Effects of receive-only inserts on specific absorption rate, B1 (+) field, and Tx coil performance.
Purpose: To evaluate the effect of different cylindrical and close-conforming receive-only array designs on spin excitation and specific absorption rate (SAR) of a 7 T transmit-only head coil.Materials and Methods: We developed finite difference time domain (FDTD) models of different receive-only ar...
| Publicado en: | Journal of Magnetic Resonance Imaging Vol. 39; no. 2; pp. 475 - 485 |
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| Autores principales: | , , |
| Formato: | research Journal Article |
| Publicado: |
Wiley-Blackwell
Feb2014
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=ccm&AN=104009300&site=ehost-live header: @attributes: shortDbName: ccm uiTerm: 104009300 longDbName: CINAHL Complete uiTag: AN controlInfo: bkinfo: dissinfo: jinfo: jid: 10531807 O63 jtl: Journal of Magnetic Resonance Imaging issn: 10531807 maglogo: Y pubinfo: dt: Feb2014 vid: 39 iid: 2 pid: 480 pub: Wiley-Blackwell place: Malden, Massachusetts artinfo: ui: 104009300 104009300 NLM23913474 2012453304 10.1002/jmri.24152 NLM23913474 PMC4501854 104009300 ppf: 475 ppct: 10 formats: tig: atl: Effects of receive-only inserts on specific absorption rate, B1 (+) field, and Tx coil performance. aug: au: Krishnamurthy, Narayanan Zhao, Tiejun Ibrahim, Tamer S affil: Bioengineering Department, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. sug: subj: Brain Anatomy and Histology Image Enhancement Equipment and Supplies Magnetic Resonance Imaging Equipment and Supplies Magnetics Equipment and Supplies Models, Biological Computer Simulation Computer-Aided Design Equipment Design Equipment Failure Human Image Enhancement Methods Magnetic Resonance Imaging Methods Phantoms, Imaging Reproducibility of Results Sensitivity and Specificity ab: Purpose: To evaluate the effect of different cylindrical and close-conforming receive-only array designs on spin excitation and specific absorption rate (SAR) of a 7 T transmit-only head coil.Materials and Methods: We developed finite difference time domain (FDTD) models of different receive-only array geometries. Cylindrical and close-fitting helmet arrays with varying copper trace widths, a TEM Tx coil model, and two head models were used in numerical simulations. Tx coil coupling was experimentally measured and validated with FDTD modeling.Results: Changing copper trace width of loops in array models caused subtle changes in radiofrequency (RF) absorption (<5%). Changes in SAR distribution were observed in the head models with Rx-only inserts. Peak SAR increased (-1 to +15%) in different tissues for a mean B1 (+) in the brain of 2 μT. Total absorption in the head models for 1 W forward power increased (5%-21%) in the heads with Rx-only inserts. Changes in RF absorption with different Rx inserts indicate a change in RF radiation of the Tx coil even when changes in B1 (+) and coupling between ports of Tx coil were minimal.Conclusion: Changes in local/global SAR and subtle changes in B1 (+) field distributions were observed in the presence of Rx-only inserts. Thus, incorporation of the receive-only array effects are needed when evaluating SAR and designing RF transmit pulse waveform parameters for shimming and/or Tx-SENSE for 7 T MRI. pubtype: Academic Journal doctype: research Journal Article ougenre: Article language: English refInfo: holdings: @attributes: islocal: N |
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