This document discusses occupational radiation safety in radiotherapy. It outlines potential radiation hazards from teletherapy equipment like telecobalt units and linear accelerators, as well as brachytherapy sources. Case studies of accidents are presented to illustrate hazards that can occur from equipment malfunctions, improper safety procedures, and lack of regulatory oversight. The document recommends strict adherence to safety guidelines and regulatory standards to minimize risks and ensure occupational exposures are kept as low as reasonably achievable. Regular equipment maintenance, staff training, and quality assurance are emphasized.

1. OCCUPATIONAL RADIATION SAFETY IN
RADIOTHERAPY
DEPARTMENT OF RADIOTHERAPY
CHRISTIAN MEDICAL COLLEGE, VELLORE
Timothy Peace S

2. PRESENTATION OUTLINE
• INTRODUCTION
• POTENTIAL AREAS OF RADIATION HAZARDS IN RT
• TELETHERAPY
– TELECOBALT
– MEDICAL LINEAR ACCELERATOR
• BRACHYTHERAPY
• GENERAL RADIATION SAFETY MEASURES
• RECOMMENDATIONS

3. INTRODUCTION
• Radiation therapy aims to
– Destroy the cancer
– using gamma rays, high-energy x-rays
electrons, protons and heavy ions
– generated from radioisotopes, medical
linear accelerators and synchrotrons
• Double-edged sword
– The cancer destroying radiation can also
destroy normal cells
– Deterministic effects
• Gastrointestinal syndrome, CNS
syndrome, cataract, pneumonitis, sterility,
erythema, alopecia, cataract
– Stochastic effects
• Radiation carcinogenesis and genetic
effects

4. POTENTIAL AREAS OF RADIATION HAZARDS IN RT
• Teletherapy
– Telecobalt treatment unit (1.25 MeV, gamma photons)
– Medical linear accelerator (6 & 15 MV high energy x-ray photons),
electrons ranging from 4-21 MeV and neutrons arising from linear accelerators
delivering more than 10 MV x-ray photons)
• Brachytherapy
– Pre-loaded system
– Manual after-loading system (only low dose rate brachytherapy)
– Remote after-loading system (also high dose rate brachytherapy)
• Simulator
– Diagnostic x-ray-based simulator unit

5. * The whole body dose limit is 20 mSv a year when averaged
over 5 years with a maximum of 30 mSv in any one year (AERB)
Source: International Commission on Radiological Protection 26
Tissue or Organ Radiation Worker Member of Public
Whole of body 20* mSv /yr 1 mSv /yr
Lens of eye 150 mSv /yr 15 mSv /yr
Skin 500 mSv/yr 50 mSv /yr
Hands and feet 500 mSv /yr 50 mSv /yr
Pregnancy once
declared
2 mSv to lower
trunk
(1 mSv to foetus)
Foetus is
considered to be
member of public
ANNUAL DOSE LIMITS

6. TELETHERAPY TELECOBALT UNIT
• Potential Hazard 1: Source stuck
during treatment
– Emergency situation when the
Cobalt-60 source gets stuck in
between the “off” and “on” position
– Potential Occupational Exposure:
The radiographer has to enter the
treatment room to push the source
back
• Steps for minimizing exposure:
• Ask the patient (via intercom) to come out
– If not possible, enter from maze wall side (TLD badge
must be worn)
– Rotate gantry to side opposite to maze wall
– Insert “T-rod” and push it till the source reaches “safe”
position

7. TELETHERAPY TELECOBALT UNIT
Potential Hazard 2: Telecobalt Source transfer
– Replacement of Co-60 source
• Removal of old source
• Insertion of new source
– Occupational exposure during transfer
• Steps for minimizing exposure:
– Plan the procedure, minimize time and limit personnel
– Wear TLD badge and pocket dosimeter
– Monitor dose level using survey meter
Aligned with the machine head, “T-rod “used to exchange the source drawers

8. TELETHERAPY TELECOBALT UNIT
Potential Hazard 3: Dismantling without Decommissioning
– The telecobalt unit is dismantled or scrapped without
decommissioning the unit (AERB-approved procedure for
removal and disposal of source)
Case Study: Goiânia, Brazil
• 1985: Private radiotherapy clinic
closed down
• 1375 Ci – Cs -137 teletherapy
machine abandoned
• 1987: teletherapy head stolen
• Unit dismantled, source capsule
ruptured causing major
contamination
• 249 people contaminated
• 0.1 - 6.2 Gy (6200 mSv)
• Permissible limit: 1 mSv for public
• 4 people died

9. CASE STUDY: SAMUT PRAKARN,THAILAND
• October 1999: 3 disused teletherapy
sources stored by a private company
at unsecured parking lot
• Jan/Feb 2000: unauthorized removal
of one unit - dismantled for scrap
• 425 Ci - cobalt-60 source unshielded
• 10 people highly exposed
• 3 of whom died
Steps for avoiding this radiation disaster:
• Proper decommissioning procedure
• Proper removal of source
• Survey, contamination check & documentation
• Disposal of source
• Each step approved by regulatory body

10. TELETHERAPY – MEDICAL LINEAR ACCELERATOR
• The linear accelerator does not consist of a radioactive
source and hence poses a lesser radiation hazard
• It generates high energy electrons (4-21 MeV) and x-rays
(6-15MV)
• Potential hazard: Personnel entering the room when the
radiation is „on‟ can potentially receive lifetime dose in a
single exposure
• Case study: St Teresa’s Hospital (STH), Hong Kong
– Two physicists performed quality assurance check on a medical
linac
– discovered the accidental presence of a female ward assistant
– through the room's CCTV
– As for the affected female staff received 70 Sv (very low)

11. TELETHERAPY –LINEAR ACCELERATOR
• Case study: Industrial Accelerator
– 15 MV food irradiation facility in Hanoi.
– An individual entered the irradiation room without the operators‟
knowledge
– unwittingly exposed his hands to the x-ray beam.
– The individual received doses
• 10 - 25,000 mSv to the left hand
• 20 - 50,000 mSv to the right hand.
– Within one month one hand had to be amputated as well as the
fingers on the other hand.
• Simple steps that could have avoided these unnecessary
exposures
– Console to face treatment room door
– Door interlock
– “Last man out” switch
– Check CCTV before starting exposure
Limit for hand: 500 mSv

12. BRACHYTHERAPY
• Method of treatment in which the
sealed radioactive sources are
used to deliver high radiation at
short distance
• Pre-loading or “Hot” loading
– Radioactive sources loaded in the
applicators which are then inserted
into the patient
– High occupational dose to
personnel
– Dr Cyril Jayachandran developed
a remote-controlled trolley to
transfer the source to the „radium
theater‟
– Now an obsolete technique
– Replaced by manual and remote
afterloading systems

13. BRACHYTHERAPY - MANUAL AFTERLOADING
• Case study from another country:
Mishandling of source ribbons
– Patient scheduled for endobronchial
implant
• Ir 192 seeds: Activity- 2516 MBq.
– Staff mistakenly gave the attending
physician the inactive end of source
ribbon who inserted it into patient.
– Staff, assumed pieces of ribbon
contained no radioactive material,
coiled them and held them in her
hands.
– Dose to the staff‟s hand
• ~2.7 Gy (~2700 mSv – Allowed
500 mSv),

14. HDR BRACHYTHERAPY
• Case study from another country: Malfunction
of high dose rate equipment
– Patient was to be treated with a HDR
containing 159 GBq of Ir192
– The source wire had been broken and the
source had remained in the patient.
– Personnel disregarded the alarm from an area
radiation monitor because the unit console
indicated 'safe'.
– The source remained in the patient for
almost four days and the patient received
16,000 Gy at 1cm (Prescription: 18 Gy)
– The patient died shortly after removal of the
source
– The loss of the source resulted in radiation
exposure to 94 individuals
• Persons at the cancer clinic and the
nursing home,
• Ambulance staff and workers at the waste
disposal company

15. GENERAL RADIATION SAFETY MEASURES
• Area Monitor
– Gamma zone monitor for telecobalt
and brachytherapy installations
• Personnel Monitoring
– TLD, pocket dosimeters
– OSLD
• Audio-visual system
• Door interlocks

16. GENERAL RADIATION SAFETY MEASURES
• “Last man out” switch
– First in India (2005)
• Emergency Buttons
• Radiation warning symbols

17. SURVEY OF HDR ROOM AND UNIT

18. DISCUSSION
• History shows that accidents rarely occur due to a single
equipment failure or a single human error. In most accident
cases there was a combination of elements such as:
– a) no prior safety assessment
– b) poor education and lack of training, especially when faced
with an unusual situation,
– c) management pressure (real or perceived) to continue work
even when safety systems were inoperable or deficient,
– d) poor maintenance programme or none at all, leading to a
reduction in layers of safety, and non-investigated false
alarms leading to persons ignoring warning systems.

19. RECOMMENDATIONS
• Each radiation professional in RT must cooperate with the Radiation
Safety Officer to ensure
– Effective organisation of all radiotherapy practice
– Education, training and awareness
– Communication
– Follow-up of equipment faults
– Frequent Quality assurance
– General radiation safety measures (Area and personnel monitoring,
routine survey, audio-visual system, safety interlocks and warning symbols)
– AERB guidelines must be followed for installation, commissioning and
decommissioning of radiotherapy equipment
– AERB approved procedure for procurement, replacement and
disposal of sources
– This will enable each radiation worker to handle radiation in a safe
environment and limit the occupational exposure to “As Low as
Reasonably Achievable - ALARA”

20. ACKNOWLEDGEMENTS
• Dr I Rabi Raja Singh, Radiation Safety Officer, CMC, Vellore
• Mr Jose Solomon Raj, Medical Physics Intern
• Mr Mohamathu Rafic, Lecturer in Medical Physics