The objective of this project is to develop a channeling x-ray source for non-invasive screening for coronary artery disease. Under the Phase I grant the investigators demonstrated the feasibility of using channeling radiation, produced by the passage of a moderate-energy electron beam through a crystal, for dual-energy, digital subtraction coronary angiography. To continue developing a channeling x-ray source, we have set four goals for our proposed Phase II research: 1_ Measure the channeling radiation energy spectrum at high peak currents; 2) Design, construct, and test a precision crystal rotator to maintain low average crystal temperature during the production of high intensity channeling radiation; 3) Develop a dual-energy source that can easily change the peak photon energy; 4) Measure x-ray images of inanimate phantoms to test the performance of the channeling radiation source; evaluate the influence of coronary artery iodine concentration and source brightness on image quality.