Accurate estimation of the liver volume may be important for the diagnosis of several pathological processes in patients and for the study of new therapies in experimental oncology. Although sonography and computed tomography (CT) have been used for this purpose in patients, the lack of spatial resolution and tissue differentiation is a source of measurement errors which, at present, makes it impossible to accept sonography and CT widely for the determination of the liver volume. In the present study, the liver volumes of seven rats were measured by magnetic resonance imaging (MRI) and an automated image analysis system before and after the animals were killed. Volume computation was carried out by adding up the individual volumes in the sequential MR sections. Adequate MR images with high contrast between the liver and surrounding structures were obtained with spin echo pulse sequence and retarded phase encoding while no contrast material was used. The mean volumes of the livers measured by MR in vivo and in cadavers were 11.91 +/- 0.40 and 11.92 +/- 0.45 ml, respectively. When compared with the actual liver volumes measured in vitro after resection, the errors of determinations in vivo and in cadavers were as small as 3.1 and 2.1%, respectively. These data indicate that MR imaging is an accurate means to determine the liver volume in vivo and that it may be potentially useful to measure small intrahepatic lesions in patients.

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PubMedDate not supplied

In vitro peel/shear bond strength evaluation of orthodontic bracket base design.

OBJECTIVES: The adhesive capacity of 17 different bracket types was evaluated in an in vitro peel/shear test. METHODS: Silane-treated metal bars were used as substrates with all bonding being performed using the orthodontic adhesive Concise. The effect of aluminium oxide air abrasion on the bonding performance of recycled metal bracket bases was evaluated. Morphological examination of the bracket bases was carried out under scanning electron microscopy. Statistics analysis included one-way ANOVA with Tukey's Studentized Range Test, two-way ANOVA and Weibull analysis. RESULTS: Mean peel/shear bond strength values range from 13.9 MPa for Allure Accu Arch, a ceramic bracket type, to 1.6 MPa for the plastic bracket CeramaFlex Advant Edge. Allure Accu Arch performed the best of all the ceramic brackets. However, bracket wing fracture was observed. The metal brackets Mini masters and Omni Arch showed no significant difference in bond strength compared with the ceramic bracket Allure Accu Arch (P < 0.01). CONCLUSION: The type of the bracket base determines its adhesive capacity. Sandblasting the base of recycled metal brackets had no uniform effect.

Adhesiveness↗