We wish to examine the clinical efficacy of a new dual-energy imaging technique that can potentially increase the sensitivity and specificity of pulmonary disease diagnosis on the chest x-ray. Selective tissue imaging ("bone-only" or "soft-tissue-only") is possible with the acquisition of two distinct x-ray images using different energies, which are processed by computer weighted image subtraction. Currently available, commercial dual-energy computed radiography (CR) systems have been limited by poor energy separation due to their use of relatively ineffective dual plate, copper filter technology.  The technique proposed here, which we call an active detector system, is unique because it offers an ability to acquire low-voltage and high-voltage images separately in time but with no motion of the detector. This achieves superior energy separation yielding a high signal and low noise. The exposure times are kept very short with the use of CR digital imaging receptors, which can be erased in an extremely short period (~5 milliseconds). A prototype  "active-detector" system in the UC Davis Radiology research laboratory has been previously examined with a pilot research study of ten human volunteers in a previously approved human subjects protocol. Review of the tissue-only images suggested that increased conspicuity of pulmonary lesions that may improve sensitivity and specificity over conventional chest images, by eliminating confounding images of overlying bones. Comparison of the dual-energy images to the CT "gold-standard" examination will allow us to determine the sensitivity, specificity, and accuracy of interpretation using the active-detector, dual-energy images. Comparison of the active detector to dual plate, copper filter technology will show the advantages and disadvantages of the new technique compared to the commercial state-of-the-art. We are seeking to enroll approximately 25-30 volunteer patients with known pulmonary lesions and who are already scheduled for a standard chest x-ray and pulmonary CT scan, to participate in this research study.