A reduced micro-dose protocol for 3D reconstruction of the spine in children with scoliosis: results of a phantom-based and clinically validated study using stereo-radiography.

Purpose: The aim of this study was to validate the reproducibility of 3D reconstructions of the spine using a new reduced micro-dose protocol.

Methods: First, semi-quantitative image analysis was performed using an anthropomorphic child phantom undergoing low-dose biplanar radiography. This analysis was used to establish a "lowest dose" allowing for acceptable visibility of spinal landmarks. Subsequently, a group of 18 scoliotic children, 12 years of age or younger, underwent full-spine biplanar radiography with both micro-dose and the newly defined reduced micro-dose. An intra- and inter-observer reliability study of 3D reconstructions of the spine was performed according to the International Organization for Standardization (ISO)-5725 standard, with three operators.

Results: The reduced micro-dose setting corresponded to a theoretical reduction of radiation dose exposure of approximately 58%. In vivo results showed acceptable intra- and inter-observer reliability (for instance, 3.8° uncertainty on Cobb angle), comparable to previous studies on 3D spine reconstruction reliability and reproducibility based on stereo-radiography.

Conclusion: A new reduced micro-dose protocol offered reliable 3D reconstructions of the spine in patients with mild scoliosis. However, the quality of 3D reconstructions from both reduced micro-dose and micro-dose was inferior to standard-dose protocol on most parameters. Standard-dose protocol remains the option of choice for most accurate assessment and 3D reconstruction of the spine. Still, this new protocol offers a preliminary screening option and a follow-up tool for children with mild scoliosis yielding extremely low radiation and could replace micro-dose protocol for these patients.

Key Points: • We investigated the reliability of 3D reconstructions of the spine based on a new stereo-radiography protocol reducing radiation dose by 58% compared with established micro-dose imaging protocol. • The new reduced micro-dose protocol offers a reproducible preliminary screening option and a follow-up tool in the necessarily frequent repeat imaging of children with mild scoliosis yielding extremely low radiation and could replace existing micro-dose protocol for these patients. • EOS standard-dose protocol remains the option of choice for exact radiographic assessment of scoliosis, offering more exact 3D reproducibility of the spine compared to both micro-dose and the new reduced micro-dose protocols.