Use of three-dimensional MR angiography for tracking a contrast bolus in the carotid artery.
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Contrast-bolus tracking in the carotid bifurcation was accomplished using an MR angiographic technique with a 3D turbo field-echo readout (TR/TE = 6/3, flip angle = 50 degrees) modified by a keyhole scheme. Optimal visibility of the contrast bolus was achieved by digital subtraction from a reference volume. This technique reliably time-resolves the carotid arteries from the jugular veins. (+info)
A new sonographic technique for assessing carotid artery disease: extended-field-of-view imaging.
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We describe a new sonographic technique, extended-field-of-view imaging, and its clinical application for carotid artery disease. The technique identifies identical structures on two successive images for position registration to make a panoramic image in real time without position sensors. In 39 of 41 subjects, this technique provided high-quality panoramic images that could not be obtained with conventional real-time sonography, and made findings in the carotid artery more interpretable. (+info)
Helical CT angiography: dynamic cerebrovascular imaging in children.
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BACKGROUND AND PURPOSE: The purpose of this study was to assess the feasibility of helical CT cerebrovascular imaging (CTCVI) in children and to make initial comparisons with MR angiography and digital subtraction angiography (DSA). METHODS: Twenty-six patients, ages 3 days to 17 years, were examined with CTCVI. Patients were scanned with 1-mm collimation and 2:1 pitch 30 seconds after the initiation of a hand injection of 2 mL/kg nonionic contrast material (320 mg/dL iodine) with a maximum dose that did not exceed 80 mL (minimum volume, 5 mL in a 2.5-kg infant). Reconstructions were done using maximum intensity projection and integral rendering algorithms. Four patients had CTCVI, MR angiography, and DSA (42 vessels studied) and nine patients had CTCVI and DSA (136 vessels studied). Scores of 1 (not present) to 3 (present in continuity to the first bifurcation) were assigned independently by two radiologists to 32 vessels in each correlated case for each available technique. RESULTS: There were no technical failures. CTCVI depicted 18 thrombosed dural sinuses, three vascular malformations, one intracranial aneurysm, and four tumors. Ninety-five percent of the vessels seen with DSA were also seen with CTCVI. CTCVI identified all vessels seen on MR angiography. CONCLUSION: Helical CTCVI is an effective technique for assessing the intracranial circulation in children. In this initial comparison, CTCVI showed more vascular detail than MR angiography, and had fewer technical limitations. (+info)
A vital stain for studying membrane dynamics in bacteria: a novel mechanism controlling septation during Bacillus subtilis sporulation.
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At the onset of sporulation in Bacillus subtilis, two potential division sites are assembled at each pole, one of which will be used to synthesize the asymmetrically positioned sporulation septum. Using the vital stain FM 4-64 to label the plasma membrane of living cells, we examined the fate of these potential division sites in wild-type cells and found that, immediately after the formation of the sporulation septum, a partial septum was frequently synthesized within the mother cell at the second potential division site. Using time-lapse deconvolution microscopy, we were able to watch these partial septa first appear and then disappear during sporulation. Septal dissolution was dependent on sigma E activity and was partially inhibited in mutants lacking the sigma E-controlled proteins SpoIID, SpoIIM and SpoIIP, which may play a role in mediating the degradation of septal peptidoglycan. Our results support a model in which sigma E inhibits division at the second potential division site by two distinct mechanisms: inhibition of septal biogenesis and the degradation of partial septa formed before sigma E activation. (+info)
Toward objective selection of representative microscope images.
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Scientists wishing to communicate the essential characteristics of a pattern (such as an immunofluorescence distribution) currently must make a subjective choice of one or two images to publish. We therefore developed methods for objectively choosing a typical image from a set, with emphasis on images from cell biology. The methods involve calculation of numerical features to describe each image, calculation of similarity between images as a distance in feature space, and ranking of images by distance from the center of the feature distribution. Two types of features were explored, image texture measures and Zernike polynomial moments, and various distance measures were utilized. Criteria for evaluating methods for assigning typicality were proposed and applied to sets of images containing more than one pattern. The results indicate the importance of using distance measures that are insensitive to the presence of outliers. For collections of images of the distributions of a lysosomal protein, a Golgi protein, and nuclear DNA, the images chosen as most typical were in good agreement with the conventional understanding of organelle morphologies. The methods described here have been implemented in a web server (http://murphylab.web.cmu.edu/services/TyplC). (+info)
Solution x-ray scattering-based estimation of electron cryomicroscopy imaging parameters for reconstruction of virus particles.
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Structure factor amplitudes and phases can be computed directly from electron cryomicroscopy images. Inherent aberrations of the electromagnetic lenses and other instrumental factors affect the structure factors, however, resulting in decreased accuracy in the determined three-dimensional reconstruction. In contrast, solution x-ray scattering provides absolute and accurate measurement of spherically averaged structure factor amplitudes of particles in solution but does not provide information on the phases. In the present study, we explore the merits of using solution x-ray scattering data to estimate the imaging parameters necessary to make corrections to the structure factor amplitudes derived from electron cryomicroscopic images of icosahedral virus particles. Using 400-kV spot-scan images of the bacteriophage P22 procapsid, we have calculated an amplitude contrast of 8.0 +/- 5.2%. The amplitude decay parameter has been estimated to be 523 +/- 188 A2 with image noise compensation and 44 +/- 66 A2 without it. These results can also be used to estimate the minimum number of virus particles needed for reconstruction at different resolutions. (+info)
Stresses at the cell-to-substrate interface during locomotion of fibroblasts.
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Recent technological improvements in the elastic substrate method make it possible to produce spatially resolved measurements of the tractions exerted by single motile cells. In this study we have applied these developments to produce maps of the tractions exerted by 3T3 fibroblasts during steady locomotion. The resulting images have a spatial resolution of approximately 5 micrometers and a maximum intensity of approximately 10(2) kdyn/cm2 (10(4) pN/micrometers2). We find that the propulsive thrust for fibroblast locomotion, approximately 0.2 dyn, is imparted to the substratum within 15 micrometers of the leading edge. These observations demonstrate that the lamellipodium of the fibroblast is able to generate intense traction stress. The cell body and posterior seem to be mechanically passive structures pulled forward entirely by this action. (+info)
Three-dimensional reconstruction of the color Doppler-imaged vena contracta for quantifying aortic regurgitation: studies in a chronic animal model.
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BACKGROUND: The purpose of this study was to investigate the use of 3-dimensional (3D) reconstruction of color Doppler flow maps to image and extract the vena contracta cross-sectional area to determine the severity of aortic regurgitation (AR) in an animal model. Evaluation of the vena contracta with 2-dimensional imaging systems may not be sufficiently robust to fully characterize this region, which may be asymmetrically shaped. METHODS AND RESULTS: In 6 sheep with surgically induced chronic AR, 18 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flowmeters (EMFs) as reference standards, and aortic regurgitant effective orifice areas (EOAs) were determined from EMF regurgitant flow rates divided by continuous-wave (CW) Doppler velocities. Composite video data for color Doppler imaging of the aortic regurgitant flows were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. After the 3D data transverse to the flow jet were sectioned, the smallest proximal jet cross section was identified for direct measurement of the vena contracta area. Peak regurgitant flow rates and regurgitant stroke volumes were calculated as the product of these areas and the CW Doppler peak velocities and velocity-time integrals, respectively. There was an excellent correlation between the 3D-derived vena contracta areas and reference EOAs (r=0.99, SEE=0.01 cm2) and between 3D and reference peak regurgitant flow rates and regurgitant stroke volumes (r=0.99, difference=0.11 L/min; r=0.99, difference=1.5 mL/beat, respectively). CONCLUSIONS: 3D-based determination of the vena contracta cross-sectional area can provide accurate quantification of the severity of AR. (+info)