Normal roentgenography, which is used for as many as 99.3% of radiographic examinations (UNSCARE Report 1977), is of value in the determination of lesions within the body, and for preserving the record as a roentgenogram. However, as normal roentgenography takes images of the three-dimensional human body, one dimension is lost, leaving the third dimension unknown. Overlaps occur on the picture when a substance of strong X-ray absorption exists in front or behind the tissue or lesion to be recorded, resulting in the subject of interest disappearing due to low contrast. Such results may be interpreted incorrectly, especially when the tissue in front or behind the subject has strong X-ray absorption. Diagnostic errors may be made due to the production of shadows overlapping the images of the tissue or lesion, causing pseudoimages even when the degree of absorption is adequate. It is therefore better to examine the subject in two dimensions, imaged on two-dimensional film, in order to prevent any of the above miscalculations. This is the essence of tomography.
KeywordsAttenuation Coefficient Axial Cross Section Normal Soft Tissue Rotatory Cross Compute Body Tomography
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