Prospective motion correction methods utilizing an optical system, DW-PACE or a free induction decay (FID) navigator, have recently been applied to correct for motion in DTI. These methods have some limitations and drawbacks. This paper describes a novel technique using a 3D-EPI navigator, of which the contrast is independent of the b-value, to perform prospective motion correction in diffusion weighted images, without having to reacquire volumes during which motion occurred, unless motion exceeded some pre-set thresholds. Water phantom and human brain data were acquired using the standard and navigated diffusion sequences, and the mean and whole brain histogram (WBH) of the fractional anisotropy (FA) and mean diffusivity (MD) were analysed. Our results show that adding the navigator does not influence the diffusion sequence. With head motion, the WBH-FA shows a shift toward lower anisotropy with a significant decrease in both the mean FA and the FA histogram peak location (p<0.01), while the WBH-MD shows a shift toward higher diffusivity with a significant increase in the mean MD (p<0.01), even after retrospective motion correction. These changes in the mean and the shape of the histograms are recovered substantially in the prospective motion corrected data acquired using the navigated sequence.

Prenatal alcohol exposure is known to have severe, long-term consequences for brain and behavioral development already detectable in infancy and childhood. Resulting features of fetal alcohol spectrum disorders (FASD) include cognitive and behavioral effects, as well as facial anomalies and growth deficits. Diffusion tensor imaging (DTI) and tractography were used to analyze white matter development in 11 newborns (age since conception <45 weeks) whose mothers were recruited during pregnancy. Comparisons were made with 9 age-matched controls born to abstainers or light drinkers from the same Cape Coloured (mixed ancestry) community near Cape Town, South Africa. DTI parameters, T1 relaxation time, proton density and volumes were used to quantify and investigate group differences in white matter (WM) in the newborn brains. Probabilistic tractography was used to estimate and to delineate similar tract locations among the subjects for transcallosal pathways, cortico-spinal projection fibers and cortico-cortical association fibers. In each of these WM networks, the axial diffusivity AD was the parameter that showed the strongest association with maternal drinking. The strongest relations were observed in medial and inferior WM, regions in which the myelination process typically begins. In contrast to studies of older individuals with prenatal alcohol exposure, FA did not exhibit a consistent and significant relation with alcohol exposure. To our knowledge, this is the first DTI-tractography study of prenatally alcohol exposed newborns.

Spectral editing allows direct measurement of low-concentration metabolites, such as GABA, glutathione (GSH) and lactate (Lac), relevant for understanding brain (patho)physiology. The most widely used spectral editing technique is MEGA-PRESS, which has been diversely implemented across research sites and vendors, resulting in variations in the final resolved edited signal. In this paper, we describe an effort to develop a new universal MEGA-PRESS sequence with HERMES functionality for the major MR vendor platforms with standardized RF pulse shapes, durations, amplitudes and timings. New RF pulses were generated for the universal sequence. Phantom experiments were conducted on Philips, Siemens, GE and Canon 3 T MRI scanners using 32-channel head coils. In vivo experiments were performed on the same six subjects on Philips and Siemens scanners, and on two additional subjects, one on GE and one on Canon scanners. On each platform, edited MRS experiments were conducted with the vendor-native and universal MEGA-PRESS sequences for GABA (TE ¼ 68 ms) and Lac editing (TE ¼ 140 ms). Additionally, HERMES for GABA and GSH was performed using the universal sequence at TE ¼ 80 ms. The universal sequence improves inter-vendor similarity of GABA-edited and Lac-edited MEGA-PRESS spectra. The universal HERMES sequence yields both GABA-and GSH-edited spectra with negligible levels of crosstalk on all four platforms, and with strong agreement among vendors for both edited spectra. In vivo GABAþ/Cr, Lac/Cr and GSH/Cr ratios showed relatively low variation between scanners using the universal sequence. In conclusion, phantom and in vivo experiments demonstrate successful implementation of the universal sequence across all four major vendors, allowing editing of several metabolites across a range of TEs.

Background, purpose Fractional anisotropy in the frontal white matter, corpus callosum and internal capsule are abnormal in HIV+ adults. We describe the distribution, nature of white matter abnormalities in a cohort of children who started ART within the first year of life - and benefit of early treatment using DTI measures (fractional anisotropy, mean, axial and radial diffusion). Materials, methods DTI was performed on children in a neurodevelopmental sub study from the Children with HIV Early Antiretroviral (CHER) trial. Voxel-based group comparisons were performed to determine regions where fractional anisotropy and mean diffusion differed between HIV+ and uninfected children. Associations of DTI parameters with timing of ART initiation were examined. Results 39 HIV+ children (15 male, mean age 5.4 years) and 13 controls (5 male, mean age 5.7 years) were imaged. 2 Clusters with lower fractional anisotropy and 7 clusters with increased mean diffusion were identified in the HIV+ group with symmetrical distribution predominantly due to increased radial diffusion, suggestive of decreased myelination. Corticospinal tracts rather than the corpus callosum were predominantly involved. Children on early interrupted ART had lower fractional anisotropy compared to those receiving continuous treatment. Conclusion HIV+ children at 5 years have white matter abnormalities measured by fractional anisotropy, despite early ART, suggesting that early ART does not fully protect the white matter either from peripartum or in utero infection. In contrast to adults, the corticospinal tracts are predominantly involved rather than the corpus callosum, possibly due to early ART. Continuous early ART can limit white matter damage.