Incorporation of patient displacement into a trunk reconstruction technique

Three-dimensional stereoradiographic reconstruction of scoliotic spines and rib cages is routinely done at Ste-Justine Hospital. For each patient, two postero-anterior X-ray views (PA-0/spl deg/ and PA-20/spl deg/) are taken at approximately 25 seconds interval to obtain 3-D reconstruction of rib midlines. One major source of error in this reconstruction technique is related to the possible displacement of the patient between the two X-ray exposures even if positioning devices are used. Results of a new rib cage reconstruction method which evaluates and takes into account the patient displacement are presented. Graphical 3-D representation of the rib cage reconstruction showed an evident improvement compared to the previous reconstruction method. This new reconstruction technique has important clinical significance because it allows to measure patient displacement during stereoradiography and to improve the quality of the 3-D rib cage representation given to the clinician for evaluation of scoliotic deformities.