Digital Tomography Incorporating a Priori Information

Abstract

The technique of tomography has long been used in radiography and in nuclear medicine to sharpen images of objects on the tomographic plane and to blur images of objects on the off-planes. The method is illustrated in Figure 1. Suppose one is interested in examining the plane Tin the object. The x-ray source and the film are moved parallel to each other in the opposite directions with the plane of interest as the fulcrum. This is achieved by choosing the velocity v1 of the x-ray source and the velocity v 2 of the film such that the ratio v1/v2 is equal to difd 2 , where d 1 is the source-to-plane distance, and d 2 is the plane-to-film distance. The objects on the plane of interest are in focus, whereas the objects on the other planes are out of focus and blurred. However, the blurrings could become quite serious in some cases and interfere with the objects of interest.

A Priori Information and Off-Axis Measurements in Terahertz Tomography

“…Modeling the sample a priori is a common tool in the field of NDT, to assure the quality of objects made out of a well-known material by either extraction or additive manufacturing based on a geometric model. Prior works on enhancing the imaging capabilities of different tomographic reconstruction techniques based on a priori information can be found for microwave tomography in [19], [20], [21], [22], and [23], for X-Ray tomography in [24], and in the context of terahertz tomography in [25], [26], and [27]. Ding et al [19] distinguish between two categories of a priori information: The first category represents information about the target or sample, such as internal or external boundaries or regions and the respective refractive indices [20], [21], [22], [24].…”

Material Density Distribution of a Radial Symmetric Product from a Single X-Ray Radiograph

“…As the number of projections decreases, the information provided for the reconstruction becomes more incomplete. The decrease in the information content may sometimes be compensated by the use of a priori knowledge about the product and thus alleviate to some extent the ill-posedness of the problem [1][2][3][4].…”