Dr. Rolf Pohmann

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 3.B.02
Tel.: 07071 601 903
Fax: 07071 601 702
E-Mail: Rolf.Pohmann


Bild von Pohmann, Rolf, Dr.

Rolf Pohmann

Position: Projektleiter  Abteilung: Scheffler

Magnetic Resonance Imaging at ultra high fields requires novel techniques, both concerning hardware and imaging sequences. At field strengths of 9.4 T (human) and 14.1 T (rodents), I investigate the capabilities of ultra high field MRI. Specifically, our aim is to

  • quantify the MR parameters at ultra high field strength,
  • find solutions to some of the major challenges involved in ultra high field MRI, like B1-homogeneity or safety,
  • develop techniques that take full advantage of the potential of the high field strength and assess the gain compared to conventional MR instruments
  • help in appying those techniques to medical or biological applications
  • help in combining ultra-high field MRI with other techniques to gain additional information in neuroscientific studies.

In addition, I assist other groups by developing or optimizing specialized techniques for their applications.





For a comprehensive overview over our projects, please see our project group web page.

Evaluation of Signal Gain and MR tissue parameters at ultra-high field

While the number of ultra-high field MR scanners is still growing rapidly, mainly due to the desired SNR gain with increasing fields, surprisingly little is known about the actual SNR that can be obtained with higher fields. In this project we compared the SNR and tissue parameters at 3 T, 7 T and 9.4 T. The same subjects were scanned with the same gradient echo sequence at all three fields, and the SNR of the resulting maps were corrected for the differences in relaxation times and transmit field. Since it is not easily possible to obtain reliable values for the sensitivity of the receive coils, arrays with similar number of elements and geometry were used. The SNR was found to increase supralinearily with the field strength, following a relation of SNR ≈ B01.65.

SNR (top) and relative SNR differences (bottom) at 3 T, 7 T and 9.4 T. Data are from the same subject at all fields. SNR increases supralinearily, growing by 3.3 from 3 T to 7 T and another factor of 1.67 from 7 T to 9.4 T.



Ultra-high Resolution Imaging with Acquisition Weighting

High spatial resolutions are one of the main goals of ultra-high field imaging. In this study we demonstrated the possibility to obtain images with voxel sizes down to 14 nl with sufficient SNR in an acceptable scan time by combining the ultra-high field with a highly sensitive 31 channel array coil and a special, SNR optimized imaging technique. By performing a k-space weighting during acquisition, it can be shown that this method not only avoids ringing artifacts, but also increases SNR by up to 36% without losses in spatial resolution or scan time (publication).

High resolution images (0.2 × 0.2 × 0.5) mm3 acquired with a conventional (top) and the acquisition weighted sequence (bottom). The weighted images show greater fine detail and a higher SNR.


High sensitivity perfusion imaging with Arterial Spin Labeling

Arterial Spin Labeling is a promising technique for quantitative perfusion imaging without the need for contrast agents. Since ASL generally suffers from a low signal-to-noise ratio, we concentrate on implementing and developing techniques with high sensitivity. To reach this goal, we follow several different approaches:

  • In contrast to the most commonly used techniques of pulsed arterial spin labeling, continuous arterial spin labeling has a considerably increased sensitivity, but also a higher complexity. We have implemented a number of different variants of continuous ASL, which are now used in neuroscientific and biological applications (publication).

    Perfusion images acquired with different CASL and a PASL technique.

  • In contrast to the cortex in the brain, which has a very high perfusion, the white matter or, even more, the skeletal muscle are only poorly perfused, making highly quantitative measurement difficult. For making it possible to obtain quantitative values of the perfusion from those tissues, a highly sensitive technique based on single-voxel spectroscopy was developed. This FAIRPRESS techniques has been successfully used to quantify the perfusion in the white matter as well as in muscels in the legs of rats and humans.
  • In addition to the gain in intrinisc signal-to-noise ration at ultra-high field, the longer longitudinal relaxation time will help to further improve the accuracy of perfusion images. Using the most sensitive CASL sequences is, however, hampered by the high SAR with is necessary to label the inflowing blood. Using a dual-coil CASL technique, that applies the labelling field with separate, local coils at the neck of the volunteer, it will be possible to reduce SAR far enough to be able to take full advantage of the improved signal at higher field.

Multiband fMRI in animal studies

High temporal resolution is a crucial factor in many fMRI studies. Multiband imaging is a novel technique to increase the speed of fMRI acquisition by using parallel imaging methods to obtain the signals from two or more slices simultaneously. While this technique is already used frequently in human fMRI, it has so far not been applied in animal studies. We have implemented multiband EPI on an animal scanner and evaluated its performance with different fMRI protocols.

fMRI data from a rat forepaw stimulation experiment at 7 T, acquired with a conventional sequence (left) and a dual-band EPI with double temporal resolution.

Measurement of MR imaging parameters at ultra high field

When increasing the field strength, MR relaxation times, magnetization transfer effects, and susceptibility-induced field variations will change. We have measured and quantified those parameters at field strengths up to 16.4 T and analysed the effects of those changes on SNR and contrast of the resulting images (publication).

The relaxation times T1, T2 and T2* were measured with high accuracy and spatial resolution using inversion recovery, single spin echo and gradient echo sequences, respectively, with varying delays. The MTR was measured by off-resonance irradiation at different frequencies and power levels and the resulting values were used to determine the parameters of a two-pool model [2] to allow for comparison to other field strengths. Local frequency variations were deduced from phase changes in gradient echo images with varying echo time.

With values between 1834 ms (white matter ) and 2376 ms (hippocampus), T1 was significantly increased compared to lower fields, while T2 and T2* are relatively low (corpus callosum: 20 ms / 13.6 ms, cortex: 24 ms / 21 ms). The MTR varies between 51% and 61% and thus is considerably stronger than at lower field. Image phase shows distinct differences between different anatomical structures and can be a valuable contrast mechanism at high field. In all parameter maps, all major anatomical structures were clearly visible.

Comparisons to publications at lower field show an increase in contrast-to-noise ratio with field strength for all contrast mechanisms. Especially phase and T2* imaging have great potential for use in neuroscientific and preclinical applications.


Flip angle mapping

Highly accurate, fast, and simple mapping of the excitation field is a crucial requirement for ultra high field MR imaging. In an extensive study, we are comparing the accuracy and precision of the most popular flip angle mapping techiques, both theoretically and in experiments under different settings. The results will be used to further improve the performance of these sequences to enable highly accurate shaping of the transmit field using B1-shimming or Transmit SENSE (publication).


For information about the other projects in our group, please see  our project group web page.

Current Position:

Group Leader Ultra High Field MRI

at the Max-Planck-Institute for Biological Cybernetics


University studies in physics at the universities Würzburg, Germany and Buffalo, New York.

Diploma thesis on 'Theoretical Analysis of the quality of spectroscopic NMR imaging techniques'

1995-1999 PhD thesis at the University Würzburg on "Techniques for spatially resolved NMR-spectroscopy"
1999-2002 Deparment for Mission Planning at the German Space Operation Center (GSOC) at the German Center Aerospace Center (DLR) in Oberpfaffenhofen, Germany
2002-2005 Preclinical MRI/MRS Lab at Roche Pharmaceuticals in Basle, Switzerland.
since 2006 Max-Planck Institute for biological Cybernetics, Tübingen, Germany
scientific awards:

Wilhelm-Conrad-Röntgen Wissenschaftspreis 2001

of the University of Würzburg

Scientific award 2003 of the unterfränkischen Gedenkjahrstiftung für Wissenschaft

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Artikel (44):

Gajdošík M, Chadzynski GL, Hangel G, Mlynarik V, Chmelík M, Valkovic L, Bogner W, Pohmann R, Scheffler K, Trattnig S und Krššák M (Oktober-2015) Ultrashort-TE stimulated echo acquisition mode (STEAM) improves the quantification of lipids and fatty acid chain unsaturation in the human liver at 7 T NMR in Biomedicine 28(10) 1283–1293.
Wiesner HM, Balla DZ, Shajan G, Scheffler K, Ugurbil K, Chen W, Uludag K und Pohmann R (Juni-2015) 17O relaxation times in the rat brain at 16.4 tesla Magnetic Resonance in Medicine Epub ahead.
Chadzynski GL, Pohmann R, Shajan G, Kolb R, Bisdas S, Klose U und Scheffler K (Juni-2015) 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 28(3) 239-249.
Bause J, Ehses P, Mirkes C, Shajan G, Scheffler K und Pohmann R (Mai-2015) Quantitative and functional pulsed arterial spin labeling in the human brain at 9.4 t Magnetic Resonance in Medicine Epub ahead.
Loktyushin A, Nickisch H, Pohmann R und Schölkopf B (April-2015) Blind multirigid retrospective motion correction of MR images Magnetic Resonance in Medicine 73(4) 1457–1468.
Hoffmann J, Henning A, Giapitzakis IA, Scheffler K, Shajan G, Pohmann R und Avdievich NI (April-2015) Safety testing and operational procedures for self-developed radiofrequency coils NMR in Biomedicine Epub ahead.
Hoffmann J, Mirkes C, Shajan G, Scheffler K und Pohmann R (März-2015) Combination of a multimode antenna and TIAMO for traveling-wave imaging at 9.4 Tesla Magnetic Resonance in Medicine Epub ahead.
Pohmann R, Speck O und Scheffler K (März-2015) Signal-to-noise ratio and MR tissue parameters in human brain imaging at 3, 7, and 9.4 tesla using current receive coil arrays Magnetic Resonance in Medicine Epub ahead.
Shajan G, Mirkes C, Buckenmaier K, Hoffmann J, Pohmann R und Scheffler K (März-2015) Three-layered radio frequency coil arrangement for sodium MRI of the human brain at 9.4 Tesla Magnetic Resonance in Medicine Epub ahead.
Mirkes CC, Hoffmann J, Shajan G, Pohmann R und Scheffler K (Januar-2015) High-resolution quantitative sodium imaging at 9.4 tesla Magnetic Resonance in Medicine 73(1) 342–351.
Rauscher I, Bender B, Grözinger G, Luz O, Pohmann R, Erb M, Schick F und Martirosian P (November-2014) Assessment of T1, T1ρ, and T2 values of the ulnocarpal disc in healthy subjects at 3 Tesla Magnetic Resonance Imaging 32(9) 1085–1090.
Hoffmann J, Shajan G, Scheffler K und Pohmann R (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.
Grözinger G, Pohmann R, Schick F, Grosse U, Syha R, Brechtel K, Rittig K und Martirosian P (Oktober-2014) Perfusion measurements of the calf in patients with peripheral arterial occlusive disease before and after percutaneous transluminal angioplasty using Mr arterial spin labeling Journal of Magnetic Resonance Imaging 40($) 980–987.
Balla DZ, Schwarz S, Wiesner HM, Hennige AM und Pohmann R (Juli-2014) Monitoring the stress-level of rats with different types of anesthesia: A tail-artery cannulation protocol Journal of Pharmacological and Toxicological Methods 70(1) 35-39.
Rauschenberg J, Nagel AM, Ladd SC, Theysohn JM, Ladd ME, Möller HE, Trampel R, Turner R, Pohmann R, Scheffler K, Brechmann A, Stadler J, Felder J, Shah NJ und Semmler W (Mai-2014) Multicenter Study of Subjective Acceptance During Magnetic Resonance Imaging at 7 and 9.4 T Investigative Radiology 49(5) 249-259.
Shajan G, Kozlov M, Hoffmann J, Turner R, Scheffler K und Pohmann R (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, Shajan G, Scheffler K und Pohmann R (Februar-2014) Ultra-high resolution imaging of the human brain using acquisition-weighted imaging at 9.4 T NeuroImage 86 592–598.
Budde J, Shajan G, Zaitsev M, Scheffler K und Pohmann R (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.
Loktyuschin A, Nickisch H, Pohmann R und Schölkopf B (Dezember-2013) Blind Retrospective Motion Correction of MR Images Magnetic Resonance in Medicine 70(6) 1608–1618.
Balla DZ, Gottschalk S, Shajan G, Ueberberg S, Schneider S, Hardtke-Wolenski M, Jaeckel E, Hoerr V, Faber C, Scheffler K, Pohmann R und Engelmann J (Dezember-2013) In vivo visualization of single native pancreatic islets in the mouse Contrast Media & Molecular Imaging 8(6) 495-504.
Hoffmann J, Shajan G, Budde J, Scheffler K und Pohmann R (Mai-2013) Human brain imaging at 9.4 T using a tunable patch antenna for transmission Magnetic Resonance in Medicine 69(5) 1494–1500.
Leitão J, Thielscher A, Werner S, Pohmann R und Noppeney U (April-2013) Effects of Parietal TMS on Visual and Auditory Processing at the Primary Cortical Level: A Concurrent TMS-fMRI Study Cerebral Cortex 23(4) 873-884.
Pohmann R, Shajan G, Hoffmann J, Budde J, Hagberg G, Bieri O, Bisdas S, Ernemann U, Weigel M, Ehses P, Hennig J, Chadzynski G und Scheffler K (April-2013) Imaging and Spectroscopy at 9.4 Tesla: First Results on Patients and Volunteers MAGNETOM Flash 2013(2) 58-67.
Pohmann R und Scheffler K (März-2013) A theoretical and experimental comparison of different techniques for B1 mapping at very high fields NMR in Biomedicine 26(3) 265–275.
Cavusoglu M, Pohmann R, Burger HC und Uludag K (Februar-2013) Regional effects of magnetization dispersion on quantitative perfusion imaging for pulsed and continuous arterial spin labeling Magnetic Resonance in Medicine 69(2) 524–530.
Hong S-T und Pohmann R (Januar-2013) Quantification issues of in vivo 1H NMR spectroscopy of the rat brain investigated at 16.4 T NMR in Biomedicine 26(1) 74–82.
Shajan G, Hoffmann J, Balla DZ, Deelchand DK, Scheffler K und Pohmann R (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.
Moisa M, Siebner HR, Pohmann R und Thielscher A (Mai-2012) Uncovering a context-specific connectional fingerprint of human dorsal premotor cortex Journal of Neuroscience 32(21) 7244-7252.
Ziegler A, Kunth M, Mueller S, Bock C, Pohmann R, Schröder L, Faber C und Giribet G (Dezember-2011) Application of magnetic resonance imaging in zoology Zoomorphology 130(4) 227-254.
Pohmann R, Shajan G und Balla D (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.
Hong ST, Balla DZ, Choi C und Pohmann R (Dezember-2011) Rat strain-dependent variations in brain metabolites detected by in vivo (1) H NMR spectroscopy at 16.4T NMR in Biomedicine 24(10) 1401-1407.
Shajan G, Hoffmann J, Budde J, Adriany G, Ugurbil K und 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.
Hong S-T, Balla D und Pohmann R (Juli-2011) Determination of regional variations and reproducibility in in vivo (1) H NMR spectroscopy of the rat brain at 16.4 T Magnetic Resonance in Medicine 66(1) 11-17.
Keliris A, Ziegler T, Mishra R, Pohmann R, Sauer M, Ugurbil K und Engelmann J (April-2011) Synthesis and Characterization of a Cell-Permeable Bimodal Contrast Agent Targeting β-Galactosidase Biorganic & Medicinal Chemistry 19(8) 2529-2540.
Angelovski G, Chauvin T, Pohmann R, Logothetis NK und Toth E (Februar-2011) Calcium-responsive paramagnetic CEST agents Bioorganic and Medicinal Chemistry 19(3) 1097-1105.
Budde J, Shajan G, Hoffmann J, Ugurbil K und Pohmann R (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, Balla DZ, Shajan G, Choi C, Ugurbil K und Pohmann R (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.
Pohmann R (Oktober-2010) Accurate, localized quantification of white matter perfusion with single-voxel ASL Magnetic Resonance in Medicine 64(4) 1109-1113.
Joshi R, Mishra R, Pohmann R und Engelmann J (April-2010) MR contrast agent composed of cholesterol and peptide nucleic acids: Design, synthesis and cellular uptake Bioorganic and Medicinal Chemistry Letters 20(7) 2238-2241.
Pohmann R, Budde J, Auerbach EJ, Adriany G und Ugurbil K (Februar-2010) Theoretical and Experimental Evaluation of Continuous Arterial Spin Labeling Techniques Magnetic Resononance in Medicine 63(2) 438-446.
Moisa M, Pohmann R, Uludag K und Thielscher A (Januar-2010) Interleaved TMS/CASL: Comparison of different rTMS protocols NeuroImage 49(1) 612-620.
Seeger M, Nickisch H, Pohmann R und Schölkopf B (Januar-2010) Optimization of k-Space Trajectories for Compressed Sensing by Bayesian Experimental Design Magnetic Resonance in Medicine 63(1) 116-126.
Mishra R, Su W, Pohmann R, Pfeuffer J, Sauer MG, Ugurbil K und Engelmann J (September-2009) Cell-Penetrating Peptides and Peptide Nucleic Acid-Coupled MRI Contrast Agents: Evaluation of Cellular Delivery and Target Binding Bioconjugate Chemistry 20(10) 1860-1868.
Moisa M, Pohmann R, Ewald L und Thielscher A (Januar-2009) New coil positioning method for interleaved transcranial magnetic stimulation (TMS)/functional MRI (fMRI) and its validation in a motor cortex study Journal of Magnetic Resonance Imaging 29(1) 189-197.

Beiträge zu Tagungsbänden (2):

Balla DZ, Ehses P, Pohmann R, Budde J, Mirkes C, Shajan G, Bowtell R und Scheffler K (Juli-2013) Functional QSM at 9.4T with single echo gradient-echo and EPI acquisition2nd International Workshop on MRI Phase Contrast & Quantitative Susceptibility Mapping (QSM 2013), 1-4.
Seeger MW, Nickisch H, Pohmann R und Schölkopf B (Juni-2009) Bayesian Experimental Design of Magnetic Resonance Imaging Sequences In: Advances in neural information processing systems 21, Twenty-Second Annual Conference on Neural Information Processing Systems (NIPS 2008), Curran, Red Hook, NY, USA, 1441-1448.

Beiträge zu Büchern (2):

Pohmann R: Physical Basics of NMR, 3-21. In: In vivo NMR Imaging: Methods and Protocols, (Ed) L. Schröder, Springer Science, Totowa, NJ, USA, (September-2011).
Pohmann R: Spatial Encoding: Basic Imaging Sequences, 23-43. In: In vivo NMR Imaging: Methods and Protocols, (Ed) L. Schröder, Springer Science, Totowa, NJ, USA, (September-2011).

Poster (65):

Bause J, In M-H, Ehses P, Shajan G, Speck O, Pohmann R und Scheffler K (Juni-3-2015): Distortion-Corrected High Resolution Zoomed fMRI at 9.4 T, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
Shajan G, Hoffmann J, Scheffler K und Pohmann R (Juni-2-2015): An interface to connect a 16-channel transmit array to an 8-channel parallel transmit system, 23rd Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2015), Toronto, Canada.
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Last updated: Dienstag, 18.11.2014