Patient exposures in Swedish diagnostic radiology

Variations in doses between individuals and hospitals are discussed. Mean values and collective doses for Sweden are estimated. The mean annual collective dose per individual was estimated as follows: thyroid 0.75 mGy; mammae 0.54 mGy; lungs 0.64 mGy; bone marrow 0.92 mGy; ovaries 0.68 mGy and testes 0.65 mGy. The genetically significant dose was estimated as 0.7 mGy, a doubling since 1955. The annual mean whole body dose calculated from the energy imparted was 1.00 mGy. These figures should be subject to errors of about a factor of 2, mainly originating from the poor sampling technique. Some simplified risk estimates relating to the various examinations are made using the mean organ doses. These estimates indicated that within a factor of 3 up or down, the overall cancer risk might be 10-4 J-1, that is, an imparted energy of 10 000 J would lead to one radiation induced cancer. The estimate would apply to all examinations except those on extremities. The estimate of radiation induced cancer, uncertain as it may be, totals 8 cases per million Swedes per year, which is small compared with the natural cancer incidence of about 2000 per million and year. No corresponding simplification using energy absorbed seemed possible concerning the genetic risks. The study shows that using available examination techniques a dose reduction by a factor of 2 or more should be po