"Subacute" course of chronic radiation syndrome

Abstract

Introduction. The use of ionizing radiation as a production factor in the late 1940s - early 1950s. began in the absence of a clear understanding of the permissible radiation doses for workers, as well as knowledge of diagnostic criteria and developed therapeutic measures for developing chronic radiation sickness (CRS). Since then, a great deal of experience has been accumulated in the diagnosis and treatment of CRS. Currently, there are no conditions at the workplace for chronic exposure of workers in doses exceeding the permissible ones. However, taking into account the constant expansion of the scope of using sources of ionizing radiation, it is necessary to remember about the possibility of CRS development due to prolonged exposure in case of violation of their storage or their loss. The study aimed to explore the formation of radiation bone marrow syndrome (RBS) due to chronic exposure in doses that exceed the maximum permissible, accumulated with different dose rates of radiation. Material and methods. We selected the medical records of 27 people (24 men and 3 women) who had RBS as a result of chronic professional gamma radiation exposure. The selection criteria were the diagnosis of grade II-III chronic radiation syndrome (CRS) in the presence of agranulocytosis or anemic syndrome in the period of the disease formation and, especially, in the development of myelodysplastic syndrome (MDS) or aplastic anemia in the period of the CRS consequences. Identified clinical and dosimetric CRS features of 27 patients exposed to chronic irradiation with a dose rate of 0.0002-0,009 Gy/h and the summary dose of 1.7 and 9.6 Gy, accumulated over a period of 6 to 96 months were compared the characteristics of 84 patients CRS exposed a lower dose rates (less than 0,0003 Gy/h) and 26 patients with acute radiation syndrome moderate (II) severity as a result of irradiation the dose rates of 0.14-3,7 Gy/h, total dose of 2 to 4 Gy. Results. The criteria of atypical subacute CRS course are identified: the rate of chronic radiation exposure - not less than 0.001-0.009 Gy/h with a summary dose of 1.7-9.6 Gy accumulated over a period of 6-96 months, the presence of agranulocytosis in the period of CRS formation and anemic syndrome in the periods of CRS formation and outcomes. These signs predict the development MDS in 60% of the patients in the period of the CRS consequences. Conclusion. Retrospective study determined that long-term human exposure to a dose rate of 0.001-0,009 Gy/h (0,005-0,05 Gy/day) and more in the accumulation of a summary dose of 1.7 and 9.6 Gy and duration of contact 6-96 months in 60% of cases can be expected development CRS with a subacute clinical course RBS. The main factor determining this feature of the course of RBS is the dose rate exceeding 0.001 Gy / h (2 Gy/year). In the subacute course of CRS, the early outcome in MDS is essentially deterministic. The development of agranulocytosis and anemic syndrome are typical signs of the subacute course of CRS.