MEASUREMENT OF R-2' IN THE PRESENCE OF MULTIPLE SPECTRAL COMPONENTS USING REFERENCE SPECTRUM DECONVOLUTION

A method is described for measuring R-2', the RF reversible contributi on to the effective transverse relaxation rate in yellow trabecular ma rrow, as a means to evaluate trabecular bone structure and density. Th e method exploits the similarity in spectral composition of the marrow and fat in subcutaneous tissue. Under these conditions the gradient e cho envelope of the marrow signal can be regarded as a convolution of a function describing the bone marrow intravoxel line broadening (R-2' ) with a function expressing chemical shift modulation, which is obtai ned from the echo envelope of the subcutaneous fat signal in a referen ce region. Simple division of each of a series of echoes by the refere nce signal is shown to afford a smooth decay which can be fitted to a model to extract R-2'. The method has been evaluated in the upper femu r of test subjects and a strong correlation of the thus derived R-2' v alues with those obtained by the GESFIDE technique is demonstrated. Th e close correspondence in spectral composition of proximal femur marro w and subcutaneous fat is further illustrated by means of localized sp ectroscopy. The major potential error source is global inhomogeneity i n the reference region which can lead to an underestimation of the dem odulation-derived R-2'. (C) 1998 Academic Press.