Researchers have long realized that radiographic images can be decomposed into two "component images," because there exist two predominant interactions that account for x-ray attenuation in the diapostic range of x-ray energies - Compton scattering and photoelectric absorption. Decomposition into component images is achieved through linear (or higher order) combination of radiographic images recorded using x-ray beams with differing effective energies. The component images usually chosen by researchers are those in which either soft tissue or bone is suppressed. The motivation for creating radiographic images free from either bone or soft tissue image contrast is to simplify the task of interpreting radiographic image information. By removing irrelevant structures unrelated to the likely disease being diagnosed, it is argued, detection accuracy may increase. Correspondingly, the efficiency with which soft tissue nodules (tumors) are detected from chest radiographs may be increased by removing image contrast that results from bony structures such as the ribs, whose presence may "mask" the presence of a tumor. This study focuses on dual energy subtraction techniques that produce images in which bone contrast is suppressed.
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