Two-point method for T1 estimation with optimized gradient-echo sequence

Differentiating normal hyaline cartilage from post-surgical repair tissue using fast gradient echo imaging in delayed gadolinium-enhanced MRI (dGEMRIC) at 3 Tesla

“…Another technique for fast T1 mapping is to use the contrast variation of different excitation flip angle values in gradient echo-based sequences [21,22]. The gradient echo method with variable flip angles has been reported previously; however, in earlier studies, poor reproducibility due to partial volume effects and unstable signal intensity of the first and second images due to sub-optimal flip angles were reported [23][24][25][26]. The subsequent effect is further enhanced by noiseinduced bias, which can be found below a certain signal-tonoise ratio (SNR).…”

T 1 : The Longitudinal Relaxation Time

“…Bottomley's review (Bottomley et al, 1987) remains the most extensive review of T 1 (and T 2 ) values in normal and pathological tissues across a range of field strengths. ; also Deichmann et al, 1999;Clare and Jezzard, 2001;Duewell et al, 1995;Henderson et al, 1999;Imran et al, 1999;Shah et al, 2001;Steinhoff et al, 2001; unpublished data from MR Centre University of Nottingham) Molecules containing paramagnetic materials (such as deoxyhaemoglobin or contrast agents such as Gd-DTPA) give rise to much larger local magnetic fields, and hence much more rapid longitudinal relaxation. The relaxation rate, 1/T 1 , increases proportionally to the concentration of contrast agent, and therefore by measuring T 1 it is possible to monitor changes in contrast agent concentration in MRI tracer studies.…”

“…Two-point gradient echo (FLASH) sequences have also been used to measure T 1 . Imran et al (1999) showed 12 The signal from a spoilt gradient echo sequence with flip angle θ across the whole slice, is…”

Dual-contrast echo planar imaging with keyhole: application to dynamic contrast-enhanced perfusion studies

“…Since two images are inherently acquired with different echo times, T * 2 maps can be estimated. Further, through the judicious application of the sequence with two different flip angles, T 1 maps can also be estimated (Imran et al 1999). It is explicitly noted here that the purpose of the sequence is not fast and accurate T 1 and T * 2 mapping but rather an estimation of these quantities dynamically following the injection of contrast agent.…”