**Abstract**

Due to the risk of radiation exposure, radiation dosimetry is performed regularly to ensure the occupational safety of personnel and radiation workers. Therefore, various dosimeters are widely used to detect neutrons, gamma, X-ray, and proton irradiation fields. As an example, in medical applications, routine personal dosimetry is used to monitor and limit workers' long-term occupational exposure. Radiation workers who undertake X-ray diagnostic, radiotherapy operations, in clinical and industrial application. Although, the overheads of running an in-house TLD (Thermoluminescent dosimetry) service for monitoring doses to eyes, pacemakers and so on seems rather high for the benefits conferred, however, it is still widely used for reporting doses accurately in various medical centers over the world. TLD also is widely used for measuring entrance doses on a handful of patients to validate a new LINAC/TPS combination. As well as in the industrial field as if petroleum, companies or nuclear reactor, RSO (radiation safety officer) used TLD badges to report delivered doses. In this chapter, we focus on the TLD technique for measuring doses of various ionizing radiation detection. Different methods for evaluations of TL Kinetics are covered. Modern TLD applications in the clinical field are also investigated. Some recommendations on advance dosimetry failure of TLD are concluded.

**Keywords:** TLD, TL kinetics, radiotherapy, hybrid-functional density theory, modern clinical applications
