Medknow Publications on behalf of the Association of Radiation Oncologists of India (AROI)
Abstract
PURPOSE: 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. MATERIALS AND METHODS: 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.
RESULTS: 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. Conclusion: 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