ABSTRACT
The high-dose-rate [HDR] brachytherapy might be an effective tool for palliation of dysphagia. Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment. This study aimed to measure the absorbed dose in the parotid, thyroid, and submandibular gland, eye, trachea, spinal cord, and manubrium of sternum in brachytherapy in an anthropomorphic phantom. To measure radiation dose, eye, parotid, thyroid, and submandibular gland, spine, and sternum, an anthropomorphic phantom was considered with applicators to set thermoluminescence dosimeters [TLDs]. A specific target volume of about 23 cm3 in the upper thoracic esophagus was considered as target, and phantom planned computed tomography [CT] for HDR brachytherapy, then with a micro-Selectron HDR [192Ir] remote after-loading unit. Absorbed doses were measured with calibrated TLDs and were expressed in centi-Gray [cGy]. In regions far from target [>/= 16 cm] such as submandibular, parotid and thyroid glands, mean measured dose ranged from 1.65 to 5.5 cGy. In closer regions [
ABSTRACT
Esophageal cancer is the eighth most ordinary cancer and the sixth most common cancer between the males and ninth for females in the world; its major and effective treatment is external radiotherapy. This type of cancer can be found in different areas of esophagus including cervical, upper, middle and lower esophagus. In this treatment, healthy tissues such as the trachea, spine and sternum and even thyroid receive dose and it is important that the absorbed doses by these organs be in their tolerance dose levels. We measured the surface and depth doses in an anthropomorphic phantom using thermoluminescent dosimeters. To do so, a target volume was considered in the phantom as a primary esophageal tumor with margins of 5 cm in the distal and proximal, and 3 cm in lateral. Phantom was CT planned and treatment was performed according to patient treatment. The considered measurement locations were Eye, right and left Parotid, left and right Submandibular, left and right Thyroid, Trachea, Manubrium of Sternum and Spine. Our results show that in places located further to primary beam such as Thyroid [phase one], Trachea, Spine and Sternum, the difference between dose from TPS and TLD measurements is observed. In organs which have placed within scattered radiation, the difference is insignificant [P-value>/=0.05], although some differences might cause by TLD limitations. In conclusion, the TPS calculated and TL measured doses distinguish significantly at the spine [depth], trachea [depth] and manubrium of sternum especially in phase 1 which might be due to the calculation algorithm used by the planning system which is reliable in homogeneous medium, but TL measurements were performed in the heterogeneous anthropomorphic phantom