Spine Computed Tomography Radiation Dose Reduction Protocol Refinement Based on Measurement Variation at Simulated Lower Radiation Acquisitions

Study Design. Retrospective dose-simulation comparison. Objective. To determine if sufficient detail for preoperative analysis of bony anatomy can be acquired at substantially lower doses than those typically used. Summary of Background Data. Computed tomography (CT) is a preoperative planning tool for spinal surgery. The pediatric population is at risk to express the harmful effects of ionizing radiation. Preoperative CT scans are presently performed at standard pediatric radiation doses not tailored for surgical planning. Methods. We used the validated GE Noise Injection software to retrospectively modify existing spine and chest CT scans from 10 patients to create CT images that simulated a standard dose (100%), 50% dose, and 25% dose scans. 4 orthopedic surgeons and a pediatric radiologist, blinded to dose, measured minimum mediallateral pedicle width and maximum anterior-posterior bony length along the axis of presumed pedicle screw placement. A total of 90 axial images were generated to create our sample set. Measurements were evaluated for accuracy, precision, and consistency. Results. For any given rater, there was no clinically relevant difference between measurements at the different dose levels and no apparent degradation in precision at the different dose levels. Consistent variation was observed between raters, the likely result of individual differences in measurement approach. Conclusion. Spinal CT scans done for preoperative planning can be performed at 25% of current radiation doses without a loss in surgical planning measurement accuracy or precision. These 25% dose-reduced scans would have average Computed Tomography Dose Index volume dose levels of roughly 1.0 to 2.5 mGy (depending on patient size) and size-specific dose estimates of roughly 2.5 mGy representing a substantial dose savings compared to current practice for many sites. Standardization of consistent landmarks may be useful to further improve inter-rater concordance.