Emile Schoeters

Full-leg/full-spine image stitching: a new and accurate CR-based imaging technique

This paper introduces a new imaging modality based on existing computed radiography technology to form a total body part image from a series of overlapping subimages. The subimages are exposed simultaneously but digitized individually as normal single-exposure examinations. During exposure, a rectangular grid of attenuating lines is present in the X-ray path to aid in the reconstruction process. A digital image-processing algorithm has been developed to assemble a composite image from the subimages, showing perfect geometric continuity of body parts, a technique termed image `stitching.

Primitive-based contrast enhancement method

In this article we present a new solution for the problem of contrast enhancement. The method is based on the decomposition of the original image into its primitive components. In a first stage a multiresolution representation of the image is computed yielding transform coefficients proportional to the maximum of the local gradient at a specific scale and at a specific position in the image. As an image detail exists at several scales, the transform coefficients corresponding to the same image primitive are grouped. Contrast is enhanced by groupwise non-linear amplification of the transform coefficients. An inverse transform is then applied to the modified coefficients, resulting in a uniformly contrast-enhanced image without artifacts. Preliminary results demonstrate the effectiveness of this method. It could be used in a wide range of applications.

Compensation for scattered radiation in dual-energy imaging using partially transparent shields

In this paper we present a method for the compensation for scattered radiation in dual-energy imaging. The method uses shields (PTS), partially transparent for x-radiation, positioned between the x-ray source and the detector. By comparing the detected signals under and beside the shields, and using data from the dual-energy calibration procedure with basis materials, the radiation scatter can be calculated at the location of the shields. In a first implementation of the technique many shields are positioned at regular distances in the imaging field. The radiation scatter in the entire image can then be calculated by interpolation techniques. A second implementation of the technique makes use of a robust convolution with a low-pass filter. The parameters of the convolution kernel are determined by PTS-measurements at a limited amount of well-chosen locations of the object. After substraction of the radiation scatter, the images can be compensated for the effect of the shields. We tested the method with images of an artificial polystyrene phantom and with humanoid chest images, made with a computed radiography system.