Portal de Periódicos da CAPES

The Radium Standard for Boneseekers-evaluation of the Data on Radium Patients and Dial Painters

1967; Lippincott Williams & Wilkins; Volume: 13; Issue: 3 Linguagem: Inglês

10.1097/00004032-196703000-00004

1538-5159

Robley D. Evans,

Advanced X-ray and CT Imaging

The selection in 1941 of 0.1 μg radium as the maximum permissible skeletal burden was based on the then-studied total of about 30 cases. To date approximately 420 radium cases (about two-thirds of whom were dial painters) have been studied at M.I.T. and about 275 additional cases at Argonne National Laboratory. The results from the two laboratories are in good agreement. Approximately 100 of the M.I.T. cases ingested mixtures of 226Ra and 228Ra (MsTh). We are able to express the MsTh radiation dose in terms of the amount of pure 226Ra which would produce the same skeletal dose measured in cumulative rads. Then the total effect of the mixtures is expressed as “pure radium equivalent”, or μg Ra (PRE). No clinically significant signs or symptoms have been seen in persons with residual body burdens of less than 0.5 μg Ra (PRE). Above 0.5 μg the incidence and severity of symptoms increases with increasing residual body burden. The usual clinical sign of osteoporosis is followed by symptoms which include primarily osteomyelitis, spontaneous fractures, osteogenic sarcomas, and carcinomas of the paranasal sinuses or mastoids, all referable to alpha-ray bombardment of bone or immediately adjoining tissue. In the M.I.T. series there have been no proved cases of leukemia. Out of 81 cases 0.5 μg Ra (PRE) or higher (up to 44 μg) the M.I.T. series contains 26 cases with osteogenic sarcoma and 7 cases with paranasal or mastoid carcinoma. Within any dose bandwidth, e.g. 2–5 μg Ra (PRE) or 10–15 μg Ra (PRE) the incidence (fraction of cases with sarcoma or carcinoma) is roughly 40 per cent and, within reasonable statistical limits, is the same for all dose levels. The time of onset for sarcomas is 7–43 yr (median 23 yr) after first exposure; for carcinomas it is 19–41 yr (median 34 yr) after first exposure. The M.I.T. and the Argonne groups have jointly developed a semiquantitative method for assigning a numerical “X-ray score” (running from 0 to 45 in the cases studied) as a single parameter describing the effects produced by skeletal irradiation. The dose (PRE)-response (X-ray score) relationships have been studied by computer techniques. A control group of 120 unexposed individuals (matched for age, sex, height and weight with the M.I.T. radium cases) has been studied to determine the X-ray score of a normal population, for comparison with the radium cases. At residual body burdens greater than 0.5 μg Ra (PRE) neither symptoms nor signs (i.e. zero X-ray score) are present in subjects with 2.6 μg Ra (37 yr), 1.3 μg Ra (30 yr), and 1.0 μg Ra (43 yr). At residual body burdens between 0.5 and 0.1 μg Ra (PRE) the M.I.T. series contains 32 symptom-free cases, in 5 of which minimal osteoporotic signs are present; between 0.1 and 0.05 μg Ra (PRE) there are 23 sign-and-symptom-free cases; between 0.05 and 0.01 μg Ra (PRE) there are 84 sign-and-symptom-free cases; below 0.01 μg Ra (PRE) there are 193 such cases. All the radium burdens reported here are the residual body burdens, usually 30–50 yr after radium was taken into the body. The initial or maximum skeletal radium burden was much larger, typically about twenty times the residual burden. Clearly, the present Radiation Protection Guide or standard of a maximum skeletal deposition of 0.1 μg Ra (PRE) appears abundantly safe and conservative.