Event Calendar:
![[Previous Month]](fileadmin/template/main/calendar/img/left_day.gif)
![[Next Month]](fileadmin/template/main/calendar/img/right_day.gif)
Contact
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 |
In magnetic resonance imaging, radio frequency (RF) coils are used to produce RF magnetic fields in order to excite the nuclei as well as for acquisition of the induced NMR signal. The push towards higher static magnetic field strength in search of higher signal to noise ratio increases the RF (B1) field frequency. Constructive and destructive interferences due to the resultant shorter wavelength in tissue create strong inhomogeneities in the B1+ field produced by conventional coils. Hence specialized RF hardware and B1 management methods are required to obtain high-quality images that take full advantage of the increased static field strength.
I am involved in the development of RF coils and associated front-end RF hardware like low noise preamplifiers, TR switches, quadrature hybrids etc for the 9.4 T human MRI scanner and 16.4 T small animal scanner.
RF Coils for Human Brain MRI at 9.4T
Transmit Only Receive Only Coil Arrays
At Larmor frequencies as high as 400 MHz, transmit array coils are essential tools to mitigate B1+ field inhomogeneities caused by the shorter wavelength in tissue. Additional flexibility to influence the B1+ field in the lower brain regions like the cerebellum and the lower temporal lobes can be achieved by unique coil layouts like the dual-row transmit array configuration.
In this project, an actively detunable 16-element dual row transmit loop coil was designed which could be combined with our 24-channel receive only helmet for increased sensitivity during reception. Furthermore, since this coil has built-in TR switches with preamplifiers, this coil can be easily combined with mulit-nuclei coils for co-localization.
Transceiver Arrays
In this project, the complete RF front-end required for human MRI at 9.4 T was designed and evaluated. A 16 channel elliptical transceiver array using microstrip transmission line elements was designed. To separate the transmit and receive functions, TR switches and preamplifiers were designed. The coil can be operated in circularly polarized mode or RF shimming methods can be applied to favourably influence the transmit field.
RF Coils for MRI at 16.4T
Our lab is equipped with one of the strongest horizontal bore magnets currently available for small animal MRI. RF coils optimized for rat brain imaging, whole body mouse imaging etc were developed for imaging in this scanner.
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)
Articles (5): | |
|---|---|
| • |
Shajan G  , Hoffmann J , Balla DZ , , Scheffler K and Pohmann R (January-2012) Rat Brain MRI at 16.4 T Using a Capacitively Tunable Patch Antenna in Combination with a Receive Array
NMR in Biomedicine . accepted |
| • |
Pohmann R , Shajan G and Balla D (December-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 , Hoffmann J , Budde J , , and Pohmann R (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 , Shajan G , Hoffmann J , and Pohmann R (February-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 , Balla DZ , Shajan G , , and Pohmann R (January-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.
|
Posters (16): | |
| • |
Shajan G , Hoffmann J and Pohmann R (May-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.
|
| • |
Budde J , Mühlbauer F , Shajan G , and Pohmann R (May-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.
|
| • |
Balla D , Gottschalk S , Shajan G , , , Pohmann R and Engelmann J (May-2011): In vivo visualization of pancreatic islets in the mouse, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada.
|
| • |
Shajan G , Hoffmann J , Balla DZ and Pohmann R (May-2010): A 700MHz Receive Array using Patch Antenna for Spin Excitation, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Hoffmann J , Shajan G and Pohmann R (May-2010): Capacitively Tunable Patch Antenna for Human Head Imaging at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Balla DZ , Wiesner HM , Shajan G and Pohmann R (May-2010): Functional MRI in the rat at 9.4 T and 16.4 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Budde J , Shajan G , Mühlbauer F , Hoffmann J , and Pohmann R (May-2010): Human T2* and Phase Imaging at 9.4 T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Hong S-T , Balla DZ , Shajan G , , and Pohmann R (May-2010): Localized in Vivo 1H NMR Spectroscopy of the Rat Brain at 16.4T, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Hong S-T , Balla DZ , Shajan G , and Pohmann R (May-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.
|
| • |
Hoffmann J , Budde J , Shajan G and Pohmann R (May-2010): Slice-Selective B1 Phase Shimming at 9.4 Tesla, ISMRM-ESMRMB Joint Annual Meeting 2010, Stockholm, Sweden.
|
| • |
Balla DZ , Wiesner HM , Shajan G and Pohmann R (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.
|
| • |
Hong S-T , Balla DZ , Shajan G , and Pohmann R (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.
|
| • |
Budde J , Pohmann R , Shajan G and (April-2009): Susceptibility Weighted Imaging of the Human Brain at 9.4T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
|
| • |
Balla DZ , Wiesner HM , Shajan G , and Pohmann R (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.
|
| • |
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 (May-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.
|
Talks (3): | |
| • |
Hoffmann JO , Shajan G and Pohmann R (May-2011): Human Brain Imaging at 9.4 Tesla Using a Combination of Traveling Wave Excitation with a 15-Channel Receive-Only Array, 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montréal, Canada(164).
|
| • |
Budde J , Pohmann R , Shajan G and (April-2009): Susceptibility Weighted Imaging of the Human Brain at 9.4T, 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009), Honolulu, HI, USA.
|
| • |
Balla DZ , , , Shajan G and Pohmann R (October-2-2008): Strong BOLD-effect with TurboCRAZED MRI following hyperoxia in the rat brain at 16.4 T, ESMRMB 2008 Congress: 25th Annual Meeting, Valencia, Spain, Magnetic Resonance Materials in Physics, Biology and Medicine, 21(Supplement 1) 36-37.
|