Imaging is vital for accurate radiation therapy, and modern techniques like intensity-modulated radiotherapy and functional imaging are being integrated to improve treatment precision. Functional imaging provides detailed information on tumour behaviour and characteristics, allowing for better radiation dose optimisation and minimisation of damage to normal tissues. The concept of biological target volume, incorporating tumour metabolic and physiological changes, is becoming important. Integrating advanced imaging into radiotherapy machines is crucial for improving precision and patient outcomes. Functional imaging has the potential to greatly impact the field of radiation oncology by providing a better understanding of tumour physiology and predicting treatment response, leading to more effective and targeted therapy.