| Summary: | 博士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 101 === Intracranial mass lesions include primary brain tumors, metastatic brain tumors, meningiomas, demyelination, abscesses and etc. Imaging features such as displacement of adjacent normal structures, contrast enhancement and perifocal edema are shared by these lesions. The treatment of intracranial mass lesions varies according to histopathology. Some require surgical resection, while others can be treated medically.
Conventional MRI remains the primary imaging modality for noninvasive evaluation of brain lesions. One major limitation of conventional MRI, however, is that it cannot provide physiological and metabolic information of the lesions. More advanced MR imaging techniques collectively known as physiologic MRI includes but not limited to diffusion-tensor imaging (DTI), dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI) and susceptibility-weighted imaging (SWI), hold much promise to fill that role by potentially providing novel physiology-based information.
DTI provides information on histologic architecture such as cellularity and cellular organization by measuring the directional variation of water diffusivity. Relative cerebral blood volume (CBV) derived from DSC-PWI has been shown to correlate with degree of microvascular proliferation. SWI is a high-resolution 3D gradient-echo sequence that combines phase and magnitude information to detect magnetic susceptibility differences between adjacent tissues. Its high sensitivity in the detection of paramagnetic and diamagnetic substances such as iron deposits, blood degradation products, and calcifications provides clinically useful information in the evaluation of various disorders. The true strength of physiologic MRI is the ability to provide quantitative surrogate MR markers and depict changes in the internal architecture in the setting of no overall change in the conventional MRI.
The clinical utilities of physiologic MRI have been reported. Diffusion, perfusion and susceptibility imaging have been reported to be useful in gliomas grading and differentiation between high-grade gliomas from primary CNS lymphomas. Perfusion imaging is also useful in differentiating between high-grade gliomas and tumefactive demyelination. On the other hand meningioma subtyping can be accomplished with diffusion and perfusion imaging. The ability of diffusion, perfusion and susceptibility imaging in differentiating among various intracranial mass lesions implies that these advanced imaging techniques may reflect the histologic differences of various intracranial mass lesions.
We believe that physiologic MRI may help in solving some critical clinical issues. The 5 purposes in the present thesis study are: 1) to investigate if DTI could differentiate pyogenic brain abscesses from necrotic glioblastomas and cystic metastatic brain tumors; 2) to study the role of DTI in differentiating TDLs from high-grade gliomas; 3) to evaluate the role of SWI in differentiating pyogenic abscesses from high-grade gliomas; 4) to evaluate the roles of DTI and DSC-PWI in the assessing the angiographic vascularity of meningiomas; and 5) to investigate the role of DSC-PWI in differentiating pyogenic abscesses from necrotic glioblastomas and cystic metastases.
The results of these studies show that DTI and SWI could be useful in the differentiation of intracranial rim-enhancing mass. Besides, DTI could also discriminating tumefactive demyelinating lesions from high-grade gliomas. Both DTI and DSC-PWI could predict the angiographic vascularity of meningiomas. The results indicate that DTI, DSC-PWI and SWI may reflect the histologic differences of these intracranial mass lesions, and therefore the clinical role of physiologic MRI is promising.
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