ABSTRACT
The purpose of this study is to compare the effectiveness of relative cerebral blood volume, apparent diffusion coefficient and spectroscopic imaging in differentiating between cerebral abscesses and necrotic tumours. In the prospective study, a 3-tesla MR unit was used to perform proton MR spectroscopy, diffusion and perfusion imaging in 20 patients with cerebral abscesses and 26 patients who had solitary brain tumours (14 high-grade gliomas and 12 metastases). We found the mean apparent diffusion coefficient value at the central cavities of the cerebral abscesses to be significantly lower than in necrotic tumours. The mean relative cerebral blood volume values of the necrotic tumour wall were statistically significantly higher than the mean relative cerebral blood volume values of the cerebral abscess wall by the Student's t-test. The proton spectra obtained revealed amino acids only in the cerebral abscesses. Although the conventional MRI characteristics of cerebral abscesses and necrotic tumours may sometimes be similar, diffusion, perfusion-weighted and spectroscopic MRI enables distinction between the two.
Subject(s)
Brain Abscess/diagnosis , Brain Neoplasms/diagnosis , Carcinoma/diagnosis , Glioblastoma/diagnosis , Magnetic Resonance Spectroscopy/methods , Adult , Aged , Aged, 80 and over , Blood Volume/physiology , Brain/pathology , Brain Abscess/pathology , Brain Neoplasms/pathology , Carcinoma/pathology , Cerebrovascular Circulation , Diagnosis, Differential , Diffusion Magnetic Resonance Imaging/methods , Female , Glioblastoma/pathology , Humans , Male , Middle Aged , Necrosis , Perfusion/methods , Prospective StudiesABSTRACT
The major constraint in attaining high resolution structures of membrane proteins by X-ray crystallography is the growth of well-ordered three-dimensional crystals. To enable such crystallizations, we have used lipidic cubic phases consisting of monoglycerides and water. Bacteriorhodopsin and lysozyme, as paradigms of membrane and soluble proteins, nucleate and grow to well-ordered crystals that diffract X-rays isotropically in all three dimensions to 2.0 Å. We envisage bacteriorhodopsin to partition into, and diffuse within, the bilayer of a lipidic cubic matrix, while the polar lysozyme resides in the aqueous compartment thereof. The phenomenology of bicontinuous cubic phases, consisting of curved bilayers whose structures follow infinitely periodic minimal surfaces (IPMS), is presented. Detailed prescriptions of the preparation of lipidic cubic phase matrices are given and their potential for the crystallization of other biological macromolecules is discussed. Copyright 1998 Academic Press.