Strigari L, Sciuto R, D'Andrea M, Pasqualoni R, Benassi M, Maini C L
Laboratory of Medical Physics and Expert Systems, Regina Elena Cancer Institute, Rome, Italy.
Eur J Nucl Med Mol Imaging. 2007 Jul;34(7):1031-8. doi: 10.1007/s00259-006-0302-4. Epub 2007 Jan 20.
The aim of the paper is to calculate the dose to bone surface and bone volume using a Monte Carlo particle transport model and to give quantitative arguments for activity prescription.
This study simulates the dose delivery process to skeletal metastases by bone surface- and bone volume-seeking radiopharmaceuticals. Dose distributions for three radiopharmaceuticals, 186Re-HEDP, 153Sm-EDTMP and 89SrCl2, frequently used for pain palliation therapies, were calculated using the EGSnrc Monte Carlo code. The model simulates a cylindrical geometry with regions of different constant density compositions and radioactivity distribution consistent with known biodistribution features of the three radiopharmaceuticals: superficial for phosphonates (186Re-HEDP and 153Sm-EDTMP) and volumetric for 89SrCl2. After 3D dose distribution calculation, dose-volume histogram reduction was carried out using the "preferred Lyman" method, which yields effective uniform dose (D(eff)) equivalent to the inhomogeneous dose distributions to the reference region (volume and surface).
Our simulations showed that to obtain a delivered dose to bone surface equivalent to that obtained from 89SrCl2, the administered activities of 153Sm-EDTMP and 186Re-HEDP should be increased by 37% and 48%, respectively, in comparison with those usually administered.
These results prove theoretically the empirical results from clinical observations and show that improvement in bone pain palliation by means of radiopharmaceutical therapy should be expected for dose-guided prescription.
本文旨在使用蒙特卡罗粒子传输模型计算骨表面和骨体积的剂量，并为活性处方提供定量依据。
本研究模拟了骨表面靶向和骨体积靶向放射性药物向骨转移灶的剂量传递过程。使用EGSnrc蒙特卡罗代码计算了三种常用于缓解疼痛治疗的放射性药物186Re-HEDP、153Sm-EDTMP和89SrCl2的剂量分布。该模型模拟了一个圆柱形几何体，其具有不同恒定密度组成区域和放射性分布，与三种放射性药物已知的生物分布特征一致：膦酸盐类（186Re-HEDP和153Sm-EDTMP）为浅表分布，89SrCl2为体积分布。在进行三维剂量分布计算后，使用“首选莱曼”方法进行剂量体积直方图简化，该方法产生的有效均匀剂量（D(eff)）等同于参考区域（体积和表面）的非均匀剂量分布。
我们的模拟表明，为了获得与89SrCl2相同的骨表面递送剂量，与通常给药剂量相比，153Sm-EDTMP和186Re-HEDP的给药活性应分别增加37%和48%。
这些结果从理论上证明了临床观察的经验结果，并表明对于剂量引导处方，应预期通过放射性药物治疗改善骨痛缓解情况。
