Contact

Dr. Nikolai Avdievitch

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 4.B.07
Tel.: 07071 601 713
Fax: 07071 601 702
E-Mail: Nikolai.Avdievitch

 

Bild von Avdievitch, Nikolai, Dr.

Nikolai Avdievitch

Position: Seniorwissenschaftler  Abteilung: Henning Scheffler

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Optimization of Transmit and Receive Performance of a Head Transceiver Phased Array at 9.4 T

Motivation

Despite the intrinsic advantages of ultra-high (>7 T) field (UHF) spectroscopic imaging (SI), increased signal-to noise-ratio (SNR) and spectral resolution, few studies have been reported to date. This limitation is largely due to technical hurdles associated with radio frequency (RF) magnetic field, B1, inhomogeneity and decrease in transmit (Tx) efficiency (B1/√kW) (1). Transmit phased arrays combined with RF shimming have been shown to improve both Tx performance and homogeneity for head imaging at UHF (2,3). A common approach of optimizing receive (Rx) performance is to use a nested combination of two coils/ arrays, i.e. a smaller multi-channel  Rx-only phased array placed inside of a larger Tx-only coil/ array (3). Current state-of-the-art Rx-only phased arrays contain >30 elements to satisfy requirements for both parallel reception and high SNR. Increasing the size of a Tx coil decreases its performance, which does not impose such a problem at lower (< 3T) field strength due to higher transmit efficiency and a higher available RF power at the coil plug. However, at UHF the enlarged Tx-arrays cannot satisfy anymore requirements in high B1 and bandwidth for SI. One of the solution of the problem is using transceiver (Tx/Rx) head phased arrays with a tight fit, in which the same elements are used for both transmission and reception (2). On the other side, increasing the number of elements in head transceiver arrays above 16 is rather complicated and unpractical due to difficulties in decoupling and the limited number of available independent Tx-channels (commonly 8 or 16). My work focuses on development of UHF transceiver phased arrays, which provide for efficient transmission and the same time do not compromise SNR and parallel receive performance.

 

Transmit efficiency and SAR

An important issue in designing the UHF arrays is evaluation of a local specific absorption rate (SAR), i.e. a local heat produced by an RF coil in the human tissue. Obviously a tight fit RF coil may increase the local SAR, which should be carefully evaluated. As a prove of concept we designed and constructed a tight fit 9.4 T (400 MHz) 8-channel surface loop transceiver head array shown in Fig.1.

Figure 1

We evaluated the array Tx performance and SAR. As an example Fig.2 presents experimentally measured and simulated maps of transmit B1 field obtained for a tissue-mimicking phantom for two central projections and an example of SAR simulations. The tight fit array improves the overall axial B1+ distribution with elevated maximal and peripheral efficiency. However, the small number of array elements (8) may limit the SNR and parallel Rx performance as compared with Rx-arrays with 30 and above elements (3).

 

Figure 2

Receive Performance

We plan to apply several approaches to improve receive performance of the transceiver array. To demonstrate one of them we developed and constructed a 4-channel Tx / 8-channel Rx prototype of a novel splittable transceiver phased array. The splittable array allows doubling the number of Rx-elements without necessity of moving the Tx-elements further away from the subject. Both Tx and Rx performance can be optimized at the same time using this technology. The array (Fig.3) consists of 4 flat surface Tx-loops. Each loop can be split into two smaller

Figure 3

overlapped Rx-loops during the reception (Fig. 3B). Splitting is provided by 4 PIN diode switches, S1, S2. Figure 4 shows improvements in SNR and parallel performance (g-factor map) obtained using the splittable phased array in either 4 or 8-channel Rx mode for the same coronal slice located near the surface of the array.

Figure 4

 

References: 1) Vaughan JT et al, Magn Reson Med, 46:24-30, 2001. 2) Avdievich NI et al, Appl Magn Reson, 41(2):483-506, 2011. 3) Shajan G et al, Magn Reson Med, 71:870-879, 2014.

WORK EXPERIENCE:

Jan. 2013-Current

Senior Research Scientist, Department for Ultra-High Field MRI, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.

 

July 2012- Dec 2012

Senior RF Engineer, Resonance Research Instruments, Inc., Billerica, MA, USA.

 

Jan. 2007-June 2012

Associate Research Scientist, Magnetic Resonance Research Center, Department of Neurosergery, Yale University, New Haven, CT, USA.

 

Oct. 2000-Dec. 2006

Associate in Radiology, Magnetic Resonance Research Center, Department of Radiology, Albert Einstein Medical College, Bronx, NY, USA.

 

Feb. 1998-Oct. 2000

Electron Spin Resonance (ESR) Lab Manager, ESR Research Resource Center, Department of Physiology & Biophysics, Albert Einstein Medical College, Bronx, NY, USA.

 

1994-Feb. 1998

Postdoctoral Associate, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

 

1993-1994

Researcher, Laboratory of Spin and Magnetic Phenomena, International Tomography Center, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

 

1992-1993

Researcher, Laboratory of Magnetic Phenomena, Institute of Chemical Kinetics and Combustion, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

 

1987-1992

Junior Researcher, Laboratory of Magnetic Phenomena, Institute of Chemical Kinetics and  Combustion, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

 

1985-1987

Engineer, Laboratory of Physical Methods of Chemical Kinetics, Institute of Chemical Kinetics and Combustion, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

 

1983-1985

Research Technician, Laboratory of Physical Methods of Chemical Kinetics, Institute of Chemical Kinetics and Combustion, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

 

EDUCATION:

1993

Ph.D. in Physical Chemistry, Institute of Chemical Kinetic and Combustion, Russian Academy of Science (Siberian Branch), Novosibirsk, Russia.

1985

M.S., Chemical Physics, Department of Physics, Novosibirsk State University, Novosibirsk, Russia.

1983

B.S., Radiophysics, Department of Physics, Novosibirsk State University, Novosibirsk, Russia.

Präferenzen: 
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Zeige Zusammenfassung

Artikel (51):

Bagryanskaya EG, Grishin YA, Avdievich NI, Sagdeev RZ und Molin YN (Juli-1986) Studies of various mechanisms of nuclear polarisation due to a resonant high-frequency field in radical reactions Chemical Physics Letters 128(2) 162–167.

Beiträge zu Tagungsbänden (2):

Chang Y-C, Avdievich N und Henning A (August-2014) System Identification and Signal Processing for PID Control of B0 Shim Systems in Ultra-High Field Magnetic Resonance Applications, 19th World Congress of the International Federation of Automatic Control (IFAC 2014), International Federation of Automatic Control, New York, NY, USA, IFAC Proceedings Volumes, 47(3), 7517-7522.
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Kozlov M, Turner R und Avdievich N (Oktober-2013) Investigation of decoupling between MRI array elements, 43rd European Microwave Conference (EuMC 2013), IEEE, Piscataway, NJ, USA, 1223-1226.

Beiträge zu Büchern (2):

Avdievich NI: Quadrature Transverse Electromagnetic (TEM) Surface Coils, 51-61. In: RF Coils for MRI, (Ed) J.T. Vaughan, Wiley, Chichester, UK, (2012).
Avdievich NI: Transverse Electromagnetic (TEM) Surface Coils for Extremities, 185-195. In: RF Coils for MRI, (Ed) J.T. Vaughan, Wiley, Chichester, UK, (2012).

Poster (61):

Fichtner N, Giapitzakis I-A, Avdievich N, Mekle R, Zaldivar D, Henning A und Kreis R (April-27-2017): Magnetization exchange between water and downfield metabolites in human brain at 9.4T, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Avdievich N, Giapitzakis I und Henning A (April-26-2017): Double-Row 16-element Tight-Fit Transceiver Phased Array with High Transmit Performance for Whole Human Brain Imaging at 9.4T, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Avdievich N, Giapitzakis I und Henning A (April-25-2017): Effect of Mismatching on the Transmit and Receive Performance of a Human Head 9.4T Tight-Fit Transceiver Phased Array, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Avdievich N, Giapitzakis I und Henning A (April-25-2017): Optimization of the Receive Performance of a Tight-Fit Transceiver Phased Array for Human Brain Imaging at 9.4T, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Shao T, Avdievich NI und Henning A (Mai-12-2016): 3D volumetric parallel excitation at 9.4T using the trajectory container concept, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore.
Fichtner ND, Giapitzakis IA, Avdievich N, Henning A und Kreis R (Mai-11-2016): Downfield spectra of human brain obtained with and without water suppression at 9.4T, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore.
Pfrommer A, Avdievich NI und Henning A (Mai-11-2016): Effect of the RF Shield on the Mutual Coupling Between Adjacent and Non-Adjacent Array Elements, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore.
Zoelch N, Hock A, Avdievich NI und Henning A (Mai-11-2016): In vivo metabolite quantification using ERETIC with corrections for changes in the RF transmission and recepetion field, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore.
Avdievich NI, Pfrommer A, Giapitzakis IA und Henning A (Mai-10-2016): Analytical Modeling of the Coupling within a Human Head Surface Loop Transmit Phased Array at Ultra-High Fields, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore.
Fichtner N, Henning A, Giapitzakis I, Zoelch N, Avdievich N, Boesch C und Kreis R (März-31-2016): Downfield MR Spectroscopy at Ultrahigh Magnetic Fields, 11th Annual Meeting Brain Connectivity, Bern, Switzerland.
Avdievich NI, Walzog J, Steffen T und Henning A (Oktober-2015): Development of a low cost multi-channel tune and match device for transceiver arrays at high magnetic fields, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S452-S453.
Giapitzakis IA, Nassirpour S, Avdievich N, Kreis R und Henning A (Juni-4-2015): Metabolite cycled single voxel 1H spectroscopy at 9.4T, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Avdievich NI, Giapitzakis IA und Henning A (Juni-2-2015): Novel Splittable N-Tx/2N-Rx Transceiver Phased Array to Optimize both SNR and Transmit Efficiency at 9.4 T, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Kuehne A, Laistler E, Eschelbach M, Henning A, Moser E und Avdievich NI (Juni-1-2015): Analytical Performance Evaluation and Optimization of Resonant Inductive Decoupling (RID), 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Avdievich NI, Giapitzakis IA und Henning A (Juni-1-2015): Asymmetric Transceiver Phased Array for Functional Imaging and Spectroscopy of the Visual Cortex at 9.4 T, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Shao T, Avdievich NI, Chang P, Hoffmann J, Scheffler K und Henning A (Juni-1-2015): Systematic investigation of influence factor on parallel transmit pulse performance at 9.4 Tesla, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Giapitzakis IA, Nassirpour S, Kreis R, Avdievich NI und Henning A (März-19-2015): Metabolite cycled proton magnetic resonance spectroscopy at 9.4T, 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015), Tübingen, Germany.
Chang Y-C, Eschelbach M, Avdievitch N, Scheffler K und Henning A (Mai-15-2014): Fast Method for Parametric System Identification of Gradient Systems, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Giapitzakis IA, Shao T, Avdievich N, Kreis R und Henning A (Mai-15-2014): Optimisation of Asymmetric Adiabatic Pulses for Single Voxel Metabolite Cycled 1H-MRS in the Human Brain at 9.4 Tesla, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Pfrommer A, Avdievich N und Henning A (Mai-12-2014): Four Channel Transceiver Array for Functional Magnetic Resonance Spectroscopy in the Human Visual Cortex at 9.4 T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Avdievich NI, Pan JW und Hetherington HP (April-25-2013): Densely-Populated Transceiver Surface Coil Array for the Human Brain Studies at 7T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
Hetherington HP, Avdievich NI und Pan JW (April-25-2013): Improved Volume Localization for MRSI at 7T Using RF Shimming and RF Multiplexing, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
Lee J-H, Norris M, Fugate EM, Avidievich NI und Hetherington HP (April-24-2013): A Novel Double Tuned 4T 1H/17O Head Volume Coil, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
Hetherington HP, Avdievich NI und Pan J (April-24-2013): Reducing SAR and Imaging Time at 7T Using RF Multiplexing and Transceiver Arrays at 7T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
Avdievich NI, Pan JW und Hetherington HP (Mai-7-2012): Novel Inductive Decoupling for Single- and Double-Tuned Transceiver Phased Arrays to Compensate for both Reactive and Resistive Components of the Mutual Impedance, 20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), Melbourne, Australia.
Avdievich NI, Pan JW und Hetherington HP (Oktober-2011): Double Tuned 31P/1H Elliptical Transceiver Phased Array for the Human Brain Studies at 7T, 28th Annual Scientific Meeting ESMRMB 2011, Leipzig, Germany, Magnetic Resonance Materials in Physics, Biology and Medicine, 24(Supplement 1) 421-422.
Hetherington HP, Avdievich NI, Gonen O und Pan JW (Mai-9-2011): Hadamard Encoded 3D MRSI of Human Brain at 7T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
Pan JW, Avdievich NI und Hetherington HP (Mai-9-2011): Thalamic and subcortical GABA in human brain at 7T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
Pan JW, Avdievich N, Ibrahim TS und Hetherington HP (Mai-9-2011): The inductively decoupled transceiver array: simulations and performance at 7T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
Oh S, Avdievich NI, Pan JW, Hetherington HP und Collins CM (Mai-6-2010): Enhanced RF Excitation Homogeneity by Combining TEM and Counter Rotating Current Surface Coil Array: Numerical Simulations and Experiments at 4.0 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
Avdievich NI, Pan JW und Hetherington HP (Mai-5-2010): Double Tuned 31P/1H Elliptical Transceiver Phased Array for the Human Brain Studies at 7 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
Hetherington HP, Avdievich NI und Pan JW (Mai-5-2010): An 8 Element Inductively Decoupled Transceiver Array for 1H MR of the Brain at 7T: Performance Characteristics Across 82 Subjects, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
Pan JW, Avdievich NI und Hetherington HP (Mai-5-2010): J Refocused Coherence Transfer Spectroscopic Imaging at 7T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
Avdievich NI, Pan JW, Kuznetsov AM und Hetherington HP (April-21-2009): Variable Geometry Elliptical Transceiver Phased Array for Imaging of the Human Brain at 7 T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
Avdievich NI, Peshkovsky AS und Hetherington HP (Mai-21-2007): Comparison of Transceive Phased Array with TEM Volume Coil for Human Brain Imaging at 4 T, 2007 Joint Annual Meeting ISMRM-ESMRMB, Berlin, Germany.
Avdievich NI und Hetherington HP (Mai-10-2006): 4T Actively-Detunable Double-Tuned 1H/31P TEM Head Volume Coil and Four-Channel 31P Phased Array for Human Brain Spectroscopy, 14th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2006), Seattle, WA, USA.
Avdievich NI, Bradshaw K, Lee J-H und Hetherington HP (Mai-10-2006): 4T Split TEM Volume Head and Knee Coils for Improved Sensitivity and Patient Comfort, 14th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2006), Seattle, WA, USA.
Avdievich NI und Hetherington HP (Mai-10-2006): Improved Homogeneity of the Transmit Field Due to Simultaneous Transmission with Phased Arrays and Volume Coils, 14th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2006), Seattle, WA, USA.
Hetherington HP, Avdievich NI und Pan JW (Mai-11-2005): Improved Spectral Editing for Measurements of Cerebral GABA, 13th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2005), Miami Beach, FL, USA.
Avdievich NI und Hetherington HP (Mai-10-2005): Experimental Comparison of TEM and Birdcage Small Animal Volume Coils at 9.4 T, 13th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2005), Miami Beach, FL, USA.
Avdievich NI, Peshkovsky A, Kennan RP und Hetherington HP (Mai-19-2004): SENSE imaging with quadrature half-volume TEM coil at 4T, 12th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2004), Kyoto, Japan.
Avdievich NI und Hetherington HP (Mai-17-2004): 4T Human Brain Spectroscopic Imaging with Four-Channel Phased Array, 12th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2004), Kyoto, Japan.
Peshkovsky A, Kennan RP, Fabry ME und Avdievich NI (Mai-17-2004): Open volume TEM quadrature coil for high-field imaging, 12th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2004), Kyoto, Japan.
Nagaoka T, Kennan RP, Netsiri C, Avdievich NI, Hetherington HP und Ogawa S (Juli-15-2003): Excitory and Inhibitory Process Observed by fMRI and SEP in Rat Somatosensory Cortex, 11th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2003), Toronto, Canada.
Avdievich NI und Hetherington HP (Juli-15-2003): Modified Perturbation Method for TEM Coil Tuning and Evaluation, 11th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2003), Toronto, Canada.
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Last updated: Montag, 22.05.2017