1、Basic Radiation -Production of X-RayX-Rays and RoentgenX-rays were discovered by Roentgen in 1895 while studying the cathode rays (streams of electrons) in a tube.This new radiation could penetrate opaque substance, produce flourescence, blacken a photographic plate, and ionize gas. It is a form of
2、electromagnetic radiation.Wilhelm Conrad Roentgen (1845-1923) the radiograph of Mrs. Roentgens handX-Ray Tube ProductionX-Ray TubeX-ray tubeX-ray tubeThe main components of an x-ray tube are the cathode and the anode, sealed opposite to each other in a highly evacuated vacuum tube.The cathode is a t
3、ungsten filament which when heated emits electrons.The anode consists of a copper rod and a piece of tungsten target (for producing the x-rays).The x-ray beam emerges through a thin glass window in the tube envelope.X-ray tubeTungsten is used as target because of its high Z (74) and high melting poi
4、nt (3370C).Copper is used for its high heat conduction, heat is removed by oil (which also serves as an insulator to the tube housing from high voltage applied to the tube), water or air from outside the tube. Sometimes, a rotating anode is used to reduce the temperature of the target at any one spo
5、t.Anode hood is used to shield unwanted stray radiation.X-ray tubeX-ray tubeThe focal spot is the target area from which the x-rays are emitted. It should be as small as possible for producing sharp radiographic images. For therapy tubes, relatively larger focal spots are acceptable since the image
6、quality is not a primary concern.The apparent size of the focal spot is related to the apparent side = A sin. In diagnostic radiology, the angle is small (6 -17), producing apparent focal spot sizes from 0.10.1 to 2.02.0 mm. For therapy tubes, the angle is larger (30), producing areas from 55 to 77 mm.Variation of X-Ray Intensity and Maximum X-ray Beam Size Because of the Anode Heel Effect
