| Zugriffsnummer | 17352 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Parallel imaging with SQUID arrays |
| Autor(in); Institution |
Seifert, Frank; 8.1, Medizinische Messtechnik, PTB-Berlin
Wübbeler, Gerd; 8.1, Medizinische Messtechnik, PTB-Berlin
Kilian, Wolfgang; 8.1, Medizinische Messtechnik, PTB-Berlin
|
| Quelle/Jahr | Second International Workshop Parallel MRI/Latsis. Symposium 2004 is funded by the International Latsis Foundation:(2004), 89 - 91 |
| URL | |
| Konferenzangaben | Second International Workshop on Parallel MRI, Zürich, 15-17, October, 2004, Switzerland |
| Zusammenfassung | In this paper we discuss and review the design of an imaging system which allows the direct observation of the very low frequency precession of nuclear spins at external fields as low as few nT. Since conven-tional "RF"-coils detect temporal magnetic flux changes only, these sensors are orders of magnitudes too insensitive to measure any signal from a slowly precessing nuclear spin system. However, SQUIDs (su-perconducting quantum interference devices) are native magnetic flux detectors with a sensitivity suffi-cient to detect magnetic fields as low as 1 fT at 1 Hz detection bandwidth. Nevertheless, the equilibrium nuclear spin magnetization at nT fields is too low for signal detection. To overcome these difficulties the magnetization has to be enhanced transiently either by prepolarization in mT fields or by hyperpolariza-tion. Combining single SQUIDs to a detector array one may measure simultaneously magnetic field vec-tors and some spatial derivatives of magnetic field components at typical 30 to 100 positions. Those de-tector systems with some hundred detection channels are commonly used to record magnetic fields from the human brain in a magnetoencephalography (MEG) system. |
