Robust T1 mapping in the presence of partial volume effects

نویسنده

  • V. N. Ikonomidou
چکیده

Introduction: The longitudinal relaxation time (T1) of tissues plays an important role both as a contrast mechanism for anatomical imaging and as a disease marker. To date, several techniques have been proposed for measuring it (e.g. [1,2]). Most of them are based on modeling monoexponential behavior for individual voxels. Even though brain tissue is considered to exhibit monoexponential T1 behavior, deviations from this are expected both due to partial volume effects and tissue changes due to disease. This is bound to lead to errors in T1 estimation unless multiple exponentials are taken into account. However, fitting multiple exponentials is well-known to be a mathematically ill-defined problem [3], requiring high signal to noise ratios. This study addresses partial volume problems when a voxel contains both cerebrospinal fluid (CSF) and another tissue type, as it occurs in the cortical ribbon and periventricular white matter. With a T1 value in the order of 4400 ms at 3.0T, CSF interference can cause significant errors in T1 estimation. Here, a new pulse sequence is presented that allows measuring T1 while keeping the signal from substances with CSF-like T1 values suppressed, thus minimizing interference and estimation error. Theory & Methods: The proposed sequence is shown in figure 1. It starts with a saturation pulse, followed by an inversion pulse at time a t and an imaging 90o pulse

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تاریخ انتشار 2008