^(153)Sm-EDTMP吸收剂量的MonteCarlo和MIRD算法比较

Comparison of Monte Carlo simulation and MIRD methods for absorption dose calculation of ^(153)Sm_EDTMP

目的以153Sm-乙二胺四甲撑膦酸(153Sm-EDTMP)治疗鼻咽癌多发性骨转移为例,分别用蒙特卡罗法(MonteCarlo,MC)和MIRD方法计算153Sm-EDTMP治疗后病灶和骨髓等靶器官的吸收剂量,探讨其临床应用之不同。方法基于病人时序性SPECT/CT扫描和累积尿液的放射性测定,利用优化的MCEGS4程序和MIRD方法分别计算病灶和其他靶器官的吸收剂量。结果MCEGS4法计算结果提示:病灶内剂量分布不均匀。患者注射153Sm-EDTMP33·6×37MBq,左髂骨转移病灶最高吸收剂量约为5·6Gy,病灶边缘的吸收剂量为2·0Gy,以病灶区最高剂量点为参考点,则椎体、皮质、骨髓、脊髓和盆腔组织仅相当于最高剂量的37%、12%、13%、21%和2%;MIRD方法的计算数据仅能粗略提示全身红骨髓吸收剂量,为2·39Gy。结论MCEGS4方法能准确计算病灶、骨髓和其他靶器官的内照射吸收剂量,故可以真正指导核素临床治疗;而MIRD仅能大致评估153Sm-EDTMP的骨髓毒性。

Objective With Monte Carlo and MIRD methods respectively, the absorption dose of ^153Sm- EDTMP was calculated in different target organs of nasopharygeal carcinoma （NPC） patient so as to explore their clinical value. Methods Based on time-order SPECT/CT infusion imaging and ^153Sm-EDTMP assay of patient urine, the absorption dose of bone lesion and the different organs were calculated with Monte Carlo EGS4 and MIRD methods. Results The internal nuclide dose results showed that the maximum absorption dose of left hipbone metastatic focus was 5.6 Gy after 33.6×37 MBq of ^153Sm-EDTMP injection. The dose of focus margin was 2.0 Gy, and the relative absorption dose value of vertebral body, bone cortex, bone marrow,cone body, soft tissue in pelvic cavity were 12%, 13%,21% and 2% respectively. Conclusion The accurate nuclide absorption dose with Monte Carlo method based on SPECT/CT image can guide nuclide-targeted radiotherapy, but MIRD method maybe used to evaluate to the bone morrow toxicity.