Goddu S M, Howell R W, Giuliani D C, Rao D V
Department of Radiology, UMDNJ-New Jersey Medical School, Newark 07103, USA.
J Nucl Med. 1998 Mar;39(3):547-52.
The biological response of bone marrow to incorporated radionuclides depends on several factors such as absorbed dose, dose rate, proliferation and marrow reserve. The determination of the dose rate and absorbed dose to bone marrow from incorporated radionuclides is complex. This research used survival of granulocyte-macrophage colony-forming cells (GM-CFCs) as a biological dosimeter to determine experimentally the dose rate and dose to bone marrow after administration of 90Y-citrate.
The radiochemical 90Y-citrate was administered intravenously to Swiss Webster mice. Biokinetics studies indicated that the injected 90Y quickly localized in the femurs (0.8% ID/femur) and cleared with an effective half-time of 62 hr. Subsequently, GM-CFC survival was determined as a function of femur uptake and injected activity. Finally, to calibrate GM-CFC survival as a biological dosimeter, mice were irradiated with external 137Cs gamma rays at dose rates that decreased exponentially with a half-time of 62 hr.
Femur uptake was linearly proportional to injected activity. The survival of GM-CFCs was exponentially dependent on both the initial 90Y femur activity and the initial dose rate from external 137Cs gamma rays with 5.1 kBq/femur and 1.9 cGy/hr, respectively, required to achieve 37% survival. Thus, 90Y-citrate delivers a dose rate of 0.37 cGy/hr to the femoral marrow per kBq of femur activity and the dose rate decreased with an effective half-time of 62 hr.
Survival of GM-CFCs can serve as a biological dosimeter to experimentally determine the dose rate kinetics in bone marrow.
骨髓对摄入放射性核素的生物学反应取决于多个因素，如吸收剂量、剂量率、增殖和骨髓储备。确定摄入放射性核素对骨髓的剂量率和吸收剂量很复杂。本研究使用粒细胞-巨噬细胞集落形成细胞（GM-CFCs）的存活作为生物剂量计，通过实验确定90Y-柠檬酸盐给药后骨髓的剂量率和剂量。
将放射化学纯的90Y-柠檬酸盐静脉注射给瑞士韦伯斯特小鼠。生物动力学研究表明，注入的90Y迅速定位于股骨（0.8%注入剂量/股骨），并以62小时的有效半衰期清除。随后，根据股骨摄取量和注入活度确定GM-CFCs的存活情况。最后，为了将GM-CFCs的存活校准为生物剂量计，用外部137Csγ射线以半衰期为62小时呈指数下降的剂量率对小鼠进行照射。
股骨摄取量与注入活度呈线性比例关系。GM-CFCs的存活呈指数依赖于初始90Y股骨活度和外部137Csγ射线的初始剂量率，分别达到37%存活所需的剂量率为5.1 kBq/股骨和1.9 cGy/小时。因此，90Y-柠檬酸盐每kBq股骨活度向股骨骨髓提供0.37 cGy/小时的剂量率，且剂量率以62小时的有效半衰期下降。
GM-CFCs的存活可作为生物剂量计，通过实验确定骨髓中的剂量率动力学。
