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#11 - A novel radio frequency coil circuitry scheme to obtain better signal to noise ratio in MRI
Long Title: A Novel Magnetic Resonance Radio-Frequency Coil Array that Eliminates Inductive Coupling
NIH Reference No.: E-099-2006
Executive Summary
General Description
Parallel magnetic resonance imaging (MRI) techniques employ radio frequency (RF) coil arrays for faster data acquisition, and have been shown to reduce the overall length of MRI procedures, improve signal-to–noise ratio (SNR) and image quality, thus making MRI more attractive and less costly. Elimination of inductive coupling is an essential step in designing RF coil arrays for parallel MRI. If mutual inductance remains among coils in the RF coil array, the MR signal obtained from one coil may disturb the flux in another coil, making it difficult to match the impedance of each individual element to the input impedance on its preamplifier. This non-optimal matching can lead to degradation of MR signal thereby yielding images with low quality. The most common strategy for inductive decoupling involves the use of preamplifiers with very low input impedance and decoupling networks with lumped elements. However, the construction of preamplifiers with low input impedance is not easy to accomplish, and these preamplifiers impose technical restrictions on coil design, requiring the use of overlapping loops to further minimize the amount of mutual inductance between the coils.
Scientific Progress
Investigators at NINDS have designed a new RF coils which incorporates a transformer to transfer signal from the RF coil to a preamplifier, isolating the preamplifier circuit (and MRI scanner electronics) from the RF coil. This will allow improvement of the signal to noise ratio of the images and drastic reduction in total acquisition time. The arrangement provides a perfect electrical balance which negates the use of trap or balun circuit. Both of these methods provides for increased signal to be transferred to the RF coil, without a concomitant increase in noise. Using this technique, images with excellent signal to noise have been obtained for small animals.
Future Direction
Strengths
Weaknesses
Patent Status
Relevant Publications
Paiva, FF et al. J Magn Reson Imaging. 2008 May;27 (5):970-7 (PMID: 18425844)
Leoni RF et al., Neuroimage. 2011 Sep 1;58 (1):75-81 (PMID: 21708273)
Inventor Bios
Alfonso Silva, Ph.D.
Dr. Silva received his Bachelor's Degree in Electrical Engineering from Universidade Federal de Pernambuco in Recife, Brazil, and his Ph.D. in Bioengineering from Carnegie Mellon University, where he worked on non-invasive MRI measurements of cerebral blood flow using the arterial spin labeling technique. He then went on to do post-doctoral training in the Center for Magnetic Resonance Research at the University of Minnesota, where he studied the temporal and spatial characteristics of functional brain hemodynamics under the supervision of Prof. Seong-Gi Kim. Dr. Silva joined NINDS as a Staff Scientist in 1999, and became an investigator in 2004. His laboratory combines modern neuroimaging techniques (functional MRI, and optical imaging) with electrophysiological recordings aimed at understanding the mechanisms of regulation of cerebral blood flow during normal and stimulation-induced brain activity.
NIH Reference No.: E-099-2006
Executive Summary
- Invention Type: Class II Device
- Patent Status: PCT Application No. PCT/US2007/008586, US Application No. 60/789,934, U.S. Pat: 7,932,721 issued 2011-04-26
- LINK: http://www.ott.nih.gov/technology/e-099-20060
- NIH Reference Number: E-099-2006
- NIH Institute or Center: National Institute of Neurological Disorders and Stroke (NINDS)
- Disease Focus: Imaging/MRI
- Basis of Invention: Reduction of signal-to-noise ratio via new design of an RF coil
- How it works: an RF coil incorporates a transformer to transfer signal from the RF coil to a preamplifier, isolating the preamplifier circuit (and MRI scanner electronics) from the RF coil
- Lead Inventor: Alfonso Silva, Ph.D. and George Carlos do Nascimento, Ph.D.
- Development Stage: Home-built prototype has been used in inventor’s own research. In vivo data available in lab animal as well as healthy volunteers
- Clinical Application: Functional and MR imaging for human and animal model use
General Description
Parallel magnetic resonance imaging (MRI) techniques employ radio frequency (RF) coil arrays for faster data acquisition, and have been shown to reduce the overall length of MRI procedures, improve signal-to–noise ratio (SNR) and image quality, thus making MRI more attractive and less costly. Elimination of inductive coupling is an essential step in designing RF coil arrays for parallel MRI. If mutual inductance remains among coils in the RF coil array, the MR signal obtained from one coil may disturb the flux in another coil, making it difficult to match the impedance of each individual element to the input impedance on its preamplifier. This non-optimal matching can lead to degradation of MR signal thereby yielding images with low quality. The most common strategy for inductive decoupling involves the use of preamplifiers with very low input impedance and decoupling networks with lumped elements. However, the construction of preamplifiers with low input impedance is not easy to accomplish, and these preamplifiers impose technical restrictions on coil design, requiring the use of overlapping loops to further minimize the amount of mutual inductance between the coils.
Scientific Progress
Investigators at NINDS have designed a new RF coils which incorporates a transformer to transfer signal from the RF coil to a preamplifier, isolating the preamplifier circuit (and MRI scanner electronics) from the RF coil. This will allow improvement of the signal to noise ratio of the images and drastic reduction in total acquisition time. The arrangement provides a perfect electrical balance which negates the use of trap or balun circuit. Both of these methods provides for increased signal to be transferred to the RF coil, without a concomitant increase in noise. Using this technique, images with excellent signal to noise have been obtained for small animals.
Future Direction
- We are especially interested in whether there is any plan for clinical trial.
Strengths
- Allows for increased flexibility of coil design including geometries that require array with overlapping receiver coil loops
- Can provide high level of mutual inductance decoupling within coils in the array
- Isolates the grounds from coil to coil, and cancels all ground loops related to the coil array
- Greatly increases the signal to noise ratio in MR imaging
- Can be used in both research and clinical applications
Weaknesses
- Need to show the higher SNR in comparative studies with commercial available RF coils in lab animal models
Patent Status
- PCT Application No. PCT/US2007/008586 filed April 06, 2007
- EU Patent Application #7755003.6 Pending
- U.S. Pat: 7,932,721 issued April 26, 2011
Relevant Publications
Paiva, FF et al. J Magn Reson Imaging. 2008 May;27 (5):970-7 (PMID: 18425844)
Leoni RF et al., Neuroimage. 2011 Sep 1;58 (1):75-81 (PMID: 21708273)
Inventor Bios
Alfonso Silva, Ph.D.
Dr. Silva received his Bachelor's Degree in Electrical Engineering from Universidade Federal de Pernambuco in Recife, Brazil, and his Ph.D. in Bioengineering from Carnegie Mellon University, where he worked on non-invasive MRI measurements of cerebral blood flow using the arterial spin labeling technique. He then went on to do post-doctoral training in the Center for Magnetic Resonance Research at the University of Minnesota, where he studied the temporal and spatial characteristics of functional brain hemodynamics under the supervision of Prof. Seong-Gi Kim. Dr. Silva joined NINDS as a Staff Scientist in 1999, and became an investigator in 2004. His laboratory combines modern neuroimaging techniques (functional MRI, and optical imaging) with electrophysiological recordings aimed at understanding the mechanisms of regulation of cerebral blood flow during normal and stimulation-induced brain activity.
