Slot-Scan Digital Radiography of the Lower Extremities: a Comparison to Computed Radiography with Respect to Image Quality and Radiation Dose

with Respect to Image Quality and Radiation DoseObjective: To compare the slot-scan digital radiography (SSDR) of the lower extremity region and the computed radiography (CR) method with respect to the image quality and radiation exposure. Materials and Methods:We enrolled 54 patients who underwent both the SSDR and CR of the lower extremities.The study evaluated and statistically compared the image quality of four features (outer cortex, inner cortex, trabeculae and intermuscular fat) at six different levels (pelvis, hip, femur, knee, tibia and ankle) between each method.The image quality was evaluated using a visibility scale, and the entrance skin dose was measured using a dosimeter at three different levels of a phantom (hip, knee, and ankle).Results: The mean image visibility scale values for the SSDR method were significantly higher than for the CR method.The entrance skin dose for the SSDR method was 278 μ Gy at each level, compared to the entrance skin doses of the CR method, which were 3,410 μ Gy for the hip, 1,152 μ Gy for the knee, and 580 μ Gy for the ankle.Conclusion: Both the image quality and patient entrance skin dose data suggest that the SSDR method is superior to the CR method for the lower extremity musculoskeletal examination.ollowing the introduction of low-dose digital radiography at the Budker Institute of Nuclear Physics in the beginning of the 1980s, the demand for and the use of digital image acquisition, display, and archiving systems has greatly increased in the field of radiology.Recently, the slot-scan digital radiography (SSDR) method has been introduced for chest and breast imaging as a new scanning technology of digital radiography.The system uses slot scanning geometry to acquire the radiography without the use of an anti-scatter grid.The narrow fan-like beam is synchronized with the detector when scanning a patient.As a result, the image data are obtained from the detector as the patient is scanned via the time consuming method (1).Some important advantages of the SSDR method include the limited number of detector elements, high spatial resolution, and the lack of a scatter grid (2).In comparison with the conventional computed radiography (CR), the SSDR can offer an improved dynamic range, low-contrast resolution, more rapid access to images, and the opportunity for dedicated image processing (2).Because the intrinsic features of the SSDR detector provide direct conversion, no dead zone, and no dead pixels, the SSDR method can prevent scattered X-rays as well as produce an arbitrary image size with low distortion (3, 4).Although the SSDR method has been primarily used to for chest imaging, it has also recently been used for the skeletal system of both humans