Dual-Energy Radiography with High and Low Energy Images

Dual-energy radiography is a technique that generates separate soft-tissue and bone radiographic images by utilizing the different energy-dependent attenuation characteristics of bone and soft tissue. These images have less structured noise, making the identification of anatomy and the diagnosis of pathology less difficult. High and low energy images are combined non-linearly to produce separate soft-tissue and bone images. OBJECTIVE: This study examined dual energy radiographic reconstructions derived from pairs of images taken at different kVps. METHODS: A medical General Electric x-ray generator was used to make exposures at 50 kVp and 120 kVp of two overlying stepwedge phantoms made of aluminum and lucite. The distance from source to object was 25.4" and the object to detector distance was 14.6". The detector system was Fujifilm Fugi IP cassettes type C, processed with a Fujifilm FCR XG5000 reader. The images were exported as DICOM files to a Macintosh computer where they were displayed, measured, and reconstructed using NIH ImageJ software and Java code written by one of the authors. One pair of stepwedge images was used to calibrate the reconstruction algorithm. Six pairs of images were reconstructed. The pixel values along the steps in the reconstructed images were fit by linear regression to the height of the steps. Another six pairs of images were made of a human maxilla and mandible, and the pixel values of a premolar and three molars' dentin were compared to measurements from CBCT images. RESULTS: Data from the six pairs of bone and soft-tissue reconstructed images fit the phantom step heights with mean R-squared values of 0.999 and 0.998, respectively, and were highly significant, p<0.01. The CBCT tooth thicknesses fit the reconstructed data with a R-squared value of 0.965, p<0.02. CONCLUSIONS: Dual energy radiography in dentistry may provide clearer images and quantitative bone density information.