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Abstract * Extracting meaning from speech requires the use of pragmatic, semantic, and syntactic information. A central question is: Does the processing of these different types of linguistic information have [...]

Purpose: To investigate whether, in the second trimester of pregnancy, placental T2 relaxation time (determined using magnetic resonance imaging (MRI)) is related to impedance to flow in the uterine arteries. Methods: In 40 singleton pregnancies at 24-29 weeks' gestation, uterine artery pulsatility index (PI) was measured by Doppler ultrasound and T2 relaxation time was measured by echo planar MRI at 1.5 T. The significance of the associations between T2 relaxation time, uterine artery PI and birth weight were examined. Results: In 25 pregnancies that delivered small for gestational age (SGA) neonates with birth weight below the 10th percentile, compared to those with appropriate for gestational age (AGA) birth weight, the T2 relaxation time was significantly decreased (88 ms vs. 149 ms, p < 0.0001) and uterine artery PI was increased (1.96 vs. 1.00, p < 0.0001). There were significant associations between placental T2 relaxation time and log10 uterine artery PI (r = -0.749, p < 0.0001), and between T2 relaxation and birth weight percentile (r = 0.693, p < 0.0001). Conclusion: The T2 relaxation time during the second trimester is shorter in pregnancies that subsequently deliver SGA neonates and the measurement is strongly correlated with impedance to flow in the uterine arteries. [ABSTRACT FROM AUTHOR]

Purpose: To develop a second-order and slice-specific linear shimming technique and investigate its efficiency in the mitigation of signal loss and distortions, and the increase of temporal signal-to-noise ratio (tSNR) within the spinal cord during functional Magnetic Resonance Imaging (fMRI) of the human cervical spinal cord., Methods: All scans were performed on a General Electric Discovery MR750 3 T scanner, using a head, neck and spine coil and a neurovascular array. To improve B 0 homogeneity, a field map was acquired, and second-order shims (SOS) were optimized over manually defined regions of interest (ROIs). Signal loss from dephasing by susceptibility-induced gradients was reduced by optimizing slice-specific x-, y- and z-shims to maximize signal within the spinal cord. Spectral-spatial excitation pulses were used in both the slice-specific linear shimming calibration scan and fMRI acquisitions. The shimming technique's efficiency was initially tested on eight healthy volunteers by comparing tSNR between images acquired with the manufacturer's standard linear shimming and with our SOS and xyz-shimming technique. Subsequently, using an increased spatial resolution as needed for fMRI of the spinal cord, tSNR measurements were performed on resting-state fMRI images from 14 healthy participants., Results: Spinal fMRI images acquired with only the standard linear shimming suffered from severe signal loss below the C5 vertebral level. The developed shimming technique compensated for this loss especially at levels C6 and C7, while tSNR was significantly higher at all vertebral levels with SOS and xyz-shimming than without it., Conclusion: A comprehensive shimming approach which includes the use of spectral-spatial excitation pulses along with both second-order and slice-specific linear shim optimization reduces regional signal loss and increases tSNR along the c-spine (C3-C7), improving the ability to record functional signals from the human spinal cord., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: To investigate (a) if placental perfusion in the second trimester of pregnancy, measured by two non-invasive magnetic resonance imaging (MRI) techniques, is related to impedance to flow in the uterine arteries, as assessed by Doppler ultrasound; and (b) if these measures are associated with future gestational outcome., Methods: In 37 singleton pregnancies at 24-29 weeks' gestation, uterine artery pulsatility index (PI) was measured by Doppler ultrasound and placental perfusion was measured by Arterial Spin Labelling (flow-sensitive alternating inversion recovery (FAIR)) and intravoxel incoherent motion (IVIM) echo-planar imaging at 1.5 T in basal, central and placental regions of interest. The values were compared between those delivering small for gestational age (SGA) and appropriate for gestational age (AGA) neonates., Results: In 23 pregnancies that resulted in delivery of SGA neonates, compared to the 14 with AGA neonates, the median basal FAIR measure was significantly lower (923.0 vs. 2359.0 arbitrary units; p = 0.003) as were IVIM measures of perfusing fraction (f) in basal, central and whole-placental regions (37.8 vs. 40.7%; p = 0.046; 24.3 vs. 35.1%; p = 0.014 and 27.9% vs. 36.2%; p = 0.001, respectively). In the SGA group, the median uterine artery PI was increased (1.96 vs. 1.03; p = 0.001). There were significant associations between uterine artery PI and placental perfusion assessed by both FAIR and IVIM., Conclusion: Pregnancies that result in SGA neonates exhibited reduced placental perfusion as assessed by MRI during the second trimester. This measurement was found to be strongly associated with impedance to flow in the uterine arteries. We suggest that FAIR or IVIM MRI examinations may be used to directly and non-invasively determine placental perfusion, and that the measured values are strong indicators of future gestational outcome., (Copyright © 2013. Published by Elsevier Ltd.)

Quantitative, multislice dynamic susceptibility contrast-enhanced MRI perfusion measurements were used to determine the patterns of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and normalized first moment of the tissue deltaR2-time curve (N) in 11 subjects with carotid artery occlusion or stenosis. MTT correlated with degree of carotid stenosis, whereas a range of alterations in CBF and CBV were found presumably reflecting variables degrees of collateral flow. There was no significant correlation between MRI and SPET flow perfusion measurements, with increasing disparity between the two techniques at higher inter-hemispheric flow ratios. The effect of obtaining the arterial input function (AIF) from the middle cerebral artery (MCA) ipsilateral or contralateral to the stenosis was determined. Despite the use of an AIF from the MCA, which is distal to the circle of Willis, and hence the major sources of collateral supply, there was still some extra dispersion of the contrast agent bolus due to differences in arrival time.