separation from 96.9% to 98.6% accuracy and setting a new standard for multiclass tissue separation (87.4% accuracy for eight classes). We make our dataset of histological images publicly available under a Creative Commons license and encourage other researchers to use it as a benchmark for their studies.

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A density-adapted three-dimensional radial projection reconstruction pulse sequence is presented which provides a more efficient k-space sampling than conventional three-dimensional projection reconstruction sequences. The gradients of the density-adapted three-dimensional radial projection reconstruction pulse sequence are designed such that the averaged sampling density in each spherical shell of k-space is constant. Due to hardware restrictions, an inner sphere of k-space is sampled without density adaption. This approach benefits from both the straightforward handling of conventional three-dimensional projection reconstruction sequence trajectories and an enhanced signal-to-noise ratio (SNR) efficiency akin to the commonly used three-dimensional twisted projection imaging trajectories. Benefits for low SNR applications, when compared to conventional three-dimensional projection reconstruction sequences, are demonstrated with the example of sodium imaging. In simulations of the point-spread function, the SNR of small objects is increased by a factor 1.66 for the densityadapted three-dimensional radial projection reconstruction pulse sequence sequence. Using analytical and experimental phantoms, it is shown that the density-adapted three-dimensional radial projection reconstruction pulse sequence allows higher resolutions and is more robust in the presence of field inhomogeneities. High-quality in vivo images of the healthy human leg muscle and the healthy human brain are acquired. For equivalent scan times, the SNR is up to a factor of 1.8 higher and anatomic details are better resolved using density-adapted three-dimensional radial projection reconstruction pulse sequence. Key words: sodium magnetic resonance imaging; densityadapted sampling; radial imaging; projection reconstruction; sampling density; field inhomogeneities Sodium ( 23 Na) ions play an important role in cellular homeostasis and cell viability. In healthy tissue, the extracellular sodium concentration ([Na ϩ ] ex ϭ 145 mM) is about 10 times higher than the intracellular concentration ([Na ϩ ] in ϭ 10-15 mM) (1). Using sodium MRI, volume-and relaxation-weighted signal of these compartments can be measured. Thus, sodium MRI is a promising diagnostic tool since pathologic processes can alter this ion gradient.Many studies investigating the usefulness of sodium MRI in human pathologies have been performed recently. Brain neoplasia and sustained cell depolarization, a precursor of cell division, lead to an increase of the intracellular sodium concentration and to a rise in the average tissue sodium concentration (2). Furthermore, the application of sodium MRI has been shown to be valuable for muscular channelopathies (3,4), brain tumors (5), the human kidney (6), myocardial infarction (7), and cerebral ischemia (8,9) diagnostics.However, sodium MRI remains a challenging technique for several reasons. The sodium nucleus exhibits a fast biexponential transversal relaxation in the extreme narrowing limit, i.e., if the correlation time is much shorter...

To investigate the vascular contribution to the measured apparent diffusion coefficient and to validate the Intra Voxel Incoherent Motion theory, the signal as a function of the b-value was measured in the healthy pancreas with and without suppression of the vascular component and under varying echo times (TE 5 50, 70, and 100 msec). The perfusion fraction f and the diffusion coefficient D were extracted from the measured DWdata using the original Intra Voxel Incoherent Motion-equation and a modified version of this equation incorporating relaxation effects. First, the perfusion fraction f in the blood suppressed pancreatic tissue decreased significantly (P 5 0.03), whereas the diffusion coefficient D did not change with suppression (P 5 0.43). Second, the perfusion fraction f increased significantly with increasing echo time (P 5 0.0025), whereas the relaxation time compensated perfusion fraction f 0 showed no significant dependence on TE (P 5 0.31). These results verify a vascular contribution to the diffusion weighted imaging measurement at low b values and support the Intra Voxel Incoherent Motiontheory. Magn Reson Med 64:1580-1585,