PURPOSE: Ultrasound imaging is an attractive alternative to X-ray for scoliosis diagnosis and monitoring due to its
safety and inexpensiveness. The transverse processes as skeletal landmarks are accessible by means of ultrasound and
are sufficient for quantifying scoliosis, but do not provide an informative visualization of the spine. METHODS: We
created a method for visualization of the scoliotic spine using a 3D transform field, resulting from thin-spline
interpolation of a landmark-based registration between the transverse processes that we localized in both the patient’s
ultrasound and an average healthy spine model. Additional anchor points were computationally generated to control
the thin-spline interpolation, in order to gain a transform field that accurately represents the deformation of the
patient’s spine. The transform field is applied to the average spine model, resulting in a 3D surface model depicting
the patient’s spine. We applied ground truth CT from pediatric scoliosis patients in which we reconstructed the bone
surface and localized the transverse processes. We warped the average spine model and analyzed the match between
the patient’s bone surface and the warped spine. RESULTS: Visual inspection revealed accurate rendering of the
scoliotic spine. Notable misalignments occurred mainly in the anterior-posterior direction, and at the first and last
vertebrae, which is immaterial for scoliosis quantification. The average Hausdorff distance computed for 4 patients
was 2.6 mm. CONCLUSIONS: We achieved qualitatively accurate and intuitive visualization to depict the 3D
deformation of the patient’s spine when compared to ground truth CT.
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