Journal of Medical Physics
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Year : 1986  |  Volume : 11  |  Issue : 3  |  Page : 456

Patient Dose In Diagnostic Medicine : How To Quantitate

Correspondence Address:
D Krishnan

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Diagnostic procedures, in medicine, whether they be with X-rays or radioisotopes, necessarily involve doses to part (s) of the body. Dose t o the gonads called the genetically significant dose (GSD) used to be an indicator of contribution to population exposure due to the particular procedure. This practice suffers from the obvious drawback that only genetic effects of radiation are taken into account, whereas the possible somatic effect on the population exposed is totally neglected. Alternative approaches to GSD are available in the literature. Many concepts are discussed with special reference to diagnostic radiology. Some of these are leukemia significant dose equivalent, malignancy significant dose equivalent, effective dose equivalent and somatically effective dose equivalent. The last mentioned quantity has been used in the tables given in ICRP publication 34, for a few types of diagnostic x-ray examinations. In this presentation, the basis of these calculations viz. effective dose equivalent (ede) concept is critically examined and a suggestion for further improvement is given. Quantitative radiation risk estimates, originally meant to be used for radiation worker, by the ICRP, are the basis of the ede concept. In this presentation, a new concept of population effective dose equivalent (pede) is proposed. This, it is hoped, will start new thinking on total risk. Ede is based on fatal cancers in adult population and genetic risk in first two generations. Instead if all cancers (i.e. morbidity) and all the hereditary effects are included in the total population, a higher number will be obtained. Thus population effective dose equivalent: (pede) = (p) X (ede) There p is the ratio of the two risks mentioned above. Available data (UNSCEAR, 1977, 1985) indicate that p will be greater than 1 and may be between 2 & 10. Strictly p should include population age distribution and radiosensitivity also. The effect of (pede) on weighting factors (WT) of individual organs is assumed to be small and so neglected. The reflection of this approach on the relative contribution of natural, medical and other man-made radiations to annual per capta dose to population is worth considering. This can be done after collective effective dose equivalents for different types of examinations (may be countrywide) using the above approach are calculated.

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