口腔颌面医学影像诊断学（中山大学）6.放射防护.pptVIP

Chapter 2Biologic Effects Of Radiation Protection Of Radiation Biologic Effects Of Radiation deterministic effects biologic effects of ionizing radiation stochastic effects sensitive organs: skin, eye, bone marrow, thyroid gland, genital system Gray (Gy, J·Kg-1) 1 Gy = 100 rad exposure of a periapical film: the absorption doses of radiation of eye: 280-920 uGy, thyroid gland: 300 uGy Protection of Radiation Three principles: Justice of practice Optimized protection Limitation of dose Attention: pregnant women must be avoided abdomen radiation through the period of pregnancy PE = mA· S · KV2/ D2 Four Methods of Protection (1) Reduce exposure time 1.fluoroscopy replaced by radiography if possible 2.improve the sensitivity of imaging system E-speed film (patient doses reduce 40%) periapical film digital radiography (reduce 50% more) extraoral radiography---rare earth screens of high resolution (increase sensitivity by 16 times) 3.improve efficiency of the techniques, reduce radiograph retakes 1)use calculagraph of exposure 2)improve dark-room techniques: appropriate processing time and temperature; semidarkened room with safe-light, all extraneous light should be eliminated 3)commend to use digital radiography (2)Protection of Shielding 1.Collimate the field of X-ray beam 1)use plumbeous long collimator (D7cm) 2)disuse plastic cone-shaped collimator 2. Reduce leak of X-ray beam use the standard X-ray tube and collimator 3.use film-holding instrument 4. protection with instruments for patients 1)afford leaded aprons and leaded thyroid collars 2)preclude the patient to additional radiation exposure 3)especially notice the protection of pregnant women and children 5.protective shielding of workroom 1)workroom must be set solely 2)