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There is substantial interpatient variation in recovery from upper limb impairment after stroke in patients with severe initial impairment. Defining recovery as a change in the upper limb Fugl-Meyer score (ΔFM), we predicted ΔFM with its conditional expectation (i.e., posterior mean) given upper limb Fugl-Meyer initial impairment (FM(ii)) and a putative(More)
OBJECTIVE To determine whether functional magnetic resonance imaging activation obtained in the first few days after stroke correlates with subsequent motor recovery. METHODS Twenty-three patients with hemiparesis after first-time stroke were scanned at 2.0 +/- 0.9 days while performing a simple motor task. We defined recovery as the change in Fugl-Meyer(More)
Specific absorption rate management and excitation fidelity are key aspects of radiofrequency pulse design for parallel transmission at ultra-high magnetic field strength. The design of radiofrequency pulses for multiple channels is often based on the solution of regularized least-squares optimization problems for which a regularization term is typically(More)
Electromagnetic field simulations are increasingly used to assure RF safety of patients during MRI exams. In practice, however, tissue property distribution of the patient being imaged is not known, but may be represented with a pre-existing model. Repeatedly, agreement in transmit magnetic (B1+) field distributions between two geometries has been used to(More)
PURPOSE Strict regulations are imposed on the amount of radiofrequency (RF) energy that devices can emit to prevent excessive deposition of RF energy into the body. In this study, we investigated the application of MR temperature mapping and 10-g average specific absorption rate (SAR) computation for safety evaluation of RF-emitting devices. METHODS(More)
Radiofrequency shimming with multiple channel excitation has been proposed to increase the transverse magnetic field uniformity and reduce specific absorption rate at high magnetic field strengths (≥7 T) where high-frequency effects can make traditional single channel volume coils unsuitable for transmission. In the case of deep anatomic regions and(More)
The markedly increased degrees of freedom introduced by parallel radiofrequency transmission presents both opportunities and challenges for specific absorption rate (SAR) management. On one hand they enable E-field tailoring and SAR reduction while facilitating excitation profile control. On other hand they increase the complexity of SAR behavior and the(More)
In ultra-high-field magnetic resonance imaging, parallel radiofrequency (RF) transmission presents both opportunities and challenges for specific absorption rate management. On one hand, parallel transmission provides flexibility in tailoring electric fields in the body while facilitating magnetization profile control. On the other hand, it increases the(More)
Eric Zarahn, Leeor Alon, Sophia L. Ryan, Ronald M. Lazar, Magnus-Sebastian Vry, Cornelius Weiller, Randolph S. Marshall and John W. Krakauer The Neurological Institute, New York, NY 10032, USA, Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA, Department of Neurology, University of Freiburg and(More)
PURPOSE Develop a practical comprehensive package for proactive management of parallel radiofrequency (RF) transmission. METHODS With a constrained optimization framework and predictive models from a prescan based multichannel calibration, we presented a method supporting design and optimization of parallel RF excitation pulses that accurately obey the(More)