Effects of fractionated irradiation on mouse lung and a phenomenon of slow repair.
The LD/50 between 40 and 180 days after irradiation of the thorax has been taken as a measure of lung damage in mice. The method has been used to derive the relationship between total dose, number of fractions (N) and overall treatment time (T). For X rays the results fit an Ellis type of relationship, i.e. total dose alphaN0-25 T0-07. This only applies for more than 8 fractions, below which N0-39 becomes a good fit to the results. For neutrons, the best fit is total dose alphaT0-07. Various possible explanations for the T factor are discussed, but for lung damage we attribute it to a slow repair process which possibly may only be observed in slowly proliferating tissues. Slow repair is about 100 times less rapid than Elkind-type of repair of sublethal damage and whereas Elkind repair is greatly reduced for irradiation with fast neutrons, relative to X rays, slow repair is not.
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005214:Fast Neutrons; D005260:Female; D007928:Lethal Dose 50; D008168:Lung / Q000528:radiation effects*; D051379:Mice; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental; D013997:Time Factors; D014945:Wound Healing; D014965:X-Rays