Department of Radiology
Imaging Division
University Hopital Zürich

In theory, a doubling of the static magnetic field strength results in an increase of signal-to-noise ratio by 100%, which is the reason for the increased application of field strengths of 3 Tesla or above compared to the conventional widely applied field strength of 1.5 Tesla. The increase in signal may be applied for higher spatial resolution or faster measurements. Unfortunately, the higher field strength results as well in many undesirable effects, which partly counteract the higher signal yield, among these unwanted effects are a higher chemical shift artefact caused by different resonance frequencies of fat and water, augmented power deposition in the body resulting in tissue warming (SAR effects), and increased inhomogeneities of the static background field (B0-field) and the electromagnetic irradiation field (B1-field).

We were recently able to show that dual-channel spin-excitation in a 3.0 Tesla clinical MR scanner reduces B1-field inhomogeneities over the liver resulting in a smaller risk to overlook liver metastases by an unexpected drop of the B1-amplitude and a concomittant reduction in T1w contrast .

» Pazahr S, Fischer MA, Chuck N, Lüchinger R, Schick F, Nanz D, Boss A. Segment specific analysis of B1-field homogeneity in 3.0 Tesla liver imaging with single- versus dual-source parallel RF excitation. Radiology (in press)

On the other hand, many MR imaging techniques benefit from higher field strengths not only due to the increase in signal but also by the higher effect at increasing field strength, e.g. susceptibility effects liearly scale with the field strength; therefore, BOLD examinations benefit strongly from stronger static fields. Due to the longer T1 relaxation constants at 3.0 Tesla (approximately 40% longer), labeling techniques benefit due to the longer stability of the labeled spins, an example of such a technique is Arterial Spin Labeling, a technique for quantitative tissue perfusion measurements without application of contrast-media.

Selected contributions
Jungraithmayr W, Chuck N, Frauenfeld T, Weder W, Boss A. Magnetic resonance imaging using ultra-short echo-time sequences in syngeneic mouse lung transplantation. Radiology (in press)

Donati OF, Nanz D, Serra AL, Boss A. Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5T and 3.0T. NMR Biomed. 2012 Jan 31. doi: 10.1002/nbm.2781. [Epub ahead of print]

Rossi C, Boss A, Donati OF, Luechinger R, Kollias SS, Valavanis A, Hodler J, Nanz D. Manipulation of cortical gray matter oxygenation by hyperoxic respiratory challenge: field dependence of R(2) * and MR signal response. NMR Biomed. 2012 Feb 6. doi: 10.1002/nbm.2775. [Epub ahead of print]

Boss A, Martirosian P, Jehs M, Dietz K, Rossi C, Claussen CD, Schick F. Influence of oxygen and carbogen breathing on renal oxygenation measured by T2*-weighted imaging at 3.0 T NMR Biomed 22(6):638-45. (2009)

Boss A, Martirosian P, Fritz J, Kötter I, Henes JC, Claussen CD, Schick F, Horger M. Magnetic resonance spin-labeling perfusion imaging of synovitis in inflammatory arthritis at 3.0 T. MAGMA 22(3):175-80. (2009)

Boss A, Graf H, Berger A, Lauer U, Wojtczyk H, Claussen CD, Schick F. Tissue Warming and Regulatory Responses Induced by Radio Frequency Energy Deposition on a Whole-Body 3-Tesla Magnetic Resonance Imager. J Magn Reson Imaging 26: 1334 - 1339 (2007)

Boss A, Martirosian P, Klose U, Nägele T, Claussen CD, Schick F. FAIR-TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla. J Magn Reson Imaging 25 (5): 924 - 931 (2007)

Rossi C, Boss A, Lindig TM, Martirosian P, Steidle G, Mätzler W, Claussen CD, Klose U, Schick F. Diffusion Tensor Imaging of the Spinal Cord at 1.5 and 3.0 Tesla. Fortschr Röntgenstr 179: 219 - 224 (2007)

Boss A, Martirosian P, Claussen CD, Schick F. Quantitative ASL Muscle perfusion imaging using a Fair-TrueFISP technique at 3.0 T. NMR Biomed 19 (1): 125 - 132 (2006)

Boss A, Martirosian P, Graf H, Claussen CD, Schlemmer H, Schick F. High Resolution MR Perfusion Imaging of the Kidneys at 3 Tesla without Administration of Contrast Media. Fortschr Röntgenstr 177: 1625 - 1630 (2005)

Research Topics
Contact Information
Andreas Boss
Department of Radiology
Imaging Division
University Hospital of Zürich
Rämistr. 100
8006 Zürich
Tel.: +41-44-2553677
FAX: +41-44-2554344