Contact

Dr. Nikolai Avdievitch

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 1.B.03
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.

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Poster (61):

Avdievich NI und Peisach J (August-3-1999): Multi-Frequency Electrton Spin Echo Envelope Modulation (ESEEM) Studies of Cytochrome c, 41st Rocky Mountain Conference on Analytical Chemistry, Denver, CO, USA.
Avdievich NI und Forbes MDE (Oktober-1997): Exchange Relaxation in Short-Lived Flexible Symmetryic Biradicals, Vth International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Jerusalem, Israel.
Tsentalovich YP, Morozova OB, Avdievich NI, Yurkovskaya AV und Forbes MDE (Oktober-1997): Magnetic Effects in Reactions of Consecutive Biradicals: TREPR, CIDNP, and Laser Flash Photolysis Study, Vth International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Jerusalem, Israel.
Tarasov VF, Avdievich NI und Forbes MDE (Oktober-1997): TR ESR of Slowly Encountered Spin Correlated Micellized Radical Pairs, Vth International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Jerusalem, Israel.
Forbes MDE, Avdievich NI, Schulz GS und Ball JD (August-1996): Dynamic Effects in EPR Spectra of Spin-Correlated Radical Pairs and Biradicals: Experiment and Theory, IVth International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Novosibirsk, Russia.
Avdievich NI, Jeevarajan AS und Forbes MDE (März-1996): Q–Band Time–Resolved EPR Study of the Photoionization of N,N,N’,N’–Tetramethylphenylenediamine: Separation of Singlet and Triplet Ionization Channels, 211th American Chemical Society National Meeting, New Orleans, LA, USA.
Ball D, Avdievich NI und Forbes MDE (März-1996): Spin-Spin Coupling in Flexible Organic Biradicals with Alkyl and Aryl Appendages, 211th American Chemical Society National Meeting, New Orleans, LA, USA.
Schulz GS, Avdievich NI und Forbes MDE (März-1996): Time-resolved Electron Paramagnetic Resonance Spectroscopy of Photochemically Active Amphiphiles, 211th American Chemical Society National Meeting, New Orleans, LA, USA.
Avdievich NI und Forbes MDE (Oktober-1994): Spin Relaxation Caused by J-Modulation in Spin Polarized Biradicals. Theory and Improvement of SCRP Simulation Routine, 26th Southeastern Magnetic Resonance Conference, Chapel Hill, NC, USA.
Parnachev AP, Bagryanskaya EG, Tarasov VF, Lukzen NN, Avdievich NI und Sagdeev RZ (September-1994): Investigation of Micellized Radical Pairs by Time-Resolved SNP and External Magnetic Field Switch CIDNP, IIIrd International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Chicago, IL, USA.
Avdievich NI und Forbes MDE (September-1994): Spin Relaxation Caused by J-Modulation in Spin Polarized Biradicals. Theory and Improvement of SCRP Simulation Routine, IIIrd International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Chicago, IL, USA.
Tarasov VF, Ghatlia ND, Avdievich NI und Turro NJ (Juli-1992): Exchange Interaction in Micellized Radical Pairs, International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Konstanz, Germany.
Avdievich NI, Bagryanskaya EG, Tarasov VF, Lukzen NN und Sagdeev RZ (Juli-1992): Time-Resolved Stimulated Nuclear Polarization of Micellized Radical Pair, International Symposium "Magnetic Field and Spin Effects in Chemistry and Related Phenomena", Konstanz, Germany.
Bagryanskaya EG, Grishin YA und Avdievich NI (September-1988): Study of Radical-Ion Reactions Using SNP Technique, XXIVth Congress Ampere on Magnetic Resonance and Related Phenomena, Poznan, Poland.
Bagryanskaya EG, Grishin YA, Avdievich NI und Sagdeev RZ (September-1988): Time-Resolved Stimulated Nuclear Polarization, XXIVth Congress Ampere on Magnetic Resonance and Related Phenomena, Poznan, Poland.
Salikhov KM, Sagdeev RZ, Grishin YA, Bagryanskaya EG, Mikhailov SA, Purtov PP, Koptyug IV und Avdievich NI (August-1987): Stimulated Nuclear Polarization, 9th AMPERE International Summer School, Novosibirsk, USSR.

Vorträge (26):

Shao T, Zhang Y, Avdievich N, Mirkes C, Scheffler K, Glaser S und Henning A (April-27-2017) Abstract Talk: Homogeneous high-flip-angle 3D localization by parallel transmission at 9.4T, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA 650.
Giapitzakis I-A, Shao T, Avdievitsch N, Fichtner N, Merkle R, Kreis R und Henning A (April-27-2017) Abstract Talk: Metabolite cycled semi-LASER and STEAM at 9.4T: Comparison and in vivo results, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA 619-620.
Giapitzakis IA, Avdievitch N, Manohar SM, Fichtner N, Kreis R und Henning A (April-25-2017) Abstract Talk: Functional Magnetic Resonance Spectroscopy (fMRS) using metabolite cycled semi-LASER at 9.4T: a pilot study, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA 277.
Avdievitch NI (April-23-2017) Invited Lecture: Multi-Tuned Coils, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA 47.
Avdievich N (März-23-2017) Invited Lecture: Optimization of the Transmit and Receive Performance of the Transceiver Head Phased Array for Human Brain Imaging at Ultra-High Fields, Workshop SWS04: Radiofrequency Coils for Magnetic Resonance Imaging at: 11th European Conference on Antennas and Propagation (EuCAP 2017), Paris, France.
Fichtner ND, Giapitzakis I-A, Avdievich N, Merkle R, Zaldivar D, Henning A und Kreis R (Februar-2-2017) Abstract Talk: Measuring Exchange Between Brain Metabolites and Water Using Ultra-High Field Magnetic Resonance Spectroscopy, GCB Symposium 2017: Graduate School for Cellular and Biomedical Sciences, Bern, Switzerland.
Pfrommer A, Avdievich NI und Henning A (Mai-9-2016) Abstract Talk: About the Ultimate SNR for Cylindrical and Spherical RF Arrays in a Realistic Human Head Model, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore(0175).
Avdievich NI, Giapitzakis IA, Pfrommer A und Henning A (Mai-9-2016) Abstract Talk: Optimization of the Transceiver Phased Array for Human Brain Imaging at 9.4T: Loop Overlapping Rediscovered, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore(0169).
Giapitzakis IA, Nassirpour S, Avdievich NI, Kreis R und Henning A (Oktober-2015) Abstract Talk: 1H single voxel spectroscopy at occipital lobe of human brain at 9.4 T, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S208-S209.
Shao T, Zhang Y, Avdievich NI, Glaser S und Henning A (Oktober-2015) Abstract Talk: A parallel transmit spectral-spatial pulse design method for ultra-high field MRS combining LSQR and optimal control based optimization, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S404-S405.
Avdievich NI, Giapitzakis IA und Henning A (Oktober-2015) Abstract Talk: Novel Splittable N-Tx/2N-Rx Transceiver Phased Array to Optimize both SNR and Transmit Efficiency at 9.4T, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S57.
Shao T, Zhang Y, Avdievich NI, Glaser S und Henning A (Juni-4-2015) Abstract Talk: A Parallel Transmit Spectral-Spatial Pulse Design Method for Ultra-High Field MRS Combining LSQR and Optimal Control Based Optimization, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada(0918).
Avdievich NI, Pfrommer A, Hoffmann J, Chadzynski GL, Scheffler K und Henning A (Mai-14-2014) Abstract Talk: Tranceive Phased Array with High Transmit Performance for Human Brain Application at 9.4 T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy(0622).
Avdievich NI, Pan JW und Hetherington HP (Oktober-6-2011) Abstract Talk: Improved Longitudinal Coverage For Human Brain At 7T: A 16-Coil Double-Row Transceiver Array, 28th Annual Scientific Meeting ESMRMB 2011, Leipzig, Germany, Magnetic Resonance Materials in Physics, Biology and Medicine, 24(Supplement 1) 40-41.
Pan JW, Spencer DD, Duckrow RB, Avdievich NI und Hetherington HP (Mai-12-2011) Abstract Talk: Spectroscopic Imaging of Human Medial Temporal Lobe Epilepsy At 7T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada 571.
Avdievich NI, Pan JW und Hetherington HP (Mai-10-2011) Abstract Talk: Improved longitudinal coverage for human brain at 7T: A 16 Element Transceiver Array, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada 320.
Hetherington HP, Avdievich NI und Pan JW (Mai-9-2011) Abstract Talk: Multiplexed RF Transmission for Transceiver Arrays at 7T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada 156.
Pan JW, Avdievich N, Knisely J und Hetherington HP (April-21-2009) Abstract Talk: 31P spectroscopic imaging of human brain at 7T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA 431.
Hetherington HP, Kuznetsov AM, Avdievich NI und Pan JW (April-21-2009) Abstract Talk: Short TE (15ms) Spectroscopic Imaging of the Human Brain at 7T Using Transceiver Arrays and B1 Shimming Based Localization, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA 572.
Pan JW, Avdievich N, Spencer D und Hetherington HP (April-20-2009) Abstract Talk: 31P Exchange Sensitive Imaging in Human Brain at 7T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA 239.
Hetherington HP, Kuznetsov AM, Avdievich NI und Pan JW (April-20-2009) Abstract Talk: Higher Order B0 Shimming of the Human Brain at 7T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA 236.
Avdievich NI und Hetherington HP (Mai-23-2007) Abstract Talk: Phased Array Optimized for Simultaneous Reception with a Transmit Volume Coil for SNR Improvement of the Spectroscopic Imaging of the Hippocampus, 2007 Joint Annual Meeting ISMRM-ESMRMB, Berlin, Germany 102.
Avdievich NI, Bradshaw K, Kuznetsov AM und Hetherington HP (Mai-22-2007) Abstract Talk: High-Field Actively Detuneable Transverse Electromagnetic (TEM) Coil with Low Bias Voltage for High Power RF Transmission, 2007 Joint Annual Meeting ISMRM-ESMRMB, Berlin, Germany 56.
Avdievich NI, Peshkovsky AS und Hetherington HP (Mai-22-2007) Abstract Talk: High-Field Double-Tuned TEM/Birdcage Hybrid Volume Coil for Human Brain Imaging, 2007 Joint Annual Meeting ISMRM-ESMRMB, Berlin, Germany 56.
Hetherington HP, Avdievich NI und Pan JW (Mai-8-2006) Abstract Talk: Field Map Based Automatic Shimming for Organs Outside of the Human Brain, 14th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2006), Seattle, WA, USA 14.
Avdievich NI und Hetherington HP (Mai-10-2005) Abstract Talk: Simultaneous Reception from a Head Volume Coil and an Array of Counter Rotating Current (CRC) Surface Coils at 4 T: an Alternative to Using Actively Detuned Transmit Volume Coils, 13th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2005), Miami Beach, FL, USA 72.

Patent (4):

Avdievich NI, Hetherington HP und Pan JW: Magnetic-Resonance Transceiver-Phased Array that Compensates for Reactive and Resistive Components of Mutual Impedance between Array Elements and Circuit and Method Thereof, US20130271144 A1, (Oktober-17-2013).
Avdievich NI und Hetherington HP: Surface coil arrays for simultaneous reception and transmission with a volume coil and uses thereof, US8030926 B2, (Oktober-4-2011).
Hetherington HP, Pan JW und Avdievich NI: Improved transceiver apparatus, system, and methodology for superior in-vivo imaging of human anatomy, WO2010110881 A1, (September-30-2010).
Avdievich N, Peshkovsky A und Kennan R: Open half volume quadrature transverse electromagnetic coil for high field magnetic resonance imaging, US6980003 B2, (Dezember-27-2005).
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Last updated: Montag, 22.05.2017