Abstract
A nuclear magnetic resonance (NMR) imaging system signal to noise calibration technique based on an NMR projection of distilled water in a cylindrical bottle is proposed. This measurement can characterize any arrangement of rf coils in any magnetic field as signal to noise per ml times root Hz. Inductive losses in a typical patient must be included in the calibration, and such losses can be simulated in a particular system by an externally attached resistor(s) appropriate to that system. Alternatively, an rf inductive damping phantom consisting of a conducting loop of wire containing an appropriate resistor is suggested that can be inserted into any NMR imaging coil to simulate subject Q damping. The same resistor can be used, independent of the details of the coil construction. Furthermore, if the loop inductance is tuned out at each frequency with a series capacitor, then the same loop resistance will serve for all frequencies as a good approximation to human subject damping. This “projection method” signal to noise ratio is related to the conventional signal to noise ratio measured from a Lorentzian shaped spectral line as ψP=ψL[2/T2]1/2, where ψ stands for signal to noise ratio, subscripts P and L stand, respectively, for the projection and “Lorentzian” methods, and T2 is the transverse relaxation time of the spectral line used in the Lorentzian method.
Original language | English (US) |
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Pages (from-to) | 180-185 |
Number of pages | 6 |
Journal | Medical physics |
Volume | 11 |
Issue number | 2 |
DOIs | |
State | Published - Mar 1984 |
Externally published | Yes |
Keywords
- calibration
- image forming
- nmr spectrometers
- nuclear magnetic resonance
- signalâtoânoise ratio
- water
ASJC Scopus subject areas
- Biophysics
- Radiology Nuclear Medicine and imaging