Part VIII:Medical Exposures in Radiotherapy Accidental Medical Exposure & lessons learnt Lecture 11...

Part VIII:Medical Exposures in RadiotherapyPart VIII:Medical Exposures in Radiotherapy

Lecture 11 : Accidental Medical Exposure & Accidental Medical Exposure & lessons learntlessons learnt

IAEA Post Graduate Educational Course on Radiation Protection and Safe Use of Radiation Sources

Module 5 – Accidental medical exposures

Part VIII.5.11 : Accidental Medical Exposure & lessons learntAccidental Medical Exposure & lessons learnt Slide 2

This lecture will coverThis lecture will cover

• Types of Radiation emergenciesTypes of Radiation emergencies• Radiation accident in Radiation therapy Radiation accident in Radiation therapy

treatmenttreatment• Potential for radiation emergency in Potential for radiation emergency in

RadiotherapyRadiotherapy• Case studies of Radiation accidents in External Case studies of Radiation accidents in External

beam therapybeam therapy• Case studies – Radiation Accidents in Case studies – Radiation Accidents in

BrachytherapyBrachytherapy


What is Radiation Accident in What is Radiation Accident in Radiotherpay?Radiotherpay?

• A radiation accident is an unintended event A radiation accident is an unintended event that has or may have adverse consequences.that has or may have adverse consequences.

• This could beThis could be– Operator error – human errorOperator error – human error– Equipment failureEquipment failure– Any other mishapAny other mishap


Who are the people affected by the Who are the people affected by the accidents in Radiation Therpay?accidents in Radiation Therpay?

1.1. Members of the general public Members of the general public – irradiated as a result of failure of implementation of radiation irradiated as a result of failure of implementation of radiation

protection and safety rulesprotection and safety rules

2.2. Clinical staffClinical staff– Irradiated during preparation of radiation sources or patient Irradiated during preparation of radiation sources or patient

treatment or during installation, repairs, source change, or treatment or during installation, repairs, source change, or other equipment servicing;other equipment servicing;

3.3. Patient injured during treatmentPatient injured during treatment

The main focus in this lecture will be on the third group The main focus in this lecture will be on the third group I.e accidental exposure to patient during treatmentI.e accidental exposure to patient during treatment


Possible Radiation Accidents that could Possible Radiation Accidents that could lead to exposure of General Public & lead to exposure of General Public & Clinical StaffClinical Staff

1.1. Loss of a radioactive sourceLoss of a radioactive source2.2. Loss or damage to the shielding of a radiation Loss or damage to the shielding of a radiation

sourcesource3.3. Loss of containment causing a major spill or release Loss of containment causing a major spill or release

of radioactivityof radioactivity4.4. Unintentional exposure of part or all of the body to a Unintentional exposure of part or all of the body to a

radiation beamradiation beam5.5. Unintentional radioactive contamination of part or all Unintentional radioactive contamination of part or all

of the body.of the body.


What is an accidental exposure to What is an accidental exposure to Radiotherapy patients?Radiotherapy patients?

• In Radiotherapy, a ‘normal’ radiation exposure is a In Radiotherapy, a ‘normal’ radiation exposure is a treatment that closely follows the plan specified in treatment that closely follows the plan specified in the treatment prescription. An accidental exposure the treatment prescription. An accidental exposure can therefore be considered to have occurred if can therefore be considered to have occurred if there is a substantial deviation from the there is a substantial deviation from the prescriptionprescription

• Doses significantly below that prescribed can Doses significantly below that prescribed can have severe consequences to the patient and have severe consequences to the patient and may constitute an accidentmay constitute an accident

- ICRP Publication 86


Why to bother about excess radiation to Why to bother about excess radiation to Radiotherpy patient? Radiotherpy patient?

• Very high doses are delivered to the patient (20Gy Very high doses are delivered to the patient (20Gy to 80Gy) and this is decided by the tolerance dose to 80Gy) and this is decided by the tolerance dose to normal tissues and hence any accidental over to normal tissues and hence any accidental over exposure could have adverse consequencesexposure could have adverse consequences

• Radiation beam is focused on to the patient or Radiation beam is focused on to the patient or radioactive sources are inserted in to the patient radioactive sources are inserted in to the patient body and any mistake in these could have body and any mistake in these could have negative impact on the patient treatment , some negative impact on the patient treatment , some times even lead to death of the patienttimes even lead to death of the patient..


Potential for an accident in RadiotherapyPotential for an accident in Radiotherapy

• A radiotherapy treatment, from prescription to A radiotherapy treatment, from prescription to delivery is a very complex process.delivery is a very complex process.

• It involves many professionals, a number of It involves many professionals, a number of steps and several treatment sessions with many steps and several treatment sessions with many variable parameters.variable parameters.

• A radiotherapy technologist may be required to A radiotherapy technologist may be required to treat some 50 patients a day, for which the treat some 50 patients a day, for which the parameters are similar and yet different from one parameters are similar and yet different from one patient to the next, often with personalized patient to the next, often with personalized ancillary devices.ancillary devices.


Potential for an accident in RadiotherapyPotential for an accident in Radiotherapy

• Because of this complexity of equipment, techniques Because of this complexity of equipment, techniques and procedures, there is considerable scope for and procedures, there is considerable scope for errors and mistakes and it may not be possible to errors and mistakes and it may not be possible to compensate for an error in under or over exposurecompensate for an error in under or over exposure..

• Given the complexity of radiotherapy and its Given the complexity of radiotherapy and its sensitivity to errors and mistakes, nothing should be sensitivity to errors and mistakes, nothing should be left to chance, but rather, a structured and systematic left to chance, but rather, a structured and systematic approach is needed.approach is needed.

• Defense in Depth should be the conceptDefense in Depth should be the concept


Classification of Radiation AccidentsClassification of Radiation Accidents

Radiation accidents in Radiotherapy

Events relating to Equipment

Events relating to Individual patient

Affects many patients

Affects only that patient


Which equipments’ malfunction cold Which equipments’ malfunction cold potentially affect the treatment?potentially affect the treatment?

• Radiation Measuring instrumentsRadiation Measuring instruments– Calibration of teletherapy unitsCalibration of teletherapy units

• Treatment simulatorTreatment simulator• Treatment planning systemTreatment planning system

– Incorrect input, lack of understanding of algorithmIncorrect input, lack of understanding of algorithm• Treatment machine Treatment machine

– Malfunction of interlocksMalfunction of interlocks


Where and how the dosimeter can go Where and how the dosimeter can go wrong?wrong?

Incidents involving measuring systemIncidents involving measuring system

1.1. Incorrect use of calibration factor of the Incorrect use of calibration factor of the reference dosimeterreference dosimeter

2.2. Wrong inter-comparison with the Wrong inter-comparison with the secondary systemsecondary system

3.3. Error in routine use of dosimeterError in routine use of dosimeter


Can the Treatment planning system go Can the Treatment planning system go wrong?wrong?

• Incorrect input dataIncorrect input data• Misunderstanding the algorithm Misunderstanding the algorithm • Inadequate training Inadequate training


Where could we go wrong with the Where could we go wrong with the treatment machine?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


Radiation Incidents resulting from Radiation Incidents resulting from incorrect dose calibration – Case Study Iincorrect dose calibration – Case Study I

• Incident: Local standard was calibrated Incident: Local standard was calibrated for dose to water, but incorrectly for dose to water, but incorrectly interpreted as dose in airinterpreted as dose in air

• Consequence: Consequence: – The error caused an overdose by 11%The error caused an overdose by 11%

• Cause : Inadequate training, education Cause : Inadequate training, education Incorrect use of Calibration Certificate of Incorrect use of Calibration Certificate of the local standard dosimeterthe local standard dosimeter


Radiation Incidents resulting from Radiation Incidents resulting from incorrect dose calibration – Case Study IIincorrect dose calibration – Case Study II

• Incident: Incorrect side of the parallel plate chamber Incident: Incorrect side of the parallel plate chamber was used for calibration of electron beamwas used for calibration of electron beam

• Cause : Due to a label indicating the side to be Cause : Due to a label indicating the side to be exposed pasted wronglyexposed pasted wrongly

• Consequence:Consequence:– 6MeV 20% overdose6MeV 20% overdose– 9MeV 10% overdose9MeV 10% overdose– 12MeV 8% overdose12MeV 8% overdose

• TLD inter-comparison reveled the errorTLD inter-comparison reveled the error• Action Taken: Calibration repeated Action Taken: Calibration repeated


Radiation Incidents resulting from Radiation Incidents resulting from incorrect dose calibration – Case Study IIIincorrect dose calibration – Case Study III

• Incident: Wrong value for pressure was used Incident: Wrong value for pressure was used during output calibration of a cobalt unit in a hill during output calibration of a cobalt unit in a hill station (1000m above sea level)station (1000m above sea level)

• Consequence:Consequence:– Patients were overdosed upto 21% Patients were overdosed upto 21%

• Cause:Cause:– No barometer was available to measure No barometer was available to measure

pressurepressure– Value of pressure was obtained form airport Value of pressure was obtained form airport

which was corrected for sea levelwhich was corrected for sea level


How does reading the pressure wrong How does reading the pressure wrong affect the dose?affect the dose?

KKTPTP = (273.2+T) P = (273.2+T) Po o / (273.2+T/ (273.2+Too)P)PWhere T & P are the Temperature & Pressure during measurement; TWhere T & P are the Temperature & Pressure during measurement; To o & P& Po o are the are the

Temperature & Pressure at reference condition (usually 760mmHg and 20Temperature & Pressure at reference condition (usually 760mmHg and 20ooC)C)

IF pressure P is taken as 760mmHg (sea level) & T as 20IF pressure P is taken as 760mmHg (sea level) & T as 20ooCC

KKTPTP = = (273.2+20)* 760/ ((273.2+20)* 760) (273.2+20)* 760/ ((273.2+20)* 760) = 1= 1

The error in dose estimation will be about 20% lower, will result in The error in dose estimation will be about 20% lower, will result in excess dose to patient.excess dose to patient.

Assume a pressure P is as 630mmHg (1000m above sea level) Assume a pressure P is as 630mmHg (1000m above sea level) & T as 20& T as 20ooC, thenC, then

KKTPTP = = (273.2+20)* 760 (273.2+20)* 760 / (273.2+20)* 630 / (273.2+20)* 630 = 1.206= 1.206


Radiation Incidents resulting from Radiation Incidents resulting from insufficient understanding of planning insufficient understanding of planning

system algorithm Case Study IVsystem algorithm Case Study IV

• Incident: Wedge factor was applied twice Incident: Wedge factor was applied twice • Sequence: Sequence:

– The Treatment planning system included the The Treatment planning system included the wedge correction in the dose distributionwedge correction in the dose distribution

– The wedge factor was again included in the The wedge factor was again included in the hand calculation of treatment timehand calculation of treatment time

• Consequence: Overexposure up to 14%Consequence: Overexposure up to 14%• Reasons:Reasons:

– Insufficient understanding of the treatment Insufficient understanding of the treatment planning system algorithmplanning system algorithm

Do not pay me twice


How could the wedge factor be included How could the wedge factor be included in the planning system?in the planning system?

100

90

80

70

60

5040

75

65

50

4030

Normalized isodose

Wedge factor not included in isodose

Corrected isodose

Wedge factor included in isodose


How does it change the dose distribution?How does it change the dose distribution?

Wedge correction not included in the distribution

Wedge correction included in the distribution

158 115120 100

8080

6060

Wedge factor should be included in Treatment time calculation

Wedge factor should not be included in Treatment time calculation


Error in calculation of TreatmentError in calculation of TreatmentCase Study VCase Study V

• Incident: Incident: – A 31‑month old patient, being treated for a A 31‑month old patient, being treated for a

brain tumor, was to receive two Cobalt‑60 brain tumor, was to receive two Cobalt‑60 teletherapy treatments of 150 rads each for teletherapy treatments of 150 rads each for a total dose of 300 rads to reduce swelling a total dose of 300 rads to reduce swelling behind the patient's eye. behind the patient's eye.

– The dosimetrist mistakenly prepared the The dosimetrist mistakenly prepared the dose calculations for 300 rads per dose calculations for 300 rads per treatment. The patient was treated two treatment. The patient was treated two days, with 300 rads per treatment for a total days, with 300 rads per treatment for a total dose of 600 rads.dose of 600 rads.


Error in calculation of TreatmentError in calculation of TreatmentCase Study V- CauseCase Study V- Cause

• The error was caused by the mistaken The error was caused by the mistaken calculations by the dosimetrist calculations by the dosimetrist

• Inadequate review by the physician before Inadequate review by the physician before the treatment began. the treatment began.

• There was also a problem with the legibility There was also a problem with the legibility and format of the treatment plan.and format of the treatment plan.


Error in calculation of TreatmentError in calculation of TreatmentCase Study v – Action takenCase Study v – Action taken

• The error was discovered by a student The error was discovered by a student technologist during a monthly chart review technologist during a monthly chart review

• To prevent recurrence, the licensee has To prevent recurrence, the licensee has provided additional training to treatment provided additional training to treatment personnel to eliminate the types of problems personnel to eliminate the types of problems that contributed to the misadministration.that contributed to the misadministration.


Accidents due to Machine MalfunctionAccidents due to Machine MalfunctionCase Study VICase Study VI

• Incident: Incident: – Loose wedge mounting and incorrect dose at Loose wedge mounting and incorrect dose at

the central axisthe central axis• Cause: Cause:

– Wedge mount was loose and hence for lateral Wedge mount was loose and hence for lateral beams the central axis wedge factors were beams the central axis wedge factors were incorrect and altered the dose distributionincorrect and altered the dose distribution

– Staff did not check the wedge mount and the Staff did not check the wedge mount and the wedge factor for horizontal beamswedge factor for horizontal beams


Off Centered wedgeOff Centered wedge

• Wedge factor depends on the thickness of the wedge Wedge factor depends on the thickness of the wedge ‘t’ at the central axis‘t’ at the central axis

• Consequence: Patients received higher doses across Consequence: Patients received higher doses across the beam for horizontal machine position and low for the beam for horizontal machine position and low for

opposite side horizontal treatmentopposite side horizontal treatment

t t}{ {Lack of thickness

{Excess attenuation


Use of Linear Accelerator in Physical Use of Linear Accelerator in Physical ModeMode

Case Study VIICase Study VII• Incident: Incident:

– Problem with selection of X-ray & Electron Problem with selection of X-ray & Electron energies in the clinical modeenergies in the clinical mode

– Linear accelerator was used in PHSYCAL mode Linear accelerator was used in PHSYCAL mode for treatment.for treatment.

PHYSICAL mode is meant for servicing & research as PHYSICAL mode is meant for servicing & research as most interlocks of linac are bypassed in this modemost interlocks of linac are bypassed in this mode– Linac MAY NOT terminate the radiation if errors in Linac MAY NOT terminate the radiation if errors in

Radiation output or if mechanical movements of Radiation output or if mechanical movements of target, foils or filters failtarget, foils or filters fail



Case Study VIICase Study VII• Sequence Sequence

– Linac was made to work on PHYSICAL Linac was made to work on PHYSICAL mode by the electronics engineer on mode by the electronics engineer on instruction from Radiation Oncologistinstruction from Radiation Oncologist

– Output was measured with the help of Output was measured with the help of Technologist in PHYSICAL modeTechnologist in PHYSICAL mode

– Instruction on how to operate in Physical Instruction on how to operate in Physical mode was provided by the engineer and mode was provided by the engineer and observed the first two treatmentsobserved the first two treatments



Case Study VIICase Study VII• Thirteen patients were treated with no problems Thirteen patients were treated with no problems

and the last patient was on 10 MeV electronsand the last patient was on 10 MeV electrons• Next patient was set for treatment with 20MV x Next patient was set for treatment with 20MV x

rays, dose rate 300MU/min, The treatment rays, dose rate 300MU/min, The treatment started but terminated after 21s and only a few started but terminated after 21s and only a few monitor units were deliveredmonitor units were delivered

• When the patient was removed from the room When the patient was removed from the room the radiographer noted skin reaction on the the radiographer noted skin reaction on the patient, which indicated a high degree of patient, which indicated a high degree of overexposure overexposure



Case Study VII – contributing factorsCase Study VII – contributing factors• On investigation it was found that there On investigation it was found that there

was extremely high dose at the center of was extremely high dose at the center of the field caused by the failure to deploy, the field caused by the failure to deploy, X-ray target, flattening filter and monitor X-ray target, flattening filter and monitor chamber.chamber.

• Cause: Operation in PHYSICAL mode Cause: Operation in PHYSICAL mode disabled the interlocks that could have disabled the interlocks that could have detected this dangerous conditiondetected this dangerous condition


Mishandling of equipment failureMishandling of equipment failureCase Study VIIICase Study VIII

• Incident: The linac delivered 36MeV electrons Incident: The linac delivered 36MeV electrons regardless of the energy selected on the consoleregardless of the energy selected on the console

• Sequence:Sequence:– Linear accelerator failed to produce electron Linear accelerator failed to produce electron

beamsbeams– Fault was attended by an maintenance technicianFault was attended by an maintenance technician– After the repair the analog display permanently After the repair the analog display permanently

displayed 36MeV regardless of energy selecteddisplayed 36MeV regardless of energy selected


Mishandling of equipment failureMishandling of equipment failureCase Study VIII– Consequence Case Study VIII– Consequence

27 patients were treated over a period of ten 27 patients were treated over a period of ten days till the physicians began to correlate days till the physicians began to correlate poor tolerance and severe reactions poor tolerance and severe reactions observed in some patients with mall function observed in some patients with mall function of the machineof the machine


Mishandling of equipment failureMishandling of equipment failureCase Study VIII– contributing factorCase Study VIII– contributing factor

• Failure to select electron beam was due to a Failure to select electron beam was due to a short circuit of the system that selects the short circuit of the system that selects the trajectory of the electron beamtrajectory of the electron beam

• Ineffective communication – physicists were Ineffective communication – physicists were not notified immediately about the malfunctionnot notified immediately about the malfunction

• Incorrect interpretation of conflicting signals; Incorrect interpretation of conflicting signals; the analog meter showing 36MeV was the analog meter showing 36MeV was ignoredignored


Possible causes for Radiation Accidents Possible causes for Radiation Accidents in Brachytherapyin Brachytherapy

• Improper calibration of Activity of the Improper calibration of Activity of the brachytherapy sourcebrachytherapy 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 Insufficient knowledge about the planning

system algorithmsystem algorithm• Mechanical failure or malfunction of Mechanical failure or malfunction of

brachytherapy equipmentbrachytherapy equipment


Error in activity reportingError in activity reporting Case Study I Case Study I

• Incident: Error in units of reporting the activity for Incident: Error in units of reporting the activity for brachytherpay ribbonsbrachytherpay ribbons

• Sequence:Sequence:– The licensee ordered brachytherapy ribbons containing The licensee ordered brachytherapy ribbons containing

0.79 millicurie per ribbon0.79 millicurie per ribbon– However, the vendor delivered brachytherapy ribbons However, the vendor delivered brachytherapy ribbons

containing 0.79 milligrams radium equivalent (1.36 containing 0.79 milligrams radium equivalent (1.36 millicurie) per ribbon.millicurie) per ribbon.

– the prescription order was checked against what was the prescription order was checked against what was received and noted that the quantities (0.79) matched, received and noted that the quantities (0.79) matched, but failed to note that the amount received was measured but failed to note that the amount received was measured in milligrams radium equivalent rather than the requested in milligrams radium equivalent rather than the requested millicurie unitsmillicurie units


Error in activity reportingError in activity reporting Case Study I –Consequence & Action Case Study I –Consequence & Action

takentaken• Consequence: Consequence:

The radiation dose to the patient's prostate The radiation dose to the patient's prostate gland was 5,669 rads (56.69Gy) rather than gland was 5,669 rads (56.69Gy) rather than the prescribed 3,258 (32.58Gy) radsthe prescribed 3,258 (32.58Gy) rads

• Action Taken:Action Taken:– The referring physician was notified and The referring physician was notified and

chose not to inform the patient. The patient chose not to inform the patient. The patient was examined during subsequent follow‑up was examined during subsequent follow‑up visits and has shown no adverse effects due visits and has shown no adverse effects due to the increased radiation exposure. to the increased radiation exposure.


Case Study I -Cause and lessons learntCase Study I -Cause and lessons learnt

• Reason for the Incident: Reason for the Incident: – Failure of the staff to perform adequate Failure of the staff to perform adequate

verification of source strengths prior to implanting verification of source strengths prior to implanting the brachytherapy sources.the brachytherapy sources.

– Miscommunication between the licensee and the Miscommunication between the licensee and the vendor also appears to have contributed to the vendor also appears to have contributed to the error.error.

• Lessons learnt: Lessons learnt: – To ensure that units of measurement received To ensure that units of measurement received

correspond to that was ordered source strengths correspond to that was ordered source strengths should be verified by direct measurement prior to should be verified by direct measurement prior to implantation.implantation.

•


Incident with HDR after-loading unit.Incident with HDR after-loading unit. Case Study II- Case Study II-

Incident: A patient was treated for anal Incident: A patient was treated for anal carcinoma with High Dose Rate (HDR) after carcinoma with High Dose Rate (HDR) after loading Brachytherapy unit and the patient loading Brachytherapy unit and the patient died on November 21, 1992.died on November 21, 1992.

• HDR treatment with 4.3 Ci of Iridium‑192 HDR treatment with 4.3 Ci of Iridium‑192 source was placed at various positions in each source was placed at various positions in each of the five catheters that were to remain in the of the five catheters that were to remain in the patient for subsequent treatments.patient for subsequent treatments.

• The staff experienced difficulty with source The staff experienced difficulty with source placement in one of the patient's five placement in one of the patient's five treatment catheters. treatment catheters.


Incident with HDR after-loading unit.Incident with HDR after-loading unit. Case Study II- Sequence of events Case Study II- Sequence of events

• They were unaware that a short piece of the They were unaware that a short piece of the cable containing the Iridium source had broken cable containing the Iridium source had broken off and remained in one of the catheters in the off and remained in one of the catheters in the patient. The patient was transported to a patient. The patient was transported to a nearby nursing home. The source remained in nearby nursing home. The source remained in the patient's body for four days when the the patient's body for four days when the catheter fell out.catheter fell out.

• It was placed in a medical biohazard bag (red It was placed in a medical biohazard bag (red bag) in a storage room by nursing home bag) in a storage room by nursing home personnel who did not know it contained the personnel who did not know it contained the radioactive sourceradioactive source


Incident with HDR after-loading unit.Incident with HDR after-loading unit. Case Study II- Cause Case Study II- Cause

• Cause: Cause: – Although a wall‑mounted area monitor Although a wall‑mounted area monitor

alarmed at various times when the source alarmed at various times when the source should have been retracted, the licensee's should have been retracted, the licensee's staff did not conduct a survey for radiation staff did not conduct a survey for radiation levels with the available portable radiation levels with the available portable radiation survey instrument. survey instrument.

– The only action taken was to check the The only action taken was to check the control console of the HDR remote control console of the HDR remote afterloader which gave a false indication afterloader which gave a false indication that the source was "safe“.that the source was "safe“.



The Incident Investigation Team (IIT) reported that The Incident Investigation Team (IIT) reported that the event was caused by the following:the event was caused by the following:

1.1. Weaknesses in their radiation safety programWeaknesses in their radiation safety program

2.2. Inadequate radiation safety training to the staff.Inadequate radiation safety training to the staff.

3.3. A number of weaknesses were found in the A number of weaknesses were found in the design and testing of the unit.design and testing of the unit.– Weaknesses were identified in the testing Weaknesses were identified in the testing

and validation of source‑wire design, and in and validation of source‑wire design, and in the design of certain safety features of the the design of certain safety features of the HDR afterloader.HDR afterloader.



• The safety culture contributed significantly to The safety culture contributed significantly to the event. the event. – Technologists routinely ignored the Technologists routinely ignored the

PrimAlert‑10 alarm. Its problems were PrimAlert‑10 alarm. Its problems were worked around and not fixed.worked around and not fixed.

– Technologists did not survey patients, the Technologists did not survey patients, the afterloader, or the treatment room following afterloader, or the treatment room following HDR treatments. HDR treatments.

– The authorized user failed to wear a film The authorized user failed to wear a film badge on both occasions when the source badge on both occasions when the source was encountered;was encountered;


The cause of death of the patient was reported The cause of death of the patient was reported as "Acute Radiation Exposure and as "Acute Radiation Exposure and Consequences Thereof." Consequences Thereof."

Until the source was recovered after the Until the source was recovered after the patient's death, it subjected nursing home patient's death, it subjected nursing home residents and staff, as well as visitors, to residents and staff, as well as visitors, to radiation exposure. radiation exposure.

Radiation doses to the 94 individuals associated Radiation doses to the 94 individuals associated with the event ranged from 40 mrem to 22 rem.with the event ranged from 40 mrem to 22 rem.

• Numerous residents, employees, and visitors to Numerous residents, employees, and visitors to the nursing home were unknowingly irradiated. the nursing home were unknowingly irradiated.

Incident with HDR after loading unit.Incident with HDR after loading unit. Case Study II- Consequence Case Study II- Consequence


Misadministration of the sourceMisadministration of the sourceCase Study IIICase Study III

Incident: Incident: A routine x‑ray identified that A routine x‑ray identified that the seeds were no longer implantedthe seeds were no longer implanted

Sequence of events: Sequence of events: – During a brachytherapy implant During a brachytherapy implant

procedure, two ribbons, each containing procedure, two ribbons, each containing six Ir‑192 seeds, with a total activity of six Ir‑192 seeds, with a total activity of 48.25 mCi, were implanted into two 48.25 mCi, were implanted into two catheters inserted into the patient's catheters inserted into the patient's common bile duct, through an abdominal common bile duct, through an abdominal incision. incision.


Misadministration of the sourceMisadministration of the sourceCase Study III – sequence of eventsCase Study III – sequence of events

During the night shift, the patient's dressings During the night shift, the patient's dressings on the wound were wet and loose. A licensed on the wound were wet and loose. A licensed practical nurse (LPN), who responded to the practical nurse (LPN), who responded to the patient, found the Ir‑192 ribbons dislodged patient, found the Ir‑192 ribbons dislodged and lying loose on the patient's abdomen. and lying loose on the patient's abdomen.

The LPN, not realizing that it was radioactive, The LPN, not realizing that it was radioactive, changed the patient's dressing and bed, and changed the patient's dressing and bed, and coiled each Ir‑192 ribbon around her hand coiled each Ir‑192 ribbon around her hand and taped them to the patient's abdomen. and taped them to the patient's abdomen.


Misadministration of the sourceMisadministration of the sourceCase Study III - ConsequenceCase Study III - Consequence

• The oncologist had left verbal orders The oncologist had left verbal orders with the day shift charge nurse "not to with the day shift charge nurse "not to change the dressing" but these orders change the dressing" but these orders were not passed on to the LPN..were not passed on to the LPN..

• The patient's abdominal skin received The patient's abdominal skin received an unnecessary exposure over various an unnecessary exposure over various areas ranging from 172 rad to 1032 rad. areas ranging from 172 rad to 1032 rad. The skin exposure to the hand of the The skin exposure to the hand of the LPN was 7.6 radLPN was 7.6 rad


Misadministration of the sourceMisadministration of the sourceCase Study III - CauseCase Study III - Cause

1.1. Lack of oversight of the procedure by Lack of oversight of the procedure by the licensee's Radiation Health and the licensee's Radiation Health and Safety Officer; and Safety Officer; and

2.2. Inadequate training of the nursing staff Inadequate training of the nursing staff in that they were unable to identify the in that they were unable to identify the brachytherapy ribbon and handle them brachytherapy ribbon and handle them appropriately if, and when, they appropriately if, and when, they become dislodged.become dislodged.

•


Misadministration of the sourceMisadministration of the sourceCase Study III – Action Taken & lessons Case Study III – Action Taken & lessons

learntlearnt1.1. Familiarization of personnel with the size and Familiarization of personnel with the size and

appearance of the radioactive sources used in appearance of the radioactive sources used in brachytherapy treatments at the licensee's brachytherapy treatments at the licensee's facility;facility;

2.2. Naming a new RHSO who could devote sufficient Naming a new RHSO who could devote sufficient time to the radiation safety program;time to the radiation safety program;

3.3. Developing a nurses' procedure manual;Developing a nurses' procedure manual;

4.4. Conducting formal in-service training in radiation Conducting formal in-service training in radiation safety with all nursing unit workers; andsafety with all nursing unit workers; and

5.5. Requiring a written directive be initiated before Requiring a written directive be initiated before ordering radioactive material.ordering radioactive material.


Summary – Potential accidents in Summary – Potential accidents in External Beam TherapyExternal Beam Therapy

• Possible errors in CalibrationPossible errors in Calibration– Incorrect calibration of the teletherapy unitIncorrect calibration of the teletherapy unit– Use of wrong decay chart for output of Use of wrong decay chart for output of

cobalt unit.cobalt unit.– Not updating the output chart after source Not updating the output chart after source

changechange– Lack of communication regarding units and Lack of communication regarding units and

depth of calibration. (e.g. Ddepth of calibration. (e.g. Dmax max or 5cm) or 5cm)



• Possible errors in Treatment PlanningPossible errors in Treatment Planning– Incorrect input data of Depth dose or Incorrect input data of Depth dose or

Tissue maximum ratioTissue maximum ratio– Multiple correction for use of wedge filter or Multiple correction for use of wedge filter or

compensators. compensators. – Miss application of distance correction.Miss application of distance correction.– Miss understanding the algorithmMiss understanding the algorithm– Incorrect hand calculation and inadequate Incorrect hand calculation and inadequate

training and QA proceduretraining and QA procedure



• Potential accidents due to machine malfunctionPotential accidents due to machine malfunction– Improper accessory mountingImproper accessory mounting– Use of Linear accelerator in Physical modeUse of Linear accelerator in Physical mode– Mishandling of the machine malfunctionMishandling of the machine malfunction– Inadequate training for serving personnelInadequate training for serving personnel– Improper documentation of polices and procedures for Improper documentation of polices and procedures for

use & servicing of the machineuse & servicing of the machine– Inadequate routine QA procedures for teletherapy Inadequate routine QA procedures for teletherapy

unitsunits


Summary – Potential accidents in Summary – Potential accidents in BrachytherapyBrachytherapy

• Improper calibration of the source activityImproper calibration of the source activity• Improper identification of source Improper identification of source • Inadequate routine QA for source integrity Inadequate routine QA for source integrity

checkcheck• Inadequate source movement documentationInadequate source movement documentation• Incorrect use of treatment planning systemIncorrect use of treatment planning system• Insufficient understanding of the Algorithm of Insufficient understanding of the Algorithm of

the planning systemthe planning system


Summary – Potential accidents in Summary – Potential accidents in BrachytherapyBrachytherapy

• Inadequate routine QA procedure for Remote Inadequate routine QA procedure for Remote after loading unitafter loading unit

• Improper and inadequate training of personal Improper and inadequate training of personal on radiation protection aspectson radiation protection aspects

• Insufficient documentation of policies and Insufficient documentation of policies and procedures for handling emergenciesprocedures for handling emergencies

• Use of faulty zone monitors and survey Use of faulty zone monitors and survey metersmeters


ReferencesReferences

• ‘‘Lessons Learned from accidental exposures in Radiation Lessons Learned from accidental exposures in Radiation Therapy’ Therapy’ – IAEA publication Safety Report Series No 17IAEA publication Safety Report Series No 17

• ‘‘Prevention of Accidental Exposures to Patients Prevention of Accidental Exposures to Patients undergoing Radiation Therapy’undergoing Radiation Therapy’– Annals of the ICRP Publication No 86Annals of the ICRP Publication No 86

• Basic Safety Standards Basic Safety Standards – Safety series No 115 IAEA publicationSafety series No 115 IAEA publication

• Investigation of an accidental exposure of Radiotherapy Investigation of an accidental exposure of Radiotherapy patients in Panamapatients in Panama– Report of a team of experts (IAEA publication 26 May-1June 2001)Report of a team of experts (IAEA publication 26 May-1June 2001)

Part VIII:Medical Exposures in Radiotherapy Accidental Medical Exposure & lessons learnt Lecture 11...

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Transcript of Part VIII:Medical Exposures in Radiotherapy Accidental Medical Exposure & lessons learnt Lecture 11...