Some case history of accidents in Rt (ICRP- report) and Consequences of radiation exposure.

1. ACCIDENTS IN RADIOTHERAPY
NILESH KUMAR
PG RADIATION PHYSICS
DEPARTMENT OF RADIATION PHYSICS

2.  INTRODUCTION
• Radiotherapy is concerned primarily with tumour cure or palliation.
• Modern radiotherapy has three major concerns: efficacy, quality of life, and
safety .
• It is always necessary to be aware of the potential for an accident, the
relative importance of human factors, and the wider consequences of an
accident.
• A radiation accident is an unintended event (operator error, equipment
failure, or other mishap) that has or may have adverse consequences.

3.  Errors in RT: Contributing Factors
• Insufficient education
• Lack of procedures/protocols as part of comprehensive QA program
• Lack of supervision of compliance with QA program
• Lack of training for “unusual” situations
• Lack of a “safety culture”
 Sources of Uncertainties
• During Treatment
• Machine performance
• Determination of dose from radiation
• Patient specific data for treatment planning
• Calculation of radiation dose to the patient
• Transfer of data from the treatment plan to the treatment machine
• Day to day variations in the treatment (machine/patient motion/set up)

4.  Accidents can be divided into three major groups:
I. members of the general public irradiated as a result of failure of
implementation of radiation protection and safety rules.
II. clinical staff irradiated during preparation of radiation sources or patient
treatment and maintenance staff irradiated during installation, repairs,
source change, or other equipment servicing.
III. patients injured during treatment.

5.  CASE HISTORIES OF RADIATION ACCIDENTS-

6.  Panama Radiation Accident
• The National Oncologic Institute or ION is a specialized hospital for cancer
treatment, located in Panama City, Panama.
• Between August 2000 and March 2001, patients receiving radiation treatment
for prostate cancer and cancer of the cervix received lethal doses of radiation,
resulting in eight fatalities
• As in most radiotherapy departments, the one at ION uses a treatment
planning system (TPS) to calculate the resulting dose distributions and
determine treatment times.

7. • The data for each shielding block should be entered into the TPS separately.
• The TPS allows a maximum of four shielding blocks per field to be taken into
account when calculating treatment times and dose distributions.
• Shielding blocks are used to protect healthy tissue of patients undergoing
radiotherapy at the Institute, as is the normal practice.
• In order to satisfy the request of a radiation oncologist to include five blocks in
the field, in August 2000 the method of digitizing shielding blocks was changed.
• It was found that it was possible to enter data into the TPS for multiple
shielding blocks together as if they were a single block, thereby apparently
overcoming the limitation of four blocks per field

8. • As was found later, although the TPS accepted entry of the data for multiple
shielding blocks as if they were a single block, at least one of the ways in
which the data were entered the computer output indicated a treatment time
substantially longer than it should have been.
• The result was that patients received a proportionately higher dose than that
prescribed. The modified treatment protocol was used for 28 patients, who
were treated between August 2000 and March 2001 for prostate cancer and
cancer of the cervix. There were eight deaths and 20 injuries.
• The modified protocol was used without a verification test, i.e. a manual
calculation of the treatment time for comparison with the computer
calculated treatment time, or a simulation of treatment by irradiating a water
phantomand measuring the dose delivered.

9. • In spite of the treatment times being about twice those required for correct
treatment, the error went unnoticed.
• Some early symptoms of excessive exposure were noted in some of the
irradiated patients.
• The seriousness, however, was not realized, with the consequence that the
accidental exposure went unnoticed for a number of months.
• The continued emergence of these symptoms, however, eventually led to
the accidental exposure being detected in March 2001.

10. • In May 2001, the Government of Panama requested assistance under the
terms of the Convention on Assistance in the Case of a Nuclear Accident or
Radiological Emergency.
• In its response, the International Atomic Energy Agency (IAEA) sent a team of
five medical doctors and two physicists to Panama to perform a dosimetric
and medical assessment of the accidental exposure and a medical evaluation
of the affected patients’ prognosis and treatment.
• The team was complemented by a physicist from the Pan American Health
Organization (PAHO), also at the request of the Government of Panama.

11. • The accidental exposures at the ION in Panama were very serious. Many
patients have suffered severe radiation effects due to excessive dose. Both
morbidity and mortality have increased significantly.
• The IAEA report was consistent with the report made by local investigators.
• It was found that the radiotherapy equipment was properly calibrated and
worked properly.
• The error was on the data entry, using a protocol not validated to enter more
shielding blocks, that resulted in increased dose in the treatment.
• Most of the exposed patients have died, some radiation related, others by
means of their advanced cancer.
• The Government of Panama agreed to share urgently the conclusions of the
report to help prevent similar accidents. The physicists of ION involved were
taken to trial by the patients' families

12.  Malfunction Of Brachytherapy High Dose Rate Equipment (USA, 1992)
• A patient was to be treated using a high dose rate (HDR) brachytherapy unit
equipped with a 4.3 Ci 192-Ir source.
• The prescribed dose was 18 Gy in three fractions. Five catheters were placed in
the tumor and the source was to be stepped through the pre-programmed
positions in each catheter.
• During the first fraction the radiation oncologist experienced difficulties in
positioning the source into the fifth catheter and decided to retract the source.
• The source became detached from the driving mechanism while still inside the
patient.

13. • The staff disregarded an alarm from an external area radiation monitor
because the console of the brachytherapy unit indicated ‘safe’.
• All three technologists and one physician who were attending the patient
were aware of the alarm condition but none of them conducted a survey with
the available portable radiation survey instrument.
• The patient, with the source still in the catheter, was transported back to the
nursing home.
• The source remained inside the patient for almost four days, until the catheter
containing the source fell out.
• The patient received a dose of 16,000 Gy at 1 cm distance from the source,
instead of the prescribed 18 Gy.

14. • The nursing home staff disposed of the catheter in an area used to store non-
radioactive medical waste and was removed later by an incinerator company. (
A type of company which used a kind of an apparatus for burning waste material, especially
industrial waste, at high temperatures until it is reduced to ash.)
• The source was discovered when it tripped a radiation monitor located at the
incinerator.
• The patient died shortly after the source was dislodged. The overexposure
was the major contributing cause of death.
• The lost source also caused radiation exposure to 94 other individuals,
including persons at the cancer clinic, nursing home, ambulance staff, and
workers at the waste-disposal company.

15. • A similar accident in another hospital was subsequently avoided because
the medical physicist was aware of the first case and immediately
recognized the problem.
• This is the importance of incident reporting and dissemination of the
lessons learned.

16.  October 2011 –
• At a hospital in Rio de Janeiro, a 7-year-old girl was treated for acute lymphoblastic
leukemia with whole brain radiation.
• The prescriptions were done manually in a form with no formal evaluation of work
is done.
• Because of an error in the registration of the number of sessions, she received the
full dose in each session of radiotherapy.
• Even with early toxicity, the doctor refused to assess the patient, because some of
the complaints were usual.
• The full treatment was finished in about 8 sessions and the girl was admitted with
radiation burns.
• She developed frontal lobe necrosis. and died in June 2012. After an investigation,
the physicist, technician, and physician were charged with murder.

17.  Consequences of accidental exposures in radiotherapy
• The consequences of accidental exposures can be categorised into three
types:-
1. impact on local tumour control rate.
2. early (or acute) complications.
3. late (or chronic) complications.

18.  Impact on local tumour control rate.
• In the case of an accidental over dosage, the tumour control probability
may increase.
• But it’s overdose to normal tissues, leading to death or to a severely
reduced quality of life.
• The tumour control probability (TCP) is a formalism derived to compare
various treatment regimens of radiation therapy, defined as the
probability that given a prescribed dose of radiation, a tumour has been
eradicated or controlled.

19.  Early (or acute) complications
• Acute complications are early deterministic effects (effects due to cell killing).
• They are dose related and have a threshold (i.e., below a certain dose they are
not seen).
• These effects are usually observed in tissues or organs with rapid cell turnover
rates (e.g., skin, mucosa, and bone marrow).
• These complications are observed within days or weeks after irradiation.
• They are often transient ( short-time) .

20.  Late (chronic) complications
• These late effects are mainly observed in tissues or organs with slowly
proliferating cells.
• They can also be seen in organs with rapidly proliferating cells, a consequence
of very severe acute reactions.
• These late complications usually occur more than six months after the end of
irradiation, but can be observed much later (several years).
• They are usually considered as irreversible, and are often slowly progressive.

21.  CAUSES OF AND FACTORS CONTRIBUTING TO ACCIDENTAL EXPOSURES IN
RADIOTHERAPY
 Equipment problems
 Maintenance
 Beam calibration
 Treatment planning systems
 Treatment simulation
 Treatment set-up and delivery
 In Brachytherapy
 Source preparation
 Source removal

24.  CONCLUSION
• Safety is not to be considered in isolation or as a separate chapter of the
radiotherapy syllabus for education of professionals.
• Rather, safety should be incorporated in all steps of management of
radiotherapy, so that an integrated quality management system involves both
quality and safety.
• In fact, most of the control measures to monitor quality serve to detect any
deviation concerning safety as well, since the parameters to be controlled are
often the same.
• The quality control programmes and frequency of the constancy checked can
be designed to combine both objectives (quality and safety).
• Test tools exist nowadays to make more frequent relative measurements as
constancy checks, which monitor quality and safety at the same time.

25. • THANK YOU
REFERENCES-: