Patel Narayan Prasad, Majumdar Bishnu, Hota Pradeep K, Singh Dayanidhi
Department of Medical Physics, Acharya Harihar Regional Cancer Centre, Cuttack- 753 007, India.
J Cancer Res Ther. 2005 Apr-Jun;1(2):84-91. doi: 10.4103/0973-1482.16707.
The aim of this study is to achieve dose uniformity for intraluminal implants by assessment of dose distributions for single catheter generated by using various combinations of source stopping spacing and optimization mode.
A dose distribution was generated using HDR 192Ir stepping source on single straight catheter of fixed length used for Intraluminal brachytherapy. The various combinations of source position spacing and optimization mode were used and these dose distributions were evaluated by using three different parameters. The source position spacings were 0.2, 0.5, 1.0, 1.4, 2.0, 2.5, 3.0 and 3.3 cm. Three different optimization modes that compute the source stopping times along the catheter were used. The parameters used for assessment of dose distributions were statistical analysis of doses to dose reference points, area under natural dose-volume histogram and the dose non-uniformity ratio.
None of the combinations of source position spacing and optimization mode was able to generate the desired optimum uniform dose distribution. However in a discrete manner, comparatively higher uniform dose distribution was found with short (0.2 cm) and longer (1.5 to 2.0 cm) source spacing. Optimization mode of Iterative correction was found to be suitable for the single catheter used in intraluminal brachytherapy.
The applicator dimension and irradiation target volume should be taken in to consideration while selecting either higher or smaller source position spacing for the single catheter intraluminal brachytherapy. The Anisotropy factor of the source has some role in the variation of the dose uniformity over the target volume.
本研究的目的是通过评估使用源驻留间距和优化模式的各种组合生成的单根导管的剂量分布，实现腔内植入物的剂量均匀性。
使用高剂量率192铱步进源在用于腔内近距离治疗的固定长度的单根直导管上生成剂量分布。使用源位置间距和优化模式的各种组合，并通过使用三个不同参数评估这些剂量分布。源位置间距为0.2、0.5、1.0、1.4、2.0、2.5、3.0和3.3厘米。使用三种不同的优化模式来计算沿导管的源驻留时间。用于评估剂量分布的参数是剂量参考点剂量的统计分析、自然剂量-体积直方图下的面积和剂量不均匀率。
源位置间距和优化模式的任何组合都无法生成所需的最佳均匀剂量分布。然而，以离散方式，在较短（0.2厘米）和较长（1.5至2.0厘米）的源间距下发现了相对较高的均匀剂量分布。发现迭代校正优化模式适用于腔内近距离治疗中使用的单根导管。
在为单根导管腔内近距离治疗选择较大或较小的源位置间距时，应考虑施源器尺寸和照射靶体积。源的各向异性因子在靶体积上的剂量均匀性变化中起一定作用。
