Radiation treatment planning and simulation positioning: Intensity-modulated radiation therapy is the latest radiotherapy technique. It uses multiple irradiation fields to irradiate the tumor target area at high doses according to the three-dimensional shape of the tumor, increasing the irradiated dose to the target area as much as possible while minimizing the damage to normal tissues. The key to this technique is the accurate localization of the tumor lesion. Radiation therapy is commonly known as baking electricity, often referred to as radiotherapy in clinical practice, which is the use of alpha, beta and gamma rays produced by radioisotopes and so on. In the past, the practice was to use spiral CT to localize the tumor. However, CT is often unable to accurately identify tumor residuals, tumor recurrence and necrotic scars after radiotherapy, which makes the development of appropriate treatment plans difficult. Using PET/CT to obtain anatomical images along with functional images, and using the former to identify tumor remnants, recurrence and necrosis, and the latter to precisely locate them, maximizes the efficacy of this new technology.