The three-prong method: a novel assessment of residual stress in laser powder bed fusion

<p><b>Boxplots of quantitative parameters</b> included <b>a)</b> ratio of N-acetylaspartate and N-acetylaspartylglutamate (NAA) to creatine and phosphocreatine (Cr) both for chemical shift imaging (CSI) and single voxel (SV) measurements, <b>b)</b> ratio of choline containing compounds (Cho) to Cr both for CSI and SV, <b>c)</b> myelin water fraction (MWF), <b>d)</b> magnetization transfer ratio (MTR), <b>e)</b> quantitative susceptibility mapping (QSM), and <b>f)</b> R2*. Parameters were measured in frontal white matter (WM) and two parameters within the cortico-spinal tract (CST): at the level of the posterior limb of internal capsule (PLIC) and at the level of the centrum semiovale (CS), see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167274#pone.0167274.g001" target="_blank">Fig 1</a>.</p

3D MRSI voxel localization in SN region for rostral slice.

<p>3D MRSI voxel localization in SN region for rostral slice.</p

Averaged spectra from the rostral (A) and caudal (B) SN regions of PD patients (red) and controls (green).

<p>Beside significant differences in the signal intensities of the three main metabolites NAA, creatine, and choline between both groups, there are clear differences in the range from 2.1 to 2.9</p

Individual concentrations [arbitrary units] of the three main metabolites NAA, choline, and creatine in PD patients and age-matched controls.

<p>¹ Significance values from paired t-test between the rostral and caudal values within the group.</p><p>² Significance values from two-sample t-test between both groups.</p

Malperfusion of structurally intact brain areas in the patient groups with extra-thalamic lesions.

<p>(A) Overlay plots of the normalised TTP delay maps showing the common regions of mismatch between DWI/FLAIR and PWI abnormalities, i.e. of structurally intact but abnormally perfused tissue, for the groups of patients with extra-thalamic lesions showing as well as not showing pusher syndrome. The number of overlapping areas with abnormal perfusion is illustrated by different colours, coding increasing frequencies from dark blue (n = 1) to red (n = max.). (B) Overlay plot of the subtracted superimposed mismatch images of the pusher group minus the mismatch images of the group without pusher syndrome. The percentage of overlapping areas of structurally intact but abnormally perfused tissue in the pusher group after subtraction is illustrated by five different colours, coding increasing frequencies from dark red (difference = 1–20%) to white (difference = 81–100%). Each colour represents 20% increments. The different colours from dark blue (difference = −1% to −20%) to light blue (difference = −81% to −100%) indicate regions abnormally perfused more frequently in patients without pusher syndrome than in the pusher group. Regions where there is an identical percentage of abnormal perfusion in both groups ( = 0%) are not depicted in the figure. MNI z-coordinates of the transverse sections are given. IFG, inferior frontal cortex; PreCG, precentral gyrus; SLF, superior longitudinal fasciculum; MTG, middle temporal cortex; CB, callosal body; Wh.mat., white matter; IPL, inferior parietal lobule.</p

Malperfusion of structurally intact brain areas in the patient groups with thalamic lesions.

<p>Overlay plots of the patient groups with thalamic lesions showing vs. not showing pusher syndrome. Illustrated are the common regions of structurally intact but malperfused brain tissue, i.e. the mismatch between TTP abnormalities and DWI/FLAIR. The number of overlapping areas are illustrated by different colours coding increasing frequencies from dark blue (n = 1) to red (n = max). MNI z-coordinates of the transverse sections are given.</p

Structural lesions of all patient groups investigated.

<p>Overlay plots of the normalised structural lesions (based on normalized DWI or FLAIR images) for the groups of patient with and without pusher syndrome after (A) thalamic lesions and (B) extra-thalamic lesions. The number of overlapping areas is illustrated by different colours, coding increasing frequencies from dark blue (n = 1) to red (n = max). MNI z-coordinates of the transverse sections are given.</p

Measurement results in the three regions of interest: the frontal WM, the CST at the level of the centrum semiovale (CST-CS), and at the level of the posterior limb of the internal capsule (CST-PLIC).

<p>Measurement results in the three regions of interest: the frontal WM, the CST at the level of the centrum semiovale (CST-CS), and at the level of the posterior limb of the internal capsule (CST-PLIC).</p

MRI protocol for this study.

<p>T1-weighted MPRAGE image (T1, left) in two different axial planes of a 17y-old typically developing subject indicating the measurement ROIs guided by the cortico-spinal tract fibre s outlined in red: frontal WM (in blue), cortico-spinal tract at the level of the centrum semiovale (in green) and at the level of the posterior limb of the internal capsule (in yellow). Other image parameters included in the protocol were T2-weighted axial TSE (T2), mean diffusivity (MD), fractional anisotropy (FA), intracellular volume fraction (ICVF), orientation dispersion (ODI), Magnetization Transfer Ratio (MTR), Myelin Water Fraction (MWF), Chemical Shift Imaging (CSI)–MR Spectroscopy, and quantitative susceptibility mapping (QSM, the white matter fibers have been highlighted by rendering diamagnetic effects bright, and paramagnetic dark).</p

Illustration of different underlying fibre architecture in the three measurement regions as found by histology (e.g. [58–61]: Cortico-spinal tract (CST) fibres include those with larger axon diameter and thicker myelin sheaths, which show more parallel arrangements at the level of the posterior limb of internal capsule (PLIC) and more crossing fibres at the level of the centrum semiovale (CS).

<p>On the other hand, the frontal white matter (WM) region also contains crossing fibres, however, with thinner myelin sheaths and lesser axon diameter.</p