Ja. Hopkins et Fw. Wehrli, MAGNETIC-SUSCEPTIBILITY MEASUREMENT OF INSOLUBLE SOLIDS BY NMR - MAGNETIC-SUSCEPTIBILITY OF BONE, Magnetic resonance in medicine, 37(4), 1997, pp. 494-500
Measurements of the volume magnetic susceptibility of solids using the
classical Gouy balance approach are hampered by variations in apparen
t density of the packed powder. In this paper a quantitative NMR measu
rement of the volume magnetic susceptibility of powdered solids is des
cribed and the volume susceptibility of bone is reported. The techniqu
e is based on the measurement of changes in incremental linewidth (1/p
i T-2') induced in a marker fluid whose susceptibility can be predicta
bly modified by changing the composition, such as by addition of a sol
uble diamagnetic compound. The spectroscopic linewidth of the marker f
luid is determined by the susceptibility difference between the fluid
and the suspended solid. Changes in the linewidth are accompanied by b
ulk magnetic susceptibility induced frequency shifts in the fluid reso
nance. Correlating the two dependencies allows measurement of the abso
lute volume susceptibility of the solid. The susceptibility of bovine
rib bone was found to be -0.90 +/- 0.02 x(-) 10(-6) (CGS) confirming p
revious estimates which suggested bone to be more diamagnetic than the
marrow constituents. Knowledge of the susceptibility of bone is relev
ant in view of the growing interest in MRI osteodensitometric techniqu
es.