小鼠剂量测定中影响S值的参数评估。

Evaluation of parameters influencing S values in mouse dosimetry.

作者信息

Hindorf Cecilia, Ljungberg Michael, Strand Sven-Erik

机构信息

Department of Medical Radiation Physics, The Jubileum Institute, Lund University, SE-221 85 Lund, Sweden.

出版信息

J Nucl Med. 2004 Nov;45(11):1960-5.

PMID:15534069

Abstract

UNLABELLED

Clinical radionuclide therapy studies are commonly preceded by studies with small animals. Reliable evaluation of therapeutic efficacy must be based on accurate dosimetry. This study was performed to evaluate the influence of the mass of organs, the shape of organs, and the distances between organs on S values for mice.

METHODS

A voxel-based version of a geometric model of a mouse was developed for input in our Monte Carlo program based on EGS4. Simulations were made for each source organ separately to resolve the S values for each organ. For verification purposes, S values were calculated for spheres of different masses and compared with the S values in the MIRDOSE3.1 software and with the S values on the Radiation Dose Assessment Resource Web site. The variation in the mass of the organs was determined from dissected mice. The influence of the shape of an organ was investigated by successive elongation of a sphere into spheroids with a constant mass. The right kidney was moved in the phantom of the mouse to evaluate the effect of organ distances on S values. The absorbed fractions for the mouse model presented here were compared with the results from some previously published models. The radionuclides used were (90)Y, (131)I, (111)In, and (99m)Tc.

RESULTS

The results showed that the organ mass for one animal can differ by up to 33% from the mean mass. If linear interpolation from S value tables is used to obtain an S value for the specific mass of an organ, then the S value can differ by up to 80% from its true value. The corresponding deviation obtained by scaling according to mass is 20%. The shape of an organ was found to be the least important parameter for the S value. The cross-absorbed S value is strongly dependent on the geometry and the emitted radiation. For example, a 9.2-mm movement of the kidney can cause the S value from the liver to the right kidney to decrease to 0.05% of its original value for (90)Y.

CONCLUSION

We conclude that the mass and the shape of organs and their locations relative to each other have considerable effects on mouse dosimetry.

摘要

未标注

临床放射性核素治疗研究通常先进行小动物研究。治疗效果的可靠评估必须基于准确的剂量测定。本研究旨在评估器官质量、器官形状以及器官间距离对小鼠S值的影响。

方法

基于EGS4开发了小鼠几何模型的基于体素的版本，用于输入我们的蒙特卡罗程序。分别对每个源器官进行模拟以解析每个器官的S值。为进行验证，计算了不同质量球体的S值，并与MIRDOSE3.1软件中的S值以及辐射剂量评估资源网站上的S值进行比较。通过解剖小鼠确定器官质量的变化。通过将球体连续伸长为质量恒定的椭球体来研究器官形状的影响。在小鼠模型中移动右肾以评估器官距离对S值的影响。将此处呈现的小鼠模型的吸收分数与一些先前发表的模型结果进行比较。使用的放射性核素为（90）Y、（131）I、（111）In和（99m）Tc。

结果

结果表明，一只动物的器官质量与平均质量的差异可达33%。如果使用从S值表进行线性插值来获得特定器官质量的S值，那么该S值与其真实值的差异可达80%。根据质量进行缩放得到的相应偏差为20%。发现器官形状是S值最不重要的参数。交叉吸收S值强烈依赖于几何形状和发射的辐射。例如，肾脏移动9.2毫米可导致肝脏到右肾的S值对于（90）Y降至其原始值的0.05%。