Introduction
Endoscopic retrograde cholangiopancreatography (ERCP) is a common interventional procedure
used for examination and treatment of the pancreatic and bile ducts. In addition to
endoscopy, ERCP utilizes ionizing radiation, which is harmful to health. Therefore,
various dose-optimization methods to reduce radiation burden both to the patient and
personnel are required. The risk of stochastic effects (e. g., cancer) is assumed
to increase linearly with radiation dose [1 ]
[2 ]
[3 ].
Ionizing radiation may also cause cataract, a clouding of the normally clear lens
of the eye. Due to recently updated radiosensitivity knowledge of various tissues,
the dose limit for the lens of the eye for occupational exposure in planned exposure
settings was reduced from 150 mSv/year to 20 mSv/year, averaged over 5 years, with
no annual dose in a single year exceeding 50 mSv [4 ]
[5 ]
[6 ]. Some of the most recent epidemiological studies have indicated that the radiation-induced
cataract has a lower threshold dose than previously expected or could, similarly to
radiation-induced cancer, even be a stochastic harmful effect of ionizing radiation
and follow the linear no-threshold model [7 ]
[8 ]
[9 ]
[10 ]
[11 ]. There is a higher prevalence of radiation-induced cataract among staff working
with higher radiation levels, such as cardiologists and interventional radiologists,
than in normal population and reference groups [10 ]
[12 ]
[13 ]. Previous studies have shown occupational radiation dose to eyes to vary in ERCP
from 10 to > 100 µSv, depending especially on operator, the fluoroscopy system used,
and x-ray tube position during the procedure [14 ]
[15 ]
[16 ]. Some studies have also anticipated that the annual dose limits for eye lenses could
be exceeded in medical staff who frequently perform ERCP procedures [15 ]
[16 ]
[17 ].
The aim of this prospective study was to determine occupational radiation doses in
gastrointestinal endoscopy procedures, with special emphasis on eye lens doses in
ERCP. The study also produced mean conversion coefficients from kerma-area product
(KAP) to Hp (10), KAP to Hp (0.07), and KAP to Hp (3) and further from personal dose equivalents Hp (10) and Hp (0.07) to Hp (3). These conversion coefficients were determined for the purpose of possibly estimating
e. g., eye lens dose without a dedicated eye dosimeter.
Methods
Study design and population
This prospective observational study to determine occupational radiation doses was
performed at the Helsinki University Hospital Endoscopy department between March 2021
and July 2021. The COVID-19 pandemic did not affect the number or type of performed
procedures. Altogether 604 consecutive fluoroscopy-guided procedures to patients were
included in the study. From these interventions, 560 were ERCPs and 44 were other
gastrointestinal endoscopy procedures, such as duodenal stentings or dilatations of
anastomotic strictures. Personal dose equivalents Hp (10), Hp (0.07), and Hp (3) for four gastrointestinal surgeons (S1-S4) and four gastroenterologists (G1-G4)
and for assisting nurses (N_Zee and N_Cios) were measured using thermoluminescent
dosimeters (TLD) and direct-ion storage dosimeters (DIS). Details of dosimetry practices
and dose uncertainty estimation are provided as supplementary material. In the endoscopy
department, ERCPs for diagnosis and follow up of primary sclerosing cholangitis (PSC)
and dilatations and stentings for these patients are performed by gastroenterologists;
surgeons perform all other ERCP procedures. Distributions of the performed and assisted
procedures by endoscopist and assisting nurse are given in Table 1 s (supplementary
materials). The study was approved by the Institutional Review Board and no patient
informed consent was required.
Endoscopy suite
All procedures were performed using CO2 insufflation with the patient in prone or left lateral decubitus position under conscious
sedation controlled by an anesthesiologist and a nurse. The study procedures were
performed using a floor-mounted Siemens Artis zee multi-purpose (MP) fluoroscopy system
(Siemens Healthcare, Erlangen, Germany) or a mobile Siemens Cios Alpha c-arm device
(Siemens Healthcare, Erlangen, Germany). Fixed, mobile, and ceiling-mounted radiation
shields and personal protective equipment, such as protective aprons, thyroid shields,
and leaded eyewear were used during all the procedures. A more detailed description
of the imaging protocols and radiation protection tools implemented is provided as
supplementary material.
Other data collected for each procedure included patient characteristics (age, height,
weight, and body mass index [BMI]), fluoroscopy time, KAP, and air-kerma at reference
point (Ka,r ). Moreover, the procedural complexity of each ERCP was determined and collected based
on the 4-point American Society for Gastrointestinal Endoscopy (ASGE) complexity-grading
system [18 ]
[19 ]. The radiation doses in ERCP and other gastrointestinal endoscopy procedures were
compared. ERCPs performed for diagnosis and follow up of PSC included a significantly
larger number of single image exposures compared to other ERCPs and were thus categorized
separately. The effect of ERCP procedural complexity level and fluoroscopy system
on radiation doses was then analyzed.
Statistical analysis
The data are presented as median (interquartile range [IQR], i. e., first quartile
– third quartile). To compare categorical and continuous variables between patient
characteristics, procedure types, fluoroscopy systems, ERCP procedural complexity
levels, and interventionists, either Fisher’s Exact test or Mann-Whitney U -test and Kruskal-Wallis test were used, respectively. All statistical tests were
two-sided, and a P < 0.05 was considered significant. Statistical analysis was performed with SPSS statistical
software (IBM, Armonk, New York, United States, version 25.0).
Results
Clinical features of patients
Patient characteristics are summarized in [Table 1 ]. Patient age ranged from 0 to 97 years and BMI from 14.5 to 48.1 kg/m2 . Patients in the PSC ERCP group were significantly younger (P < 0.001), taller (P < 0.001), and somewhat heavier (P = 0.049) than patients in other groups. No other statistically significant differences
in patient characteristics were observed between the procedure types.
Table 1
Selected patient characteristics provided as medians (IQR, i. e. first quartile –
third quartile) unless otherwise indicated.
Variable
Patients in ERCP w/o PSC
(n = 424)
Patients in ERCP PSC
(n = 136)
Patients in other GE procedures
(n = 44)
P value
Age, years
65 (54–75)
37 (30–47)
69 (54–76)
< 0.001
Sex, male; n (%)
225 (53.1)
81 (59.6)
29 (65.9)
0.146
Height, cm
170 (162–178)
176 (169–182)
170 (165–178)
< 0.001
Weight, kg
74 (63–86)
77 (68–86)
73 (57–80)
0.049
BMI, kg/m2
25.5 (22.2–28.3)
24.7 (22.6–28.6)
23.6 (21.5–27.7)
0.156
BMI: body mass index; ERCP: endoscopic retrograde cholangiopancreatography; GE: gastrointestinal
endoscopy; PSC: primary sclerosing cholangitis
Radiation dose indices and fluoroscopy times of the procedures
[Table 2 ] (and Fig. 1s in supplementary materials) summarizes the radiation dose indices and
fluoroscopy times of the procedures. The accumulated KAP varied from 0.01 to 22.89
Gy·cm2 in non-PSC ERCPs, from 0.26 to 12.04 Gy·cm2 in PSC ERCPs, and from 0.01 to 6.57 Gy·cm2 in other gastrointestinal endoscopic x-ray interventions. The PSC ERCPs resulted
in significantly higher KAP, Ka,r , and fluoroscopy times and contained more single image acquisitions compared to other
interventions (P < 0.001). The study Ka,r was higher in non-PSC ERCPs compared to other gastrointestinal endoscopy interventions
(P = 0.043), while no differences in KAP (P = 1.000) or fluoroscopy time (P = 0.238) were detected. The floor-mounted system produced remarkably lower patient
doses than the mobile c-arm. The ASGE complexity level 3 ERCP procedures typically
yielded highest doses and fluoroscopy times.
Table 2
Dose indices and fluoroscopy times of the procedures provided as median (IQR) for
different procedure types, systems, and in ERCP procedures also according to procedural
complexity level.
Procedure and system
Fluoroscopy time (s)
KAPstudy
(Gy·cm2 )
KAPexposure
(Gy·cm2 )
Ka,r,study
(mGy)
Ka,r,exposure
(mGy)
Number of single images
ERCP w/o PSC: Artis Zee MP (n = 276)
47 (22–92)
0.6 (0.3–1.4)
0.0 (0.0–0.2)
2.5 (1.0–5.8)
0.1 (0.0–0.9)
1.0 (0.0–1.0)
19 (10–46)
0.3 (0.1–1.5)
0.1 (0.0–0.6)
0.9 (0.4–6.5)
0.5 (0.0–2.2)
1.0 (0.0–2.0)
36 (21–62)
0.6 (0.3–0.9)
0.0 (0.0–0.2)
2.0 (1.0–3.8)
0.0 (0.0–0.8)
0.0 (0.0–1.0)
58 (32–145)
0.8 (0.3–2.0)
0.1 (0.0–0.3)
3.3 (1.2–7.2)
0.3 (0.0–1.1)
1.0 (0.0–1.0)
36 (19–136)
0.5 (0.2–1.2)
0.0 (0.0–0.2)
1.8 (0.8–8.1)
0.0 (0.0–0.7)
0.0 (0.0–1.0)
0.001
0.060
0.281
0.050
0.330
0.378
ERCP w/o PSC: Cios Alpha (n = 148)
48 (27–114)
2.0 (0.8–4.1)
0.0 (0.0–0.0)
7.0 (3.0–15.5)
0.0 (0.0–0.1)
0.0 (0.0–1.0)
25 (19–30)
1.0 (0.8–1.3)
0.0 (0.0–0.0)
3.6 (2.7–4.1)
0.0 (0.0–0.1)
0.5 (0.0–1.0)
32 (19–65)
1.2 (0.5–2.4)
0.0 (0.0–0.0)
4.0 (2.2–8.3)
0.0 (0.0–0.0)
0.0 (0.0–0.5)
103 (48–214)
3.5 (1.6–7.8)
0.0 (0.0–0.0)
12.9 (5.2–28.2)
0.0 (0.0–0.1)
0.0 (0.0–1.0)
27 (16–39)
1.2 (0.6–3.1)
0.0 (0.0–0.0)
2.9 (1.6–7.3)
0.0 (0.0–0.0)
0.0 (0.0–0.0)
< 0.001
< 0.001
0.609
< 0.001
0.708
0.696
0.092
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
ERCP PSC: Artis Zee MP (n = 135)
82 (35–143)
1.3 (0.8–2.2)
0.6 (0.4–0.9)
8.3 (5.1–12.7)
3.7 (2.6–4.6)
5.0 (5.0–7.0)
61 (26–98)
1.2 (0.8–1.8)
0.7 (0.5–0.8)
6.8 (4.8–11.5)
3.7 (2.7–4.6)
5.0 (5.0–7.0)
134 (96–202)
2.1 (1.2–4.2)
0.6 (0.4–0.9)
11.0 (7.8–20.3)
3.6 (2.5–4.7)
5.0 (3.0–5.5)
116 (57–301)
1.4 (0.9–3.4)
0.5 (0.3–0.6)
9.4 (5.2–15.5)
2.9 (1.5–3.7)
4.0 (3.0–5.5)
–
–
–
–
–
–
< 0.001
< 0.001
0.385
0.001
0.359
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
ERCP PSC: Cios Alpha (n = 1)
113 (113–113)
2.4 (2.4–2.4)
0.0 (0.0–0.0)
5.6 (5.6–5.6)
0.0 (0.0–0.0)
0.0 (0.0–0.0)
–
–
–
–
–
–
113 (113–113)
2.4 (2.4–2.4)
0.0 (0.0–0.0)
5.6 (5.6–5.6)
0.0 (0.0–0.0)
0.0 (0.0–0.0)
–
–
–
–
–
–
–
–
–
–
–
–
N/A
N/A
N/A
N/A
N/A
N/A
0.735
0.426
0.029
0.563
0.029
0.029
0.523
0.859
0.738
0.913
0.738
0.738
Other GE procedure: Artis Zee MP (n = 26)
37 (11–72)
0.6 (0.2–1.7)
0.0 (0.0–0.1)
1.4 (0.9–4.4)
0.0 (0.0–0.5)
0.0 (0.0–0.8)
Other GE procedure: Cios Alpha (n = 18)
63 (12–95)
1.7 (0.4–4.1)
0.0 (0.0–0.0)
4.0 (1.0–9.6)
0.0 (0.0–0.0)
0.0 (0.0–0.0)
0.214
0.053
0.018
0.129
0.018
0.018
< 0.001
0.001
< 0.001
< 0.001
< 0.001
< 0.001
ERCP, endoscopic retrograde cholangiopancreatography; GE, gastrointestinal endoscopy;
KAPstudy , kerma-area product for the entire examination including contributions from fluoroscopy
and exposures/single digital radiographic images; KAPexposure , kerma-area product resulting from the exposures/single images; Ka,r,study , air-kerma at reference point for the entire examination; Ka,r,exposure , air-kerma at reference point resulting from the exposures/single images; PSC, primary
sclerosing cholangitis
Occupational radiation exposure
The calculated mean conversion coefficients from KAP to Hp (10) over all DIS and TLD-100 readings were 0.86 ± 0.76 µSv/Gy·cm–2 (min-max: 0.03–2.24 µSv/Gy·cm–2 ) and 1.55 ± 1.05 µSv/Gy·cm–2 (min-max: 0.55–3.36 µSv/Gy·cm–2 ), respectively. Similarly, KAP-normalized Hp (0.07) for DIS and TLDs were 1.04 ± 0.83 µSv/Gy·cm–2 (min-max: 0.26–2.54 µSv/Gy·cm–2 ) and 2.27 ± 1.71 µSv/Gy·cm–2 (min-max: 0.79–5.77 µSv/Gy·cm–2 ), respectively. The mean KAP-normalized Hp (3) was 0.57 ± 0.27 µSv/Gy·cm–2 (min-max: 0.30–1.07 µSv/Gy·cm–2 ). Furthermore, the conversion factor from Hp (10) to Hp (3) was 0.49 ± 0.23 (min-max: 0.22–2.13) for DIS and 0.34 ± 0.13 (min-max: 0.13–1.01)
for TLD-100. The conversion factor from Hp (0.07) to Hp (3) was 0.48 ± 0.22 (min-max: 0.22–1.19) for DIS and 0.24 ± 0.11 (min-max: 0.08–0.73)
for TLD-100.
[Table 3 ] summarizes the estimated Hp (10), Hp (0.07), and Hp (3) of an operator per procedure. The mobile c-arm typically produced higher doses
than the floor-mounted system. Personal eye lens dose equivalent Hp (3) per procedure, measured on the left temple and outside the leaded eyewear of each
surgeon, ranged from 0.0 to 12.5 µSv in non-PSC ERCPs, from 0.2 to 7.9 µSv in PSC
ERCPs, and from 0.0 to 3.5 µSv in other procedures. On average, PSC ERCPs resulted
in higher eye lens doses than other procedures (P < 0.001). In non-PSC ERCPs, deep-dose equivalent Hp (10) per procedure ranged from 0.0 to 32.4 µSv and from 0.0 to 48.7 µSv with DIS and
TLD-100 dosimeters, respectively. In PSC ERCPs, Hp (10) per procedure ranged from 0.0 to 26.9 µSv with DIS and from 0.4 to 40.5 µSv with
TLD-100. Similarly, Hp (10) per other gastrointestinal endoscopy procedure varied from 0.0 to 6.7 µSv and
from 0.0 to 9.2 µSv with DIS and TLD-100, respectively. Personal shallow-dose equivalent
Hp (0.07) of operator per non-PSC ERCP and PSC ERCP ranged from 0.0 to 36.7 µSv and from
0.0 to 26.9 µSv with DIS, respectively, and from 0.0 to 83.6 µSv and from 0.8 to 69.5 µSv
with TLD-100, respectively. The operator Hp (0.07) per other gastrointestinal procedure ranged from 0.0 to 5.5 µSv with DIS and
from 0.0 to 11.4 µSv with TLD-100. According to TLD-100 results, PSC ERCPs yielded
on average higher Hp (10) and Hp (0.07) to operator than non-PSC ERCPs or other procedures (P < 0.001). However, no such differences in operator Hp (10) and Hp (0.07) were observed with DIS. Occupational dose results achieved with DIS and TLD-100
correlated well (correlation coefficient was at lowest 0.82 [95 % confidence interval
0.79–0.84, P < 0.001] and at highest 0.97 [95 % confidence interval 0.97–0.98, P < 0.001]). However, TLDs showed systematically higher doses than DIS dosimeters.
Table 3
Calculated personal dose equivalents Hp (10), Hp (0.07), and Hp (3) resulting from a single procedure to the operator.
Procedure and system
DIS
TLD-100
EYE-D TLD
Hp (10), µSv
Hp (0.07), µSv
Hp (10), µSv
Hp (0.07), µSv
Hp (3), µSv
ERCP w/o PSC: Artis Zee MP (n = 276)
0.3 (0.1–0.9)
0.4 (0.1–0.9)
0.5 (0.2–1.4)
0.8 (0.3–2.1)
0.3 (0.1–0.7)
0.2 (0.0–1.5)
0.2 (0.1–1.8)
0.2 (0.1–1.9)
0.3 (0.1–2.5)
0.2 (0.1–1.0)
0.3 (0.1–0.8)
0.3 (0.1–0.8)
0.5 (0.3–1.2)
0.7 (0.3–1.6)
0.2 (0.1–0.5)
0.5 (0.2–1.1)
0.5 (0.2–1.1)
0.7 (0.3–1.7)
0.9 (0.4–2.4)
0.4 (0.1–0.9)
0.3 (0.1–0.8)
0.3 (0.1–0.9)
0.4 (0.2–1.3)
0.7 (0.3–2.0)
0.2 (0.1–0.5)
0.383
0.520
0.305
0.281
0.185
ERCP w/o PSC: Cios Alpha (n = 148)
1.2 (0.5–3.2)
1.2 (0.5–2.7)
1.7 (0.8–4.5)
2.4 (1.1–5.8)
1.0 (0.4–2.0)
0.8 (0.7–1.1)
1.0 (0.8–1.4)
1.0 (0.8–1.4)
1.4 (1.1–1.9)
0.6 (0.4–0.7)
0.6 (0.3–1.8)
0.7 (0.3–1.7)
1.1 (0.5–2.6)
1.5 (0.7–3.6)
0.6 (0.3–1.3)
2.3 (1.0–6.8)
1.8 (0.9–5.6)
3.3 (1.4–8.7)
4.3 (1.9–11.7)
1.4 (0.7–4.1)
1.1 (0.6–1.2)
1.1 (0.5–1.3)
1.4 (0.8–1.7)
1.8 (1.0–2.8)
0.7 (0.3–0.9)
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
ERCP PSC: Artis Zee MP (n = 135)
1.5 (0.0–3.0)
1.5 (0.0–3.1)
3.1 (1.4–5.5)
3.7 (2.3–7.1)
1.0 (0.6–1.9)
0.9 (0.0–2.3)
0.9 (0.0–2.3)
2.1 (1.1–4.5)
3.3 (1.9–5.2)
0.9 (0.5–1.6)
3.2 (0.6–7.7)
3.2 (0.6–8.1)
5.5 (3.0–12.5)
7.3 (4.3–18.1)
1.5 (0.7–3.0)
1.0 (0.0–5.7)
1.1 (0.0–6.0)
1.8 (1.5–9.9)
3.4 (2.7–13.4)
0.8 (0.5–2.3)
–
–
–
–
–
< 0.001
< 0.001
< 0.001
< 0.001
0.015
0.158
0.326
< 0.001
< 0.001
< 0.001
ERCP PSC: Cios Alpha (n = 1)
3.1 (3.1–3.1)
3.0 (3.0–3.0)
6.0 (6.0–6.0)
6.7 (6.7–6.7)
2.5 (2.5–2.5)
–
–
–
–
–
3.1 (3.1–3.1)
3.0 (3.0–3.0)
6.0 (6.0–6.0)
6.7 (6.7–6.7)
2.5 (2.5–2.5)
–
–
–
–
–
–
–
–
–
–
N/A
N/A
N/A
N/A
N/A
0.485
0.529
0.471
0.544
0.309
0.550
0.483
0.416
0.443
0.456
Other GE procedure: Artis Zee MP (n = 26)
0.3 (0.1–0.6)
0.4 (0.1–0.8)
0.7 (0.2–1.2)
0.9 (0.3–1.6)
0.3 (0.1–0.8)
Other GE procedure: Cios Alpha (n = 18)
0.8 (0.3–3.0)
0.9 (0.4–3.7)
1.3 (0.4–3.9)
1.9 (0.6–5.2)
0.7 (0.2–2.3)
0.032
0.030
0.038
0.050
0.056
0.547
0.748
< 0.001
< 0.001
< 0.001
ERCP, endoscopic retrograde cholangiopancreatography; GE, gastrointestinal endoscopy;
Hp (10), personal deep-dose equivalent; Hp (0.07), personal shallow-dose equivalent; Hp (3), personal eye lens dose equivalent; PSC, primary sclerosing cholangitis; TLD,
thermoluminescent dosimeter.
Hp (10) and Hp (0.07) were measured with DIS and TLD-100 dosimeters positioned on the protective
apron at chest level of each surgeon, while Hp (3) was measured with EYE-D TLD dosimeter attached on the left temple and outside
the leaded eyewear of each endoscopist. Results are given as median (IQR).
[Fig. 1a–c ] shows the estimated operator-specific personal dose equivalents from ERCPs according
to procedural complexity level. Considering all ERCPs, the ASGE complexity grading
significantly affected operator doses (P < 0.001 to P = 0.002). Significant differences were also observed between the interventionists
(P < 0.001).
Fig. 1 Occupational radiation doses in a single ERCP intervention according to complexity
level of procedure. Operator-specific personal dose equivalents a Hp (10), b Hp (0.07), and c Hp (3) and d assistant-specific eye lens dose equivalent Hp (3) per ERCP procedure. The Hp (10) and Hp (0.07) shown represent doses estimated from TLD-100 measurements. Logarithmic scale
is used on the y-axis.
The estimated assisting staff doses are shown in [Table 4 ]. Assisting physician and nurse doses were systematically lower than doses measured
for an operator ([Table 3 ]). Dose differences observed in TLD readings were significant between operators and
assisting staff members for Hp (10) (P = 0.016), Hp (0.07) (P = 0.005), and Hp (3) (P = 0.002). The estimated Hp (3) per procedure to an assisting staff member ranged from 0.0 to 12.2 µSv in non-PSC
ERCPs, from 0.1 to 6.3 µSv in PSC ERCPs, and from 0.0 to 1.8 µSv in other gastrointestinal
endoscopy procedures. Significant differences in assisting staff eye lens doses were
seen between the procedure types (P < 0.001). Hp (10) per non-PSC ERCP ranged from 0.0 to 22.0 µSv with DIS and from 0.0 to 30.3 µSv
with TLD-100. Hp (0.07) per non-PSC ERCP ranged from 0.0 to 22.8 µSv with DIS and from 0.0 to 37.7 µSv
with TLD-100. Considering all ERCPs, ASGE complexity level of the procedure ([Fig. 1d ]) significantly affected the assisting staff doses (P < 0.001).
Table 4
Calculated personal dose equivalents Hp (10), Hp (0.07), and Hp (3) resulting from a single procedure to assisting staff member.
Procedure and system
DIS
TLD-100
EYE-D TLD
Hp (10), µSv
Hp (0.07), µSv
Hp (10), µSv
Hp (0.07), µSv
Hp (3), µSv
ERCP w/o PSC: Artis Zee MP (n = 276)
0.4 (0.2–1.0)
0.4 (0.2–1.1)
0.6 (0.3–1.5)
0.9 (0.4–2.1)
0.3 (0.1–0.7)
0.2 (0.1–0.4)
0.1 (0.1–0.3)
0.2 (0.2–0.6)
0.3 (0.2–0.7)
0.1 (0.0–0.8)
0.3 (0.2–0.8)
0.3 (0.2–0.7)
0.5 (0.2–1.2)
0.8 (0.3–1.5)
0.3 (0.1–0.5)
0.6 (0.3–1.6)
0.6 (0.3–1.8)
0.8 (0.4–2.4)
1.1 (0.5–3.3)
0.4 (0.2–1.0)
0.3 (0.1–1.0)
0.3 (0.1–0.9)
0.4 (0.2–1.4)
0.6 (0.3–1.7)
0.2 (0.1–0.7)
0.043
0.020
0.052
0.036
0.075
ERCP w/o PSC: Cios Alpha (n = 148)
1.5 (0.5–2.8)
1.3 (0.5–3.2)
2.0 (0.8–4.5)
2.7 (1.0–6.4)
0.5 (0.2–1.3)
1.8 (1.8–1.8)
1.3 (1.3–1.3)
2.5 (2.5–2.5)
3.1 (3.1–3.1)
0.1 (0.1–0.3)
0.6 (0.5–1.3)
0.7 (0.4–1.3)
1.1 (0.6–1.7)
1.4 (0.8–2.3)
0.3 (0.1–0.6)
2.7 (0.9–5.2)
2.7 (0.9–4.9)
3.9 (1.7–7.5)
5.6 (2.3–11.6)
0.8 (0.3–2.5)
1.7 (0.5–2.8)
2.2 (0.3–2.5)
3.5 (0.6–4.2)
4.7 (0.8–5.3)
0.2 (0.1–1.7)
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.005
ERCP PSC: Artis Zee MP (n = 135)
0.7 (0.6–1.1)
0.8 (0.6–1.1)
1.3 (1.0–2.1)
1.4 (1.1–2.3)
0.7 (0.5–1.1)
0.6 (0.6–0.9)
0.6 (0.6–0.8)
1.3 (1.1–1.7)
1.4 (1.3–1.9)
0.6 (0.4–0.9)
1.7 (1.7–1.7)
1.7 (1.7–1.7)
3.4 (3.4–3.4)
3.8 (3.8–3.8)
1.2 (0.6–2.2)
0.7 (0.7–0.7)
0.8 (0.8–0.8)
0.8 (0.8–0.8)
1.1 (1.1–1.1)
0.7 (0.5–1.8)
–
–
–
–
–
0.344
0.344
0.202
0.202
< 0.001
0.139
0.135
0.069
0.130
< 0.001
ERCP PSC: Cios Alpha (n = 1)
0.0 (0.0–0.0)
0.0 (0.0–0.0)
20.0 (20.0–20.0)
20.0 (20.0–20.0)
2.0 (2.0–2.0)
–
–
–
–
–
0.0 (0.0–0.0)
0.0 (0.0–0.0)
20.0 (20.0–20.0)
20.0 (20.0–20.0)
2.0 (2.0–2.0)
–
–
–
–
–
–
–
–
–
–
N/A
N/A
N/A
N/A
N/A
0.333
0.333
0.333
0.333
0.221
0.024
0.024
0.119
0.143
0.349
Other GE procedure: Artis Zee MP (n = 26)
0.3 (0.1–1.1)
0.4 (0.1–1.3)
0.8 (0.1–1.7)
1.1 (0.2–2.3)
0.3 (0.1–1.0)
Other GE procedure: Cios Alpha (n = 18)
1.2 (0.8–1.7)
1.5 (1.0–2.1)
1.8 (1.4–2.2)
2.5 (2.0–3.0)
0.2 (0.0–0.4)
0.308
0.308
0.231
0.231
0.262
0.415
0.698
0.153
0.243
< 0.001
ERCP, endoscopic retrograde cholangiopancreatography; GE, gastrointestinal endoscopy;
Hp (10), personal deep-dose equivalent; Hp (0.07), personal shallow-dose equivalent; Hp (3), personal eye lens dose equivalent; PSC, primary sclerosing cholangitis; TLD,
thermoluminescent dosimeter.
Hp (10) and Hp (0.07) were measured with DIS and TLD-100 dosimeters positioned on the protective
apron at chest level of each assisting surgeon or gastroenterologist, while Hp (3) was measured with EYE-D TLD attached on the left temple and outside the leaded
eyewear of each assisting staff member. Results are given as median (IQR).
[Fig. 2 ] shows the extrapolated annual personal dose equivalents for the exposed endoscopy
unit workers. For each staff member and personal dose equivalent value, the annual
dose estimation was achieved by multiplying the accumulated dosimeter reading by 365
days divided by 140 days (total measurement period of this study). The highest estimated
annual Hp (10) for an interventionist was approximately 1.7 mSv, annual Hp (0.07) was 2.4 mSv, and annual Hp (3) was 0.8 mSv. The highest estimated annual Hp (3) for nurse group dosimeter was approximately 0.5 mSv in the floor-mounted fluoroscopy
system examination room. TLDs measured systematically higher doses than DIS dosimeters.
Fig. 2 Estimated annual personal dose equivalents Hp (10), Hp (0.07), and Hp (3) for endoscopy staff (operators and assistants) based on measurements from various
dosimeters. Surgeons are indicated as S1-S4, gastroenterologists as G1-G4, and group
dosimeters for nurses as N_Zee and N_Cios. The error bars represent expanded uncertainties
with coverage factor k = 2, corresponding to approximately 95 % confidence level.
Discussion
In this study, we estimated personal dose equivalents Hp (10), Hp (0.07), and Hp (3) resulting from gastrointestinal endoscopy procedures to operators and assisting
staff. We also produced conversion coefficients from KAP to personal eye lens dose
equivalent Hp (3) and from personal deep-dose Hp (10) and shallow-dose equivalent Hp (0.07) to Hp (3).
PSC ERCPs were observed to yield higher dose indices and fluoroscopy times compared
to non-PSC ERCPs and other gastrointestinal x-ray interventions. Compared to previous
publications, this study showed remarkably lower KAP and personal dose equivalent
values per ERCP procedure. For example, the European ORAMED study [20 ] reported a median eye lens dose of 18 µSv and an average of 102 µSv for surgeons
during ERCP. More recently, O’Connor et al. [14 ] reported surgeon eye lens doses to vary from 10 to 100 µSv per procedure, depending
on the endoscopy site, equipment, and x-ray tube position during the procedure. For
nurses, they reported eye lens doses from < 10 to 30 µSv. The current study estimated
median operator eye lens dose (measured on the left temple and outside the leaded
eyewear) per ERCP to be 0.6 µSv (0.4 and 1.0 µSv for non-PSC and PSC ERCPs, respectively)
with a maximum dose of 12.5 µSv per procedure. For nurses and assisting physicians,
the median Hp (3) per procedure was estimated to be 0.4 µSv (0.3 and 0.7 µSv for non-PSC and PSC
ERCPs, respectively) with a maximum dose of 12.2 µSv per procedure. The median KAP
per ERCP in this study was 1.0 Gy·cm2 (0.8 and 1.3 Gy·cm2 in non-PSC and PSC ERCP, respectively) and third quartile 2.3 Gy·cm2 . O’Connor et al. [14 ] reported remarkably higher KAP, with mean KAP per procedure being 5.4 to 14.5 Gy·cm2 and third quartiles 7.9 to 19.6 Gy·cm2 , depending on the endoscopy site and image intensifier fluoroscopy system used. Both
systems used in this study were flat-panel devices, which together with regular staff
training and special focus on radiation protection and dose-optimization practices
explain the lower observed doses to patients and staff. In this study, the floor-mounted
fluoroscopy system had significantly lower KAP and personal dose equivalents per procedure
than the movable c-arm. This was expected, as the floor-mounted system contained a
greater amount of additional copper filtration than the movable c-arm. Additionally,
the floor-mounted system had adjustable tube-detector distance. In contrast, this
was fixed on the mobile c-arm, which also affected optimal positioning of the x-ray
tube and detector.
Saukko et al. [21 ] reported median KAP to be 1.83 Gy·cm2 (IQR: 1.20–2.90 Gy·cm2 ) in their ERCP study. They also observed that procedural complexity level affects
KAP and fluoroscopy time; complexity level 3 yielded significantly higher doses than
level-1 and level-2 procedures. In the current study, ERCP procedural complexity level
in terms of ASGE grading system was also shown to affect dose indices, fluoroscopy
times, and occupational doses. On average, ERCPs belonging to complexity level 3 produced
the highest dose indices and fluoroscopy times. ERCPs performed to diagnose and follow
up PSC, which were often graded as complexity level 1, involved more single image
acquisitions than other procedures. This together with the longer fluoroscopy times
caused higher KAP.
All personal dose equivalents varied significantly between operators. This observation
together with KAP differences may be signs of operator-specific differences in dose
optimization and radiation protection practices. For example, variation in positioning
the ceiling-suspended lead glass shield during the procedure may have occurred and
affected the occupational exposure. This may also explain why some operators received
significantly higher Hp (10) and Hp (0.07) values per procedure than others, while no such large differences in Hp (3) were seen. In general, when the ceiling-mounted lead glass shield is not positioned
low enough and as close as possible to the patient body during fluoroscopy, more scattered
radiation may be exposed to the stomach and chest area of an operator, although the
head of an operator would already be sufficiently protected. Radiation protection
practices are not only important for the operating interventionist but also for the
assisting staff. As ceiling-mounted shields are specifically designed to protect the
operator from scattered radiation, assistants should be positioned as far from the
scattering patient as practically possible and preferably behind the operator. Based
on the measured occupational doses, there was probably also some variation in positioning
of assisting staff members.
Remarkable differences in operator-specific KAP-normalized personal dose equivalents
were observed in this study. The mean conversion coefficient from KAP to Hp (10) was 0.86 ± 0.76 µSv/Gy·cm–2 with DIS and 1.55 ± 1.05 µSv/Gy·cm–2 with TLDs. Particularly high standard deviations of the determined conversion coefficients
support the anticipated differences in working practices. Moreover, the mean KAP-normalized
Hp (3) was 0.57 ± 0.27 µSv/Gy·cm–2 , reflecting more equal protection of cranial tissues. The KAP-normalized Hp (3) values were smaller than those reported by O’Connor et al. [14 ], who reported 0.98–1.43 µSv/Gy·cm–2 and 14.5–21.2 µSv/Gy·cm–2 in sites using under couch and over couch x-ray tube geometry during the procedure,
respectively. Their study highlights the necessity of using under couch irradiation
instead of over couch geometry, which results in a significant amount of scattered
radiation to the upper body of the operator and assisting staff.
Although this study revealed statistically significant differences in occupational
doses between operators, systems, ERCP procedure types (i. e., PSC or non-PSC ERCP),
and ASGE procedural complexity levels, the absolute dose differences remained particularly
small, mostly because the doses were generally very low. For example, the greatest
difference in interventionists’ median Hp (3) was < 1.5 µSv, which is equivalent to less than 1 day of background radiation.
Thus, although statistically significant, the dose differences remained mostly insignificant
in terms of excess radiation risk. For the sake of comparison, the excess relative
cataract risk has been estimated to be 1.31 per Gy for a linear no-threshold model
by the EURALOC study [10 ]. Another comparison can be made to the nominal threshold dose of 0.5 Gy for the
deterministic model of cataract formation described by the International Commission
on Radiological Protection (ICRP) [22 ].
Use of ionizing radiation should be optimized to reduce radiation doses to patients
and staff. Protective aprons, thyroid collars, leaded eyewear, ceiling-mounted lead
glasses, table-mounted shields, and mobile shielding screens should be used consistently
to protect the staff. By following good practices of using ionizing radiation, estimated
occupational doses remained clearly below the given dose limits for radiation workers
[5 ]. For example, the greatest annual Hp (10) and Hp (3) for the interventionist were estimated to be 1.7 mSv and 1.3 mSv, respectively.
These doses are not only clearly below the maximum allowed levels but are considerably
lower than the respective annual limits for category B workers [5 ]. Further, dose equivalents were measured outside the protective aprons, and to estimate
effective doses from the measured Hp (10) values, the reported values should be divided by a factor of 30–120 [23 ]. Similarly, the eye lens doses were measured by positioning TLDs outside the leaded
eyewear. As protective glasses typically lower the eye lens dose by 50–80 %, a conversion
factor of 0.5 may be used to estimate Hp (3) under the glasses to account for the effect of protective glasses [17 ]
[20 ]
[24 ]
[25 ]. Regarding these essential dose aspects, the occupational exposure in gastrointestinal
endoscopy procedures may be kept very low when proper optimization practices are followed.
However, some of the previous studies focused on operator ocular doses have anticipated
that the given annual dose limit for the eye lenses may be exceeded in surgeons who
frequently perform ERCP procedures [15 ]
[16 ]
[17 ]. Based on the measured personal dose equivalents of this study, monitoring interventionists’
eye lens doses with a specific dosimeter is not required in dose-optimized gastrointestinal
endoscopy procedures. The Hp (3) may be estimated with sufficiently good agreement from the Hp (10) and Hp (0.07) to ensure compliance to the eye lens equivalent dose limits, especially considering
that the conversion factors from Hp (10) and Hp (0.07) to Hp (3) were < 1, thus providing conservative estimates of the eye lens dose.
This study has certain limitations. First and foremost, operator and assisting staff
doses were estimated using the same dosimeters. Therefore, the exact contributions
of each role on personal dose equivalent cannot be determined. However, measurements
performed for educational purposes with an anthropomorphic phantom and dosimeters
resulted in similar dose behavior between operator and assisting staff members. Second,
only five 4-week data collection periods with a limited number of patients for each
operator were gathered. Ideally, the dosimeters should have been read after each procedure.
However, this was not feasible practically. Third, the Hp (10) and Hp (0.07) results from TLDs differed remarkably from DIS results. This may have been
due to the longer periods between preparing and reading the TLDs. The TLDs arrived
at the hospital from the dosimetry service approximately 1 week before a new measurement
period began and they were read 1 to 2 weeks after each measurement period due to
shipping and other delays in the process. Although the background correction was performed
for the TLDs at the dosimetry service, there may have been some remaining uncertainties.
Furthermore, both dosimeters had particularly high expanded uncertainty (e. g., 36 %
and 23 % for Hp (10) with DIS and TLD-100, respectively). Fourth, ERCP complexity level was evaluated
and recorded after each procedure by the staff. There may have been some ambiguous
differences in the grading used between operators. Fifth, procedural classification
into three groups may not be ideal as, for example, PSC ERCPs and other gastrointestinal
procedures may vary widely. Some previous publications also recommend evaluating diagnostic
and therapeutic ERCPs separately. In our hospital, most diagnostic ERCPs, excluding
PSCs, have been replaced with other diagnostic methods (e. g. magnetic resonance imaging).
The classification to PSC or non-PSC ERCPs was done to further categorize procedures
in a way that is relevant in terms of radiation exposure. More single image acquisitions
were performed in PSC ERCPs than in other ERCPs, producing higher radiation exposures.
Finally, a limited number of staff members participated in the study and only two
fluoroscopy systems were used. The radiation protection practices used in other centers
may vary remarkably from what has been reported here, and therefore the resultant
patient and occupational doses may not be interchangeable with other endoscopy departments
and fluoroscopy systems.
Conclusions
In conclusion, by following good working practices and focusing on dose optimization
in gastrointestinal x-ray interventions, including ERCPs, personal dose equivalents
Hp (10), Hp (0.07), and Hp (3) for an operator and assisting staff member per procedure remain low and annual
dose limits are unlikely to be exceeded. The eye lens dose equivalent Hp (3) may be estimated with sufficiently good agreement from the Hp (10) and Hp (0.07) measurements to ensure compliance to dose limits in gastrointestinal procedures.
However, relatively high variation in patient dose and occupational exposure may be
seen due to operator-specific and fluoroscopy system-related reasons.
