1. Part VIII:Medical Exposures in Radiotherapy Accidental Medical Exposure & lessons learnt Lecture 11 : Accidental Medical Exposure & lessons learnt IAEA Post Graduate Educational Course on Radiation Protection and Safe Use of Radiation Sources Module 5 – Accidental medical exposures

2. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 2 This lecture will cover Types of Radiation emergenciesTypes of Radiation emergencies Radiation accident in Radiation therapy treatmentRadiation accident in Radiation therapy treatment Potential for radiation emergency in RadiotherapyPotential for radiation emergency in Radiotherapy Case studies of Radiation accidents in External beam therapyCase studies of Radiation accidents in External beam therapy Case studies – Radiation Accidents in BrachytherapyCase studies – Radiation Accidents in Brachytherapy

3. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 3 What is Radiation Accident in Radiotherpay? A radiation accident is an unintended event that has or may have adverse consequences.A radiation accident is an unintended event that has or may have adverse consequences. This could beThis could be –Operator error – human error –Equipment failure –Any other mishap

4. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 4 Who are the people affected by the accidents in Radiation Therpay? 1.Members of the general public –irradiated as a result of failure of implementation of radiation protection and safety rules 2.Clinical staff –Irradiated during preparation of radiation sources or patient treatment or during installation, repairs, source change, or other equipment servicing; 3.Patient injured during treatment The main focus in this lecture will be on the third group I.e accidental exposure to patient during treatment

5. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 5 Possible Radiation Accidents that could lead to exposure of General Public & Clinical Staff 1.Loss of a radioactive source 2.Loss or damage to the shielding of a radiation source 3.Loss of containment causing a major spill or release of radioactivity 4.Unintentional exposure of part or all of the body to a radiation beam 5.Unintentional radioactive contamination of part or all of the body.

6. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 6 What is an accidental exposure to Radiotherapy patients? In Radiotherapy, a ‘normal’ radiation exposure is a treatment that closely follows the plan specified in the treatment prescription. An accidental exposure can therefore be considered to have occurred if there is a substantial deviation from the prescriptionIn Radiotherapy, a ‘normal’ radiation exposure is a treatment that closely follows the plan specified in the treatment prescription. An accidental exposure can therefore be considered to have occurred if there is a substantial deviation from the prescription Doses significantly below that prescribed can have severe consequences to the patient and may constitute an accidentDoses significantly below that prescribed can have severe consequences to the patient and may constitute an accident - ICRP Publication 86

7. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 7 Why to bother about excess radiation to Radiotherpy patient? Very high doses are delivered to the patient (20Gy to 80Gy) and this is decided by the tolerance dose to normal tissues and hence any accidental over exposure could have adverse consequencesVery high doses are delivered to the patient (20Gy to 80Gy) and this is decided by the tolerance dose to normal tissues and hence any accidental over exposure could have adverse consequences Radiation beam is focused on to the patient or radioactive sources are inserted in to the patient body and any mistake in these could have negative impact on the patient treatment, some times even lead to death of the patient.Radiation beam is focused on to the patient or radioactive sources are inserted in to the patient body and any mistake in these could have negative impact on the patient treatment, some times even lead to death of the patient.

8. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 8 Potential for an accident in Radiotherapy A radiotherapy treatment, from prescription to delivery is a very complex process.A radiotherapy treatment, from prescription to delivery is a very complex process. It involves many professionals, a number of steps and several treatment sessions with many variable parameters. It involves many professionals, a number of steps and several treatment sessions with many variable parameters. A radiotherapy technologist may be required to treat some 50 patients a day, for which the parameters are similar and yet different from one patient to the next, often with personalized ancillary devices. A radiotherapy technologist may be required to treat some 50 patients a day, for which the parameters are similar and yet different from one patient to the next, often with personalized ancillary devices.

9. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 9 Potential for an accident in Radiotherapy Because of this complexity of equipment, techniques and procedures, there is considerable scope for errors and mistakes and it may not be possible to compensate for an error in under or over exposure.Because of this complexity of equipment, techniques and procedures, there is considerable scope for errors and mistakes and it may not be possible to compensate for an error in under or over exposure. Given the complexity of radiotherapy and its sensitivity to errors and mistakes, nothing should be left to chance, but rather, a structured and systematic approach is needed.Given the complexity of radiotherapy and its sensitivity to errors and mistakes, nothing should be left to chance, but rather, a structured and systematic approach is needed. Defense in Depth should be the conceptDefense in Depth should be the concept

10. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 10 Classification of Radiation Accidents Radiation accidents in Radiotherapy Events relating to Equipment Events relating to Individual patient Affects many patients Affects only that patient

11. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 11 Which equipments’ malfunction cold potentially affect the treatment? Radiation Measuring instrumentsRadiation Measuring instruments –Calibration of teletherapy units Treatment simulatorTreatment simulator Treatment planning systemTreatment planning system –Incorrect input, lack of understanding of algorithm Treatment machineTreatment machine –Malfunction of interlocks

12. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 12 Where and how the dosimeter can go wrong? Incidents involving measuring system 1.Incorrect use of calibration factor of the reference dosimeter 2.Wrong inter-comparison with the secondary system 3.Error in routine use of dosimeter

13. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 13 Can the Treatment planning system go wrong? Incorrect input dataIncorrect input data Misunderstanding the algorithmMisunderstanding the algorithm Inadequate trainingInadequate training

14. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 14 Where could we go wrong with the treatment machine? Commissioning or acceptance testingCommissioning or acceptance testing Calibration of the unitCalibration of the unit Constancy check (daily, weekly)Constancy check (daily, weekly) Malfunction of the machineMalfunction of the machine Incorrect use of the machineIncorrect use of the machine

15. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 15 Radiation Incidents resulting from incorrect dose calibration – Case Study I Incident: Local standard was calibrated for dose to water, but incorrectly interpreted as dose in airIncident: Local standard was calibrated for dose to water, but incorrectly interpreted as dose in air Consequence:Consequence: –The error caused an overdose by 11% Cause : Inadequate training, education Incorrect use of Calibration Certificate of the local standard dosimeterCause : Inadequate training, education Incorrect use of Calibration Certificate of the local standard dosimeter

16. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 16 Radiation Incidents resulting from incorrect dose calibration – Case Study II Incident: Incorrect side of the parallel plate chamber was used for calibration of electron beamIncident: Incorrect side of the parallel plate chamber was used for calibration of electron beam Cause : Due to a label indicating the side to be exposed pasted wronglyCause : Due to a label indicating the side to be exposed pasted wrongly Consequence:Consequence: –6MeV 20% overdose –9MeV 10% overdose –12MeV 8% overdose TLD inter-comparison reveled the errorTLD inter-comparison reveled the error Action Taken: Calibration repeatedAction Taken: Calibration repeated

17. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 17 Radiation Incidents resulting from incorrect dose calibration – Case Study III Incident: Wrong value for pressure was used during output calibration of a cobalt unit in a hill station (1000m above sea level)Incident: Wrong value for pressure was used during output calibration of a cobalt unit in a hill station (1000m above sea level) Consequence:Consequence: –Patients were overdosed upto 21% Cause:Cause: –No barometer was available to measure pressure –Value of pressure was obtained form airport which was corrected for sea level

18. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 18 How does reading the pressure wrong affect the dose? K TP = (273.2+T) P o / (273.2+T o )P Where T & P are the Temperature & Pressure during measurement; T o & P o are the Temperature & Pressure at reference condition (usually 760mmHg and 20 o C) IF pressure P is taken as 760mmHg (sea level) & T as 20 o C K TP = (273.2+20)* 760/ ((273.2+20)* 760) = 1 The error in dose estimation will be about 20% lower, will result in excess dose to patient. Assume a pressure P is as 630mmHg (1000m above sea level) & T as 20 o C, then K TP = (273.2+20)* 760 / (273.2+20)* 630 = 1.206

19. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 19 Radiation Incidents resulting from insufficient understanding of planning system algorithm Case Study IV Incident: Wedge factor was applied twiceIncident: Wedge factor was applied twice Sequence:Sequence: –The Treatment planning system included the wedge correction in the dose distribution –The wedge factor was again included in the hand calculation of treatment time Consequence: Overexposure up to 14%Consequence: Overexposure up to 14% Reasons:Reasons: –Insufficient understanding of the treatment planning system algorithm Do not pay me twice

20. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 20 How could the wedge factor be included in the planning system? 100 90 80 70 60 50 40 75 65 50 40 30 Normalized isodose Wedge factor not included in isodose Corrected isodose Wedge factor included in isodose

21. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 21 How does it change the dose distribution? Wedge correction not included in the distribution Wedge correction included in the distribution 158 115120 100 80 60 Wedge factor should be included in Treatment time calculation Wedge factor should not be included in Treatment time calculation

22. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 22 Error in calculation of Treatment Case Study V Incident:Incident: –A 31 ‑ month old patient, being treated for a brain tumor, was to receive two Cobalt ‑ 60 teletherapy treatments of 150 rads each for a total dose of 300 rads to reduce swelling behind the patient's eye. –The dosimetrist mistakenly prepared the dose calculations for 300 rads per treatment. The patient was treated two days, with 300 rads per treatment for a total dose of 600 rads.

23. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 23 Error in calculation of Treatment Case Study V- Cause The error was caused by the mistaken calculations by the dosimetristThe error was caused by the mistaken calculations by the dosimetrist Inadequate review by the physician before the treatment began.Inadequate review by the physician before the treatment began. There was also a problem with the legibility and format of the treatment plan.There was also a problem with the legibility and format of the treatment plan.

24. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 24 Error in calculation of Treatment Case Study v – Action taken The error was discovered by a student technologist during a monthly chart reviewThe error was discovered by a student technologist during a monthly chart review To prevent recurrence, the licensee has provided additional training to treatment personnel to eliminate the types of problems that contributed to the misadministration.To prevent recurrence, the licensee has provided additional training to treatment personnel to eliminate the types of problems that contributed to the misadministration.

25. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 25 Accidents due to Machine Malfunction Case Study VI Incident:Incident: –Loose wedge mounting and incorrect dose at the central axis Cause:Cause: –Wedge mount was loose and hence for lateral beams the central axis wedge factors were incorrect and altered the dose distribution –Staff did not check the wedge mount and the wedge factor for horizontal beams

26. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 26 Off Centered wedge Wedge factor depends on the thickness of the wedge ‘t’ at the central axisWedge factor depends on the thickness of the wedge ‘t’ at the central axis Consequence: Patients received higher doses across the beam for horizontal machine position and low for opposite side horizontal treatmentConsequence: Patients received higher doses across the beam for horizontal machine position and low for opposite side horizontal treatment tt }{ { Lack of thickness { Excess attenuation

27. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 27 Use of Linear Accelerator in Physical Mode Case Study VII Incident:Incident: –Problem with selection of X-ray & Electron energies in the clinical mode –Linear accelerator was used in PHSYCAL mode for treatment. PHYSICAL mode is meant for servicing & research as most interlocks of linac are bypassed in this mode PHYSICAL mode is meant for servicing & research as most interlocks of linac are bypassed in this mode –Linac MAY NOT terminate the radiation if errors in Radiation output or if mechanical movements of target, foils or filters fail

28. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 28 Use of Linear Accelerator in Physical Mode Case Study VII SequenceSequence –Linac was made to work on PHYSICAL mode by the electronics engineer on instruction from Radiation Oncologist –Output was measured with the help of Technologist in PHYSICAL mode –Instruction on how to operate in Physical mode was provided by the engineer and observed the first two treatments

29. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 29 Use of Linear Accelerator in Physical Mode Case Study VII Thirteen patients were treated with no problems and the last patient was on 10 MeV electronsThirteen patients were treated with no problems and the last patient was on 10 MeV electrons Next patient was set for treatment with 20MV x rays, dose rate 300MU/min, The treatment started but terminated after 21s and only a few monitor units were deliveredNext patient was set for treatment with 20MV x rays, dose rate 300MU/min, The treatment started but terminated after 21s and only a few monitor units were delivered When the patient was removed from the room the radiographer noted skin reaction on the patient, which indicated a high degree of overexposureWhen the patient was removed from the room the radiographer noted skin reaction on the patient, which indicated a high degree of overexposure

30. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 30 Use of Linear Accelerator in Physical Mode Case Study VII – contributing factors On investigation it was found that there was extremely high dose at the center of the field caused by the failure to deploy, X-ray target, flattening filter and monitor chamber.On investigation it was found that there was extremely high dose at the center of the field caused by the failure to deploy, X-ray target, flattening filter and monitor chamber. Cause: Operation in PHYSICAL mode disabled the interlocks that could have detected this dangerous conditionCause: Operation in PHYSICAL mode disabled the interlocks that could have detected this dangerous condition

31. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 31 Mishandling of equipment failure Case Study VIII Incident: The linac delivered 36MeV electrons regardless of the energy selected on the consoleIncident: The linac delivered 36MeV electrons regardless of the energy selected on the console Sequence:Sequence: –Linear accelerator failed to produce electron beams –Fault was attended by an maintenance technician –After the repair the analog display permanently displayed 36MeV regardless of energy selected

32. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 32 Mishandling of equipment failure Case Study VIII– Consequence 27 patients were treated over a period of ten days till the physicians began to correlate poor tolerance and severe reactions observed in some patients with mall function of the machine

33. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 33 Mishandling of equipment failure Case Study VIII– contributing factor Failure to select electron beam was due to a short circuit of the system that selects the trajectory of the electron beamFailure to select electron beam was due to a short circuit of the system that selects the trajectory of the electron beam Ineffective communication – physicists were not notified immediately about the malfunctionIneffective communication – physicists were not notified immediately about the malfunction Incorrect interpretation of conflicting signals; the analog meter showing 36MeV was ignoredIncorrect interpretation of conflicting signals; the analog meter showing 36MeV was ignored

34. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 34 Possible causes for Radiation Accidents in Brachytherapy Improper calibration of Activity of the brachytherapy sourceImproper calibration of Activity of the brachytherapy source Improper identification of the sourceImproper identification of the source Mishandling of the sourceMishandling of the source Incorrect input data to the planning systemIncorrect input data to the planning system Insufficient knowledge about the planning system algorithmInsufficient knowledge about the planning system algorithm Mechanical failure or malfunction of brachytherapy equipmentMechanical failure or malfunction of brachytherapy equipment

35. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 35 Error in activity reporting Case Study I Incident: Error in units of reporting the activity for brachytherpay ribbonsIncident: Error in units of reporting the activity for brachytherpay ribbons Sequence:Sequence: –The licensee ordered brachytherapy ribbons containing 0.79 millicurie per ribbon –However, the vendor delivered brachytherapy ribbons containing 0.79 milligrams radium equivalent (1.36 millicurie) per ribbon. –the prescription order was checked against what was received and noted that the quantities (0.79) matched, but failed to note that the amount received was measured in milligrams radium equivalent rather than the requested millicurie units

36. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 36 Error in activity reporting Case Study I –Consequence & Action taken Consequence:Consequence: The radiation dose to the patient's prostate gland was 5,669 rads (56.69Gy) rather than the prescribed 3,258 (32.58Gy) rads The radiation dose to the patient's prostate gland was 5,669 rads (56.69Gy) rather than the prescribed 3,258 (32.58Gy) rads Action Taken:Action Taken: –The referring physician was notified and chose not to inform the patient. The patient was examined during subsequent follow ‑ up visits and has shown no adverse effects due to the increased radiation exposure.

37. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 37 Case Study I -Cause and lessons learnt Reason for the Incident:Reason for the Incident: –Failure of the staff to perform adequate verification of source strengths prior to implanting the brachytherapy sources. –Miscommunication between the licensee and the vendor also appears to have contributed to the error. Lessons learnt: Lessons learnt: –To ensure that units of measurement received correspond to that was ordered source strengths should be verified by direct measurement prior to implantation.

38. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 38 Incident with HDR after-loading unit. Case Study II- Incident: A patient was treated for anal carcinoma with High Dose Rate (HDR) after loading Brachytherapy unit and the patient died on November 21, 1992. HDR treatment with 4.3 Ci of Iridium ‑ 192 source was placed at various positions in each of the five catheters that were to remain in the patient for subsequent treatments.HDR treatment with 4.3 Ci of Iridium ‑ 192 source was placed at various positions in each of the five catheters that were to remain in the patient for subsequent treatments. The staff experienced difficulty with source placement in one of the patient's five treatment catheters.The staff experienced difficulty with source placement in one of the patient's five treatment catheters.

39. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 39 Incident with HDR after-loading unit. Case Study II- Sequence of events They were unaware that a short piece of the cable containing the Iridium source had broken off and remained in one of the catheters in the patient. The patient was transported to a nearby nursing home. The source remained in the patient's body for four days when the catheter fell out.They were unaware that a short piece of the cable containing the Iridium source had broken off and remained in one of the catheters in the patient. The patient was transported to a nearby nursing home. The source remained in the patient's body for four days when the catheter fell out. It was placed in a medical biohazard bag (red bag) in a storage room by nursing home personnel who did not know it contained the radioactive sourceIt was placed in a medical biohazard bag (red bag) in a storage room by nursing home personnel who did not know it contained the radioactive source

40. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 40 Incident with HDR after-loading unit. Case Study II- Cause Cause:Cause: –Although a wall ‑ mounted area monitor alarmed at various times when the source should have been retracted, the licensee's staff did not conduct a survey for radiation levels with the available portable radiation survey instrument. –The only action taken was to check the control console of the HDR remote afterloader which gave a false indication that the source was "safe“.

41. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 41 Incident with HDR after-loading unit. Case Study II- Cause The Incident Investigation Team (IIT) reported that the event was caused by the following: 1.Weaknesses in their radiation safety program 2.Inadequate radiation safety training to the staff. 3.A number of weaknesses were found in the design and testing of the unit. –Weaknesses were identified in the testing and validation of source ‑ wire design, and in the design of certain safety features of the HDR afterloader.

42. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 42 Incident with HDR after-loading unit. Case Study II- Cause The safety culture contributed significantly to the event.The safety culture contributed significantly to the event. –Technologists routinely ignored the PrimAlert ‑ 10 alarm. Its problems were worked around and not fixed. –Technologists did not survey patients, the afterloader, or the treatment room following HDR treatments. –The authorized user failed to wear a film badge on both occasions when the source was encountered;

43. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 43 The cause of death of the patient was reported as "Acute Radiation Exposure and Consequences Thereof." Until the source was recovered after the patient's death, it subjected nursing home residents and staff, as well as visitors, to radiation exposure. Radiation doses to the 94 individuals associated with the event ranged from 40 mrem to 22 rem. Numerous residents, employees, and visitors to the nursing home were unknowingly irradiated.Numerous residents, employees, and visitors to the nursing home were unknowingly irradiated. Incident with HDR after loading unit. Case Study II- Consequence

44. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 44 Misadministration of the source Case Study III Incident: A routine x ‑ ray identified that the seeds were no longer implanted Sequence of events: –During a brachytherapy implant procedure, two ribbons, each containing six Ir ‑ 192 seeds, with a total activity of 48.25 mCi, were implanted into two catheters inserted into the patient's common bile duct, through an abdominal incision.

45. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 45 Misadministration of the source Case Study III – sequence of events During the night shift, the patient's dressings on the wound were wet and loose. A licensed practical nurse (LPN), who responded to the patient, found the Ir ‑ 192 ribbons dislodged and lying loose on the patient's abdomen. The LPN, not realizing that it was radioactive, changed the patient's dressing and bed, and coiled each Ir ‑ 192 ribbon around her hand and taped them to the patient's abdomen.

46. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 46 Misadministration of the source Case Study III - Consequence The oncologist had left verbal orders with the day shift charge nurse "not to change the dressing" but these orders were not passed on to the LPN..The oncologist had left verbal orders with the day shift charge nurse "not to change the dressing" but these orders were not passed on to the LPN.. The patient's abdominal skin received an unnecessary exposure over various areas ranging from 172 rad to 1032 rad. The skin exposure to the hand of the LPN was 7.6 radThe patient's abdominal skin received an unnecessary exposure over various areas ranging from 172 rad to 1032 rad. The skin exposure to the hand of the LPN was 7.6 rad

47. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 47 Misadministration of the source Case Study III - Cause 1.Lack of oversight of the procedure by the licensee's Radiation Health and Safety Officer; and 2.Inadequate training of the nursing staff in that they were unable to identify the brachytherapy ribbon and handle them appropriately if, and when, they become dislodged.

48. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 48 Misadministration of the source Case Study III – Action Taken & lessons learnt 1.Familiarization of personnel with the size and appearance of the radioactive sources used in brachytherapy treatments at the licensee's facility; 2.Naming a new RHSO who could devote sufficient time to the radiation safety program; 3.Developing a nurses' procedure manual; 4.Conducting formal in-service training in radiation safety with all nursing unit workers; and 5.Requiring a written directive be initiated before ordering radioactive material.

49. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 49 Summary – Potential accidents in External Beam Therapy Possible errors in CalibrationPossible errors in Calibration –Incorrect calibration of the teletherapy unit –Use of wrong decay chart for output of cobalt unit. –Not updating the output chart after source change –Lack of communication regarding units and depth of calibration. (e.g. D max or 5cm)

50. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 50 Summary – Potential accidents in External Beam Therapy Possible errors in Treatment PlanningPossible errors in Treatment Planning –Incorrect input data of Depth dose or Tissue maximum ratio –Multiple correction for use of wedge filter or compensators. –Miss application of distance correction. –Miss understanding the algorithm –Incorrect hand calculation and inadequate training and QA procedure

51. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 51 Summary – Potential accidents in External Beam Therapy Potential accidents due to machine malfunctionPotential accidents due to machine malfunction –Improper accessory mounting –Use of Linear accelerator in Physical mode –Mishandling of the machine malfunction –Inadequate training for serving personnel –Improper documentation of polices and procedures for use & servicing of the machine –Inadequate routine QA procedures for teletherapy units

52. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 52 Summary – Potential accidents in Brachytherapy Improper calibration of the source activityImproper calibration of the source activity Improper identification of sourceImproper identification of source Inadequate routine QA for source integrity checkInadequate routine QA for source integrity check Inadequate source movement documentationInadequate source movement documentation Incorrect use of treatment planning systemIncorrect use of treatment planning system Insufficient understanding of the Algorithm of the planning systemInsufficient understanding of the Algorithm of the planning system

53. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 53 Summary – Potential accidents in Brachytherapy Inadequate routine QA procedure for Remote after loading unitInadequate routine QA procedure for Remote after loading unit Improper and inadequate training of personal on radiation protection aspectsImproper and inadequate training of personal on radiation protection aspects Insufficient documentation of policies and procedures for handling emergenciesInsufficient documentation of policies and procedures for handling emergencies Use of faulty zone monitors and survey metersUse of faulty zone monitors and survey meters

54. Accidental Medical Exposure & lessons learnt Part VIII.5.11 : Accidental Medical Exposure & lessons learntSlide 54 References ‘Lessons Learned from accidental exposures in Radiation Therapy’‘Lessons Learned from accidental exposures in Radiation Therapy’ –IAEA publication Safety Report Series No 17 ‘Prevention of Accidental Exposures to Patients undergoing Radiation Therapy’‘Prevention of Accidental Exposures to Patients undergoing Radiation Therapy’ –Annals of the ICRP Publication No 86 Basic Safety StandardsBasic Safety Standards –Safety series No 115 IAEA publication Investigation of an accidental exposure of Radiotherapy patients in PanamaInvestigation of an accidental exposure of Radiotherapy patients in Panama –Report of a team of experts (IAEA publication 26 May-1June 2001)