Optimization of imaging conditions for infant hip imaging using flat panel detectors.

To investigate the optimal low-dose imaging conditions for infant hip radiography, using a commercially available infant phantom, and to identify conditions that are satisfactory to orthopedic surgeons, using a combination of low tube voltage, mAs, and Cu filters. Hip joint radiographs were taken with Cu filters (0, 0.1, 0.2 mm) at tube voltages from 40 to 70 kV in 5 kV increments. Seven radiographers graded the images, and the five images with the lowest dose and an average score of 3.5 or higher were selected. These images were then subjected to paired comparisons by six orthopedic surgeons. The selected acquisition settings all used low tube voltages (40-55 kV), and none used a 0.2-mm Cu filter. The optimal imaging condition was identified as 40 kV, 5 mAs, and a 0.1-mm Cu filter, giving the patient entrance surface dose of 11 μGy, which was the lowest dose investigated and was highly preferred by the orthopedic surgeons. Low-dose imaging using a Cu filter at low tube voltage can produce images that are satisfactory for orthopedic surgeons, with lower radiation doses than previously possible.