You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Which of the following technique is employed in radiotherapy to counteract the effect of tumour motion due to breathing? and explain in detail?
The technique employed in radiotherapy to counteract the effect of tumour motion due to breathing is known as gating. In gated radiotherapy, beam is turned on only during a ceain phase of respiratory cycle, generally at the end of expiration. Respiration is monitored using external markers placed on the patients chest, which are assumed to move similarly to the tumor. This is done in patients who can breathe regularly and reproducibly. Advantage of this technique is that, it decreases the internal target volume and reduce the volume of normal tissue that is irradiated. Disadvantage of this approach is prolonged treatment time and lack of direct imaging of tumor position during treatment. Ref: Lung Cancer By Kemp H. Kernstine, Page 209; Biomedical Physics in Radiotherapy for Cancer By Barry Allen, 2012