Figure 4b: Electron-beam CT, also known as fifth-generation CT. (a) Diagram shows electron-beam CT scanner architecture. Target is a long continuous tungsten strip that makes a 210° arc around the patient. Electron beam and focal spot traverse the entire arc in 50–100 msec. Electron beam and target reside in a single funnel-shaped evacuated chamber (not shown). Detector array does not move. (b) Transverse electron-beam CT image in a patient with obstructive coronary artery disease who had undergone bypass surgery. Calcium is visible in left main coronary artery (lower left arrow), left anterior descending coronary artery (lower right arrow), and aorta (upper left arrow). Surgical clip (upper right arrow) from bypass surgery is also visible.