The Relative Biological Effectiveness of 22-Mevp X-Rays, Cobalt-60 Gamma Rays, and 200-Kvcp X-Rays. VII. Summary of Studies for Five Criteria of Effect
The effectiveness of Co60 GAMMA rays and 22-Mevp x rays was found to be the same for five separate biological criteria (yeast LD50, mouse LD50, rat LD50, Fe59 uptake in rats, and chick embryo LD50) within the limits of experimental error. Thus there is presumably no difference in effect due to the pulse rate of the betatron productng the 22-Mevp x rays (except in the unlikely event that a possible energy effect and pulse effect cancel). When all doses are expressed in terms of the absorbed dose to soft tissue the RBE for Co60 gamma rays and 22-Mevp x rays relative to 200- kvcp x rays has an average value of about 0.87, but appears to range between 0.82 and 0.93, depending on the end point. (The mammalian end points studied here appear to have lower RBE values than do the nonmammalian end points.) If the dose in the mammalian cases is expressed as the absorbed dose to bone marrow, the RBE of the supervoltage radiations relative to 200-kvcp x rays for these end points is increased and the sgreement between the RBE values for all the end points becomes very good. Co60 gamma rays and 22-Mevp x rays can then be represented as less effective by a factor of 0.90 plus or minus 0.02 than 200- kvcp x rays for all the biological criteria studied. Co60 gamma rays are to be preferred to x rays in the 200 to 250-kwp region as a standard of comparison , for Rbe experiments. With Co60 Egg rays as the standard, 22- Mewp x rays have an RBE of 1.00, and 200kvcp x rays (absorbed dose to bone marrow) have an RBE of 1.10. No qualitative differences between the three radiations were evident.
- Research Organization:
- Univ. of Texas, M.D. Anderson Hospital and Tumor Inst., Houston
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-16-017519
- OSTI ID:
- 4785703
- Journal Information:
- Radiation Research, Journal Name: Radiation Research Journal Issue: 3 Vol. 16; ISSN 0033-7587
- Publisher:
- Radiation Research Society
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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