| 广义付里叶变换及其在磁共振成像中的应用 |
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| 作者单位： | Wang Weidong 1 Bai Kezhuang 2 Zu Donglin 4 Bao Shanglian 4 Jerome Z. Liang 3 1)The Biomedical engineering research office，Chinese PLA General Hospital，Beijing 100853 2)Beijing document service，Beijing 100871 3)The department of radiology |
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| 摘 要： | 许多共振成像（ＭＲＩ）的应用，要求人体组织磁化强度的空间分布Ｆｏｕｒｉｅｒ变换的幅度和相位的精确分离，及利用正交双通道采集时间和空间高分辨图象序列。在传统的基于Ｆｏｕｒｉｅｒ变换的成象方法中，图象序列从一帧空间编码独立地重建得到，因此给定空间分辨率的情况下，每帧空间编码的数量限制了图象序列的时间分辨力；又常通过牺牲空间分辨率来提高图象序列的空间分辨录。由于传统Ｆｏｕｒｉｅｒ变换的核函数是线性相位，若变换ＭＲＩ技术必须很好地满足主磁场均匀性和梯度场线性的条件，因此传统Ｆｏｕｒｉｅｒ变换成象方法对临床应用中常出现ＭＲ信号相位失真极为敏感。本文提出：利用主磁场中组织的磁化强度不变，能很好消除图象的相位失真。
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| 关 键 词： | 广义Fourier变换 磁共振成象 磁化强度 |
Generalized Fourier Transform and its Application to Magnetic Resonance Imaging * |
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| Authors: | Wang Weidong Bai Kezhuang Zu Donglin Bao Shanglian Jerome Z Liang The Biomedical engineering research office Chinese PLA General Hospital Beijing Beijing document service Beijing The |
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| Institution: | Wang Weidong 1 Bai Kezhuang 2 Zu Donglin 4 Bao Shanglian 4 Jerome Z. Liang 3 1)The Biomedical engineering research office,Chinese PLA General Hospital,Beijing 100853 2)Beijing document service,Beijing 100871 3)The department of radiology |
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| Abstract: | Many magnetic resonance imaging (MRI) applications require the accurate separation of the phase and amplitude of the Fourier transform (FT) of spatial distribution of tissue magnetization, and the acquisition of a time series of images with both spatial and temporal high resolution as well as with an orthogonal dual channel. In conventional Fourier transform based imaging methods, on the one hand, each of these images is independently reconstructed from a frame of spatial encodings, so that temporal resolution is limited by the number of the spatial encodings of each frame collected in the case of given spatial resolution, or one has to sacrifice spatial resolution to obtain temporal resolution. On the other hand, by the reason that the kernel of conventional Fourier transform is a linear phase, FT based MRI techniques must be well satisfied with the homogeneity of main field and the linearity of gradient fields. Therefore, the conventional linear Fourier transform is susceptible to the phase distortion of MR signals, which usually occur in clinical applications. In this paper, Generalized Fourier transform (GFT) based MR imaging technique is introduced and proposed to address these problems. This technique makes use of the facts that tissue magnetization in main field is invariable, MR images are real, and the support extent of high resolution image (morphology) does not change from one image to another in most time sequential imaging problem, and it improve imaging efficiency and resolutions over the conventional Fourier imaging method by eliminating the repeated encodings of this stationary information. Additional advantages of the proposed imaging technique include a reduced number of radio frequency (RF) pulses for data collection and thus lower RF power deposition. This method should prove useful for a variety of dynamic imaging applications such as dynamic studies of contrast agents and functional brain imaging. |
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| Keywords: | Generalized Fourier transform MR imaging Magnetization |
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