Dosimetry: The forgotten art

To do dosimetry properly we need to exercise control in three areas. First, the dosimeter must be both reliable and accurate and its calibration should be traceable to a national or international standard. Second, it must be used with some understanding to ensure that it is measuring what we want and not something else. It must also be used within recognized limits of dose and dose rate and under conditions of electronic (or charged particle) equilibrium. Corrections for irradiation temperature and measurement temperature may also have to be made. Finally, we may need to apply corrections to the dosimeter response based on cavity theory to take account of the perturbation in the medium caused by the presence of the dosimeter or we may need to use mass energy absorption coefficients or mass electron stopping powers to calculate the dose absorbed in one medium from the dose absorbed in another. The selection of the correct values is not as straightforward as you might think, and is the subject of this chapter.