Lenarczyk M, Goddu S M, Rao D V, Howell R W
Department of Radiology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark 07103, USA.
J Nucl Med. 2001 Jan;42(1):162-9.
Bone marrow is the dose-limiting organ in targeted radionuclide therapy. Hence, determination of the absorbed dose to bone marrow from incorporated radionuclides is a critical element in treatment planning. This study investigated the potential of the micronucleus assay in peripheral blood reticulocytes (MnRETs) as an in vivo biologic dosimeter for bone marrow.
After intravenous administration of 32P-orthophosphate or 90Y-citrate in Swiss Webster mice, DNA damage induced in bone marrow erythroblastoid cells was measured by subsequent scoring of MnRETs in peripheral blood. The response to exponentially decreasing dose rates was calibrated by irradiating animals with external 137Cs-gamma-rays. The gamma-ray dose rate was decreased exponentially, with the dose-rate decrease half-time corresponding to the effective clearance half-time (Te) of the radioactivity from the femoral bone (Te = 64 h for 90Y-citrate and Te = 255 h for 32P-orthophosphate).
The maximum MnRETs frequency occurred on the second and third day after injection of 90Y-citrate and 32P-orthophosphate, respectively. The same pattern was observed for exponentially decreasing dose rates of 137Cs-gamma-rays. For each type of exposure, the maximum MnRETs frequency increased in a dose-dependent manner. Using the calibrated dosimeter, the initial dose rates to the marrow per unit of injected activity were 0.0020 cGy/h/kBq and 0.0026 cGy/h/kBq for 32P-orthophosphate and 90Y-citrate, respectively.
Micronuclei in peripheral blood reticulocytes can be used as a noninvasive biologic dosimeter for measuring absorbed dose rate and absorbed dose to bone marrow from incorporated radionuclides.
骨髓是靶向放射性核素治疗中的剂量限制器官。因此，确定摄入的放射性核素对骨髓的吸收剂量是治疗计划中的关键要素。本研究调查了外周血网织红细胞微核试验（MnRETs）作为骨髓体内生物剂量计的潜力。
给瑞士韦伯斯特小鼠静脉注射32P-正磷酸盐或90Y-柠檬酸盐后，通过随后对外周血中MnRETs进行评分来测量骨髓成红细胞样细胞中诱导的DNA损伤。通过用外部137Cs-γ射线照射动物来校准对指数下降剂量率的反应。γ射线剂量率呈指数下降，剂量率下降半衰期对应于放射性从股骨的有效清除半衰期（Te）（90Y-柠檬酸盐的Te = 64小时，32P-正磷酸盐的Te = 255小时）。
分别在注射90Y-柠檬酸盐和32P-正磷酸盐后的第二天和第三天出现最大MnRETs频率。对于137Cs-γ射线指数下降的剂量率也观察到相同模式。对于每种暴露类型，最大MnRETs频率以剂量依赖性方式增加。使用校准后的剂量计，32P-正磷酸盐和90Y-柠檬酸盐每单位注射活度对骨髓的初始剂量率分别为0.0020 cGy/h/kBq和0.0026 cGy/h/kBq。
外周血网织红细胞中的微核可作为一种非侵入性生物剂量计，用于测量摄入的放射性核素对骨髓的吸收剂量率和吸收剂量。
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