Estimation of in vivo proton intrinsic and cross‐relaxation rates in human brain

Abstract

By using on-resonance binomial pulse saturation of the immobile component in tissues and by monitoring the time development of the longitudinal decay of the free water magnetization, it has been shown that it is possible to estimate physical model parameters not directly measurable by conventional methods. Since pulsed saturation is easy and safe to implement in a clinical MRI machine, it should be possible to estimate these parameters in vivo by the same means. In this article, we report the results of such estimates of the parameters of the principal components (gray and white matter) in brains of two normal volunteers.

Quantitative magnetization transfer ultrashort echo time imaging using a time‐efficient 3D multispoke Cones sequence

“…The final number of independent parameters is, therefore, reduced to five, which can be estimated by fitting Equation [13] using five or more measurements with different combinations of w 1 and Df .…”

Pulsed Z‐spectroscopic imaging of cross‐relaxation parameters in tissues for human MRI: Theory and clinical applications

“…To date, progress in this area has been limited by the absence of adequate methods for cross-relaxation measurements in human MRI. Although several attempts to develop such techniques have been reported (11)(12)(13)(14), none of them are suitable for extensive clinical application.Generally, existing NMR methods (both imaging and non-imaging) for quantitative studies of cross-relaxation in biologic materials can be classified by their technical principles into two groups: on-resonance cross-relaxometry (1,8,11,12) and cross-relaxation spectroscopy (or Z-spectroscopy) (4 -7,13-16). The first group relies on a semiselective inversion of free spins (1,8,12) or a binomial pulsed excitation of bound fraction (8,11) followed by an analysis of a time-dependent response.…”

“…To date, progress in this area has been limited by the absence of adequate methods for cross-relaxation measurements in human MRI. Although several attempts to develop such techniques have been reported (11)(12)(13)(14), none of them are suitable for extensive clinical application.…”

“…Generally, existing NMR methods (both imaging and non-imaging) for quantitative studies of cross-relaxation in biologic materials can be classified by their technical principles into two groups: on-resonance cross-relaxometry (1,8,11,12) and cross-relaxation spectroscopy (or Z-spectroscopy) (4 -7,13-16). The first group relies on a semiselective inversion of free spins (1,8,12) or a binomial pulsed excitation of bound fraction (8,11) followed by an analysis of a time-dependent response.…”

“…The first group relies on a semiselective inversion of free spins (1,8,12) or a binomial pulsed excitation of bound fraction (8,11) followed by an analysis of a time-dependent response. However, by taking advantage of short RF pulses these techniques suffer from a relatively low accuracy and lack of information about the spectral characteristics of the semisolid pool.…”