Magnetic resonance imaging at frequencies below 1 kHz.
Within the magnetic resonance imaging (MRI) community the trend is going to higher and higher magnetic fields, ranging from 1.5 T to 7 T, corresponding to Larmor frequencies of 63.8-298 MHz. Since for high-field MRI the magnetization increases with the applied magnetic field, the signal-to-noise-ratio increases as well, thus enabling higher image resolutions. On the other hand, MRI is possible also at ultra-low magnetic fields, as was shown by different groups. The goal of our development was to reach a Larmor frequency range of the low-field MRI system corresponding to the frequency range of human brain activities ranging from near zero-frequency (near-DC) to over 1 kHz. Here, first 2D MRI images of phantoms taken at Larmor frequencies of 100 Hz and 731 Hz will be shown and discussed. These frequencies are examples of brain activity triggered by electrostimulation of the median nerve. The method will allow the magnetic fields of the brain currents to influence the magnetic resonance image, and thus lead to a direct functional imaging modality of neuronal currents.
Physikalisch-Technische Bundesanstalt (PTB), Abbestrasse 2-12, 10587 Berlin, Germany.
Ingo
I
Hilschenz
Rainer
R
Körber
Hans-Jürgen
HJ
Scheer
Tommaso
T
Fedele
Hans-Helge
HH
Albrecht
Antonino
A
Mario Cassará
Stefan
S
Hartwig
Lutz
L
Trahms
Jürgen
J
Haase
Martin
M
Burghoff
D000465:Algorithms; D001921:Brain / Q000473:pathology; D003198:Computer Simulation; D004867:Equipment Design; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009474:Neurons / Q000473:pathology; D019047:Phantoms, Imaging; D017785:Photons; D059629:Signal-To-Noise Ratio; D013997:Time Factors