RESUMO
PROBLEM: The purpose of the investigation was a comparison of two different digital X-ray techniques with conventional standing full spine films. Evaluation of dose area product, image quality and inter-observer error of Cobb-angle measurement in patients with scoliosis and kyphoscoliosis were studied. METHODS: A consecutive series of 150 patients were prospectively randomized into three groups. Patients in group 1 (n=53) received a conventional standing postero-anterior full spine radiograph. All films were evaluated on the light box. Patients in group 2 (n=48) received a X-ray using the digital storage phosphor plate system (CR). For group 3 (n=49) digital pulsed fluoroscopy was used. In groups 2 and 3 images were exported to a picture archiving and communicating system (PACS) workstation and viewed on a monitor (Siemens SMM 21140P, Germany). Dose area product measurements were performed in all three groups (Diamentor-M, PTW, Freiburg). Three experienced investigators independently reviewed all pictures. Pedicles and endplates were counted. Cobb-angles of the main curves were measured. RESULTS: The mean dose area product was 97.0 cGy cm(2) (37.0-380.0 cGy cm(2)) for conventional films, 31.5 cGy cm(2) (6.0-66.0 cGy cm(2)) for CR imaging and 5.0 cGy cm(2) (1.0-29.0 cGy cm(2)) for digital fluoroscopy. The differences of Cobb-angle measurements were not significantly different for the three methods. Differences in the count of pedicles and endplates between the investigators were significantly lower for the conventional film as an indicator for the best detail presentation. CONCLUSION: A significant reduction in dose area product is possible with modern digital X-ray methods. The inter-observer error of Cobb-angle measurement is not significantly altered. The detail information is decreased in comparison to conventional films.