Unfolded Cylindrical Projection For Rib Fracture Diagnosis

The recommended exam for assessing chest trauma is a computed tomography (CT) chest scan. Using multi-planar reconstructions to evaluate a CT volume to assess the ribcage is a tedious and time-consuming task. We have designed an application that provides an automatically rendered unfolded unobstructed view of the entire ribcage using an unfolded cylindrical projection. This paper describes the underlying algorithm which has two main steps: ribcage segmentation and ribcage unfolding. The unfolding technique we developed preserves the relative size and location of the ribs and surrounding tissue, providing a natural anatomical reference for the reader. It also demonstrated usefulness to identify other musculoskeletal conditions such us scoliosis, calcified cartilage, bone tumours. To evaluate the usefulness of the application, we evaluated it on 70 representative CT chest scans. The evaluation was performed by a clinical expert who graded the specialized unfolded cylindrical projection view on a 5 point Likert scale according to the level of diagnostic confidence. Results showed that 84% of the studies were clinically useful (above grade 3). The algorithm is fully automatic and it runs in an average time of 24 s. The evaluation described in this paper gives positive initial feedback on the usefulness of the application. A recent multi-reader clinical study showed that using the specialized unfolded cylindrical projection view obtains similar diagnostic accuracy to conventional multi-planar reconstructions while reducing the reading time.