Decomposing the bony thorax in X-ray images

Abstract

The identification and segmentation of target objects from medical images is often confused by other more salient objects in the image. This is a specific problem for X-ray projection images where the shadows of semi-transparent objects are overlaid. A bone shadow may confuse the automated detection of other crossing bones and of important soft tissue findings in the lung like lung nodules. We present a method to identify and remove such bone shadows from a chest radiograph for the purpose of suppressing all bone shadows overlapping with the lung field in a standard posterior-anterior view. In this context an elegant novel approach to the problem of identifying and segmenting overlaid objects is followed: Disturbing objects are identified first and literally removed from the image, therefore no longer confusing the detection of other more subtle objects. This method allowed the identification, segmentation, and suppression of the clavicles, the posterior and the anterior parts of the ribs — one after another. In a clinical study the detection of lung nodules by experienced radiologists was improved after bone suppression.