The Research On Cine Imaging And Application In Cardiac Magnetic Resonance

Among many medical imaging modalities,magnetic resonance imaging(MRI)has many advantages,such as excellent soft tissue contrast,non-ionizing radiation,and multi-contrast imaging,and therefore has become a routine examination technique in clinic.Cardiac cine magnetic resonance(MR)imaging has routinely been used for the diagnosis of cardiovascular diseases because of its exclusive abilities of obtaining heart anatomy,morphology,and function in a single examination.However,MRI sampling speed is relatively slow due to the physical and physiological limits.The slow sampling speed makes the dynamic MRI have to be tradeoff between temporal and spatial resolutions.The current method of choice is two-dimensional(2D)balanced steady-state free precession(bSSFP)in combination with electrocardiography(ECG)triggering and breath holding.However,multiple breath holds for collecting a series of slices to cover the entire ventricular chamber may cause inter-slice misregistration and sometimes can be poorly tolerable by patients.In addition,ECG triggering involves practical and technical drawbacks such as considerable patient preparation time as well as false triggering due to interference by magnetic fields,and magnetohydrodynamic effect,particularly at high magnetic field strength in clinical settings.Thus,MR methods for cardiac cine imaging without external gating devices are needed and remain under investigation.To resolve these problems,and realize rapid cardiac cine imaging under free breathing at 3T obviating the use of ECG triggering,we have developed and evaluated several cardiac cine imaging techniques without the use of external ECG triggering or breath holding/or respiratory gating.The main contributions of this theis can be summarized in four sections:1.A new method,named PS-CS,was proposed to significantly accelerate partial separability model-based dynamic MRI by exploiting the partial separability and sparse constraint separately.The proposed PS-CS method sequentially reconstructs a set of aliased dynamic images in each channel based on partial separability model and then the final dynamic images from the aliased images using compressive sesing.The results from numerical simulations and in vivo experiments demonstrate that PS-CS could significantly reduce data acquisition time while preserving high spatiotemporal resolution.2.To develop and assess an accelerated 3D self-gated method for the evaluation of myocardial infarction(MI)in rat models without the use of external ECG triggering or respiratory gating.A 3D stack-of-stars T1-weighted GRE sequence was performed on rats with MIs that were injected with a gadolinium-based contrast agent at 3 Tesla.Respiratory and cardiac self-gating signals were derived from the Cartesian mapping of the k-space center along the partition encoding direction by bandpass filtering in the image domain.The data were then realigned according to the predetermined self-gating signals for image reconstruction by exploiting the image sparsity in the k-t space.Compared to the conventional self-gated method,the proposed method reconstructed images with much less streaking artifact,as well as a better contrast-to-noise ratio(CNR)between the blood and myocardium.The MI regions detected by the proposed method were in agreement with histological standards,demonstrating the feasibility of the proposed method for MI detection in the rat heart.3.To developed and evaluated an accelerated 3D self-gated cardiac cine imaging technique at 3T without the use of external ECG triggering or respiratory gating.A 3D hybrid-radial bSSFP sequence with a tiny golden angle sampling scheme was developed for data acquisition to reduced eddy current effect-related artefacts at 3T.Respiratory and cardiac motion information were derived from a central 5-point self-gating signal extraction approach.The acquired data were then realigned according to the predetermined motion signals for image reconstruction by exploiting the image sparsity in the k-t space.The proposed method achieved rapid cardiac cine imaging at 3 Tesla with a whole-heart spatial coverage.Compared to the conventional self-gated method,the proposed method reconstructed images with much less streaking artifact and yielded better image quality.Left ventricular functional measurements between the proposed method and routine 2D multi-slice technique were all well in agreement.4.A novel technique for real-time cardiac cine imaging was developed and used to evaluate the left ventricular(LV)function in patients with arrhythmia.The proposed real-time cardiac cine imaging technique adopted bSSFP sequence with radial sampling trajectories.In addition,to improve temporal stability and cine image quality,a view-sharing technique and compressive sensing model exploits image sparsity in k-t space was employed for data acquisition and image reconstruction.Compared to the clinical ECG-triggering approach,the proposed method was feasibility for accurately evaluating patient's LV function.For the study of the patients with arrhythmia,the images obtained by the proposed method showed significant improvement of image quality with better CNR between blood and myocardium.The thesis was organized as follows.Firstly,a brief review of the development of cardiac magnetic resonance(CMR),the principle of MRI,and main clinical CMR techniques were presented.Secondly,a detailed description of the proposed methods were given.Finally,a brief conclusion and the prediction in futrue work were summarized.