Effective application of tumour treatment with high-dose radiation in radiotherapy provides an increase in the treatment rate and quality of life. Intensity-modulated radiotherapy (IMRT) can conform the radiation dose to the target while minimising the dose given to the surrounding healthy tissue. IMRT was started to be used in radiotherapy about 40 years ago and it is applied in almost all radiotherapy centers today. The IMRT technique, which has been strengthened with new software and applications (such as image-guided radiotherapy and adaptive radiotherapy) has increased the advantages of treatment. This book consists of 18 chapters covering important topics of IMRT.