Black blood late gadolinium enhancement using combined T2 magnetization preparation and inversion recovery
Journal of Cardiovascular Magnetic Resonance volume 17, Article number: O14 (2015)
Late gadolinium enhancement (LGE) imaging allows assessment of focal scar . An inversion recovery based sequence is commonly used to achieve suppression of healthy myocardium signal. However, the blood pool and subendocardial scar typically have similar signal, making it difficult to distinguish subendocardial scar. Several methods have been proposed to increase the blood-scar contrast including a double inversion technique , and T2-prepared (T2prep) sequences [3, 4]. However, all these approaches suffer from either reduced SNR or reduced scar-myocardium contrast. In this work, we propose a novel pulse sequence that uses an optimized combination of an inversion pulse and a T2prep composite pulse to simultaneously null both the healthy myocardium and blood signals, producing a black-blood LGE (BB-LGE) image without losing significant scar-myocardium contrast. We also developed a quick navigation sequence, analogous to the Look-Locker, to help determine the ideal nulling time before imaging.
Figure 1.a shows a schematic of the proposed sequence. A T2prep pulse is inserted between the inversion pulse and the acquisition. Numerical simulation was conducted to simulate the effect of this pulse configuration on the signal intensity of healthy myocardium, blood, and infarcted myocardium assuming their T1 to be 500, 350, and 200 ms respectively. Six healthy adult subjects and 2 patients with suspected scar (35±21 y, 4 males) were imaged using a 1.5T Philips scanner. A standard LGE sequence was used to acquire a stack of five 2D short-axis slices, and one long-axis slice 20 min after Gd-contrast injection with the following parameters: FOV = 320×320mm2, slice gap = 5mm, in-plane resolution = 1.5×1.5 mm2, slice thickness = 10mm, TR/TE = 6.2/3.0ms, α = 25°, SENSE rate = 2, acquisition window = 80 ms, NSA = 2, breath-hold = 8s per slice. Then, the proposed BB-LGE, with the same sequence parameters, was used to acquire the same slices while setting the sequence timing to the null point of both the normal myocardium and the blood pool. The BB-LGE was preceded by a short navigation scan to determine the timing parameters that achieve the perfect nulling of both blood and myocardium signals.
Figure 1b shows the numerical simulation for signal intensity in healthy myocardium, blood and infarct tissues using both regular LGE sequence, and the proposed BB-LGE for Δt2=35ms. In the standard LGE sequence, there is no intersection that achieves a common null point for both myocardium and blood pool, while this null point can easily be obtained with the BB-LGE sequence. Figure 2 shows for the BB-LGE images examples in two healthy subjects (i.e. no infarct), and one patient with an infarction.
A new BB-LGE sequence was developed to simultaneously null both healthy myocardium and blood pool in LGE sequences based on the higher T2 value of the blood.
Kwong : Circulation. 2006
Foo : MRM. 2005
Kellman : JMRI. 2005
Liu : JMRI. 2008
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Basha, T., Roujol, S., Kissinger, K.V. et al. Black blood late gadolinium enhancement using combined T2 magnetization preparation and inversion recovery. J Cardiovasc Magn Reson 17 (Suppl 1), O14 (2015). https://doi.org/10.1186/1532-429X-17-S1-O14