Medical Physics

Ian Paddick, Chief Physicist

Ian began his career as a Medical Physicist in 1989, working at the Hammersmith hospital, London. Since 1998 he has worked almost exclusively with the Gamma Knife using the B, 4C, Perfexion and Icon Gamma Knife models.

He is a regular speaker and moderator at Radiosurgery conferences, teaching on training courses and helping start up new Gamma Knife centres worldwide.

His publications in Radiosurgery have established him as an authority in Radiosurgery dose planning. In 2003, Ian became a freelance physicist, providing physics services to Gamma Knife centres, as well as the manufacturers of the Gamma Knife; Elekta Instruments. In 2009 he published “Radiosurgery Treatment Planning”, the first book covering practical techniques of dose planning.

He currently serves as President of the International Stereotactic Radiosurgery Society and Vice President of the British Stereotactic Radiosurgery Society.


Chris Bragg, Senior Physicist

Chris graduated from Imperial College, London, in 1997 with an MSci in Physics before training in Medical Physics at King’s College Hospital, being awarded an MSc in Medical Physics and Clinical Engineering in 1999. Based in Sheffield since 1999, he gained sixteen years’ experience in radiation therapy physics at Weston Park Hospital, where he led the treatment planning service for ten years and the introduction of Stereotactic Body Radiation Therapy planning and treatment. He was awarded his PhD in radiation therapy physics in 2008 and has authored a number of publications on dose planning. Through his role as Associate Lecturer at Sheffield Hallam University, he contributes to the development of Radiographers.

Chris joined the Gamma Knife team in 2017.

Phil Tapper, Senior Radiosurgery Physicist

After graduating in Physics & Astrophysics from Queen Elizabeth College, London Phil trained in Radiation Physics at the Medical College of St Bartholomew’s Hospital which led to the award of an MSc in 1985. He then worked for a number of years in the NHS before moving into the private sector, eventually becoming Head of the Medical Physics Department including the London Gammaknife Centre at the Harley Street Cancer Centre. Since 2008 he has been providing radiosurgical physics support as a consultant, to Gamma Knife Centres.

Alex Dimitriadis , Senior Radiosurgery Physicist

Alex graduated with a BSc (Hons) in Radiotherapy and Oncology in 2010 from the University of Hertfordshire, having completed three years of clinical placements at Imperial College NHS Trust hospitals. He then went on to study for an MSc in Human Anatomy at the University of Edinburgh where he developed a keen interest in neuroanatomy and chose it as the subject of his dissertation. He was awarded with an MSc in 2011 and subsequently in the same year he joined Poole Hospital NHS Trust as a radiographer. In 2012 he joined the Royal Surrey County Hospital NHS Trust where he worked as a radiographer. He then gravitated towards radiotherapy physics and took a post in the radiotherapy physics department of the same hospital, working predominantly in prostate seed brachytherapy and in performing in-vivo dosimetry for patients undergoing external beam radiotherapy. Parallel to that, he developed an interest in radiosurgery physics and started conducting research in 2012 as part of his PhD studies at the University of Surrey. As part of his PhD work, Alex developed a method for assessing the dosimetric and geometric accuracy of stereotactic radiosurgery. His method was used to conduct a national audit of all 32 radiosurgery centres in the UK, the results of which were utilised in an assessment performed by NHS England to commission SRS services. This work was also endorsed the Radiotherapy Trials and Quality Assurance group as the dosimetric study required for the CORE and SARON clinical trials. Alex has presented his research findings in several national and international conferences and has also produced a number of publications in peer-reviewed journals. Since the completion of his PhD studies in 2016, he joined Medical Physics Limited and provides Radiosurgery physics services to Queen Square Radiosurgery Centre, Thornbury Radiosurgery Centre, Cromwell GammaKnife Centre and London GammaKnife Centre at Barts. He continues conducting research in radiosurgery physics and is an active member of the national, European and international radiosurgery and oncology societies.