Introduction
The estimated risk associated with exposure to ionizing radiation is based on evaluation
of the effective dose (E), starting from the equivalent dose (H) received during X-ray-guided
procedures. Concerning endoscopic procedures, risks have been widely studied, with
special focus on the potential risk of radiation-induced cancer [1 ]
[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ]
[8 ]
[9 ].
As fluoroscopy is fundamentally necessary in endoscopic retrograde cholangiopancreatography
(ERCP) and any other interventional procedure (such as enteral stent placement, balloon
dilatation of stenosis, advanced endoscopic ultrasound (EUS)-guided procedures, and
radiation exposure), potential occupational hazards are inevitable for advanced endoscopists
[1 ]
[10 ].
Many aspects, including complexity of procedures, patient size (e. g. pediatric patients,
obese patients), and experience of the operator, influence the annual effective doses
received by the operators. In addition, the type of X-ray equipment used to perform
endoscopy procedures, a correctly operated C-arm, including patient-detector distance,
and pulsed fluoroscopy, may affect staff radiation doses [11 ]. However, the use of bed-mounted or ceiling-mounted shields, lead aprons, thyroid
shields, protective glasses, and a distance as far as possible from the radiation
source are established methods for reducing staff exposure.
Endoscopists can work with radiation, and reduce the possibility of suffering radiation
effects by following radioprotection recommendations, such as correctly using personnel
monitoring devices to estimate radiation exposure. In fact, as strongly recommended
by the International Commission on Radiological Protection (ICRP), it is essential
that professionals wear dosimeters correctly because no dose to which an individual
is exposed can be accurately estimated without having some type of individual monitoring
during all times of exposure [12 ]. There are studies and recommendations with regard to the correct evaluation of
occupational dose of interventional radiology staff using two dosimeters [12 ]
[13 ]. However, the design of these studies is based only on dosimeters positioned one
under and the other over the lead apron. Problems with improper wearing of dosimeters
may include not only registration of high doses, but also very low doses that may
suggest misuse of the devices or failure to wear them properly [12 ].
It has been shown that the numerical values of the personal dose equivalent depend
on the position of the dosimeter [14 ]. While wearing a standard lead apron and thyroid shield can give us some form of
reassurance of radiation safety, some people may not worry about how the position
of the personal dosimeter related to their own position with respect to the radiation
source can affect the correct personal dose assessment.
Depending on the different types of procedure or the habits of the operator, endoscopists
can change their position in the endoscopy suite by turning their back, side or front
toward the X-ray source. Thus, this study aimed to establish whether the position
of personal dosimeters affects the correct evaluation of endoscopists’ radiation exposure
during X-ray-guided procedures.
Materials and methods
This study was approved by our institutional review board, which waived the need for
consent for data collection. An informed consent specific to each procedure was obtained
in all cases.
Patient population
Between January and February 2018, data from 62 consecutive X-ray-guided endoscopic
procedures performed in a single tertiary care center were prospectively collected.
The study population included patients with either biliopancreatic or upper/lower
gastrointestinal pathologies.
X-ray equipment
A flat-panel detector mobile C-arm (Cios Alpha, Siemens Healthineers, Erlangen, Germany),
in our suites since 2017, was used to perform all procedures, with postero-anterior
projection. A fluoroscopy trajectory pre-set by the manufacturer, a fluoroscopy pulse-rate
fixed at 15 pulses/second, last image hold, and image loop functions were all routinely
employed. During the study, a high frame rate, magnification, and oblique projections
were only used at certain times during some procedures. The technique parameters,
including tube kilovoltage (kV) and tube current – time product (mAs), were determined
automatically by the automatic exposure control system.
This equipment does not allow any change in the source-to-detector distance; however,
the patient-to-detector distance was reduced as much as possible during every procedure.
In addition, patients were placed on a separate angiographic-bed system (Cmax Xray
operating table, STERIS, Mentor, OH, USA), with a bed-mounted shield (0.5 mm lead
equivalent) used during all of the procedures.
Dose measurement
All procedures were performed by endoscopists who always wore protective aprons with
thyroid shields (0.5 mm lead equivalent) and protective glasses with side protection
(0.75 mm lead equivalent).
Electronic dosimeters have been proven to be effective for studies of radiation exposure
[12 ]. In our study, we used two electronic personal dosimeters (EPD MK2.3, Thermo Fisher
Scientific, Benham, UK), able to respond to photon energies down to 15 keV, with an
angular response of ± 20 % up to ± 75°, and an accuracy of ± 10 %, calibrated to measure
the personal dose equivalent at 10 mm depth [Hp(10)]. These dosimeters have a valid
calibration and quality control certificate according to ISO/IEC guide 98 and to EA-4 /02
standards requirements, updated every year.
The two dosimeters were placed with one outside the lead apron at the left upper chest
position of the endoscopist, and the other at the back, specular to the first ([Fig. 1 ]).
Fig. 1 The two dosimeters were placed with one outside the lead apron at the left upper
chest position of the endoscopist, and the other at the back, specular to the first.
Hp(10) (in units of μSv) measured by the two dosimeters was manually recorded, along
with the dose area product (DAP) and fluoroscopy time (FT), after each procedure.
The working position of the endoscopist with respect to the radiation source was also
registered.
In order to differentiate Hp from the two dosimeters (anterior and posterior), Hp
values were named, Hp(10)-ANT and Hp(10)-POST, respectively.
Statistical analysis
According to the working position of the endoscopist, procedures were divided into
three groups: frontal position, back position, and side or mixed position.
Operators’ Hp, patients’ DAP, and FT-related data were analyzed for every single procedure,
and are expressed as mean value ± standard deviation (SD), median, and range.
The differences between mean Hp(10)-ANT and mean Hp(10)-POST of each group were also
calculated using two-tailed Student’s t tests, with statistical results considered significant at P values less than 0.05.
Results
A total of 62 endoscopic X-ray-guided procedures were performed in 59 adult and 3
pediatric patients by 6 endoscopists. The procedures were as follows: 42 ERCP; 5 esophageal
stricture dilatation (2 with and 3 without stenting); 4 colonic dilatation; 4 enteroscopy;
3 colonic stent placement; 1 rectovaginal fistula closure; 3 esophageal stent removal.
According to the working position of the endoscopist, 17 procedures were performed
in the frontal position, 31 in the back position, and 14 in the side or mixed position.
[Table 1 ] summarizes the type and number of procedures included in the study.
Table 1
Type and number of procedures included in the study. The table shows the number of
procedures according to endoscopist’s working position.
Procedure name
No. of procedures/endoscopist’s position
Total no.
Front
Back
Side/mixed
ERCP
7
28
7
42
Esophageal stricture dilatation
2
2
1
5
Colonic dilatation
2
1
1
4
Enteroscopies
0
0
4
4
Colonic stent placement
2
0
1
3
Rectovaginal fistula closure
1
0
0
1
Esophageal stent removal
3
0
0
3
Total
17
31
14
62
ERCP, endoscopic retrograde cholangiopancreatography.
[Table 2 ] summarizes mean Hp(10)-ANT and mean Hp(10)-POST, SD, median and range values (given
in μSv), and the t test results obtained from comparison of mean Hp(10)-ANT and mean Hp(10)-POST of
each group. As shown, Hp(10)-ANT μSv and Hp(10)-POST μSv were higher when the endoscopist
assumed frontal and back positions (11.8 and 32.3 μSv, respectively) ([Fig. 2 ]). The results of the t tests showed that there was a statistically significant difference in the means for
the endoscopists’ frontal position (P = 0.014) and for the endoscopists’ back position (P < 0.00001). However, there was no statistically significant difference between means
for the endoscopists’ side/mixed position (P = 0.31).
Table 2
Equivalent doses (H) at a depth of 10 mm of tissue [(Hp(10)] measured by the dosimeter
placed outside the lead apron at the left upper chest position of the endoscopist
[Hp(10)-ANT], and by the dosimeter at the back [Hp(10)-POST].
Endoscopist’s position
Hp(10)-ANT, µSv
Hp(10)-POST, µSv
P value
Mean (SD)
Median; Range
Mean (SD)
Median; Range
Frontal
11.8 (13.9)
8; 0 – 39
0.5 (0.9)
0; 0 – 3
0.014
Back
1.3 (2.0)
1; 0 – 7
32.3 (33.2)
24; 3 – 130
< 0.00001
Side/mixed
13.5 (12.4)
10; 0 – 40
23.5 (28.2)
12.5; 0 – 83
0.31
SD = standard deviation; μSv = μSievert.
Fig. 2 Comparison between mean Hp(10)-ANT and Hp(10)-POST for front, back and side/mixed
positions.
Hp received during X-ray-guided procedures are shown in [Table 3 ]. In the frontal position, the posterior dosimeter measured 4.45 % of the total H
received by the endoscopist ([Table 3 ]). In back and side/mixed positions, the posterior dosimeter measured the majority
of the total H received by the endoscopist (96.16 % and 63.50 %, respectively).
Table 3
Hp received during X-ray guided procedures monitored by the anterior and posterior
dosimeter.
Endoscopist’s position
Hp(10)-ANT
Hp(10)-POST
Mean
%
Mean
%
Frontal
11.82
95.55
0.55
4.45
Back
1.29
3.84
32.32
96.16
Side/mixed
13.5
36.50
23.5
63.50
Data are expressed as mean and percentage.
Discussion
Many studies are available on risks concerning endoscopic X-ray-guided procedures,
focusing especially on the potential risks of radiation exposure.
It has been proven that variations of occupational doses are related to the positioning
of the operators within the working suite in relation to the X-ray equipment [15 ]
[16 ]. In addition, incorrect wearing of dosimeters may result in detection of excessively
high doses, but also in registration of very low doses. In fact, both of these cases
may indicate a misuse of dosimeter wearing [12 ].
A significant difference in Hp(10) between anterior and posterior dosimeter was registered
in this study, particularly when frontal and back positions were required. This means
that when the procedure requires the endoscopist to take a frontal or back position,
the whole-body personal dosimeter should be worn on the chest or back, respectively,
for correct monitoring of personal dose. Moreover, in consideration of the statistically
non-significant difference of Hp when the endoscopist takes a lateral/mixed position,
only a side dosimeter would probably be sufficient for correct evaluation of the dose
to the endoscopist.
The position of a personal whole-body dosimeter is usually on the torso at waist or
chest level [10 ]. Our data demonstrate that if a whole body dosimeter is worn without taking into
consideration the operator’s position within the suite in relation to the radiation
source, the operator’s dose monitoring will be inaccurate, or even incorrect. Data
measured by a posterior dosimeter correspond to the H not monitored if only using
the anterior placement of the whole-body personal dosimeter. The H not monitored is:
4.45 % for endoscopist’s frontal position; 96.16 % for the back position, and 63.50 %
for the side/mixed position. This results in a greater potential risk of fatal cancer
to endoscopists due to radiation exposure, especially when the back position is taken.
The possibility of using two dosimeters, one worn on the chest and the other on the
back, should be considered for effective monitoring of endoscopists’ occupational
dose. In addition, adequate educational programs for endoscopists could be helpful
in avoiding misuse of radiation protection protocols.
Some limitations of this study should be considered. First, unlike hepatobiliary procedures
performed by radiologists, for which the occupational dose is related to the type
of procedure being performed [16 ], the position taken by endoscopists likely does not depend on the kind of procedure,
but may depend on their own behavior or approach to each procedure and patient. However,
we need a greater number of procedures and operators to confirm this hypothesis. Second,
pediatric procedures should be considered separately due to the lack of a sufficient
number of procedures, and the difference in the patients’ size, which could influence
the results.
Future assessments with regard to dose evaluation of a larger number of endoscopists
performing a single type of procedure and a pediatric population are needed.
This study found that the position of personal dosimeters significantly affects the
correct evaluation of endoscopists’ radiation exposure during X-ray-guided procedures
when frontal and back positions are taken. On the basis of these results, the whole-body
personal dosimeter should be worn according to the position of the operator within
the suite in relation to the radiation source. If this does not occur, it may result
in a substantial underestimation of personal exposure. The possibility of using two
dosimeters, one worn on the chest and the other on the back, should be considered
for correct monitoring of endoscopists’ occupational dose.
Roberta Gerasia, Dario Ligresti, Fabio Cipolletta et al. Endoscopist’s occupational
dose evaluation related to correct wearing of dosimeter during X-ray-guided procedures Endoscopy International Open 2019; 07: E367 – E371. DOI: 10.1055/a-0841-33501 , Dario Ligresti2 , Fabio Cipolletta2 , Antonino Granata2 , Ilaria Tarantino2 , Luca Barresi2 , Michele Amata2 , Sabrina Benenati1 , Giuseppe Gallo1 , Corrado Tafaro1 , Roberto Miraglia1 , Mario Traina2 2 IRCCS-ISMETT (Istituto Mediterraneo per i Trapianti e Terapie ad alta specializzazione),
Palermo, Italy – Endoscopy Service, Department of Diagnostic and Therapeutic Services,
Palermo, Italy
