Potish R A
Department of Therapeutic Radiology, University of Minnesota Hospital and Clinic, Minneapolis 55455.
Int J Radiat Oncol Biol Phys. 1990 Jun;18(6):1513-20. doi: 10.1016/0360-3016(90)90329-i.
The effect of variation of applicator geometry on classic parameters of dose specification was studied in 90 Fletcher-Suit radium applications in women with cervical cancer. Five statistically significant factors were identified by multiple linear regression analysis and quantified: mg of radium in the colpostats, mg of radium in the tandem, lateral displacement of the colpostats in the frontal plane, vertical separation between the colpostat and tandem sources, and anterior-posterior displacement of the colpostats relative to the tandem. These factors were used to predict "traditional" (i.e., bladder, rectum, and point A) and ICRU dose specification parameters as a function of applicator geometry. Applicator geometry had little effect on the product of ICRU volume specification components, but it greatly affected the individual ICRU components and "traditional" calculation points. Linear regression equations were generated to predict the magnitude of such changes so that the effects of variations in applicator geometry at various prescription points could be predicted radiographically, with subsequent confirmation by computerized dosimetry. Although such regression equations do not replace 3-dimensional computerized dosimetry, they aid applicator placement and treatment planning.
在90例宫颈癌女性患者中，研究了施源器几何形状变化对剂量规范经典参数的影响。通过多元线性回归分析确定并量化了五个具有统计学意义的因素：阴道柱状施源器中的镭毫克数、宫腔施源器中的镭毫克数、阴道柱状施源器在额面的横向位移、阴道柱状施源器与宫腔施源器源之间的垂直间距，以及阴道柱状施源器相对于宫腔施源器的前后位移。这些因素被用来预测“传统”（即膀胱、直肠和A点）和国际辐射单位与测量委员会（ICRU）剂量规范参数作为施源器几何形状的函数。施源器几何形状对ICRU体积规范分量的乘积影响很小，但对单个ICRU分量和“传统”计算点影响很大。生成了线性回归方程以预测此类变化的幅度，以便可以通过放射影像学预测不同处方点处施源器几何形状变化的影响，随后通过计算机剂量测定法进行确认。虽然此类回归方程不能替代三维计算机剂量测定法，但它们有助于施源器放置和治疗计划。
