Trabecular bone changes induced by fast neutrons versus gamma rays in mice

Background: The trabecular bone changes in the bia of C3H/HeN mice were measured 12 weeks a er whole body irradia on with various doses of fast neutrons (0-2.4 Gy) or 137 Cs-generated gamma-rays (0-6 Gy). Materials and Methods: Serum calcium, phosphorus, estradiol concentra on and alkaline phosphatase ac vity were measured. Tibiae were analyzed using microcomputed tomography. Biomechanical property and osteoclast surface level were measured. Results: There was a significant rela onship between the loss of bone architecture and the radia on dose, and the best-fi0ng dose -response curves were linear-quadra c. Mean rela ve biological effec veness (RBE) values (Ref. gamma) of 2.05 and 2.33 were es mated for fast neutron irradia on in trabecular bone volume frac on and bone mineral density, respec vely. There was a substan al reduc on in osteoclast surface level in tartrate-resistant acid phosphatase-stained histological sec ons of bial metaphyses in irradiated mice with high dose of neutrons. Conclusion: There was a significant rela onship between the loss of bone architecture and the radia on dose. The difference of osteoclas c bone resorp on may represent a contributor to the low RBE in high dose of irradia on level rela ve to that of