Dose Reduction Protocol for Full Spine X-ray Examination Using Copper Filters in Patients With Adolescent Idiopathic Scoliosis

摘要

Study Design. A prospective case series. Objective. The aim of this study was to assess a new protocol for full spine X-ray using copper (Cu) filters to reduce radiation exposure in patients with adolescent idiopathic scoliosis (AIS). Summary of Background Data. Radiation exposure is associated with an increased risk of cancer development in children. To reduce the radiation exposure without compromising the image quality using existing radiographic equipment, a new computed radiography protocol was optimized using a variety of heavy metal filters. Methods. Study 1: Whole spine radiographs were obtained using a human body phantom, and radiation doses without and with 0.1, 0.2, and 0.3mm thick Cu filters were compared. Study 2: Patients with AIS who underwent posterior fusion were radiographically evaluated at follow-ups; the X-ray protocols with or without the use of 0.2-mm Cu filters were alternated between consecutive follow-ups. The image quality was independently evaluated using six points in the anterior-posterior (AP) view and seven in the lateral [left-right (LR)] view by three spine surgeons using a three-point grading system. Results. Study 1: The surface doses while obtaining nonfiltered X-rays in AP and LR views were 0.31 and 0.93 mGy, respectively, whereas those with 0.1-, 0.2-, and 0.3-mm Cu filters were 0.16 and 0.52, 0.11 and 0.36, and 0.08 and 0.27 mGy, respectively. Study 2: In patients with AIS, the percentage of grade 3 scores (both endplates were identifiable) on AP-view images was 85% with nonfiltered X-rays and 75% with the filtered X-rays. However, there were no significant differences between the two protocols. On LR images, the frequency of grade 3 scores was significantly lower at Th2 and Th12 on filtered images than on nonfiltered ones. Conclusion. Whole spine radiographs using 0.2-mm Cu filters in patients with AIS could reduce radiation exposure more than 60% while preserving the image quality.