Direct radiofrequency phase control in MRI by digital waveform playback at the Larmor frequency. Magn Reson Med 2014 Feb;71(2):846-52
Date
03/08/2013Pubmed ID
23468035Pubmed Central ID
PMC4002655DOI
10.1002/mrm.24713Scopus ID
2-s2.0-84892444461 (requires institutional sign-in at Scopus site) 4 CitationsAbstract
PURPOSE: A scalable multiband and multichannel digital magnetic resonance imaging system has been developed with the goal of reducing the time needed for acquisition of a single volume of gradient-recalled echo-planar images of the brain.
METHODS: Transmit pulses are created by an offline computer equipped with a Pentek excitation card (PCIe model 78621) that was built around the Texas Instruments D/A converter (DAC5688).
RESULTS: The spectral purity of pulses made in this way surpasses the quality of pulses made by the standard modulators of the scanner, even when using the same pulse-creation algorithm. There is no need to mix reference waveforms with the magnetic resonance imaging signal to obtain inter-k-space coherency for different repetitions. The key was the use of a system clock to create the Larmor frequency used for pulse formation. The 3- and 4-fold slice accelerations were tested using phantoms as well as functional and resting-state magnetic resonance imaging of the human brain.
CONCLUSION: Synthesizers with limited modulation-time steps should be replaced not only because of the improved spectral quality of radiofrequency pulses but also for the exceptional coherence of pulses at different slice-selection frequencies.
Author List
Jesmanowicz A, Nencka A, Hyde JSAuthor
Andrew S. Nencka PhD Center Director, Professor in the Radiology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AlgorithmsBrain
Equipment Design
Equipment Failure Analysis
Feedback
Humans
Image Enhancement
Magnetic Resonance Imaging
Phantoms, Imaging
Radio Waves
Reproducibility of Results
Sensitivity and Specificity
Signal Processing, Computer-Assisted
