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1、Module 2.10: Accident update some newer events (UK, USA, France),IAEA Training Course,Questions,Do you think the accidents have not happened in recent years? Do you think well-developed centres are immune to these accidents?,2,Prevention of accidental exposure in radiotherapy,Overview,It should be n
2、oted that the intent is certainly not to reflect the quoted centres in this presentation in poor light Instead, the purpose is to draw lessons In many cases, the centres have a quality system in place The events are reconstructed from information in the public domain, and might differ from actual ev
3、ents due to gaps in this information.,3,Prevention of accidental exposure in radiotherapy,Overview,1st example: Incorrect manual parameter transfer (UK) 2nd example: Reversal of images (USA) 3rd example: Inappropriate measuring device (France) 4th example: Erroneous calculation for soft wedges (Fran
4、ce) 5th example: Incorrect IMRT planning (USA) 6th example: More information needed,Newer examples of accidents in radiotherapy from 2004 to 2007,4,Prevention of accidental exposure in radiotherapy,1st example: Incorrect manual parameter transfer (UK),IAEA Training Course,Background,January 2006 at
5、the Beatson Oncology Centre (BOC) in Glasgow, Scotland At the time: Radiotherapy physics staffing levels in Scotland less than 60% of the recommended level “Glasgow has problems with recruiting physicists, as shown by their high number of vacancies.”,The Beatson Oncology Centre in Glasgow,6,Preventi
6、on of accidental exposure in radiotherapy,Background,Treatment planning at BOC: 14.5 whole time equivalent (WTE) staff were available for between 4500 and 5000 new treatment plans per year. When staffing levels were compared with guidelines from IPEM, it was seen that 18 WTE staff would be the recom
7、mended level.,7,Prevention of accidental exposure in radiotherapy,Background,Treatment planning at BOC: Planning staff members and planning procedures were both categorized A to C denotes senior to junior staff A to E denotes simple to complex plans The main duties per staff category is outlined in
8、column 4,Table from: “Report of an investigation by the Inspector appointed by the Scottish Ministers for The Ionising Radiation (Medical Exposures) Regulations 2000”,8,Prevention of accidental exposure in radiotherapy,Background,Treatment planning at BOC: Practice prior to 2005 had been to let the
9、treatment planning system (TPS) calculate the Monitor Units (MU) for 1 Gy followed by manual multiplication with the intended dose per fraction for the correct MU-setting to use.,9,Prevention of accidental exposure in radiotherapy,Background,Treatment planning at BOC: In May 2005, the Record and Ver
10、ify (RV) system was upgraded to be a more integrated platform. The centre decided to input the dose per fraction already in the TPS, for most but not all treatment techniques.,10,Prevention of accidental exposure in radiotherapy,What happened?,5th January 2006, Lisa Norris, 15 years old, started her
11、 whole CNS treatment at BOC The treatment plan was divided into head-fields and lower and upper spine-fields This is considered to be a complex treatment plan, performed about six times per year at the BOC.,Lisa Norris,11,Prevention of accidental exposure in radiotherapy,What happened?,The bulk of t
12、he planning was done by “Planner X” in Dec05, a junior planner “Planner X” had not yet been registered internally to be competent to plan whole CNS, or to train on these “Planner X” got initial instructions and the opportunity to be supervised when creating the plan,12,Prevention of accidental expos
13、ure in radiotherapy,What happened?,Whole CNS plans still went by the “old system”, where TPS calculates MU for 1 Gy with subsequent upscaling for dose per fx A “medulla planning form” was used, which is passed to treatment radiographers for final MU calculations,Table from: “Report of an investigati
14、on by the Inspector appointed by the Scottish Ministers for The Ionising Radiation (Medical Exposures) Regulations 2000”,13,Prevention of accidental exposure in radiotherapy,What happened?,HOWEVER “Planner X” let the TPS calculate the MU for the full dose per fx not for 1 Gy as intended Since the do
15、se per fx to the head was 1.67 Gy, the MUs entered in the form were 67% too high for each of the head-fields,Table from: “Report of an investigation by the Inspector appointed by the Scottish Ministers for The Ionising Radiation (Medical Exposures) Regulations 2000”,14,Prevention of accidental expos
16、ure in radiotherapy,What happened?,This error was not found by the more senior planners who checked the plan The radiographer on the unit thus multiplied with the dose per fx a second time 2.92 Gy per fx to the head,Table from: “Report of an investigation by the Inspector appointed by the Scottish Ministers for The Ionising Radiation (Medical Exposures) Regulations 2000”,15,Prevention of accidental exposure in radiotherapy,“Planner X” calculated another plan of the same kind and
