Development of Source Template ICRT Dose Planning Software for Uterine Cervix Using the HDR: 192Ir / 의학물리

The source position and source dwelling time in a given source arrangement in the applicators is very high effect to determine the expose time which in general is derived from the brachytherapy planning system. In high dose rate (HDR) intracavitary radiation therapy (ICRT), the treatment is often performed in based out-patient during the whole fractionation irradiations. However, the patient should be waited on coutch for ICR treatment in first start fraction as unconvinent and immobilized state until perform the dose plannings. In our experiments, the HDR source contributed dose for 55.89+/-4.20% for straight tandem source, 38.14+/-4.46% for the right ovoid soucre on the fornix and 5.97+/-0.50% for left ovoid source. It also showed the 60.33+/-6.53% for the tandem, 33.10+/-6.74% for right ovoid and 6.58+/-0.30% for the left ovoid source in 10 degrees of applicator. The authors designed the source template dose planning software for ICRT of uterine cervix results average -0.55+/-2.15% discrepancy of the full charged brachytherapy dose planning. Developed Source temperate ICRT plaanning software guide a minimized the complains and operating times within a +/-3% of dose discrepancies.

Development of Dose Planning System for Brachytherapy with High Dose Rate Using Ir-192 Source / 대한방사선종양학회지

PURPOSE: A PC based brachytherapy planning system was developed to display dose distributions on simulation images by 2D isodose curve including the dose profiles, dose-volume histogram and 3D dose distributions. MATERIALS AND METHODS: Brachytherapy dose planning software was developed especially for the Ir-192 source, which had been developed by KAERI as a substitute for the Co-60 source. The dose computation was achieved by searching for a pre-computed dose matrix which was tabulated as a function of radial and axial distance from a source. In the computation process, the effects of the tissue scattering correction factor and anisotropic dose distributions were included. The computed dose distributions were displayed in 2D film image including the profile dose, 3D isodose curves with wire frame forms and dose- volume histogram. RESULTS: The brachytherapy dose plan was initiated by obtaining source positions on the principal plane of the source axis. The dose distributions in tissue were computed on a 200x200 (mm2) plane on which the source axis was located at the center of the plane. The point doses along the longitudinal axis of the source were 4.5~9.0% smaller than those on the radial axis of the plane, due to the anisotropy created by the cylindrical shape of the source. When compared to manual calculation, the point doses showed 1~5% discrepancies from the benchmarking plan. The 2D dose distributions of different planes were matched to the same administered isodose level in order to analyze the shape of the optimized dose level. The accumulated dose-volume histogram, displayed as a function of the percentage volume of administered minimum dose level, was used to guide the volume analysis. CONCLUSION: This study evaluated the developed computerized dose planning system of brachytherapy. The dose distribution was displayed on the coronal, sagittal and axial planes with the dose histogram. The accumulated DVH and 3D dose distributions provided by the developed system may be useful tools for dose analysis in comparison with orthogonal dose planning.

Gamma Knife Radiosurgery for Craniopharyngioma

OBJECTIVE: The purpose of this study are to evaluate the effectiveness of Gamma Knife radiosurgery(GKS) as a treatment of craniopharyngioma and to investigate the proper dose planning technique in GKS for craniopharyngioma. METHOD: Between May 1992 and March 1999, seven Gamma Knife radiosurgical procedures were done for residual tumor mass of 6 patients with craniopharyngioma after microsurgical resection. Conventional radiation therapy was not performed. In this study, their clinical, radiological and radiosurgical data were analyzed and the radiation dosage to the optic pathway, hypothalamus, pituitary stalk, and cavernous sinus were calculated and correlation with clinical outcome was evaluated. The mean follow-up period was 33.5 months(12.3-55.2 months). RESULT: The mean tumor volume was 4.4cc(0.4-18.0cc) and the maximum radiation dose ranged from 14 to 32 Gy(mean 20.9Gy). The radiation was given with isodose curve, 50-90% and the marginal dose varied within 8-22.4Gy(mean 12.7Gy). The mean number of isocenter was 4.3(1-12). The tumor was well controlled in all cases. In 5 of 7 cases, the size of tumor decreased to 10-50% of pre-GKS volume and remaining two showed no volume change. The mean dose to optic pathway was 5.7Gy(5.1-11.2Gy) and there were no complications. CONCLUSION: GKS seems to be effective for control of craniopharyngioma as an adjuvant treatment after microsurgical resection and even suboptimal dose for tumor margin is considered to be enough for tumor control. It is safe with careful dose planning to protect surrounding important structures, especially optic pathway. We believe conventional radiation therapy should be avoided because it has limitation for dose planning of additional treatments such as radiosurgery or intracystic instillation of radioisotope in case of recurrence.