Contact

Dr. Shajan Gunamony

Address: Spemannstr. 41
72076 Tübingen
Room number: 3.B.06
Phone: +49 7071 601 734
Fax: +49 7071 601 702
E-Mail: Shajan.Gunamony

 

Picture of Gunamony, Shajan, Dr.

Shajan Gunamony

Position: Research Scientist  Unit: Alumni Scheffler

Radio Frequency Coils for Ultra-High Field MRI

Volume resonators, highly successful at clinical field strength, cannot be used at ultra-high field (UHF) because of the inhomogeneous distribution of the RF field in tissue caused by the shorter wavelength. Hence, at UHF, transmit array coils are an essential tool to apply static or dynamic parallel transmission methods to mitigate the inhomogeneous spatial distribution of the RF field produced by the coil.

 

It is equally important to optimize the receive performance of the setup by using receive array coils designed to maximize the signal to noise ratio (SNR) and improved parallel imaging capability.

 

I am involved in the development of RF coils and RF hardware for the different MRI scanners in the institute. The main projects are:

 

  • Design of a dual-row transmit array in combination with a receive array for optimum image SNR from the whole brain at 9.4 T.

 

  • A 23Na MRI setup designed to maximize the 23Na SNR. The setup also has B0 shimming capability.

 

  • Shaped receive arrays for simultaneous electrophysiology and fMRI.

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)

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Posters (47):

Goense J, Beyerlein M, Hoffmann J, Shajan G, Steudel T, Scheffler K, Logothetis NK and Merkle H (May-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, Ehses P, Pohmann R, Budde J, Mirkes C, Shajan G, Bowtell R and Scheffler K (July-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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Bakhtiary M, Shajan G, Hoffmann J, Scheffler K and Pohmann R (April-25-2013): 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, Hoffmann J, Shajan G, Pohmann R and Scheffler K (April-25-2013): 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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Chadzynski G, Pohmann R, Shajan G, Kolb R, Klose U and Scheffler K (April-25-2013): 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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Hagberg GE, Martirosian P, Bause J, Shajan G, Klose U and Scheffler K (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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Kozlov M, Shajan G and Turner R (April-24-2013): 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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Mirkes C, Hoffmann J, Shajan G, Pohmann R and Scheffler K (April-23-2013): 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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Chadzynski G, Bisdas S, Hagberg G, Pohmann R, Shajan G, Kolb R, Klose U and Scheffler K (April-23-2013): 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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Budde J, Shajan G, Scheffler K and Pohmann R (April-23-2013): 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, Shajan G, Scheffler K and Pohmann R (March-4-2013): 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.
Bakhtiary M, Pohmann R, Guanmony S and Scheffler K (June-8-2012): NMR phosphorus spectroscopy at 9.4 Tesla using construted Quadrature surface coil, 3rd Scientific Symposium on Ultrahigh Field MR, Berlin, Germany.
Bause J, Shajan G, Hoffmann J, Scheffler K and Pohmann R (May-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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Shajan G, Hoffmann J and Pohmann R (May-12-2011): A 15-Channel Receive Array & 16-Channel Detunable Transmit Coil for Human Brain Imaging at 9.4T, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
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Budde J, Mühlbauer F, Shajan G, Zaitsev M and Pohmann R (May-11-2011): 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, Hoffmann J, Balla DZ and Pohmann R (May-6-2010): A 700MHz Receive Array using Patch Antenna for Spin Excitation, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hoffmann J, Shajan G and Pohmann R (May-6-2010): Capacitively Tunable Patch Antenna for Human Head Imaging at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hoffmann J, Budde J, Shajan G and Pohmann R (May-6-2010): Slice-Selective B1 Phase Shimming at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Balla DZ, Wiesner HM, Shajan G and Pohmann R (May-5-2010): 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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Hong S-T, Balla DZ, Shajan G, Choi C, Ugurbil K and Pohmann R (May-5-2010): 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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Budde J, Shajan G, Mühlbauer F, Hoffmann J, Ugurbil K and Pohmann R (May-4-2010): Human T2* and Phase Imaging at 9.4 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
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Hong S-T, Balla DZ, Shajan G, Choi C and Pohmann R (May-4-2010): 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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Hong S-T, Balla DZ, Shajan G, Ugurbil K and Pohmann R (April-22-2009): 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, Wiesner HM, Shajan G, Faber C and Pohmann R (April-22-2009): 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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Balla DZ, Wiesner HM, Shajan G and Pohmann R (April-20-2009): 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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Shajan G, Balla DZ, Hoffmann J and Pohmann R (October-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, Hong S-T, Shajan G, Pohmann R and Ugurbil K (May-6-2008): 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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Theses (1):

Shajan G: Radio Frequency Coils for Ultra-high Field Magnetic Resonance Imaging, Eberhard Karls Universität Tübingen, (2016). PhD thesis

Popular Scientific Articles (1):

Buckenmaier K, Shajan G, Chadzynski G, Hoffmann J, Pohmann R and Scheffler K: Magnetresonanztomografie bei ultrahohen Feldstärken - Forschungsbericht 2014 Max-Planck-Institut für biologische Kybernetik, Jahrbuch der Max-Planck-Gesellschaft 2014.

Talks (27):

Gunamony S and Bause J (April-23-2017) Invited Lecture: Construction of Rx Arrays, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA 62.
Hagberg GE, Bause J, Ethofer T, Ehses P, Dresler T, Shajan G, Pohmann R, Herbert C, Fallgatter A, Laske C, Pavlova M and Scheffler K (May-9-2016) Abstract Talk: Consistent detection of age-dependent variations of the longitudinal relaxation time in cortical brain regions investigated by MP2RAGE at 9.4T: influence of correcting for a non-uniform transmit field, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore(0059).
Shajan G (March-23-2016) Invited Lecture: Design, performance and safety evaluation of RF coil arrays for brain imaging at 9.4T, University of Glasgow: Seminar Series in Psychology, Glasgow, UK.
Zivkovic I, Mirkes C, Shajan G and Scheffler K (October-2015) Abstract Talk: B0 shimming at 9.4T with multicoil approach: numerical investigation of different coil geometries, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S391.
Shajan G, Bause J, Pohmann R and Scheffler K (October-2015) Abstract Talk: Choice of RF coils at 9.4T: SNR and B1+ of transceiver and transmit-only receive-only arrays, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S58-S59.
Chadzynski GL, Scheffler K, Bause J, Shajan G, Pohmann R and Ehses P (October-2015) Abstract Talk: Fast and efficient free induction decay proton MRSI in the 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) S298-S299.
Hagberg GE, Bause J, Ethofer T, Dresler T, Herbert C, Pohmann R, Shajan G, Fallgatter A and Scheffler K (October-2015) Abstract Talk: T1 relaxometry and tissue segmentation of the human brain at 9.4T and 3T using MP2RAGE, 32nd Annual Scientific Meeting ESMRMB 2015, Edinburgh, UK, Magnetic Resonance Materials in Physics, Biology and Medicine, 28(1 Supplement) S234-S235.
Shajan G (September-30-2015) Invited Lecture: Design of RF Coils for Ultra-high Field MRI, University of Glasgow: Seminar Series in Psychology, Glasgow, UK.
Chadzynski GK, Hagberg G, Bause J, Shajan G, Bisdas S, Pohmann R and Scheffler K (June-5-2015) Abstract Talk: In-vivo proton MR spectroscopic imaging of the human brain gliomas at 9.4 Tesla: evaluation of metabolite coordinates, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada(0763).
Mirkes C, Shajan G and Scheffler K (June-1-2015) Abstract Talk: Fast Sodium Imaging at 9.4 Tesla, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada(0064).
Shajan G, Mirkes C, Hoffmann J, Scheffler K and Pohmann R (May-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, Mirkes C, Shajan G, Scheffler K and Pohmann R (May-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).
Mirkes C, Hoffmann J, Shajan G, Pohmann R and Scheffler K (October-5-2013) Abstract Talk: Quantitative Sodium Imaging at 9.4 T, 30th Annual Scientific Meeting ESMRMB 2013, Toulouse, France, Magnetic Resonance Materials in Physics, Biology and Medicine, 26(Supplement 1) 370.
Hoffmann J, Shajan G, Scheffler K and Pohmann R (October-4-2013) Abstract Talk: Combination of Multimode Traveling-Wave Excitation and TIAMO for Human Brain Imaging at 9.4 T, 30th Annual Scientific Meeting ESMRMB 2013, Toulouse, France, Magnetic Resonance Materials in Physics, Biology and Medicine, 26(Supplement 1) 192.
Bause J, Shajan G, Scheffler K and Pohmann R (October-4-2013) Abstract Talk: High Resolution Arterial Spin Labeling in the Human Brain at 9.4 T: Initial Results using FAIR, 30th Annual Scientific Meeting ESMRMB 2013, Toulouse, France, Magnetic Resonance Materials in Physics, Biology and Medicine, 26(Supplement 1) 257.
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Mirkes CC, Shajan G, Hoffmann J and Scheffler K (May-2013) Abstract Talk: Amide Proton Chemical Exchange Saturation Transfer at 9.4T, 3rd International Workshop on Chemical Exchange Saturation Transfer Imaging (OctoberCEST 2012), Annapolis, MD, USA, Contrast Media & Molecular Imaging, 8(3) 311-312.
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Ehses P, Budde J, Shajan G and Scheffler K (April-24-2013) Abstract Talk: T2-weighted BOLD fMRI at 9.4 T using a S2-SSFP-EPI sequence, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA 1090.
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Hoffmann J, Shajan G, Scheffler K and Pohmann R (April-23-2013) Abstract Talk: RF Shimming Capabilities at 9.4 Tesla using a 16-channel Dual-Row Array, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA 901.
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Shajan G, Hoffmann J, Scheffler K and Pohmann R (October-2012) Abstract Talk: A 31-Element Receive Array for Human Brain Imaging at 9.4T, 29th Annual Scientific Meeting ESMRMB 2012, Lisboa, Portugal, Magnetic Resonance Materials in Physics, Biology and Medicine, 25(Supplement 1) 265-266.
Chadzynski GI, Shajan G, Kolb R, Pohmann R, Klose U and Scheffler K (October-2012) Abstract Talk: In-vivo Proton Chemical Shift Imaging at 9.4 T: initial results, 29th Annual Scientific Meeting ESMRMB 2012, Lisboa, Portugal, Magnetic Resonance Materials in Physics, Biology and Medicine, 25(Supplement 1) 270.
Shajan G, Hoffmann J, Scheffler K and Pohmann R (May-8-2012) Abstract Talk: A 16-Element Dual-row Transmit Coil Array for 3D RF Shimming at 9.4 T, 20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012), Melbourne, Australia(308).
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Last updated: Tuesday, 18.11.2014