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Magnetic resonance imaging of semi-solid tissues.

机译：半固体组织的磁共振成像。

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Magnetic resonance imaging (MRI) is a powerful medical imaging modality that provides unique and flexible tissue contrast. It uses no ionizing radiation and can image arbitrary scan planes. MRIs have excellent contrast for soft tissues, such as gray and white matter in the brain, muscles, bone marrow, and internal organs, and also for blood and other fluids. However, conventional imaging methods have little to no signal from solid and semi-solid tissues, such as tendons, ligaments, menisci, cortical and trabecular bone, and many other connective and structured tissues in the body. These solid and semi-solid tissues are characterized by their short transverse relaxation time, T2, and can be imaged with an MRI technique known as ultra-short echo time (UTE) imaging. This dissertation will present two novel methods for improving the contrast of these tissues and a set of design algorithms for improving the imaging efficiency that also can be applied to some other MRI techniques.; The contrast of tissues with short-T2 values can be improved by suppressing the signal from tissues with long- T2 values, such as fluid and soft tissues. The first method is based on RF pulses, and provides precise long-T2 component suppression. It is an improvement in robustness over previous suppression pulses and can also include fat suppression. The second method is similarly based on RF pulses, and is additionally robust to RF inhomogeneities, improving the reliability of the suppression.; A set of algorithms was developed to improve the scan efficiency of semi-solid tissue imaging. These algorithms design variable field-of-view shapes for radial imaging techniques, allowing for imaging of non-circular and non-spherical regions that was previously unsupported. Using tailored field-of-view shapes and sizes can be used to improve the speed or quality of the images, and also allows for new radial imaging applications. In addition to semi-solid tissue imaging, radial techniques are also used for cardiac imaging, angiography, and diffusion imaging applications, all of which will also benefit from these design algorithms.
机译：磁共振成像（MRI）是一种强大的医学成像方法，可提供独特而灵活的组织对比度。它不使用电离辐射，并且可以对任意扫描平面成像。 MRI对软组织（例如大脑，肌肉，骨髓和内脏的灰白色物质）以及血液和其他液体的对比度极佳。但是，传统的成像方法几乎没有或几乎没有来自实体和半实体组织的信号，例如肌腱，韧带，半月板，皮质和小梁的骨以及人体中许多其他结缔组织和结构化组织。这些实体和半实体组织的特征在于其较短的横向弛豫时间T2，并且可以使用称为超短回波时间（UTE）成像的MRI技术进行成像。本论文将介绍两种改善这些组织对比度的新颖方法，以及一套可以提高成像效率的设计算法，这些算法也可以应用于其他一些MRI技术。具有T2值短的组织的对比度可以通过抑制来自具有T2值长的组织（例如液体和软组织）的信号来改善。第一种方法基于RF脉冲，并提供精确的长T2分量抑制。与以前的抑制脉冲相比，它具有更高的鲁棒性，并且还可以抑制脂肪。第二种方法类似地基于RF脉冲，并且对于RF不均匀性也很健壮，从而提高了抑制的可靠性。开发了一套算法来提高半固体组织成像的扫描效率。这些算法为径向成像技术设计了可变的视场形状，从而可以对以前不受支持的非圆形和非球形区域进行成像。使用量身定制的视场形状和大小可用于提高图像的速度或质量，也可用于新的径向成像应用。除半实体组织成像外，放射线技术还用于心脏成像，血管造影和扩散成像应用，所有这些技术也将从这些设计算法中受益。

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