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 functional magnetic resonance imaging (fMRI) recovery measure. Patients with first time, ischemic stroke were imaged at 2.5 ± 2.2 days poststroke with 1.5-T fMRI during a hand closure task alternating with rest (fundamental frequency = 0.025 Hz, scan duration = 172 s). Confirming a previous finding, we observed that the prediction of ΔFM by FM(ii) alone is good in patients with nonsevere initial hemiparesis but is not good in patients with severe initial hemiparesis (96% and 16% of the total sum of squares of ΔFM explained, respectively). In patients with severe initial hemiparesis, prediction of ΔFM by the combination of FM(ii) and the putative fMRI recovery measure nonsignificantly increased predictive explanation from 16% to 47% of the total sum of squares of ΔFM explained. The implications of this preliminary negative result are discussed.

The markedly increased degrees of freedom introduced by parallel RF transmission present both opportunities and challenges for SAR management. On the one hand they enable E field tailoring and SAR reduction while facilitating excitation profile control. On the other hand they increase the complexity of SAR behavior and the risk of inadvertently exacerbating SAR by improper design or playout of RF pulses. The substantial subject-dependency of SAR in high field MR can be a compounding factor. Building upon a linear system concept and a calibration scheme involving a finite number of in situ measurements, the present work establishes a clinically applicable method for characterizing global SAR behavior as well as channel-by-channel power transmission. The method offers a unique capability of predicting, for any excitation, the SAR and power consequences that are specific to the subject to be scanned and the MRI hardware. The method was validated in simulation and experimental studies, showing promise as the foundation to a prospective paradigm where power and SAR are not only monitored but, through prediction-guided optimization, proactively managed.

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 Ϯ 0.9 days while performing a simple motor task. We defined recovery as the change in Fugl-Meyer score from time of scan to approximately 3 months later (90 Ϯ 8 days). We performed three different tests to assess correlations between brain activation and change in Fugl-Meyer score: (1) multivariate (most sensitive to spatially diffuse activation); (2) voxel-wise Statistical Parametric Mapping (most sensitive to focal activation), and (3) primary motor cortex region-of-interest analysis (most sensitive to average activation within this region). All tests controlled for initial stroke severity and lesion volume, as well as other established clinical variables. Results: The multivariate test was significant [F (595, 4,934) ϭ 1.93; p Ͻ 0.001]. The Statistical Parametric Mapping test detected two small clusters of focal activity located in the ipsilesional postcentral gyrus and cingulate cortex ( p Ͻ 0.05, corrected). The region-of-interest test was not significant. Interpretation: There is a pattern of brain activation present in the first few days after stroke, of which the postcentral gyrus and cingulate cortex are a part, that correlates with subsequent motor recovery. This result suggests that there are recovery processes engaged early after stroke that could provide a target for intervention.Ann Neurol 2009;65:596 -602 There is unexplained variability in the extent to which patients recover after stroke, particularly from the reference point of the first few days after onset. Among studies that track motor impairment and recovery, only 30 to 50% of the variance of recovery is explained by the most commonly reported predictors: lesion volume and initial stroke severity.1,2 We hypothesized that functional imaging early after stroke could provide information over and above initial severity and lesion volume about the degree of subsequent recovery. Several prior functional imaging studies have reported altered brain activation patterns in patients at various stages of motor recovery after stroke.3-6 These studies describe brain activation related to concurrent recovered performance at the time of scanning that differs to varying degrees from what is seen in age-matched control subjects. In this study, we used functional imaging to ask a specific and unique question about motor recovery after stroke: Can functional imaging in the early period after stroke detect brain activation related to subsequent recovered performance? Should such activation be identified, then it could serve as a physiological target for intervention (eg, noninvasive brain stimulation) in this early time period.To investigate whether brain activation early after stroke can be correlated with subsequent recovery, we scanned patients approximately 48 hours after stroke using functional ma...

PVP-based phantoms are easy to prepare and nontoxic, and their semitransparency makes air bubbles easy to identify. The polymer can be used to create simulated material with a range of dielectric properties, negligible spectral side peaks, and long T relaxation time, which are favorable in many MR applications. Magn Reson Med 80:413-419, 2018. © 2017 International Society for Magnetic Resonance in Medicine.