Slice-selective implementation of an adiabatic T 2 Prep sequence increases coronary artery conspicuity at 3T
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ORAL PRESENTATION
Open Access
Slice-selective implementation of an adiabatic T2Prep sequence increases coronary artery conspicuity at 3T Sahar Soleimanifard1*, Michael Schär1,2, Jerry L Prince1, Robert G Weiss1, Matthias Stuber1,3 From 15th Annual SCMR Scientific Sessions Orlando, FL, USA. 2-5 February 2012 Background In non-contrast coronary MRA, the non-selective T2 Prep1-2 has been widely used for contrast enhancement between the coronary blood-pool and the myocardium 3-5 . This non-selective pre-pulse affects the magnetization both inside and outside the field-of-view, resulting in a reduced steady-state magnetization of the inflowing blood, and consequently a penalty in SNR. We hypothesize that a slice-selective T2Prep would leave the magnetization of blood outside the imaged volume unaffected, and thereby minimize SNR penalty for inflowing blood. The purpose of this work was to implement a slice-selective T2Prep coronary MRA sequence and to assess the SNR gain quantitatively. Methods Simulations
bloch equations were simulated to test the above hypothesis and to estimate the expected SNR gain. Implementation
the selective T2Prep was implemented by replacing the non-selective 90° RF pulses with slice-selective versions plus flow-compensating gradients, and an additional time gap between the T 2Prep and other pre-pulses to allow for inflow of a larger volume of spins with equilibrium magnetization (Figure1). The T2Prep volume was graphically selected along the arterial axis and orthogonal to the imaged volume without covering the ventricles (Figure 1c) to avoid saturation of the inflow spins in the ascending aorta.
Experiments
volume-targeted 3D free-breathing navigator-gated and corrected coronary MRA 5 were acquired on a Philips Achieva 3T a) without T2Prep, b) with the conventional T2Prep, and c) with the proposed slice-selective T2Prep (Tgap=150ms) in 10 healthy volunteers. Repeated measures of blood SNR, vessel-neighborhood CNR, and vessel sharpness were statistically compared using ANOVA with Tukey post hoc test.
Results Consistent with the hypothesis, numerical simulations suggest that the slice-selective T2Prep leads to an SNR increase in the blood-pool (Figure 1A) when compared to its non-selective counterpart. Figure 1C shows an in vivo result obtained with the slice-selective T2Prep localized along the dark bar (arrows). When compared to the non-selective T2Prep, vessel sharpness improved significantly using the proposed implementation (54.1 ±2.4% vs. 48.5±2.4%, p
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