Contact

Dr. Nikolai Avdievitch

Address: Spemannstr. 41
72076 Tübingen
Room number: 1.B.03
Phone: +49 7071 601 713
Fax: +49 7071 601 702
E-Mail: Nikolai.Avdievitch

 

Picture of Avdievitch, Nikolai, Dr.

Nikolai Avdievitch

Position: Senior Research Scientist  Unit: Henning Scheffler

Optimization of Transmit and Receive Performance of a Transceiver Phased Array

Motivation

In spite of great benefits offered by ultra-high field (UHF, > 7T) MRI, its further developments toward clinical applications are associated with significant technical issues, which include low transmit (Tx) efficiency and strong inhomogeneity of the RF magnetic field, B1+ (1). To improve Tx-efficiency and provide for a full coverage of the human brain, UHF multi-element multi-row arrays (2-6) have to be used in combination with 3D RF shimming or parallel transmission (pTx). There are two major types of human head array coils currently developed for the full-brain imaging at UHF. First type, a so called transmit-only/ receive-only (ToRo) array, consists of two nested layers of elements (5). Inner layer, which is positioned closer to a head, contains multiple elements (commonly loops) used only during reception, i.e. receive (Rx)-only elements. Larger array, positioned in the outer layer, provides for local transmission. Second design, a so called transceiver (TxRx) array, consists of a single layer of elements used during both transmission and reception (2-4,6). The Rx-performance of a human head coil can be easier optimized within the frame of the ToRo-design. Current state of the art UHF ToRo-arrays contain 30 and more Rx-only elements (5), which is critical for high SNR and parallel Rx-performance. In turn, TxRx-arrays provide for more efficient transmission, B1+/√P, due to tighter fit and, thus, higher tissue loading. TxRx-design is also simpler then the ToRo-design since it does not require detuning of elements. However, a drawback of the TxRx-design is that the number of elements in an array is limited by the number of available high power RF Tx-channels (commonly 8 or 16). My work focuses on development of new UHF arrays, which combine benefits of both designs, i.e. provide for efficient transmission and the same time do not compromise SNR and parallel receive performance.

Transmit efficiency

Previously we demonstrated that at 400 MHz a 16-loop double-row (2x8) tight-fit human head TxRx-array can be well decoupled entirely by overlapping surface loops without any additional decoupling strategy (7). This based on our analytical findings that at 400 MHz the mutual resistance between adjacent overlapped loops combined within this specific array geometry is minimal, and both the mutual inductance and mutual resistance can be minimized at the same time (8). As a result, the constructed 2x8 array demonstrated very good decoupling, a full brain coverage, and Tx-efficiency, which was 50% higher than that of the larger ToRo-array of similar length (7). Adding two perpendicular TxRx-loops at the superior position of a head (Fig.1A) improves uniformity of the array transmit B1+ profile (Fig.2).

Receive Performance

In the next step we developed a method of increasing the number of Rx-elements in a TxRx-array without compromising the array’s Tx-performance (9). First, we constructed a human head array prototype, which consisted of a single row of 8 TxRx surface loops circumscribing a head, and 8 Rx-only “vertical” loops positioned in the center of each TxRx-loop such to produce B1+ field perpendicularly to magnetic field B0 (similarly as in Fig.1B). All vertical loops were actively detuned during transmission and preamplifier decoupled during reception. Evaluation of the new array demonstrated that neither Tx-efficiency nor maximum SAR was compromised due to addition of Rx-only vertical loops (9). At the same time SNR was substantially improved (~30% near the brain center). Following prototyping 16-loop array, we extended this idea by constructing 32-element tight-fit human head array consisted of 18 TxRx-loops (Fig.1A) and 14 Rx-only vertical loops (Fig.1B) with the total number of Rx elements equal to 32. The general idea of this approach is that the total number of array elements should not exceed the number of available Rx-channels, i.e. 32 in our case. During designing, first, the required number (e.g. 18, Fig.1A) of TxRx-loops is placed around the object tightly to provide for high Tx-performance. Then, the rest of the loops are used as Rx-only elements, which are positioned to minimize interaction with the TxRx-loops, e.g. “vertically” (Fig.1B). In comparison to the common ToRo-design, this method preserves tight fit of the TxRx-loops and, thus, does not compromise the Tx-performance. In addition, it minimizes the total number of array elements as well as the number of active detuning circuits, which are not required for the TxRx-elements. As seen from Fig.3, the ToRo-array still provides for somewhat higher peripheral SNR.

At the same time, the new 32-channel tight-fit array has substantially (~30%) higher SNR near the center of the brain. It is well known that increasing the number of surface loops in a helmet human-head Rx-array only improves peripheral SNR, while SNR near the center practically doesn’t change (10,11). Combination of surface and vertical loops improves SNR near the center. Overall, the new tight-fit array demonstrates high SNR over the entire brain and a substantially more uniform SNR distribution than that of the ToRo-array. Both arrays provide for comparable Rx parallel performance.

References: 1) Vaughan JT et al, Magn Reson Med, 46:24-30, 2001. 2) Adriany G et al. Magn Reson Med 2010; 63(6):1478-1485. 3) Avdievich NI et al, Appl Magn Reson 2011, 41(2):483-506. 4) Gilbert KM et al, Magn Reson Med 2012;67:1487–1496. 5) Shajan G et al, Magn Reson Med, 71:870-879, 2014. 6) Avdievich NI et al, NMR in Biomedicine. 2017;30(2):1-12. 7) Avdievich et al, Proc. ISMRM 25, 2017, 759. 8) Avdievich et al, NMR in BioMed 2017, DOI: 10.1002/nbm.3759. 9) Avdievich et al, Proc. ISMRM 25, 2017, 4309. 10) Wiggins GC et al, Magn Reson Med 2009;62:754-762. 11) Vaidya MV et al, Conc Magn Reson Part B 2014; 44B(3):53–65.

Optimization of Transmit and Receive Performance of a Transceiver Phased Array

Motivation

In spite of great benefits offered by ultra-high field (UHF, > 7T) MRI, its further developments toward clinical applications are associated with significant technical issues, which include low transmit (Tx) efficiency and strong inhomogeneity of the RF magnetic field, B1+ (1). To improve Tx-efficiency and provide for a full coverage of the human brain, UHF multi-element multi-row arrays (2-6) have to be used in combination with 3D RF shimming or parallel transmission (pTx). There are two major types of human head array coils currently developed for the full-brain imaging at UHF. First type, a so called transmit-only/ receive-only (ToRo) array, consists of two nested layers of elements (5). Inner layer, which is positioned closer to a head, contains multiple elements (commonly loops) used only during reception, i.e. receive (Rx)-only elements. Larger array, positioned in the outer layer, provides for local transmission. Second design, a so called transceiver (TxRx) array, consists of a single layer of elements used during both transmission and reception (2-4,6). The Rx-performance of a human head coil can be easier optimized within the frame of the ToRo-design. Current state of the art UHF ToRo-arrays contain 30 and more Rx-only elements (5), which is critical for high SNR and parallel Rx-performance. In turn, TxRx-arrays provide for more efficient transmission, B1+/√P, due to tighter fit and, thus, higher tissue loading. TxRx-design is also simpler then the ToRo-design since it does not require detuning of elements. However, a drawback of the TxRx-design is that the number of elements in an array is limited by the number of available high power RF Tx-channels (commonly 8 or 16). My work focuses on development of new UHF arrays, which combine benefits of both designs, i.e. provide for efficient transmission and the same time do not compromise SNR and parallel receive performance.

Transmit efficiency

Previously we demonstrated that at 400 MHz a 16-loop double-row (2x8) tight-fit human head TxRx-array can be well decoupled entirely by overlapping surface loops without any additional decoupling strategy (7). This based on our analytical findings that at 400 MHz the mutual resistance between adjacent overlapped loops combined within this specific array geometry is minimal, and both the mutual inductance and mutual resistance can be minimized at the same time (8). As a result, the constructed 2x8 array demonstrated very good decoupling, a full brain coverage, and Tx-efficiency, which was 50% higher than that of the larger ToRo-array of similar length (7). Adding two perpendicular TxRx-loops at the superior position of a head (Fig.1A) improves uniformity of the array transmit B1+ profile (Fig.2).

Receive Performance

In the next step we developed a method of increasing the number of Rx-elements in a TxRx-array without compromising the array’s Tx-performance (9). First, we constructed a human head array prototype, which consisted of a single row of 8 TxRx surface loops circumscribing a head, and 8 Rx-only “vertical” loops positioned in the center of each TxRx-loop such to produce B1+ field perpendicularly to magnetic field B0 (similarly as in Fig.1B). All vertical loops were actively detuned during transmission and preamplifier decoupled during reception. Evaluation of the new array demonstrated that neither Tx-efficiency nor maximum SAR was compromised due to addition of Rx-only vertical loops (9). At the same time SNR was substantially improved (~30% near the brain center). Following prototyping 16-loop array, we extended this idea by constructing 32-element tight-fit human head array consisted of 18 TxRx-loops (Fig.1A) and 14 Rx-only vertical loops (Fig.1B) with the total number of Rx elements equal to 32. The general idea of this approach is that the total number of array elements should not exceed the number of available Rx-channels, i.e. 32 in our case. During designing, first, the required number (e.g. 18, Fig.1A) of TxRx-loops is placed around the object tightly to provide for high Tx-performance. Then, the rest of the loops are used as Rx-only elements, which are positioned to minimize interaction with the TxRx-loops, e.g. “vertically” (Fig.1B). In comparison to the common ToRo-design, this method preserves tight fit of the TxRx-loops and, thus, does not compromise the Tx-performance. In addition, it minimizes the total number of array elements as well as the number of active detuning circuits, which are not required for the TxRx-elements. As seen from Fig.3, the ToRo-array still provides for somewhat higher peripheral SNR. At the same time, the new 32-channel tight-fit array has substantially (~30%) higher SNR near the center of the brain. It is well known that increasing the number of surface loops in a helmet human-head Rx-array only improves peripheral SNR, while SNR near the center practically doesn’t change (10,11). Combination of surface and vertical loops improves SNR near the center. Overall, the new tight-fit array demonstrates high SNR over the entire brain and a substantially more uniform SNR distribution than that of the ToRo-array. Both arrays provide for comparable Rx parallel performance.

References: 1) Vaughan JT et al, Magn Reson Med, 46:24-30, 2001. 2) Adriany G et al. Magn Reson Med 2010; 63(6):1478-1485. 3) Avdievich NI et al, Appl Magn Reson 2011, 41(2):483-506. 4) Gilbert KM et al, Magn Reson Med 2012;67:1487–1496. 5) Shajan G et al, Magn Reson Med, 71:870-879, 2014. 6) Avdievich NI et al, NMR in Biomedicine. 2017;30(2):1-12. 7) Avdievich et al, Proc. ISMRM 25, 2017, 759. 8) Avdievich et al, NMR in BioMed 2017, DOI: 10.1002/nbm.3759. 9) Avdievich et al, Proc. ISMRM 25, 2017, 4309. 10) Wiggins GC et al, Magn Reson Med 2009;62:754-762. 11) Vaidya MV et al, Conc Magn Reson Part B 2014; 44B(3):53–65.

WORK EXPERIENCE:

Feb 2017-Current

Senior Research Scientist (100%), Institute of Physics, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany.

 

May. 2017-Current

Senior Research Scientist (20%), Department for Ultra-High Field MRI (Department chair Prof. K. Scheffler), Max Planck Institute for Biological Cybernetics, Tübingen, Germany.

 

Jan. 2013- Feb. 2017

Senior Research Scientist, Department for Ultra-High Field MRI (Department chair Prof. K. Scheffler), 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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Show abstracts

Posters (63):

Nagaoka T, Kennan RP, Netsiri C, Avdievich NI, Hetherington HP and Ogawa S (July-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 and Hetherington HP (July-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.
Avdievich NI and 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 and Forbes MDE (October-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 and Forbes MDE (October-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 and Forbes MDE (October-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 and 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 and Forbes MDE (March-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 and Forbes MDE (March-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 and Forbes MDE (March-1996): Time-resolved Electron Paramagnetic Resonance Spectroscopy of Photochemically Active Amphiphiles, 211th American Chemical Society National Meeting, New Orleans, LA, USA.
Avdievich NI and Forbes MDE (October-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 and 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 and 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 and Turro NJ (July-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 and Sagdeev RZ (July-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 and 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 and 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 and Avdievich NI (August-1987): Stimulated Nuclear Polarization, 9th AMPERE International Summer School, Novosibirsk, USSR.

Talks (29):

Avdievich N, Giapitzakis I and Henning A (October-20-2017) Abstract Talk: Combined Surface Loop/"Vertical" Loop Elements Improve Receive Performance of a Human Head Transceiver Phased Array at 9.4T: an Alternative to Surface Loop/Dipole Antenna Combination, 34th Annual Scientific Meeting of the European Society for Magnetic Resonance in Medicine and Biology (ESMRMB 2017), Barcelona, Spain, Magnetic Resonance Materials in Physics, Biology and Medicine, 30(Supplement 1) S297-S298.
Giapitzakis I-A, Fichtner N, Zaldivar D, Avdievich N, Manohar S, Kreis R and Henning A (October-20-2017) Abstract Talk: Simultaneous detection of water and metabolites alternations under visual stimulation in human visual cortex utilizing metabolite cycled semi-LASER at 9.4T: preliminary results, 34th Annual Scientific Meeting of the European Society for Magnetic Resonance in Medicine and Biology (ESMRMB 2017), Barcelona, Spain, Magnetic Resonance Materials in Physics, Biology and Medicine, 30(Supplement 1) S246-S247.
Bause J, Aghaeifar A, Hagberg G, Engel E-M, Avdievitch N, Scheffler K and Pohmann R (September-11-2017) Abstract Talk: 350 μm Isotropic Whole-Brain MP2RAGE without Averaging, ISMRM Workshop on Motion Correction in MRI & MRS (MoCor 2017), Cape Town, South Africa.
Shao T, Zhang Y, Avdievich N, Mirkes C, Scheffler K, Glaser S and 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 and 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 and 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 (March-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 and Kreis R (February-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 and Henning A (May-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 and Henning A (May-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 and Henning A (October-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 and Henning A (October-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 and Henning A (October-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 and Henning A (June-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 and Henning A (May-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 and Hetherington HP (October-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 and Hetherington HP (May-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 and Hetherington HP (May-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 and Pan JW (May-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 and 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 and 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 and 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 and 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 and Hetherington HP (May-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 and Hetherington HP (May-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 and Hetherington HP (May-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 and Pan JW (May-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 and Hetherington HP (May-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 and 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, (October-17-2013).
Avdievich NI and Hetherington HP: Surface coil arrays for simultaneous reception and transmission with a volume coil and uses thereof, US8030926 B2, (October-4-2011).
Hetherington HP, Pan JW and Avdievich NI: Improved transceiver apparatus, system, and methodology for superior in-vivo imaging of human anatomy, WO2010110881 A1, (September-30-2010).
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Last updated: Monday, 22.05.2017