Biomedical Engineering; Brain Chemistry; Magnetic Resonance Imaging; Metabolism; Multiple Sclerosis; Neurology; Magnetic Resonance Spectroscopy; Medical Laboratory Science; Technology, Radiologic; Clinical Medicine; Biomedical Technology
Functional MR imaging and spectroscopy methods are commonly applied to study cognitive function in the human and animal brain. Strong and localized magnetic field homogeneities in brain areas such as the human prefrontal cortex, however, limit the achievable data quality and the validity of the results. These magnetic field distortions are caused by air-tissue interfaces and scale with the scanner B0 field strength. The continuous trend towards ultra-high field MR for improved sensitivity and spectral dispersion therefore further enhances the problem. Conventional, low order spherical harmonic correction fields are able to compensate ('shim') for the large-scale, shallow field variations, but they are not able to deal with such strong and localized field foci.
My current research focuses on the development of advanced magnetic field modeling techniques for shimming the human/animal brain as a whole or slices thereof. Optimal magnetic field homogeneity is essential for meaningful functional MR imaging and spectroscopy and will open up a large range of fundamental neuroscience applications.
Together with my co-workers, I was able to show that generic, individual coils can be used to establish a powerful field modeling system. The combination of simple, unspecific (i.e. not spherical harmonic shaped) basis fields allows the flexible synthesis of complex and high amplitude shim fields in the human and animal brain that are much better suited for the task at hand than the shallow low-order spherical harmonics used so far. In fact, the multi-coil approach permits the simultaneous generation of linear MRI encoding fields and complex shim fields by the same setup and allows the integration of conventional imaging and shim coils into a single multi-coil system.
- Juchem, C*, Rudrapatna SU*, Nixon TW, de Graaf RA, Dynamic Multi-Coil Technique (DYNAMITE) Shimming for Echo-Planar Imaging of the Human Brain at 7 Tesla. NeuroImage 105, 462-472 (2015)
- Juchem C, Herman P, Sanganahalli BG, Nixon TW, Brown PB, McIntyre S, Hyder F, de Graaf RA. Dynamic Multi-Coil Technique (DYNAMITE) Shimmed EPI of the Rat Brain at 11.7 Tesla. NMR Biomed 27, 897-906 (2014)
- Juchem C, Green D, de Graaf RA, Multi-Coil Magnetic Field Modeling. J Magn Reson 236, 95-104 (2013)
- Juchem C, Nixon TW, McIntyre S, Boer VO, Rothman DL, de Graaf RA, Dynamic Multi-Coil Shimming of the Human Brain at 7 Tesla. J Magn Reson 212, 280-288 (2011)
- Juchem C, Brown PB, Nixon TW, McIntyre S, Rothman DL, de Graaf RA, Multi-Coil Shimming of the Mouse Brain. Magn Reson Med 66, 893-900 (2011)
- Juchem C, Nixon TW, McIntyre S, Rothman DL, de Graaf RA, Magnetic field modeling with a set of individual localized coils. J Magn Reson 204, 281-9 (2010)
- Juchem C, Nixon TW, Diduch P, McIntyre S, Rothman DL, Starewicz P, de Graaf RA. Dynamic Shimming of the Human Brain at 7 Tesla. Conc Magn Reson 37B(3), 116-128 (2010)
- Juchem C, Nixon TW, McIntyre S, Rothman DL, de Graaf RA, Magnetic field homogenization of the human prefrontal cortex with a set of localized electrical coils. Magn Reson Med 63, 171-180 (2010)
- Juchem C, Nixon TW, de Graaf RA. Magnetic Field Homogenization Using Arrays of Localized Electrical Coils. Provisional Patent Application, US 61/156,077 (2009)
- Juchem C. Passive Shimming for MR Spectroscopy at High Magnetic Fields. US Patent 7,459,908 B2 (2008)
- Juchem C, Logothetis NK, Pfeuffer J. 1H MR Spectroscopy of the Macaque Primary Visual Cortex at 7 Tesla: Strategies and Pitfalls of Shimming at the Brain Surface. Magn Reson Imaging 25, 902-912 (2007)
- Juchem C, Muller-Bierl B, Schick F, Logothetis NK, Pfeuffer J. Combined Passive and Active Shimming for In Vivo MR Spectroscopy at High Magnetic Fields. J Magn Reson 183, 278-289 (2006)
- Juchem C, Logothetis NK, Pfeuffer J. High-resolution (1)H chemical shift imaging in the monkey visual cortex. Magn Reson Med 54(6), 1541-6 (2005)