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Lechner-Greite S.M.,General Electric | Mathieu J.-B.,General Electric | Amm B.C.,Magnetic Resonance Imaging Laboratory | Amm B.C.,General Electric
IEEE Transactions on Applied Superconductivity | Year: 2012

Gradient coils generate a magnetic field with a linear spatial variation that superimposes over the main magnetic field of a magnetic resonance imaging (MRI) system; such superimposition of the magnetic fields enables the encoding of the spatial position in MRI. A rapid change in the gradient field induces eddy currents in the conducting structures of an MRI system, resulting in the production of image artifacts. An objective of the gradient coil design phase is to predict both the coil's performance with respect to eddy currents and the image quality (IQ) before the coil is manufactured. In this paper, an integrated simulation environment is presented that combines the gradient coil design with an image formation simulation to predict the IQ. Here, an unshielded, uni-planar gradient set was simulated. Further, a study was conducted to determine the effect of frequency on the eddy currents induced in the conducting structures of the main magnet coil while exciting the uni-planar gradient set. The knowledge acquired from this study was applied to the IQ simulation, and a time-dependent simulation of a gradient echo pulse sequence was performed. The IQ of the uni-planar gradient set was predicted, and the input and reference images as well the images distorted by the eddy currents are shown. © 2012 IEEE. Source

Wang H.,Hospital for Special Surgery | Wang H.,Laboratory for Soft Tissue Research | Koff M.F.,Magnetic Resonance Imaging Laboratory | Potter H.G.,Magnetic Resonance Imaging Laboratory | And 4 more authors.
Journal of Biomechanics | Year: 2015

It has been suggested that the extent and location of cartilage deformation within a joint under compressive loading may be predictive of predisposition to further degeneration. To explore this relationship in detail requires the quantification of cartilage deformation under controlled loads on a per-patient basis in a longitudinal manner. Our objectives were (1) to design a device capable of applying controllable axial loads while ensuring repeatable within-patient tibiofemoral positioning during magnetic resonance imaging (MRI) scans and (2) to determine the duration for which load should be maintained prior to the image acquisition, for a reproducible measurement of cartilage deformation, within the restraints of a clinical setting. A displacement control loading device was manufactured from MRI-compatible materials and tested on four volunteers for the following five scans: an unloaded scan, two repeat immediate scans which were started immediately after the application of 50% body weight, and two repeat delayed scans started 12. min after load application. Outcome measures included within-patient changes in tibiofemoral position and cartilage deformation between repeat loaded scans. The differences in tibiofemoral position between repeat loaded scans were <1. mm in translation and <2° in rotation. Cartilage deformations were more consistent in the delayed scans compared to the immediate scans. We conclude that our loading device can ensure repeatable tibiofemoral positioning to allow for longitudinal studies, and the delayed scan may enable us to obtain more reproducible measurements of cartilage deformation in a clinical setting. © 2015 Elsevier Ltd. Source

Musialek P.,Jagiellonian University | Mazurek A.,Jagiellonian University | Jarocha D.,Jagiellonian University | Tekieli L.,John Paul II Hospital | And 13 more authors.
Postepy w Kardiologii Interwencyjnej | Year: 2015

Introduction: In large-animal acute myocardial infarction (AMI) models, Wharton's jelly (umbilical cord matrix) mesenchymal stem cells (WJMSCs) effectively promote angiogenesis and drive functional myocardial regeneration. Human data are lacking. Aim: To evaluate the feasibility and safety of a novel myocardial regeneration strategy using human WJMSCs as a unique, allogenic but immuno-privileged, off-the-shelf cellular therapeutic agent. Material and methods: The inclusion criterion was first, large (LVEF ≤ 45%, CK-MB > 100 U/l) AMI with successful infarct-related artery primary percutaneous coronary intervention reperfusion (TIMI ≥ 2). Ten consecutive patients (age 32-65 years, peak hs-troponin T 17.3 ±9.1 ng/ml and peak CK-MB 533 ±89 U/l, sustained echo LVEF reduction to 37.6 ±2.6%, cMRI LVEF 40.3 ±2.7% and infarct size 20.1 ±2.8%) were enrolled. Results: 30 × 106 WJMSCs were administered (LAD/Cx/RCA in 6/3/1) per protocol at ≈ 5-7 days using a cell delivery-dedicated, coronary-non-occlusive method. No clinical symptoms or ECG signs of myocardial ischemia occurred. There was no epicardial flow or myocardial perfusion impairment (TIMI-3 in all; cTFC 45 ±8 vs. 44 ±9, p = 0.51), and no patient showed hs-troponin T elevation (0.92 ±0.29 ≤ 24 h before vs. 0.89 ±0.28 ≤ 24 h after; decrease, p = 0.04). One subject experienced, 2 days after cell transfer, a transient temperature rise (38.9°C); this was reactive to paracetamol with no sequel. No other adverse events and no significant arrhythmias (ECG Holter) occurred. Up to 12 months there was one new, non-index territory lethal AMI but no adverse events that might be attributable to WJMSC treatment. Conclusions: This study demonstrated the feasibility and procedural safety of WJMSC use as off-the-shelf cellular therapy in human AMI and suggested further clinical safety of WJMSC cardiac transfer, providing a basis for randomized placebo-controlled endpoint-powered evaluation. Source

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