Computer-Based Reconstruction and Temporal Subtraction of Radiographs

Abstract

The most important physical parameter limiting the diagnostic performance achieved with radiographic images is the signal-to-noise ratio (SNR). In most dental applications, the normal anatomical structures contribute to a background pattern in the image that is limiting the SNR attainable. Hence, the projection direction of radiographs is a fundamental determinant of the SNR. The acquisition of a basis set of projection images obtained from a plurality of spatially registered sampling directions permits the reconstruction of any desired slice lying within a limited volume by tomosynthesis. Alternatively, the multi-projection strategy permits synthesis of any arbitrary radiographic image whose projection direction lies within the cone spanned by the basis projection directions. This feature can be used to synthesize a desired image at the proper projection angle required for meaningful subtraction from a previously obtained radiograph, and thus to suppress anatomy-related background variations.