• Progress in Medical Physics
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• v.20 no.2
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• pp.112-118
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• 2009

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$55.89{\pm}4.20%$ for straight tandem source, $38.14{\pm}4.46%$ for the right ovoid soucre on the fornix and$5.97{\pm}0.50%$ for left ovoid source. It also showed the $60.33{\pm}6.53%$ for the tandem, $33.10{\pm}6.74%$ for right ovoid and $6.58{\pm}0.30%$ 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 $-0.55{\pm}2.15%$ discrepancy of the full charged brachytherapy dose planning. Developed Source temperate ICRT plaanning software guide a minimized the complains and operating times within a ${\pm}3%$ of dose discrepancies.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.735-740
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• 2022

In order to reduce side effects such as rectal bleeding in the Brachytherapy, the rectal retractor and wet gauze have been used to increase the distance between the rectum and the tandem. However, there were disadvantages that it was difficult to insert through a narrow entrance into the vagina and poor reproducibility. Also, based on the CT image of the selected catheter, the distance from the tandem to the rectum with or without the balloon catheter was checked and the reduction of the dose to the rectum was confirmed. As a result of the experiment, catheter No. 7 was selected considering the maximum balloon size at a level that does not affect the distance between the start point of the balloon and the end of the catheter, and the ovoid applicator. Based on the CT image of the selected catheter, the degree of expansion according to the presence or absence of the balloon catheter was compared, and it was found that the distance difference was 0.3 - 1 cm. In addition, it was confirmed that a decrease of about 32% was observed due to this distance difference. Therefore, the actual clinical application of the selected catheter can be used as a substitute for the existing rectal retractor and wet gauze.

• Progress in Medical Physics
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• v.13 no.2
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• pp.79-84
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• 2002

In this study, a cylindrical ultrasound applicator is developed for the treatment of vagina and rectum in combination with high dose rate brachytherapy. A cylindrical transducer (PZT-8, 1=1.5 cm, thickness=1.5mm OD=2.5 cm) was used as an energy source for induction of hyperthermia. Three single-element applicators were constructed to examine the performance of the PZT material. Vector impedance was measured to determine driving frequency. The efficiencies of the elements were determined using a radiation force technique to evaluate the feasibility of using the applicator as a hyperthermia source. A multi-element ultrasound applicator was designed using the PZT-8 material for the treatment of vagina. Results from the vector impedance measurements showed maximum magnitude at 1.78, 1.77, and 1.77 MHz for applicator 1,2, and 3, respectively. The radiation force measurements showed that the acoustic power of 40 watts was obtained in all three elements. The average efficiencies of the elements were 61.4, 65.2, and 54.0% for element 1, 2, and 3, respectively. The designed ultrasound hyperthermia applicator could be used in combination with high dose rate brachytherapy for the treatment of vagina and rectum. The use of this applicator with intracavitary brachytherapy could offer improved tumor control by increasing radiosensitiyity of the tumor.

• Journal of Radiation Protection and Research
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• v.23 no.4
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• pp.259-266
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• 1998

There are three different types of gynecological applicator sets available in microSelectron-high dose-rate(HDR) System by Nucletron; standard applicator set(SAS), standard shielded applicator set(SSAS), and Fletcher-Williamson applicator set(FWAS). Shielding effect of a SAS without shielding material was compared with that of a SSAS with shielding material made of stainless steel(density ${\varrho}=8,000kg/m^3$) at the top and bottom of each ovoid, and of a FWAS with shielding material made of tungsten alloy(density ${\varrho}=14,000kg/m^3$ at the top and bottom of each ovoid. The shielding effects to the rectum and bladder of these two shielded applicator sets were to be measured at reference points with an ion chamber and specially designed supporting system for applicator ovoids inside of the computerized 3-dimensional water phantom. To determine the middle point of two ovoids the measurement was performed with the reference tip of ion chamber placed at the same level and at the middle point from the two ovoids, while scanning the dose with the ion chamber on each side of ovoids. The doses to the reference points of rectum were measured at 20(Rl), 25(R2), 30(R3), 40(R4), 50(R5), and 60(R6) mm located posteriorly on the vertical line drawn from M5(the middle dwell position of ovoid), and the doses to the bladder were measured at 20(Bl), 30(B2), 40(B3), 50(B4), and 60(B5) mm located anteriorly on the vertical line drawn from M5. The same technique was employed to measure the doses on each reference point of both SSAS and FWAS. The differences of measured rectal doses at 25 mm(R2) and 30 mm(R3) between SAS and SSAS were 8.0 % and 6.0 %: 25.0% and 23.0 % between SAS and FWAS. The differences of measured bladder doses at 20 mm(Bl) and 30 mm(B2) between SAS and SSAS were 8.0 % and 3.0 %: 23.0 % and 17.0 % between SAS and FWAS. The maximum shielding effects to the rectum and bladder of SSAS were 8.0 % and 8.0 %, whereas those of FWAS were 26.0 % and 23.0 %, respectively. These results led to the conclusion that FWAS has much better shielding effect than SSAS does, and when SSAS and FWAS were used for gynecological intracavitary brachytherapy in microSelectron-HDR system, the dose to the rectum and bladder was significantly reduced to optimize the treatment outcome and to lower the complication rates in the rectum and bladder.