Mike Kirby and Kerrie-Anne Calder are well-respected authors and radiotherapy professionals, who have worked in radiotherapy physics/radiotherapy clinical and academic practice for nearly 35 years and 25 years respectively. Mike Kirby is a Senior Lecturer in Radiotherapy Physics at the University of Liverpool, UK, and an Honorary Lecturer at the University of Manchester, UK. He holds graduate and postgraduate qualifications in medical physics and has in total over 200 books, papers, oral and poster presentations to his name in the field of radiotherapy. Dr. Kirby holds professional membership of the Institute of Physics and Engineering in Medicine, the American Association of Physicists in Medicine, the American Society for Radiation Oncology, the European Society for Radiotherapy and Oncology and the British Institute of Radiology, is a Fellow of the Higher Education Academy and the British Institute of Radiology in the UK. Kerrie-Anne Calder is a Lecturer at the University of Liverpool, UK, where she educates undergraduate and post graduate students in many aspects of radiotherapy with a special interest and role in imaging training. Kerrie-Anne has graduate and postgraduate qualifications in radiotherapy, education and academic practice, is a member of the Society and College of Radiographers, and is a Fellow of the Higher Education Academy in the UK. She was a clinical and professional lead in IGRT (on-treatment verification imaging) within the NHS in the UK for over ten years.