Abstract
In cases of bronchial constriction caused by malignant diseases, we performed endobronchial high dose rate brachytherapy inside a stent using a microSelectron HDR after placing the stent in the respiratory tract for the purpose of achieving effective treatment of the primary disease as well as maintaining the respiratory tract. Initially, the necessity of dose correction when using indwelling stent was tested. An applicator for the bronchus connected to a microSelectron HDR and a dosimeter were fixed in a water phantom made of acrylic resin at a distance of 20mm using an eye protector for systemic irradiation, and then, immersed in water. Dumon stents (10, 13 and 15mm in inside diameter, 50mm long ; Novatech) were used. In order to examine the difference between the materials, Z stents (6, 8, and 12mm in inside diameter, 50mm long ; Cooks) were also tested. In the test of each stent, the dose was measured at 4 different points (20, 22, 28 and 36mm) from the radiation source simultaneously, and the cumulative doses for 2 minutes at each point were compared. In the control group, the dose was measured twice without using a stent. In the stents, the deviation of dose due to the stent was less than 1% at all the measuring points. Therefore, in intra-stent endobronchial high dose rate brachytherapy, contribution of radiation-scattering caused by the stent was found to be less than 1%, and no particular correction for the curative radiation dose was thought necessary. On the basis of these results, endobronchial high dose rate brachytherapy using microSelectron HDR inside the stent was performed by placing a Dumon stent in the carina to treat recurrence in the left main bronchus after right pneumonectomy.
