difference between diagnostic radiography and radiotherapy and oncologyWatch
Comparing this to therapeutic radiography, therapeutic radiographers perform radiotherapy for cancer patients typically and are more likely to see some more of the same patients day in day out as opposed to seeing lots of different patients as diagnostic radiographers do.
That is my understanding of it and this is from the Society of Radiographers website:
"Diagnostic radiographers work in areas that include X-ray, Ultrasound, Fluoroscopy, Computerised Tomography (CT), Magnetic Resonance Imaging (MRI), Nuclear Medicine, Angiography and Mammography.
Therapeutic radiographers are responsible for the planning and delivery of accurate radiotherapy treatments using a wide range of technical equipment. Accuracy is critical, for example, the aim of treatment may be to treat a tumour and destroy diseased tissue while minimising the amount of radiation exposure to surrounding healthy tissue."
That website and that thread will go into more detail for you