42组织替代材料之间的转换.PPT

Chapter1 fundamental physics of radiation dosimetry The main contents Production of Radiation（review） Interactions of ionizing radiation（r) Basic concepts in radiation dosimetry（r） Phantom Dose measurement methology 1.Production of Radiation The classification of radiation 1.Production of Radiation The classification of radiation 1.Production of Radiation The classification of radiation Both directly and indirectly ionizing radiations are used in treatment of disease, mainly but not exclusively malignant disease. The branch of medicine that uses radiation in treatment of disease is called radiotherapy, therapeutic radiology or radiation oncology. Diagnostic radiology and nuclear medicine are branches of medicine that use ionizing radiation in diagnosis of disease. 1.Production of Radiation The kind of rays can be used for radiation therapy： X-rays γ-rays Electron beam Neutron beam and proton beam 1.Production of Radiation X-rays were discovered by Roentgen in 1895 while studying cathode rays in a gas discharge tube. He observed that another type of radiation was produced (presumably by the interaction of electrons with the glass walls of the tube) which could be detected outside the tube. This radiation could penetrate opaque substances, produce fluorescence, blacken a photographic plate, and ionize a gas. He named the new radiation x-rays. 1.Production of Radiation 1.1 Production of X-Rays There are two different mechanisms by which x-rays are produced. One give rise to bremsstrahlung x-rays (braking radiation) and the other characteristic x-rays. 1.Production of Radiation 1.1.1 Kilovoltage units (eliminated through selection or contest )(千伏级x线机) Grenz-ray therapy: used to describe treatment with beams of very soft (low-energy) x-rays produced at potentials below 20kV Contact therapy: potentials of 40 to 50 kV Superficial therapy: from 50 to 150 kV Orthovoltage therapy or deep therapy: from 150 to 500 kV Supervoltage therapy(high-voltage)