[1] Univ Sheffield, Weston Pk Hosp, Acad Unit Clin Oncol, Sheffield, S Yorkshire, England
[2] Univ Sheffield, Acad Unit Radiol, Sheffield, S Yorkshire, England
[3] Sheffield Teaching Hosp, Weston PK Hosp, Dept Radiotherapy Phys, Sheffield, S Yorkshire, England
[4] Royal Hallamshire Hosp, Sheffield Teaching Hosp, Directorate Med Imaging & Med Phys, Sheffield S10 2JF, S Yorkshire, England