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Methods for monitoring motion using multi-transmit electrical coupling in imaging of the subject
Described herein are methods for monitoring and / or extract ing subject motion from multi - channel electrical coupling in imaging of the subject , in particular in magnetic resonance ( MR ) imaging of the subject .
Methods for extracting subject motion from multi-transmit electrical coupling in imaging of the subject
Described herein are methods and systems for extracting or determining subject motion from multi-channel electrical coupling in imaging of the subject, in particular in magnetic resonance (MR) imaging of the subject. The motion can be of a region of interest of the subject (such as an organ or specific tissue). Changes in the position of the subject and the subject's organs can be monitored by measuring how external coils, such as RF coils, couple to the subject and to one another and change the scattering of the RF coils, for example scattering of RF pulses transmitted by the coils. Changes in position influence this coupling and the scattering and can be detrimental to the quality of the imaging. The present methods and systems address and overcome this problem.
Magnetic resonance imaging
The present invention relates generally to medical imaging and, more particularly, relates to systems and methods for obtaining magnetic resonance (MR) images of tissues and organs (particularly of the heart) or parts thereof.
Quality of 186 child brain spectra using motion and b0 shim navigated single voxel spectroscopy
© 2013 Wiley Periodicals, Inc. Purpose: To evaluate B0 shim and motion navigated single voxel spectroscopy in children. Assess the repeatability of metabolite concentrations in three regions: medial frontal grey matter, peritrigonal white matter, and basal ganglia. Determine the extent of intra-And interacquisition movement in this population. Methods: Linewidth and signal to noise ratio were calculated to assess spectral quality of 186 spectra at 3 Tesla. Repeatability was assessed on 31 repeat scans. Navigator images were used to assess localization errors, while navigator motion and shim logs were used to demonstrate the efficacy of correction needed during the scans. Results: Average linewidths 6 standard deviations of Nacetyl aspartate are 3.8 ± 0.6 Hz, 4.4 ± 0.5 Hz, and 4.7 ± 0.8 Hz in each region, respectively. Scan-to-scan measurement variance in metabolite concentrations closely resembled the expected variance. A total of 73% and 32% of children moved before and during the acquisition, causing a voxel shift of more than 10% of the voxel volume, 1.5 mm. The predominant movement directions were sliding out of the coil and nodding (up-down rotation). First-order B0 corrections were significant (>10 μT/m) in 18 % of acquisitions. Conclusion: Prospective motion and B0 correction provides high quality repeatable spectra. The study found that most children moved between acquisitions and a substantial number moved during acquisitions.
Optimized saturation pulse train for human first-pass myocardial perfusion imaging at 7T
© 2014 Wiley Periodicals, Inc. Purpose To investigate whether saturation using existing methods developed for 3T imaging is feasible for clinical perfusion imaging at 7T, and to propose a new design of saturation pulse train for first-pass myocardial perfusion imaging at 7T. Methods The new design of saturation pulse train consists of four hyperbolic-secant (HS8) radiofrequency pulses, whose peak amplitudes are optimized for a target range of static and transmit field variations and radiofrequency power deposition restrictions measured in the myocardium at 7T. The proposed method and existing methods were compared in simulation, phantom, and in vivo experiments. Results In healthy volunteer experiments without contrast agent, average saturation efficiency with the proposed method was 97.8%. This is superior to results from the three previously published methods at 86/95/90.8%. The first series of human first-pass myocardial perfusion images at 7T have been successfully acquired with the proposed method. Conclusion Existing saturation methods developed for 3T imaging are not optimal for perfusion imaging at 7T. The proposed new design of saturation pulse train can saturate effectively, and with this method first-pass myocardial perfusion imaging is feasible in humans at 7T.
A comparison of spectral quality in magnetic resonance spectroscopy data acquired with and without a novel EPI-navigated PRESS sequence in school-aged children with fetal alcohol spectrum disorders
Single voxel spectroscopy (SVS) can generate useful information regarding metabolite concentrations provided that the MR signal can be averaged over several minutes during which the subject remains stationary. This requirement can be particularly challenging for children who cannot otherwise be scanned without sedation. To address this problem we developed an EPI volume navigated (vNav) SVS PRESS sequence, which applies real-time head pose (location and orientation), frequency, and first-order B0 shim adjustments. A water-independent preprocessing algorithm removes residual frequency and phase shifts resulting from within-TR movements. We compare results and performance of the standard and vNav PRESS sequences in a sample of 9- to 10-year-olds from a South African cohort of children with fetal alcohol spectrum disorders (FASD) and healthy controls. Magnetic resonance spectroscopy (MRS) data in the deep cerebellar nuclei were initially acquired with the standard PRESS sequence. The children were re-scanned 1 year later with the vNav PRESS sequence. Good quality data were acquired in 73 % using the vNav PRESS sequence, compared to only 50 % for the standard PRESS sequence. Additionally, tighter linewidths and smaller variances in the measured concentrations were observed. These findings confirm previous reports demonstrating the efficacy of our innovative vNav sequence with healthy volunteers and young children with HIV and expand its application to a school-aged population with FASD - disorders often associated with attention problems and hyperactivity. This study provides the most direct evidence to date regarding degree to which these new methods can improve data quality in research studies employing MRS. © 2014 Springer Science+Business Media.