Abstract
The radiograph is a shadow image of the X-ray beam as it passes through a bone. Variations in mineral content or subtle changes in the shape or contour of the tissue can indicate either an increase or loss of mineral consistent with alterations in bone turnover. The ability of standard X-ray units to detect such changes is limited by the poor image quality due to the large size of their X-ray source (0.3–1 mm), whereas microfocal X-ray units are characterized by a micron-sized X-ray source (5–100 µm) in which the object being examined is placed close to the X-ray tube, with the film at 1.5–2 m away, resulting in magnification (macroradiographs) of the image with high spatial resolution (Fig. 10.1). Such techniques have been used widely in the United States [1] and Japan [2]. The work carried out by these groups has failed largely due to limitations in the design of their X-ray machines, in which the minute size of the X-ray source could not be maintained. The macroradiographs they obtained, of either the hand or fingers, tended to be restricted in radiographic magnification (usually ×4, rarely ×6) and spatial resolution [1,3]. The design of the British tube [3, 4], based on a different approach, ensures that the micron-sized X-ray source is retained throughout the life of the machine. The present equipment is capable of producing radiographs of small specimens (post-mortem samples, animals) to most parts of the human body at higher magnifications (from ×5 to ×20) and at a spatial resolution approximating to that of histology [3]. This is clearly better than those of other non-invasive medical imaging techniques.
Published Version
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