Gradient echo single scan inversion recovery: application to proton and fluorine relaxation studies

Abstract

Single scan longitudinal relaxation measurement experiments enable rapid estimation of the spin-lattice relaxation time (T1 ) as the time series of spin relaxation is encoded spatially in the sample at different slices resulting in an order of magnitude saving in time. We consider here a single scan inversion recovery pulse sequence that incorporates a gradient echo sequence. The proposed pulse sequence provides spectra with significantly enhanced signal to noise ratio leading to an accurate estimation of T1 values. The method is applicable for measuring a range of T1 values, thus indicating the possibility of routine use of the method for several systems. A comparative study of different single scan methods currently available is presented, and the advantage of the proposed sequence is highlighted. The possibility of the use of the method for the study of cross-correlation effects for the case of fluorine in a single shot is also demonstrated.

Bloch-Siegert Shift and its Kramers-Kronig Pair

“…Inspired by the WALTZ-8 decoupling scheme, we find, through simulations with τ c ∼ 10 −12 s, that the super-cycle S = R 3 R3 R3 R 3 R3 R 3 R 3 R3 , (where R3 = {−π, 2π, −π}) is more effective than the simple 3-pulse block R 3 in minimizing M y (t) and thus we use it as our driving protocol [19]. In order to further eliminate the effect of the diffusion (spins diffusing to regions having a different ω 1 ), we select a thin slice (∼ 1 mm) near the middle of the sample (effective height ∼ 25 mm), for detection, by using a selective Gaussian π/2 pulse along x in presence of an applied z-gradient having strength ∼ 0.05Tm −1 [20,21]. The duration of the positive gradient is 2 ms whereas that of the compensatory gradient is 1.1 ms.…”

“…For detection, we have applied a Gaussian selective pulse of flip angle ∼ π/2 in the presence of the applied gradient +G to facilitate slice selection using spatial encoding. Immediately after the slice selection, an opposite compensatory gradient −G is used to minimize phase distortion during slice-selection [20]. The Free Induction Decay (FID) has been recorded in the absence of any gradient.…”

Non-Bloch decay of Rabi oscillations in liquid state NMR

“…For detection, we have applied a Gaussian selective pulse of flip angle ∼π/2 in the presence of the applied gradient +G to facilitate slice selection using spatial encoding. Immediately after the slice selection, an opposite compensatory gradient −G is used to minimize phase distortion during slice-selection [27]. The free induction decay (FID) is recorded in the absence of any gradient.…”

“…at these places. Hence, during the detection, we exclude the contribution from the edges by selecting a slice (of thickness ∼1 mm) from the sample using spatial encoding techniques [26,27]. We use a selective Gaussian π/2 pulse along x in the presence of an applied z-gradient of about 0.05 Tm −1 .…”

“…We use a selective Gaussian π/2 pulse along x in the presence of an applied z-gradient of about 0.05 Tm −1 . Immediately after the slice selection, an opposite compensatory gradient is used to minimize phase distortion during slice-selection [27]. The duration of the positive gradient is 2 ms whereas that of the compensatory gradient is 1.1 ms.…”