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Shajan Gunamony

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 3.B.06
Tel.: 07071 601 734
Fax: 07071 601 702
E-Mail: Shajan.Gunamony

 

Bild von Gunamony, Shajan

Shajan Gunamony

Position: Wissenschaftler  Abteilung: Scheffler

RF Coils for Ultra-High Field MRI

The magnetic resonance center of our institute is equipped with a 9.4 T scanner, the strongest magnet ever used for human magnetic resonance imaging (MRI) till date. The promise of increase in signal to noise ratio proportional to the main magnetic field strength motivated a few academic laboratories to pursue MRI research at ultra-high field (UHF, ≥ 7 T), much higher than the field strength approved for clinical use. In addition to conventional 1H imaging, multi nuclei imaging / spectroscopy is expected to gain from the increased field strength.

 

Radio frequency (RF) coils and the corresponding RF hardware are the front-end in the imaging chain and play a significant role in realizing the benefits offered by this unique scanner. However, UHF MRI operates in a regime where the shorter wavelength due to the high Larmor frequency leads to constructive and destructive interference of the transmit (B1+) field in the human body.

 

The focus in the RF lab is to develop RF transmit arrays that provides control over the B1+ field for RF shimming and dynamic parallel transmission (pTx) methods. The transmit arrays are combined with form fitting receive arrays to increase the image signal-to-noise ratio (SNR). I am also involved in the development of SNR optimized coil arrays for multi-nuclei applications and nun-human primate research. All custom-built RF coils for these unique frequencies are supported with custom-built RF hardware like splitters, combiners, TR switches and preamplifiers.

16-channel transmit and 31-channel receive array

Arranging transmit array elements in multiple rows provides an additional degree of freedom to correct B1+ field in-homogeneities and to achieve whole-brain excitation at frequencies as high as 400 MHz. Receive arrays shaped to the contours of the human anatomy increase the signal-to-noise ratio (SNR) of the image. We developed a cutting-edge RF setup that exploits the benefits of UHF brain MRI: a dual-row transmit array with 16 mutually decoupled transmit elements was combined with a 31-channel tight-fitting receive array to achieve B1+ field control and high-SNR parallel signal reception in the entire brain even at 9.4 T.

Figure 1

Multi-nuclei coils

Figure 2UHF MR scanners constitute a significant benefit for non-proton imaging because the SNR has been found to scale at least linearly with the static magnetic field B0. A multi-nuclei imaging setup with the capability to acquire both 23Na and proton (1H) signals at 9.4 T was developed. It consists of a combination of three RF coil arrays to cover the entire human brain. The main objective was to optimize coil performance at the 23Na frequency while still having the ability to also acquire whole-brain 1H images for B0 shimming and anatomical localization.

The three layered coil design method originally proposed by our group for 23Na MRI was adapted for phosphorus (31P) spectroscopy and 1H imaging to perform 31P 3D chemical shift imaging (CSI) of the human brain at 9.4 T.

Shaped Arrays for non-human Primate Research

Simultaneous investigation of electrophysiology and fMRI in non-human primates presents several challenges on RF coil design. In addition to homogeneous excitation, the transmit coil structure should allow access for the electrodes from different orientations to allow recordings from different brain regions. Receive array designs aimed at maximizing the SNR of the fMRI experiment must be designed around head posts fixed on the animal head, leading to non-optimum coil orientations in the helmet. In cases with more than one head posts, the receive array structure must be splittable so that the two separable halves of the receive helmet can be fixed tightly on the monkey’s head. We developed an RF coil arrangement that optimizes the SNR and also allow access for recordings from different regions of the brain. The RF hardware development in combination with method development improved the signal sampling efficiency of fMRI by a considerable factor.

Figure 3

 

 


Professional Experience:

1998-2000               Scientist/Engineer at the ISRO Satellite Center, Indian Space Research Organization, Bangalore, India
2001-2007     Senior Engineer in the MR Engineering Group, GE Healthcare, Bangalore, India
Since July 2007 Research Scientist at the Max Planck Institute for Biological Cybernetics, Tuebingen, Germany

Education:

1991 - 1995                   Bachelor of Engineering in Electronics and Communication Engineering, Karunya Institute of Technology, Coimbatore, India
1996 - 1998 Master of Engineering in Communication Systems, Thiagarajar College of Engineering, Madurai, India

Patent:

RF Coil Assembly US patent No. 7605588 / HF-Spulenanordnung (DE102006050989A1)

Präferenzen: 
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Artikel (15):

Mirkes CC Person, Hoffmann J Person, Shajan G Person, Pohmann R Person und Scheffler K Person (Januar-2015) High-resolution quantitative sodium imaging at 9.4 tesla Magnetic Resonance in Medicine 73(1) 342–351.
Ehses P Person, Bause J Person, Shajan G Person und Scheffler K Person (Dezember-2014) Efficient generation of T2*-weighted contrast by interslice echo-shifting for human functional and anatomical imaging at 9.4 Tesla Magnetic Resonance in Medicine Epub ahead.
Hoffmann J Person, Shajan G Person, Scheffler K Person und Pohmann R Person (Oktober-2014) Numerical and experimental evaluation of RF shimming in the human brain at 9.4 T using a dual-row transmit array Magnetic Resonance Materials in Physics, Biology and Medicine 27(5) 373-386.
Chadzynski GL Person, Pohmann R Person, Shajan G Person, Kolb R , Bisdas S , Klose U und Scheffler K Person (September-2014) In vivo proton magnetic resonance spectroscopic imaging of the healthy human brain at 9.4 T: initial experience Magnetic Resonance Materials in Physics, Biology and Medicine Epub ahead.
Shajan G Person, Kozlov M , Hoffmann J Person, Turner R , Scheffler K Person und Pohmann R Person (Februar-2014) A 16-channel dual-row transmit array in combination with a 31-element receive array for human brain imaging at 9.4 T Magnetic Resonance in Medicine 71(2) 870–879.
Budde J Person, Shajan G Person, Scheffler K Person und Pohmann R Person (Februar-2014) Ultra-high resolution imaging of the human brain using acquisition-weighted imaging at 9.4 T NeuroImage 86 592–598.
Budde J Person, Shajan G Person, Zaitsev M , Scheffler K Person und Pohmann R Person (Januar-2014) Functional MRI in human subjects with gradient-echo and spin-echo EPI at 9.4 T Magnetic Resonance in Medicine 71(1) 209–218.
Balla DZ Person, Gottschalk S Person, Shajan G Person, Ueberberg S , Schneider S , Hardtke-Wolenski M , Jaeckel E , Hoerr V , Faber C , Scheffler K Person, Pohmann R Person und Engelmann J Person (Dezember-2013) In vivo visualization of single native pancreatic islets in the mouse Contrast Media & Molecular Imaging 8(6) 495-504.
Hoffmann J Person, Shajan G Person, Budde J Person, Scheffler K Person und Pohmann R Person (Mai-2013) Human brain imaging at 9.4 T using a tunable patch antenna for transmission Magnetic Resonance in Medicine 69(5) 1494–1500.
Pohmann R Person, Shajan G Person, Hoffmann J Person, Budde J Person, Hagberg G Person, Bieri O , Bisdas S , Ernemann U , Weigel M , Ehses P Person, Hennig J , Chadzynski G und Scheffler K Person (April-2013) Imaging and Spectroscopy at 9.4 Tesla: First Results on Patients and Volunteers MAGNETOM Flash 2013(2) 58-67.
Shajan G Person, Hoffmann J Person, Balla DZ Person, Deelchand DK , Scheffler K Person und Pohmann R Person (Oktober-2012) Rat brain MRI at 16.4T using a capacitively tunable patch antenna in combination with a receive array NMR in Biomedicine 25(10) 1170–1176.
Pohmann R Person, Shajan G Person und Balla D Person (Dezember-2011) Contrast at high field: Relaxation times, magnetization transfer and phase in the rat brain at 16.4 T Magnetic Resonance in Medicine 66(6) 1572-1581.
Shajan G Person, Hoffmann J Person, Budde J Person, Adriany G , Ugurbil K und Pohmann R Person (August-2011) Design and Evaluation of an RF Front-End for 9.4 T Human MRI Magnetic Resonance in Medicine 66(2) 594–602.
Budde J Person, Shajan G Person, Hoffmann J Person, Ugurbil K und Pohmann R Person (Februar-2011) Human imaging at 9.4 T using T2*-, phase-, and susceptibility-weighted contrast Magnetic Resonance in Medicine 65(2) 544-550.
Hong S-T Person, Balla DZ Person, Shajan G Person, Choi C , Ugurbil K und Pohmann R Person (Januar-2011) Enhanced neurochemical profile of the rat brain using in vivo 1H NMR spectroscopy at 16.4 T Magnetic Resonance in Medicine 65(1) 28-34.
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Beiträge zu Tagungsbänden (1):

Balla DZ Person, Ehses P Person, Pohmann R Person, Budde J Person, Mirkes C Person, Shajan G Person, Bowtell R und Scheffler K Person (Juli-2013) Functional QSM at 9.4T with single echo gradient-echo and EPI acquisition 2nd International Workshop on MRI Phase Contrast & Quantitative Susceptibility Mapping (QSM 2013), 1-4.
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Poster (32):

Ehses P Person, Shajan G Person und Scheffler K Person (Mai-15-2014): 3D Radial GRE-EPI with Up to 8-Fold Acceleration for Functional Imaging at 9.4T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Chadzynski GL Person, Henning A Person, Ehses P Person, Hoffmann J Person, Shajan G Person und Scheffler K Person (Mai-15-2014): High-Resolution Free Induction Decay Proton MRSI in the Human Brain at 9.4 T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Mirkes CC Person, Shajan G Person, Hoffmann J Person, Brenner D , Pohmann R Person und Scheffler K Person (Mai-15-2014): Sodium B1 mapping at 9.4 T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Bause J Person, Ehses P Person, Shajan G Person, Scheffler K Person und Pohmann R Person (Mai-12-2014): Functional ASL at 9.4 T: a Comparison Between Balanced SSFP and GRE-EPI Readout, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Goense J Person, Beyerlein M Person, Hoffmann J Person, Shajan G Person, Steudel T Person, Scheffler K Person, Logothetis NK Person und Merkle H Person (Mai-12-2014): Novel RF-Coil Assembly to Simultaneously Investigate fMRI and Electrophysiology in Non-Human Primates in a Large Bore Vertical Magnet, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy.
Balla DZ Person, Ehses P Person, Pohmann R Person, Budde J Person, Mirkes C Person, Shajan G Person, Bowtell R und Scheffler K Person (Juli-2013): Functional QSM at 9.4T with single echo gradient-echo and EPI acquisition, 2nd International Workshop on MRI Phase Contrast & Quantitative Susceptibility Mapping (QSM 2013), Ithaca, NY, USA.
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Hagberg GE Person, Martirosian P , Bause J Person, Shajan G Person, Klose U und Scheffler K Person (April-25-2013): Time-Of-Flight Angiography in Humans at 9.4T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Bakhtiary M Person, Shajan G Person, Hoffmann J Person, Scheffler K Person und Pohmann R Person (April-2013): 31P-spectroscopy on humans at 9.4 T in combination with a patch antenna for proton imaging: Initial results, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Mirkes C Person, Hoffmann J Person, Shajan G Person, Pohmann R Person und Scheffler K Person (April-2013): Amide Proton Chemical Exchange Saturation Transfer at 9.4 T with Optimized RF Transmit Field Through B1 Shimming, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Mirkes C Person, Hoffmann J Person, Shajan G Person, Pohmann R Person und Scheffler K Person (April-2013): Combination of a sodium birdcage coil with a tunable patch antenna for B0 shimming and anatomical localization at 9.4 T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Kozlov M , Shajan G Person und Turner R (April-2013): Effects of Tuning Condition, Head Size and Position on the SAR of a 9.4T Dual Row Array, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Chadzynski G Person, Bisdas S , Hagberg G Person, Pohmann R Person, Shajan G Person, Kolb R , Klose U und Scheffler K Person (April-2013): First Proton CSI of a Human Brain Tumor at 9.4T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Chadzynski G Person, Pohmann R Person, Shajan G Person, Kolb R , Klose U und Scheffler K Person (April-2013): Gradient Induced Sideband Artifacts in non Water-Suppressed Proton CSI of the Human Brain at 9.4 T, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Budde J Person, Shajan G Person, Scheffler K Person und Pohmann R Person (April-2013): Ultra-High-Resolution Imaging of the Human Brain at 9.4 T Using k-Space Weighted Acquisition, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
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Budde J Person, Shajan G Person, Scheffler K Person und Pohmann R Person (März-2013): k-Space Weighted Acquisition for Ultra-High-Resolution Imaging of the Human Brain at 9.4 T, ISMRM Workshop Ultra High Field MRI: What is in Full Bloom & What is Sprouting?, Noordwijk aan Zee, Netherlands.
Bause J Person, Shajan G Person, Hoffmann J Person, Scheffler K Person und Pohmann R Person (Mai-7-2012): Design and SAR Estimation of a Segmented Loop for Dual Coil CASL at 9.4 T, 20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), Melbourne, Australia.
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Ehses P Person, Budde J Person, Shajan G Person und Scheffler K Person (Mai-2012): Distortion-free high-resolution fMRI at 9.4 T, 20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), Melbourne, Australia.
Budde J Person, Shajan G Person, Zaitsev M , Scheffler K Person und Pohmann R Person (Mai-2012): Human functional imaging at 9.4 T: Spin echo and gradient echo EPI, 20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), Melbourne, Australia.
Shajan G Person, Hoffmann J Person und Pohmann R Person (Mai-2011): A 15-channel receive array and 16 channel detunable transmit coil for human brain imaging at 9.4 T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
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Budde J Person, Mühlbauer F Person, Shajan G Person, Zaitsev M und Pohmann R Person (Mai-2011): Human fMRI at 9.4 T: Preliminary Results, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
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Shajan G Person, Hoffmann J Person, Balla DZ Person und Pohmann R Person (Mai-2010): A 700MHz Receive Array using Patch Antenna for Spin Excitation, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hoffmann J Person, Shajan G Person und Pohmann R Person (Mai-2010): Capacitively Tunable Patch Antenna for Human Head Imaging at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Balla DZ Person, Wiesner HM Person, Shajan G Person und Pohmann R Person (Mai-2010): Functional MRI in the rat at 9.4 T and 16.4 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Budde J Person, Shajan G Person, Mühlbauer F Person, Hoffmann J Person, Ugurbil K und Pohmann R Person (Mai-2010): Human T2* and Phase Imaging at 9.4 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hong S-T Person, Balla DZ Person, Shajan G Person, Choi C , Ugurbil K und Pohmann R Person (Mai-2010): Localized in Vivo 1H NMR Spectroscopy of the Rat Brain at 16.4T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hong S-T Person, Balla DZ Person, Shajan G Person, Choi C und Pohmann R Person (Mai-2010): Regional Variations of Metabolite Concentrations in the Rat Brain Assessed with in vivo 1H MR Spectroscopy at 16.4T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hoffmann J Person, Budde J Person, Shajan G Person und Pohmann R Person (Mai-2010): Slice-Selective B1 Phase Shimming at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Balla DZ Person, Wiesner HM Person, Shajan G Person und Pohmann R Person (April-2009): Functional MRI in the rat brain with single-shot gradient echo EPI at 16.4 T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
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Hong S-T Person, Balla DZ Person, Shajan G Person, Ugurbil K und Pohmann R Person (April-2009): Highly Accurate Quantification of Proton MR Spectroscopy in Rat Brain in Vivo at 16.4 T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
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Balla DZ Person, Wiesner HM Person, Shajan G Person, Faber C und Pohmann R Person (April-2009): TurboCRAZED BOLD imaging detects specific activation in the rat brain after somatosensory stimulation at 16.4 Tesla, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
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Shajan G Person, Balla DZ Person, Hoffmann J Person und Pohmann R Person (Oktober-2008): A Microstrip Resonator for Animal MRI at 16.4 T, ESMRMB 2008 Congress: 25th Annual Meeting, Valencia, Spain, Magnetic Resonance Materials in Physics, Biology and Medicine, 21(Supplement 1) 449-450.
Balla DZ Person, Hong S-T Person, Shajan G Person, Pohmann R Person und Ugurbil K (Mai-2008): Single Voxel MR Spectroscopy with Echo Times Below 2 ms at 16.4 T in the Rat Brain: First in vivo Results, 16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008), Toronto, Canada.
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Vorträge (15):

Shajan G Person, Mirkes C Person, Hoffmann J Person, Scheffler K Person und Pohmann R Person (Mai-14-2014) Abstract Talk: A Three-Layered Coil Arrangement for Sodium Imaging of the Human Brain at 9.4T, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy(0620).
Hoffmann J Person, Mirkes C Person, Shajan G Person, Scheffler K Person und Pohmann R Person (Mai-13-2014) Abstract Talk: A 3-Port Traveling-Wave Antenna in Combination with TIAMO for the Acquisition of Void-Free Brain Images at 9.4 Tesla, Joint Annual Meeting ISMRM-ESMRMB 2014, Milano, Italy(0399).
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Last updated: Dienstag, 18.11.2014