Shielding calculation in radiation oncology therapy facilities

• Κύριος συγγραφέας: Γανού, Χαραλαμπία
• Άλλοι συγγραφείς: Ganou, Charalampia
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Shielding; Calculation; Radiation therapy; Ακτινοθεραπεία; Έκθεση σε ακτινοβολία

The first patient treatment with X-rays occurred only one year after their discovery. Thus, a physics discovery launched the field of radiation therapy. Radiation therapy involves the use ionizing radiation. Exposure to ionizing radiation carries the risk of causing cancers. This is likely proportional to the level of exposure. Accordingly, it is of fundamental importance to ensure that exposures are always kept as low as possible.52 The safety of patients, staff and the public in general, is a high priority issue in the implementation of a radiation treatment program. The radiation beams and sources used in radiotherapy, have the potential to injure those within or in the proximity of the facility if not properly handled. Radiation safety has two primary aims: a strongly safe facility design and other physical safeguards against accidental exposure, as well as policies and procedures which, when followed, will ensure the radiation exposure to staff is kept As Low As Reasonably Achievable with social and economic factors being taken into account.51 This strongly safe design depends mainly on the shielding that a radiotherapy department needs, and in particular the treatment rooms. By the term shielding, the required thickness of specific materials to attenuate the radiation penetrating the room is meant. The radiotherapy bunkers contain the machines performing the radiation treatments and hence, the most amount of radiation appears inside these places. Therefore, they need to be shielded accordingly. However, since such a new machine is established in a facility once in every fifteen to twenty years, very few medical physicists and other health professionals know how to calculate the exact shielding that is needed. Most radiotherapy departments rely on various publications on the subject of bunker design -such as the NCRP Report No. 151- and use empirical formulae to estimate the protection required. Even so, the shielding calculation is an extremely time consuming process. For these reasons, the need for a computerized algorithm that could be used to accurately assess the protection required (in terms of material thickness) in the design of radiotherapy bunkers, has grown greatly over the years. Today, there are computerized models available (usually Monte Carlo based), but they are expensive, difficult to use and slow in performance. Thus small institutes do not have direct access to these models. The aim of this thesis is to design a user – friendly computer program that calculates the required thickness of shielding, in order to limit radiation exposure of staff, patients and the public, to acceptable levels. The code of the program was written in the language of MATLAB but the use of the platform is not needed. The user downloads the respective app pack and the program is installed in the computer. When the program opens, it displays a GUI (Graphical User Interface) which contains empty cells for numerical values to be entered for the different quantities. Depending on that values, the code that the GUI is based on, calculates the necessary shielding thickness for primary and secondary barriers. The code is built on the data and formulae of NCRP Report No. 151 by AAPM, since this is the report that most health institutes use for shielding calculations. It has been confirmed that the program works properly based on the given data by this report as well as on the data of other shielding reports. This program is intended to be used primarily by health physicists, medical physicists and other radiation protection professionals in the planning and shielding of new radiotherapy facilities and in the remodeling of existing ones.