[1
]
Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK; National
Physical Laboratory, London, UK; NCRI Radiotherapy Trials Quality Assurance Group,
UK. Electronic address: catharine.clark@nhs.net.
[2
]
Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK; Centre
for Nuclear and Radiation Physics, University of Surrey, UK.
[3
]
NCRI Radiotherapy Trials Quality Assurance Group, UK; Mount Vernon Hospital, Northwood,
London, UK.
[4
]
National Physical Laboratory, London, UK.
[5
]
Christie Hospital, Manchester, UK; Institute of Physics and Engineering in Medicine,
York, UK.