original studies
Radiological Incident in the Radiotherapy Department.
Presentation and Actions of Intervention
Mihaela Dumitru1, Laura Rebegea1,2, Dorel Firescu2,3
1) 1 „Sf.Ap.Andrei” Emergency Clinical Hospital; 2) „Dunarea de Jos” University of Galati, Faculty of Medicine,
Clinic Department; 3) „Sf. Ap. Andrei” Emergency Clinical Hospital, Galati, Surgery Clinic II, Galati Romania
This paper presents a radiological incident which occurred with the radiotherapy equipment, Theratron Elite 100 from the Radiotherapy Department
- Emergency Clinical Hospital „Sf. Ap. Andrei”, Galati at the beginning of February 2009 and describes the actions of subsequent intervention. The
radiological incident concerned the framework which lies in a 180° position, under the treatment table, which prevented the possibility of manually
returning to the source using the T-bar, a problem which is not mentioned in the operator’s manual of the radiotherapy unit. The radiological incident
consisted of a radioactive source blocking in the TRANSIT position between BEAM OFF and BEAM ON positions at the start of treatment. We want
to state that all personnel - physicians, physicists, operators and service staff acted with professionalism and promptitude, conforming to emergency
procedures and and regulations. After this incident the Radiotherapy Department’s Emergency Plan was modified and updated including the emergency
procedures described in this paper; the night shift was removed from the Radiotherapy Department’s work program. Also, we want to mention that
misinformation and confusion regarding this incident must be avoided in order not to raise false alarms with other hospital staff and the public.
Keywords: radiological incident, radioactive source, emergency procedure
Introduction
The radiological incident description that occurred in
the Radiotherapy Department of the Emergency Clinical
Hospital „Sf. Ap. Andrei”, Galati, February, 2009 was a
unique situation concerning the framework which lies in a
180° position, under the treatment table, which prevented
the possibility of manually returning to the source using the
T-bar. The present paper aims to demonstrate the exposure
danger for occupational personnel who did act conforming
to emergency procedures from the Radioprotection Program
but we also would like to state that neither the public or
the environment was affected by this incident. Also under
discussion is that this situation is not mentioned in the
operator’s manual and public opinion and the press created
very bad media regarding this incident, stating incorrectly
that that there had been a radioactive leakage (we work
with sealed radioactive Co-60 source) in the Radiotherapy
Department and that an explosion had happened which had
hurt other staff from other hospital departments.
Methods and materials
A description of the incident and the actions taken.
This paper presents a radiological incident occurring with
Journal of Radiotheraphy & Medical Oncology
August 2012 Vol. 18 No 1: 18-21
Address for correspondence:
Dr. Laura Rebegea
„Sf.Ap.Andrei” Emergency Clinical
Hospital, Radiotherapy Department
Brailei St. 177, 800830
Galati, Romania
Email: [email protected]
the radiotherapy equipment, Theratron Elite 100 from the
Radiotherapy Department - Emergency Clinical Hospital
„Sf. Ap. Andrei”, Galati at the beginning of February
2009.
In February 2009, 90 patients per day ( both day and also
at the night shift, because of the great number of patients)
were in treatment at one radiotherapy equipment, Theratron
Elite 100,; the other radiotherapy equipment, Rokus M 40
was not functional at that date.
The radiotherapy equipment specifications:
- Name: Theratron Elite 100, SAD=100 cm, SDD=
45cm;
- Radiation source: Co-60 sealed source, activity
of 14000Ci (at November 2002) and dose rate of
102,23cGy/min at the moment of incident.
The radiological incident consisted of the radioactive
source blocking in the TRANSIT position between BEAM
OFF and BEAM ON positions at the start of treatment.
After positioning the patient (an elderly woman) and
fixing the treatment parameters, the operators left the
treatment room, and from the command room started the
treatment. However, the source did not reach the BEAM ON
position but remained blocked in the IN TRANSIT position.
At that moment the unit went into the „inhibited state”, the
automatic collimator closure feature was activated but the
unit power shut off. Under normal circumstances, the source
would have returned to the fully shielded position, but in
our case the source remained exposed.
Emergency procedures (1) for the automatic retreat of the
source (push the emergency button from the command room)
did not have any result. This situation forced the 2 operators
Radiological incident in the radiotherapy department
to open the treatment room door and enter the treatment room
(source situated in the IN TRANSIT position) and evacuate
the patient; this action took no more that 20 seconds. After
the patient’s evacuation, the operators closed the treatment
room door turned off the key switch at the control console
and notified the Radiation Safety Officers.
When they arrived, the Radiation Safety Officers entered
the corridor of the treatment room with a portable survey
meter. The survey meter indicated that the radiation level
had increased and they decided to leave the room.
Afterwards the radiation safety officers measured the
dose rate at different points conforming to Fig. 1. The
recorded values are indicated in Table I.
Conforming to the inverse square distance low
calculation, the dose rate in the exposure room had high
values and staff exposure was not justified (conforming to
specifications from the Operator’s Manual), and the patient
had to be evacuated and the treatment room closed (1). The
distance between the measurement point number 4 and the
position of source was 7.5 meters (Fig. 1).
Figure 1. The location of measuring points for the dose
rate measurement at radiological incident data
19
on the front part of the treatment machine head. The T-bar
has a 50cm length and the maneuver space has a 15 cm
length, Figs 2 and 3.
Fig. 2. Treatment unit’s position at the moment of the source
blocking in the TRANSIT position.
Fig. 1. The numbers in the figure specify the measure points: 1
– treatment unit command console, 2 – access door in treatment
room, 3 – the middle of thecorridor , 4 – the end of corridor , 5
– dosimetry room.
Table I. Dose rate values recorded at the radiological incident date
Measure point*
Dose rate values (µSv/h)
1
0,1
2
0,1
3
2
4
5
5
0,1
* the measure points are specified in fig. 1
Given the head of treatment machine position – under
the treatment table, without sufficient space, the insertion
of the T-bar was IMPOSSIBLE. The T-bar hole is situated
Fig. 3. Irradiation head’s position at the moment of the source
blocking in the TRANSIT position.
In these conditions the radiation safety officers decided to
notify the service unit – accredited Representative of MDS
Nordion whose advice was to not intervene in this danger
situation and to wait the arrival of service personal, to isolate
the controlled zone and limit the staff’s and patient’s access
even in the supervised zone beside the treatment room.
The Radiation Safety Officers notified the Licensee who
decided to wait for the arrival of the service personal. After
that the competent authorities and the medical physics expert
were also notified.
20
Dumitru et al
Since the source remained in the TRANSIT position for
an extended time, the Radiation Safety Officers made sure
that all access to high radiation areas were prevented by
locking doors and appointing knowledgeable staff to prevent
unauthorized entry to these areas.
The service team arrived the next day. They accessed
the service menu of radiotherapy unit (for that they used
a password which is not accessible to the radiotherapy
department’s staff). For 3-4 hours they tried to rotate
the gantry through repeated operations ON-OFF of the
radiotherapy unit and the source returned itself in the fully
shielded position.
Immediately the decision was made to verify carefully
with the radiotherapy installation and to command and
replace the “5-years Kit”.
First off all we have to reiterate that this decision – the
waiting of the service team, after the patient was evacuated,
did not put neither the occupational personnel, nor others
from other departments of hospital, nor the public in danger
because of the following reasons:
- The shielding of treatment room, conforming with IAEA
Reports Standards and Regulations (2), and conforming with
NCRP 49 (3);
- The treatment room walls are 150 cm of concrete with
2.35gm/cc;
- The presence of the corridor with a wall of 100 cm,
concrete with 2.35gm/cc, which attenuated the leakage and
scattered radiation;
- The installation’s particularity – the existing of the
beam-stopper attached on the unit, a massive bloc of lead
which protects almost 99.44% of the primary beam; behind
this beam stopper the level of the dose rate is very low even
during of exposure (Table II), so the public and environment
was not affected during the incident.
■ The treatment installation passed into the INHIBIT
state i.e.:
■ The Collimator closed at the minimum field,
■ Any maneuver of the installation was impossible,
so the unnecessary motions of the treatment table
or of the treatment machine, which could cause
collisions, were impossible.
For the staff who evacuated the patient from treatment
room all measures to estimate the dose were taken; the
electronic dosimeters indicated the following dose rates:
Table II. Comparative dose rate values measured at different points
and at different moments of time
Measure point
Dose rate (mSv/h)
[February 2009*]
Dose rate (mSv/h)
[March 2010**]
Behind beam-stopper at
1.5 m
0.58
0.5
Behind irradiation head on
the collimator axe
2.71
2.35
T – bar insertion’s hole
2.61
2.26
* In February 2009 the reference dose rate was 102.23cGy/min; ** In
March 2010 the reference dose rate was 88.66cGy/min.
30µSv/h and 25µSv/h, respectively, for each operator. The
dosimetric films were immediately sent to the accredited
dosimetric organisation for the staff affected. The values
of the dose equivalent Hp (10) were 300±40µSv and
260±40µSv, respectively for each operator, were found to
be in the range of the limits of a monthly equivalent dose
[170-1700µSv].
The differences between the two determinations can
be explained by the characteristics and the conditions
of measurements: the positions of the two dosimeters
respectively of the radioactive source. The dosimetric film
accumulates through time the received dose, ( Some days
had passed since the dosimetric films had been changed). The
maximal admitted errors for Hp (10) ≤400µSv are +100%
/ -50%, conforming to AECB S-106 (E), IAEA – Safety
Guide No. RS-G-1.3 % standards.
The electronic dosimeters were calibrated to signal
optically and acoustically the high dose rate detection and
the intervention was very rapid.
Also, specific blood tests and cytogenetic tests were
taken at the Public Health Institute in Bucharest. These
results were also within normal limits.
Discussions and Conclusions
In the literature there are many incidents and accidents
due, in many cases, to human mistakes but also due to
technical deficiencies.
Some human mistakes we can mention here are: wrong
commissioning or calibrating machines or the treatment
planning system that can lead to a systematic under-dose
(e.g. at the Department of Radiation Oncology, Royal
Adelaide Hospital the radiotherapy to cancer patients,
incorrectly delivered 5% less than what had been prescribed
for cancer patients treated on that treatment machine between
July 2004 and July 2006.) or systematic over-exposure,
maintenance problems, errors associated with human
machine interfaces, errors related to reading or entering from
the patients chart, mistakes involving the wrong patient, the
wrong field or the wrong site, the wrong beam or source,
errors in communication, mistakes associated with special
situations, personnel changes, special treatments (4-6).
A notorious incident happened at the National Oncology
Institute (Instituto Oncológico Nacional, ION) of Panama
when 28 radiation therapy patients were overexposed,
treated with the cobalt-60 therapy unit at the ION, in late
2000 and early 2001 (7-9). They had received a dose greater
than the normal dose with errors ranging from +10 to +105%
(7, 10, 11). Twenty-three of the 28 overexposed patients died
by September 2005, with at least 18 of the deaths being from
radiation effects (8).
In our case the incident occurred due to a technical
deficiency and in Romania this is the first time when such
an incident has occurred and been reported. This was the
reason why we considered it useful to publish all the facts
related to this incident.
Radiological incident in the radiotherapy department
However, after these events we must point out some
important aspects. First of all, this situation: the source
blocked in the IN TRANSIT position, the framework under
the treatment table in rotation at 180° without sufficient
space to use the T-bar IS NOT specified in the Operator’s
Manual of therapy unit. Even under these circumstances,
the operator personnel demonstrated their professionalism,
courage, evacuating the patient rapidly from the exposure
room and taking all necessary actions, conforming to
emergency procedures. Also, the radiation safety officers
had the capacity to keep the situation under control and to
make good decisions conforming to the complexity and the
seriousness of the situation.
On the other hand, precautions are required to be taken
when this radiological incident become public information,
because of the false alarming of other hospital’s staff and
the public. Misinformation and confusion must be avoided
at all costs. Therefore, the information to be given out to
the media and the public must be taken from qualified staff
of the therapy department or from a responsible source of
the hospital.
Radiotherapy is very much dependent on human
performance and the professionalism of a very strong team
is the key to its success.
After this incident the Radiotherapy Department’s
Emergency Plan was modified and updated including the
emergency procedures described in this paper; the night
shift was removed from the Radiotherapy Department’s
work program.
Also, these procedures were included in the personneltraining program, and simulations of emergency interventions
with all staff, are now a regular occurrence.
Disclosures: The authors indicated no potential conflict of interest
21
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