MR susceptometry: an external-phantom method for measuring bulk susceptibility from field-echo phase reconstruction maps.
A novel method for estimating the susceptibility of an object by using the magnetic resonance (MR) imaging field distortions in an external-reference water bath next to the object is described. The field measurement was obtained with a phase reconstruction from a gradient-echo acquisition. A field model of an arbitrary object in a static magnetic field was discretely calculated from geometry determined from the magnitude reconstruction. Least-squares estimation yields the susceptibility of the object. Required (and proven) assumptions include validity of superposition, object homogeneity, negligible higher-order field terms, field-model accuracy, geometric-model accuracy, and correlation of gradient-echo phase to field distortion. MR susceptometry estimation of phantoms yielded susceptibility estimates that correlated well with known values (r > .9975). This MR susceptometry method is a first step toward quantitation of iron levels through MR imaging phase information in patients with iron overload.
Holt
R W
RW
Department of Radiology, MetroHealth Medical Center, Cleveland, Ohio.
Diaz
P J
PJ
Duerk
J L
JL
Bellon
E M
EM
D000465:Algorithms; D016477:Artifacts; D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry; D005583:Fourier Analysis; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007501:Iron; D007840:Latex; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods; D008280:Magnetics; D008961:Models, Structural; D008962:Models, Theoretical; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water
D002712:Chlorides; D005290:Ferric Compounds; D007840:Latex; D014867:Water; D007501:Iron; C024555:ferric chloride