Effective motion‐sensitizing magnetization preparation for black blood magnetic resonance imaging of the heart

Abstract

Purpose:To investigate the effectiveness of flow signal suppression of a motion-sensitizing magnetization preparation (MSPREP) sequence and to optimize a 2D MSPREP steadystate free precession (SSFP) sequence for black blood imaging of the heart. Materials and Methods:Using a flow phantom, the effect of varying field of speed (FOS), b-value, voxel size, and flow pattern on the flow suppression was investigated. In seven healthy volunteers, black blood images of the heart were obtained at 1.5T with MSPREP-SSFP and double inversion recovery fast spin echo (DIR-FSE) techniques. Myocardium and blood signal-to-noise ratio (SNR) and myocardium-toblood contrast-to-noise ratio (CNR) were measured. The optimal FOS that maximized the CNR for MSPREP-SSFP was determined.Results: Phantom data demonstrated that the flow suppression was induced primarily by the velocity encoding effect. In humans, FOS ϭ 10 -20 cm/s was found to maximize the CNR for short-axis (SA) and four-chamber (4C) views. Compared to DIR-FSE, MSPREP-SSFP provided similar blood SNR efficiency in the SA basal and mid-views and significantly lower blood SNR efficiency in the SA apical (P ϭ 0.02) and 4C (P ϭ 0.01) views, indicating similar or better blood suppression. Conclusion:Velocity encoding is the primary flow suppression mechanism of the MSPREP sequence and 2D MSPREP-SSFP black blood imaging of the heart is feasible in healthy subjects. THE CLINICAL EVALUATION of cardiac and vascular structures using magnetic resonance imaging (MRI) often requires the suppression of intravascular signal (black blood [BB] imaging) to improve vessel wall and cardiac chamber visualization. BB imaging is commonly performed using double inversion recovery (DIR) (1-5) or spatial saturation of upstream blood (6,7). Both techniques rely on the inflow of blood with nulled signal into the imaging volume and consequently become less effective for thick imaging volumes and for in-plane flow. To overcome this problem, a BB magnetization preparation technique was developed by utilizing motion-sensitizing gradients to dephase all moving blood spins prior to imaging (8 -10). BB images of the aortic and carotid vessel walls were obtained successfully in humans using this approach (11-13). Because the preparation sequence-consisting of 90 -180 -90 nonselective RF pulses and a pair of identical unipolar gradients around the 180 pulse-was originally developed for diffusion sensitization, this technique is often referred to as "diffusion-prepared" or "diffusion-based" in the literature (10 -12). In the presence of weak diffusion-sensitizing gradients such as those used in BB imaging, this description is inadequate because the flow signal attenuation originates primarily from the velocity encoding effect on coherently moving spins and only slightly from the diffusion effect on incoherently moving spins, as briefly pointed out in recent works (13,14). A full experimental investigation of the underlying signal attenuation mechanisms is therefore important and, to the best of our knowledge, has ...

Visualization of the Trochlear Nerve in the Cistern with Use of High-Resolution Turbo Spin-Echo Multisection Motion-Sensitized Driven Equilibrium

“…Previous reports [8][9][10][11][12] have discussed TSE-MSDE regarding the atherosclerotic change in vessels, the existence of brain metastasis, and focal deformation of nerves by vessels in neurovascular compression syndrome. In our study, we obtained HR images with TSE-MSDE (ie, HR-MSDE) to visualize the trochlear nerve.…”

“…8,9 TSE-MSDE has also been applied for assessment of the existence of brain metastasis with contrast media. 10 This method takes advantage of a preparative sequence, a diffusion pulse with a very low b-value consisting of 3 nonselective radio-frequency pulses with flip angles of 90 -180 -90°, and symmetric gradients around the 180°pulse.…”

Contrast-enhanced, three-dimensional, whole-brain, black-blood imaging: Application to small brain metastases

“…Despite these advantages, a potential confound is the distribution of contrast agents within blood vessels and the tumor parenchyma resulting in the simultaneous enhancement of both regions, thereby impairing the accuracy of metastatic lesion detection. Thus, since the blood vessels close to the brain tumors may result in diagnostic confusion, it is necessary to selectively enhance the signal intensity of the brain tumors while suppressing the blood vessels elsewhere in the brain.Black-blood imaging methods (9-14), wherein blood signals are selectively suppressed using spatial presaturation (9,10), double inversion recovery (11,12), or motion-sensitizing magnetization preparation (13,14), if successfully combined with CE 3D MP-RAGE, may have the potential to provide an excellent differentiation between blood and tumors. However, it is challenging to achieve CE black-blood imaging due to a rapid recovery of blood signals along the echo train in MP-RAGE.…”

“…Black-blood imaging methods (9)(10)(11)(12)(13)(14), wherein blood signals are selectively suppressed using spatial presaturation (9,10), double inversion recovery (11,12), or motion-sensitizing magnetization preparation (13,14), if successfully combined with CE 3D MP-RAGE, may have the potential to provide an excellent differentiation between blood and tumors. However, it is challenging to achieve CE black-blood imaging due to a rapid recovery of blood signals along the echo train in MP-RAGE.…”

Evaluation of Modified Turbo Spin Echo Technique Compared with Double Inversion Recovery Technique in Acquisition of Black Blood Brain Vessel Image

“…For example, several DIR preparation techniques have been recently developed, including multislice acquisition techniques. Also, parallel acquisition techniques reduce scan time by combining the signals of several coil elements in a phased array to reconstruct the image [17][18][19][20][21][22]. However, DIR still needs longer time and may lead to motion artifact which make radiologist misunderstand.…”