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

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