Radiographs Projections

There are excellent descriptions of the basic radiographic projections, familiar to every radiographer (Cook et al. 1998 Khon et al. 1996). These texts not only describe the projections but also discuss the radiation dose implications of them and the measures by which the quality of the image can be measured so that standards can be kept high by regular audit. 

A tomographic measurement is based on the acquisition of several radiographic projection of the sample from different viewing angles. For this purpose, the sample is rotated around an axis perpendicular to the beam (Figure 18.3). A complete tomographic measurement typically contains between 300 and 3000 images. 

Figure 6.9 Radiographic projections or shadow images of a mouse acquired with a cone-beam micro-CT at two different angles.

For safety reasons, the main components of industrial installations must undergo NDT so as to guarantee the functional capacities of equipment by verifying the integrity of the materials. This paper presents the EDF project to improve the quality for detection, localization and characterization of incoming faults inside materials, and to increase the performance of X or y radiographic analysis. 

A complete analysis is made by acquiring a number of radiographs (typically about 1000) of the same sample under different viewing angles (one orientation for each radiograph). A final computed reconstruction step is required to produce a 3D map of the linear attenuation coefficients in the material. This 3D map indirectly gives a picture of the structure density. In the X-ray-computed tomography, the X-ray source and detector are placed at the opposite sides of the sample. The spatial resolution of the attenuation map depends on the characteristics of both the detector and number of X-ray projections. 

Armstrong DM, Schild RE (1978a) An investigation of the cerebellar cortico-nuclear projections in the rat using an auto-radiographic tracing method. I. Projections from the vermis. Brain Res., 141, 1-19. 

Snaith, B. (2007) Radiographer-led discharge in accident and emergency - the results of a pilot project. Radiography, 13(1), 13-17. 

Westbrook, K. and Hodgetts, A. (1997) Development of a Limited Formulary Prescribing Scheme for Therapy Radiographers and Oncology Nurses NHS Executive (S W) R D Project Grant RefD/12/11.95/Westbrook Abstract Reporting Back the Results of R D Conference. 

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