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Biomedical subjects

D C Barber

Publications and source records attributed to D C Barber.

101 records · Page 6Linked to original sources
PubMed1970

Diagnostic accuracy in venous thrombosis.

A group of 111 surgical patients at high risk of venous thrombosis were studied after operation by independent clinical assessment and with (125)I-fibrinogen to detect venous thrombosis. Almost half of the patients developed venous thrombosis. Of these, two-thirds were not suspected clinically despite careful scrutiny. In the patients in whom a clinical diagnosis of venous thrombosis was made this diagnosis was falsely positive in a quarter. More than half of all thrombotic episodes were detectable on the day after operation.The prevalence of venous thrombosis, together with the difficulty in diagnosing it, strongly supports the argument that a reduction in the incidence of pulmonary embolism must depend on widespread adoption of effective prophylaxis, especially in the large number of patients at high risk of venous thrombosis. Prophylactic trials must be objectively assessed, and it is in this field that the (125)I-fibrinogen technique probably has the most to offer.

Adult↗
PubMed1970

Dextran 70 in prophylaxis of postoperative venous thrombosis. A controlled trial.

A controlled prospective trial was carried out in a group of 80 women undergoing gynaecological surgery and thought to be at risk of developing postoperative venous thrombosis. The patients, who had been randomly allocated to prophylaxis with either dextran 70 or warfarin, were well matched in age, weight and other predisposing factors.In the warfarin group, 12 out of 40 patients developed deep vein thrombosis, six of these episodes being classified as major and six as minor. In the dextran 70 group, 4 out of 40 patients developed deep vein thrombosis, all of them minor. The protective effect of dextran 70 is significantly better than that of warfarin (P<0.01) as used in the present study.

Clinical Trials as Topic↗
PubMedDate not supplied

Automatic segmentation of medical images using image registration: diagnostic and simulation applications.

Automatic identification of the boundaries of significant structure (segmentation) within a medical image is an are of ongoing research. Various approaches have been proposed but only two methods have achieved widespread use: manual delineation of boundaries and segmentation using intensity values. In this paper we describe an approach based on image registration. A reference image is prepared and segmented, by hand or otherwise. A patient image is registered to the reference image and the mapping then applied to ther reference segmentation to map it back to the patient image. In general a high-resolution nonlinear mapping is required to achieve accurate segmentation. This paper describes an algorithm that can efficiently generate such mappings, and outlines the uses of this tool in two relevant applications. An important feature of the approach described in this paper is that the algorithm is independent of the segmentation problem being addresses. All knowledge about the problem at hand is contained in files of reference data. A secondary benefit is that the continuous three-dimensional mapping generated is well suited to the generation of patient-specific numerical models (e.g. finite element meshes) from the library models. Smoothness constraints in the morphing algorithm tend to maintain the geometric quality of the reference mesh.

Algorithms↗
PubMedDate not supplied

Efficient nonlinear registration of 3D images using high order co-ordinate transfer functions.

There is an increasing interest in image registration for a variety of medical imaging applications. Image registration is achieved through the use of a co-ordinate transfer function (CTF) which maps voxels in one image to voxels in the other image, including in the general case changes in mapped voxel intensity. If images of the same subject are to be registered the co-ordinate transfer function needs to implement a spatial transformation consisting of a displacement and a rigid rotation. In order to achieve registration a common approach is to choose a suitable quality-of-registration measure and devise a method for the efficient generation of the parameters of the CTF which minimize this measure. For registration of images from different subjects more complex transforms are required. In general function minimization is too slow to allow the use of CTFs with more than a small number of parameters. However, provided the images are from the same modality and the CTF can be expanded in terms of an appropriate set of basis functions this paper will show how relatively complex CTFs can be used for registration. The use of increasingly complex CTFs to minimize the within group standard deviation of a set of normal single photon emission tomography brain images is used to demonstrate the improved registration of images from different subjects using CTFs of increasing complexity.

Brain↗
PubMedDate not supplied

A review of image reconstruction techniques for electrical impedance tomography.

There has recently been an increasing interest in the possibility of producing images of electrical impedance within the human body. When an electric current is applied to the body of a voltage distribution is developed across the body surface. This distribution is in part dependent on the internal impedance distribution within the body and it is possible to estimate this distribution from a suitable set of voltage measurements. Because of the nonlinear relationship between the impedance distribution and the voltage distribution at the surface of the body, the reconstruction problem is much more difficult than for other tomographic imaging techniques, but a significant amount of progress has been made, and it is now possible to produce tomographic images of in vivo distributions of impedance, albeit with low spatial resolution. Future developments should improve image quality.

Electric Conductivity↗
PubMedDate not supplied

Clinical applications of electrical impedance tomography.

This article is a preliminary review of the possible clinical applications of electrical impedance tomography (EIT). The applications to, for example, the central nervous, respiratory, cardiovascular and digestive systems are covered. It is concluded that the area of greatest potential application of EIT is monitoring cardiopulmonary function, but that studies on much larger groups of patients than have been carried out hitherto are required to fully assess the potential of EIT as a clinical tool.

Body Composition↗