Research On DANTE-based Magnetic Resonance Imaging Of Vessel Wall In Mouse

Stroke,especially ischemic stroke,is a leading cause of mortality and morbidity worldwide.The progression of carotid atherosclerosis would increase the risk of ischemic stroke.For further understanding the pathological mechanism of atherosclerosis as well as evaluating and monitoring the progress of atherosclerosis,Apolipoprotein E-deficient(ApoE-/-)mice have been widely used in atherosclerotic disease research.The magnetic resonance vessel wall imaging technique obtains information of static tissues such as the vessel wall by suppressing the blood signal in the vessel,which can be effectively applied to evaluate the morphology and composition of the atherosclerotic plaque.Two-dimensional vessel wall imaging technique(2D-IOSB-RARE)using rapid acquisition with relaxation enhancement sequence(RARE)in combination with inflow and outflow saturation bands(IOSB)has been successfully implemented in the study of carotid atherosclerosis in mice.Compared with 2D techniques,three-dimensional(3D)techniques benefit from the advantages of high signal-to-noise ratio and flexible visualization and so on,and thus they own much broader application prospects.However,the application of 3D technique to vessel wall imaging suffers from long scan time and suboptimal flow suppression effect.To this extent,the current researches on carotid atherosclerosis of mice have not included 3D vessel wall imaging.In this paper,we focused on the assessment of ApoE-/-mouse carotid atherosclerotic lesions using 3D vessel wall imaging technique.Meanwhile,the delay alternating with nutation for tailored excitation(DANTE)technique,which consists of a train of nonselective pulses combining with strong dephasing gradients to suppress blood signals was introduced in the present work.The aforementioned works are described as follows:(1)The delay alternating with nutation for tailored excitation and fast low-angle shot sequence(DANTE-FLASH)was applied for quantitative evaluation of the carotid arteriosclerotic lesions.In order to suppress the blood signals,the DANTE module was implemented in the FLASH sequence at 7.0 T high-field MRI.Meanwhile,the inherent loop structure of FLASH was modified to present segmented acquisition.Numerical simulations were performed for the imaging parameters optimization of DANTE module to achieve the maximum wall-lumen contrast.The results indicated that the blood signals can be fully suppressed by DANTE module.Compared with 2D-IOSB-RARE,the contrast-to-noise ratio(CNR)of DANTE-FLASH was reduced by 33%,while the slice resolution gained 4.2 times improvement.DANTE-FLASH and 2D-IOSB-RARE revealed excellent agreement in the area measurements.DANTE-FLASH offers isotropic spatial resolution which allows quantitative evaluation and flexible visualization of the carotid arteriosclerotic plaque of the ApoE-/-mouse.(2)The delay alternating with nutation for tailored excitation and variable-flip-angle rapid acquisition with relaxation enhancement sequence(DANTE-VF-RARE)evaluating the carotid arteriosclerotic lesions.The signal-to-noise ratio of DANTE-FLASH sequence is low,and the signal-to-noise ratio of RARE,which is also generally applied sequences,is intrinsically higher than that of FLASH.This paper investigated the feasibility of RARE sequence in 3D vessel wall imaging.This paper developed the DANTE-VF-RARE sequence based on the RARE sequence.The extended phase graph algorithm(EPG)was used to calculate variable-flip-angle.The pulse interval was redesigned to suit the variable-flip-angle pulses.According to the simulation results of VF-RARE,T1/T2 values were determined to produce a sharp edge of vessel wall.Compared with 2D-IOSB-RARE,DANTE-VF-RARE offered significantly improved contrast-to-noise-ratio efficiency(P<0.001).DANTE-VF-RARE had good consistency with the results of other magnetic resonance imaging techniques(MRI):excellent consistency with 2D-IOSB-RARE in area measurement was observed;high consistency with the degree of lumen stenosis was also observed in the corresponding 3D bright blood images.The accuracy of the MRI-based measurements was supported by the strong correlations between MRI and histopathological measurements.DANTE-VF-RARE offered high spatial resolution with excellent blood suppression and supported investigating treatment plans of arteriosclerotic lesions.