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 30 years and 20 years respectively. Mike Kirby is a 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 150 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 and is a Fellow of the Higher Education Academy in the UK. Kerrie-Anne Calder is of 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 both radiotherapy and education, 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 on-treatment radiotherapy verification at Clatterbridge Cancer Centre (Wirral, UK) for over ten years.