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The electrical resistivity of mammalian tissues varies widely and is correlated with physiological function. Electrical impedance tomography (EIT) can be used to probe such variations in vivo, and offers a non-invasive means of imaging the internal conductivity distribution of the human body. But the computational complexity of EIT has severe practical… (More)

We have developed an iterative method to correct axial and tangential patient motion occurring during tomographic acquisition. The method uses axial images reconstructed from the uncorrected projection images, which are then forward projected to form a basis for registering the original planar images and, in the process, directly seeks to establish a… (More)

Resistance imaging involves the reconstruction of the distribution of electrical resistivity within a conducting object from measurements of the voltages or voltage gradients developed on the boundary of the object while current is flowing within the object. In general, the relationship between the distribution of resistivity in the object and the voltage… (More)

Reconstruction of electrical impedance images using the filtered back projection method of Barber and Brown makes several important assumptions about the object being imaged. These are principally that the object has a circular boundary, is two-dimensional and of impedance close to uniform, and has electrodes equally spaced on its boundary. In practice few… (More)

This work describes the use of a method, based on the projection onto convex sets (POCS) algorithm, for reduction of the N/2 ghost in echo-planar imaging (EPI). In this method, ghosts outside the parent image are set to zero and a model k-space is obtained from the Fourier transform (FT) of the resulting image. The zeroth- and first-order phase corrections… (More)

There are several situations in which the registration of two medical images is desirable. One example is the registration of two images of the same organ taken using different radionuclide tracers, for example the ventilation and perfusion components of a V/Q lung scan, where the aim is to compare the regional uptake of the two tracers. Another example is… (More)

Subtraction of the two components (baseline and stimulation) of a neuroactivation study using 99Tcm HMPAO SPECT requires accurate registration of the two images. Immobilization of the subject during and between the two components of the study can prove difficult and degrades signal to noise ratio. The use of an automated image registration technique for… (More)

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… (More)

The computation of physiological factors and factor images by factor analysis in dynamic structures using the constraints of positive factors and spatial distribution of these factors (FADS), currently used by a number of research workers, is investigated. While the positivity constraints used may be quite acceptable physically, they cannot be strictly said… (More)