Usefulness of portrait imaging for intraoperative cone beam computed tomography in adolescent idiopathic scoliosis surgery: a phantom study.

STUDY DESIGN

Comparative study of radiation doses in intraoperative cone-beam computed tomography (CBCT) using an anthropomorphic phantom.

OBJECTIVE

Compare the portrait and conventional landscape CBCT imaging methods under intraoperative conditions focusing on dose reduction rate, image quality, and imaging range. Intraoperative CBCT improves the accuracy of pedicle screw (PS) insertion in posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). We recently introduced portrait imaging for intraoperative CBCT in PS insertion using surgery navigation for AIS. However, evidence is scarce on the comparative radiation dose and image quality of this orientation versus landscape imaging.

METHODS

A human body phantom was equipped with radiophotoluminescent glass dosimeters both inside and on the surface for measuring radiation doses under portrait and landscape CBCT imaging methods. Radiation doses were evaluated by average dose index (ADI), surface dose (D), central dose (D), and displayed dose (D). Image quality was assessed using the contrast-to-noise ratio (CNR) on phantom images. Imaging range was measured using sagittal image craniocaudal length and axial image diameter.

RESULTS

The respective mean ± standard deviation radiation doses for portrait and landscape imaging were 42.9 ± 0.7 and 50.6 ± 1.1 mGy for ADI (i.e., approximately 15% less radiation dose for portrait), 53.9 ± 1.6 and 65.2 ± 1.2 mGy for D, 21.1 ± 1.4 and 21.4 ± 1.0 mGy for D, and 146.6 and 145.0 mGy for D. The CNR results revealed comparable image qualities for portrait and landscape imaging of 2.23 ± 0.22 and 2.18 ± 0.19, respectively. The respective craniocaudal imaging range was 24.6 cm and 18.4 cm, while the axial imaging range was 17.6 cm and 23.7 cm.

CONCLUSION

Portrait-mode CBCT allows for a wider craniocaudal imaging range and enables intraoperative CBCT imaging at lower radiation doses without compromising image quality.