Measurement of Radiation: Instrumentation&Techniques Part Three The Physics of Radiology Measurement of Radiation: Instrumentation&Techniques Part Three BME College Sherman Sheen(辛学刚)

solid state detectors—the diode Short response time High sensitivity Enormous dynamic range Flexible forms

Thermoluminescent Dosimetry (TLD) PRECISION OF TLD AND DOSE RANGE MATERIALS FOR TLD USES OF TLD-CLINICAL DOSIMETRY PERSONNEL MONITORING DOSE CALIBRATION SERVICES

Chemical Dosimetry △Aλ is the change in absorbance at λ following a dose D to the ferrous sulphate ∈λ is the molar extinction coefficient of the ferrous ion The energy absorbed from radiation may produce a chemical change in the absorbing medium, and the amount of this may be used to measure dose. One of the most useful chemical radiation dosimeters is the Fricke dosimeter ρ is the density of the solution in kg/m3 G is the yield in number per 100 eV

Example. It is required to determine the average dose to a sample of water in a complexly shaped radiation container near a cobalt source. This is most easily done using the Fricke dosimeter. The container is filled with Fricke solution and exposed. A sample of the well-mixed irradiated solution is then placed in a quartz cuvette of 2 cm path length and its absorbance measured against the stock solution at 304 nm. Suppose the measured absorbance is 0.360. Calculate the dose.

Film as a Dosimeter radiant energy crystals of silver bromide latent image File developed film fixed X rays have the property of affecting a film in much the same way as light. The film contains very small crystals of silver bromide. When radiant energy strikes these crystals, they become more susceptible to chemical change and form what is referred to as a latent image. When the film is developed, the crystals that have been altered by the radiation are reduced to small grains of metallic silver. The film is then fixed; this dissolves the unaffected silver bromide, leaving a clear film, but does not affect the metallic silver. Thus areas that have been exposed to x rays appear dark and a negative film results negative film results areas that have been exposed to x rays appear dark