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.
J Nucl Med. 1994 Mar;35(3):521-30.
In radioimmunotherapy, the treatment of bulk tumors by radionuclides that emit energetic beta particles is the preferred approach. However, for the eradication of small clusters of cancer cells, radionuclides that emit Auger electrons or alpha particles are considered to be advantageous because of their ability to deposit radiation energy locally. If such radionuclides are internalized by the cells, the total dose to the cell nuclei is thought to be primarily determined by the self-dose (dose to cell nucleus from activity within the cell) in comparison to the cross-dose (dose to the cell nucleus from activity in all other cells).
The self-dose-to-cross-dose ratios to the cell nucleus were calculated for different cluster sizes (26-400 microns) with monoenergetic electron and alpha particle sources distributed uniformly in different cell compartments (cell surface, cytoplasm, nucleus). Model calculations were also performed for several radionuclides (Auger, beta and alpha emitters). Absorbed fractions for sources of monoenergetic electron and alpha particles, distributed uniformly in small spheres (26-5000 microns), were also calculated along with S-values for a number of radionuclides.
When most of the cells in the cluster are labeled with beta or alpha emitters, the cross-dose component of the total dose is important irrespective of cluster size and subcellular source distribution and increases as the cluster size increases. The self-dose is always important for Auger emitters. When the self-dose is negligible, the mean absorbed dose to the cell nuclei is well represented by the mean dose to the micrometastasis.
在放射免疫治疗中，通过发射高能β粒子的放射性核素治疗大块肿瘤是首选方法。然而，对于根除小簇癌细胞，发射俄歇电子或α粒子的放射性核素被认为具有优势，因为它们能够在局部沉积辐射能量。如果此类放射性核素被细胞内化，与交叉剂量（来自所有其他细胞活性对细胞核的剂量）相比，细胞核的总剂量被认为主要由自剂量（来自细胞内活性对细胞核的剂量）决定。
针对不同簇大小（26 - 400微米），计算了单能电子和α粒子源均匀分布在不同细胞区室（细胞表面、细胞质、细胞核）时细胞核的自剂量与交叉剂量之比。还对几种放射性核素（俄歇、β和α发射体）进行了模型计算。还计算了均匀分布在小球体（26 - 5000微米）中的单能电子和α粒子源的吸收分数以及多种放射性核素的S值。
当簇中的大多数细胞用β或α发射体标记时，无论簇大小和亚细胞源分布如何，总剂量的交叉剂量成分都很重要，并且随着簇大小的增加而增加。自剂量对俄歇发射体始终很重要。当自剂量可忽略不计时，细胞核的平均吸收剂量可以很好地用微转移灶的平均剂量来表示。
