An in vitro receptor binding assay, using filtration to separate bound from free [125I]insulin, was developed and used to characterize insulin receptors on membranes isolated from specific areas of rat brain. The kinetic and equilibrium binding properties of central receptors were similar to those of hepatic receptors. The binding profiles in all tissues were complex and were consistent with binding in multiple steps or to multiple sites. Similar binding properties were found among receptors in olfactory tubercle/bulb, cerebral cortex, hippocampus, striatum, hypothalamus, and cerebellum. High affinity [125I]insulin binding sites (KD = 3-11 nM) were distributed evenly between membranes isolated from P1 and P2 fractions of these brain areas, with the exception of the olfactory tubercle in which binding to P2 membranes was four-fold greater (Bmax = 150 fmol/mg protein). One difference between insulin receptors in brain and peripheral target tissues, however, was observed. Following exposure to 0.17 microM insulin for 3 h at 37 degrees C, the number of specific [125I]insulin binding sites on adipocytes decreased by 40%, while the number of binding sites on minces of cerebral cortex/olfactory tubercle remained constant. The results suggest that although the binding characteristics of central and peripheral insulin receptors are similar, these receptors do not appear to be regulated in the same manner.
BackgroundA significant limitation of existing 3D ultrasound systems comes from the fact that the majority of them work with fixed acquisition geometries. As a result, the users have very limited control over the geometry of the 2D scanning planes.MethodsWe present a low-cost and flexible ultrasound imaging system that integrates several image processing components to allow for 3D reconstructions from limited numbers of 2D image planes and multiple acoustic views. Our approach is based on a 3D freehand ultrasound system that allows users to control the 2D acquisition imaging using conventional 2D probes.For reliable performance, we develop new methods for image segmentation and robust multi-view registration. We first present a new hybrid geometric level-set approach that provides reliable segmentation performance with relatively simple initializations and minimum edge leakage. Optimization of the segmentation model parameters and its effect on performance is carefully discussed. Second, using the segmented images, a new coarse to fine automatic multi-view registration method is introduced. The approach uses a 3D Hotelling transform to initialize an optimization search. Then, the fine scale feature-based registration is performed using a robust, non-linear least squares algorithm. The robustness of the multi-view registration system allows for accurate 3D reconstructions from sparse 2D image planes.ResultsVolume measurements from multi-view 3D reconstructions are found to be consistently and significantly more accurate than measurements from single view reconstructions. The volume error of multi-view reconstruction is measured to be less than 5% of the true volume. We show that volume reconstruction accuracy is a function of the total number of 2D image planes and the number of views for calibrated phantom. In clinical in-vivo cardiac experiments, we show that volume estimates of the left ventricle from multi-view reconstructions are found to be in better agreement with clinical measures than measures from single view reconstructions.ConclusionsMulti-view 3D reconstruction from sparse 2D freehand B-mode images leads to more accurate volume quantification compared to single view systems. The flexibility and low-cost of the proposed system allow for fine control of the image acquisition planes for optimal 3D reconstructions from multiple views.
Aim: To determine the false-positive rate of pulse oximetry screening at moderate altitude, presumed to be elevated compared with sea level values and assess change in false-positive rate with time. Methods: We retrospectively analysed 3548 infants in the newborn nursery in Albuquerque, New Mexico, (elevation 5400 ft) from July 2012 to October 2013. Universal pulse oximetry screening guidelines were employed after 24 hours of life but before discharge. Newborn babies between 36 and 36 6/7 weeks of gestation, weighing >2 kg and babies >37 weeks weighing >1.7 kg were included in the study. Log-binomial regression was used to assess change in the probability of false positives over time. Results: Of the 3548 patients analysed, there was one true positive with a posteriorly-malaligned ventricular septal defect and an interrupted aortic arch. Of the 93 false positives, the mean pre- and post-ductal saturations were lower, 92 and 90%, respectively. The false-positive rate before April 2013 was 3.5% and after April 2013, decreased to 1.5%. There was a significant decrease in false-positive rate (p = 0.003, slope coefficient = −0.082, standard error of coefficient = 0.023) with the relative risk of a false positive decreasing at 0.92 (95% CI 0.88–0.97) per month. Conclusion: This is the first study in Albuquerque, New Mexico, reporting a high false-positive rate of 1.5% at moderate altitude at the end of the study in comparison to the false-positive rate of 0.035% at sea level. Implementation of the nationally recommended universal pulse oximetry screening was associated with a high false-positive rate in the initial period, thought to be from the combination of both learning curve and altitude. After the initial decline, it remained steadily elevated above sea level, indicating the dominant effect of moderate altitude.
a image and video Processing and Communications Lab, ABSTRACTIn this paper, we describe a new freehand ultrasound imaging system for reconstructing the left ventricle from 2D echocardiography slices. An important contribution of the proposed system is its ability to reconstruct from multiple standard views. The multi-view reconstruction procedure results in significant reduction in reconstruction error over single view reconstructions. The system uses object-based 3D volumetric registration, allowing for arbitrary rigid object movements in inter-view acquisition. Furthermore, a new segmentation procedure that combines level set methods with gradient vector flow(GVF) is used for automatically segmenting the 2D ultrasound images, in which low level of contrast, high level of speckle noise, and weak boundaries are common. The new segmentation approach is shown to be robust to these artifacts and is found to converge to the boundary from a wider range of initial conditions than competitive methods.The proposed system has been validated on a physical, 3D ultrasound calibration phantom and evaluated on one actual cardiac echocardiography data set. In the phantom experiment, two calibrated volumetric egg-shape objects were scanned from the top and side windows and reconstructed using the new method. The volume error was measured to be less than 4%. In a real heart data set experiment, qualitative results of 3D surface reconstruction from parasternal and apical views appear significantly improved over single view reconstructions. The estimated volumes from the 3D reconstructions were also found to be in agreement with the manual clinical measurements from 2D slices. Further extension of this work is to compare the quantitative results with more accuracy MRI data.
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