Imaging Performance with Different Doses in Skeletal Radiography: Comparison of a Needle-structured and a Conventional Storage Phosphor System with a Flat-Panel Detector

Purpose: To evaluate possible radiation dose reduction in the extremities with use of digital radiography and a needle-structured image plate (NIP) by comparing this technique with digital radiography performed with a powder-structured image plate (PIP) and a flat-panel detector (FPD). Materials and Methods: This study was approved by the local review board. A total of 72 plain radiographs of the feet of six human cadavers were obtained with four surface entrance doses (65, 43, 20, and 10 mu Gy) by using three systems. The reference image of each specimen was obtained with an 85-mu Gy dose and with use of a PIP. Five independent blinded radiologists evaluated the images. The noise level and the depiction of the cortical bone, trabecular bone, and soft tissue were rated and compared with those of the reference image by using a five-point scale. An overall image score was developed for these four criteria by calculating the unweighted mean. The Wilcoxon test was used to assess differences between overall image scores. Results: For each dose, NIP images were significantly superior (P <.001), whereas FPD images and PIP images were significantly inferior (P <.01). NIP images obtained with 65-, 43-, and 20-mu Gy doses were significantly superior to reference images and to FPD and PIP images obtained with a 65-mu Gy dose. There were no significant differences between reference images and FPD images obtained with 65- and 43-mu Gy doses. Conclusion: Radiation dose can be reduced by 75% in clinical skeletal imaging of peripheral extremities by using NIP, with no significant loss of information. For FPD images, this might be possible with a dose reduction of 50%. (C) RSNA, 2008