3D Vertebral Morphological Measurements Using Low Dose Stereoradiography Imaging: A Comparison with CT Scans Saba Pasha1, Tom Schlösser2, John Flynn1, René Castelein2 The Children’s Hospital of Philadelphia, The United States University Medical Center, Utrecht, Holland

Overview Purpose: to compare the 3D vertebral morphology measurements using low dose stereoradiography with CT scans Methods: Evaluate 9 patients with spinal deformities (ages 7.8-12.5 years) 2 observers performed EOS 3D reconstruction versus one observer for CT reconstructions Generate 3D reconstruction of CT and stereoradiography X-rays Total of 86 vertebrae included in analysis Compare 8 morphological parameters

Gold Standard Vertebral morphology analyzed on CT scan reconstructions using semi- automatic image processing technique (Scoliosis Analysis[1]) Manual identification of the vertebral endplates and spinal contour on the CT scans [1] Lam TP, Vincken KL, Castelein RM, JC. C. Three-dimensional characterization of torsion and asymmetry of the intervertebral discs versus vertebral bodies in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2014;39(19):E1159-1166.

The Local Coordinate System of Each Vertebrae 8 anatomical landmarks identified: 1.) Anterior Height (A) 2.) Posterior Height (P) 3.) Left Height (L) 4.) Right Height (R) 5.) Superior vertebral depth (S-D) 6.) Inferior vertebral depth (I-D) 7.) Superior vertebral width (S-W) 8.) Inferior vertebral width (I-W)

Comparison between stereoradiography and CT scan data Compared morphological parameters at T4-L1 levels No significant differences between the mean of A, P, L, R, S-W, and I-W p<0.05 Mean of S-D and I-D significantly greater in EOS measurements p<0.05

Agreement assessment between the stereoradiography and CT measurements Test the agreement between the two measurement techniques for each morphometric parameter Showed agreement in vertebral height (A and P) Larger measurement bias and limits of agreement for S-D, I-D, and S-W

Summary of the results Measurement bias ranged 0.2-1.5mm Lower measurement of bias in vertebral height (0.3-1.0mm) Higher measurement of bias in vertebral width (0.2-1.5mm) High intra- and interobserver reliability for EOS 3D reconstructions were 0.99 (CI: 0.98-1.00) and 0.99 (CI: 0.98- 1.00) Comparable measurements between EOS and CT for vertebral anterior, posterior, left, and right heights Comparable measurements between EOS and CT for vertebral superior and inferior vertebral width Less curved posterior vertebral body arch observed in SterEOS model (A) compared to CT (B) contributes to measurement error in S-D and I-D

Limitations and Future Analysis Only include spinal vertebrae at T4-L1 levels Excluded patients under the age of 7 years Future direction Evaluation of the lumbar vertebrae morphological parameters using EOS system

Conclusion 3D reconstruction of stereoradiography images provides accurate and reliable measurements of the vertebral dimensions for: Anterior/Posterior Height Left/Right Height Superior/Inferior Vertebral Width Incorporating these measurements into clinical assessments of patients undergoing growth-friendly treatment for spinal deformity can enhance the patient care.