Physica Medica xxx (2015) 1e4
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Physica Medica journal homepage: http://www.physicamedica.com
Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography A. Zagorska a, b, *, K. Romanova c, J. Hristova-Popova a, J. Vassileva a, K. Katzarov c a
National Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria Medical University, Sofia, Bulgaria c Military Medical Academy, Sofia, Bulgaria b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 December 2014 Received in revised form 18 March 2015 Accepted 20 March 2015 Available online xxx
The paper presents a study of the radiation doses to eye lens of medical staff during endoscopic retrograde cholangiopancreatography (ERCP) procedures performed in a busy gastroenterology department. For each procedure the dose equivalent to the eye, exposure time, dose rate, Kerma Area Product and fluoroscopy time were recorded. Measurements were performed for a period of two months in four main positions of the operating staff, and then extrapolated to estimate annual doses. The fluoroscopy time per ERCP procedure varied between 1.0 min and 28.8 min, with a mean value of 4.6 min. The calculated mean eye dose per procedure varied between 34.9 mSv and 93.3 mSv. The results demonstrated that if eye protection is not used, annual doses to the eye lens of the gastroenterologist performing the procedure and the anesthesiologist can exceed the dose limit of 20 mSv per year. © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Keywords: Eye lens exposure Medical staff Endoscopic retrograde cholangiopancreatography
Introduction Endoscopic retrograde cholangiopancreatography is a common interventional image guided procedure performed to diagnose conditions of the biliary and/or pancreatic systems, in which the bile and pancreatic ducts are visualized using radiocontrast medium [1]. When carried out with therapeutic intent, it plays an important role in reducing the number of surgeries. ERCP is most often performed in gastroenterological departments by staff with insufficient knowledge on the radiation protection measures for patient and staff dose reduction, and not necessarily in the presence of a radiologist [1]. The procedure requires the operator and other medical staff to stand in close proximity to the patient, resulting in possible higher radiation doses to the whole body and particularly to the lens of the eye. Published data for eye lens doses during the ERCP are scarce. These studies show wide variations in terms of dose, fluoroscopic time, equipment, workload, applied working practices and measurement methods [2e6]. The topic became of increased importance after the International Commission on Radiological Protection recommended the annual dose limit for equivalent dose to the lens of the
* Corresponding author. Medical University, Sofia, Bulgaria. E-mail address: [email protected] (A. Zagorska).
eye to be reduced to 20 mSv [7]. The recently published International Atomic Energy Agency (IAEA) report recommended investigations to be performed to identify whether workers receive significant dose to the lens of the eye [6]. According to the new EURATOM Directive 2013/59, all members of staff who can potentially receive an equivalent dose to the eye lens greater than 15 mSv per year should be under occupational dose monitoring [8]. The purpose of this work is to collect data on the radiation doses to eye lens of medical staff working in a busy gastroenterology department during ERCP procedures, to compare them with the new annual limit for the lens of the eye, and to explore the potential for optimization of clinical practice. Materials and methods The study was performed in the procedure room of a busy gastroenterology department. ERCP procedures were performed using a C-arm fluoroscopy system Arcadis Varic, Siemens Healthcare, with a 23 cm diameter image intensifier. The half value layer of the system was 3.1 mm Al at 80 kV. A standard vascular mode with continuous fluoroscopy, and vertical X-ray beam with a X-ray tube under the patient couch were used for all procedures. ERCP procedures involved the following medical specialists: one or two gastroenterologist, one or two nurses and an anesthesiologist.
http://dx.doi.org/10.1016/j.ejmp.2015.03.011 1120-1797/© 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
2
A. Zagorska et al. / Physica Medica xxx (2015) 1e4
Only therapeutic procedures using a duodenoscope were performed. The patient was placed on a coach in left lateral decubitus position. During the procedure all images were obtained using injection of contrast medium and under local anesthesia. An overview of the staff positions relative to the patient is shown in Fig. 1. During the procedure the main operator-gastroenterologist stands in position P1, facing the patient, or facing the monitors. The monitors are situated above the patient's head and to the right of the operator. The assistant, who can be either a second gastroenterologist or nurse, stands in position P2 behind the operator. The nurse in position P3 stands near the head of the patient to guide the duodenoscope. The anesthesiologist stands in position P4, next to the head of the patient to monitor the patient's breathing, and may occasionally he leaves his position to administer anesthesia. All members of the team wear apron and thyroid shields with 0.50 mm lead equivalent. No ceiling suspended shields or radiation protection couch drapes were available. Patient doses were measured with an integrated Air kerma-area product (KAP) meter. Eye-dose to the medical staff was measured with EDD-30 active electronic dosimeter (Unfors, Sweden), calibrated in terms of operational quantity personal dose equivalent Hp(0.07) in mSv, using N-80 X-ray beam [9] and traceable to Secondary Standards Dosimetry Laboratory e Sofia, Bulgaria. In addition, EDD 30 was tested for angular response in laboratory conditions using N-60 X-ray beam. The response of the dosimeter was within the range 0.80e0.97 for angles up to 60 and as required in the IEC 61526 standard [10,12]. Due to the specific nature of the work the readings of the EDD-30 were not corrected for angular response. The detector was placed at the level of the eye closest to the X-ray tube side. For the main operator and nurse this was the left eye, and for anesthesiologist - the right eye. All measurements were performed without any protective eye shielding. As only one active dosimeter was available, the measurements for different staff members were performed consecutively, i.e. for different procedures. Trial version SPSS Statistics desktop for Windows software was used for the statistical analysis. A Spearman's test was used due
to number of measurements in each position and a lack of normal distribution of the data. For each procedure the following information was recorded: dose equivalent to the eye, dose rate and exposure time (ET) from the EDD-30 dosimeter, and patient dose in terms of Kerma Area Product (KAP), fluoroscopy time (FT) and tube voltage, as displayed on the fluoroscopy system console. Using the departmental records, the total annual workload was estimated to be 800 procedures in 200 working days, and this value was used to estimate the annual dose to the eye lens. All procedures were performed by two gastroenterologists acting as main operators. The workload for the anesthesiologist was assumed to be the same as for the gastroenterologists, and for the nurses e half that of the gastroenterologist, as they change their position to operate monitoring equipment or to assist in other medical procedures not involving X-ray. Additionally, the daily workload was assumed to be two ERCP procedures for the gastroenterologist and anesthesiologist, and one for the nurses. Results Data collection was performed during a period of two months. Forty-nine therapeutic ERCP procedures were included. In each of these the eye lens dose was measured for one of the available positions (P1eP4). The eye lens dose was measured in position P1 (main gastroenterologist) for 15 procedures, in position P4 (anesthesiologist) for 14 procedures, in position P3 (nurse) for 13 procedures, and in position P2 (nurse or second gastroenterologist) for 7 procedures. The results for dose, dose rate, exposure time to the eye lens per procedure and FT for the main positions of the staff members in endoscopic room are presented in Table 1. For each quantity, mean values, minimum and maximum (in parentheses) and standard deviation (SD) are presented. The first, third and fourth columns in Table 1 show the mean eye dose, exposure time and fluoroscopy time respectively, averaged from the measurements in each position. The fluoroscopy time per ERCP procedure varied between 1.0 and 28.8 min, with a mean value of 4.6 min. Table 2 presents mean eye lens dose per procedure calculated by multiplying the mean dose rate in each position by the mean FT and ET respectively, obtained by averaging all measurements. The annual dose was calculated as the product of the mean eye dose per procedure and the typical workload of 400 procedures for the main operator and anesthesiologist and 200 procedures for the assisting staff and nurses. The real exposure time measured by the EDD 30 varied between 0.0 and 27.0 min, with a mean value of 3.5 min. Discussion
Figure 1. Patient and staff positions, Position 1: gastroenterologist (P1), Position 2: gastroenterologist or nurse (P2), Position 3: nurse (P3), Position 4: anesthesiologist (P4).
The equivalent dose Hp(3) is considered to be the most accurate method for monitoring the equivalent dose to the eye lens [6,11]. It is recommended that dosimeters should be type tested and calibrated in terms of Hp(3) using an appropriate phantom. At the time of this study methodology for calibration in terms of Hp(3) was not available. According to the IAEA recommendations, if a dosemeter calibrated in Hp(3) is not available, a dosemeter calibrated in terms of Hp(0.07) can be used to assess the eye dose from photon radiation with sufficient accuracy [6]. A limitation of this study was that measurements in different positions were performed during different procedures, due to the availability of only one direct dosimeter. Because of the variation in complexity of different ERCP procedures, resulting from the individual patient's pathology, the fluoroscopy time varied from 1.0 min to 28.8 min. Estimated mean eye dose per procedure in Table 1 was performed on the base of measurements in each
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
A. Zagorska et al. / Physica Medica xxx (2015) 1e4
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Table 1 Results from measurements for different positions of medical staff. Medical staff
Mean eye dose per procedure [mSv] (minemax), SD
Mean dose rate at the level of the eye [mSv/h ] (minemax), SD
Mean exposure time [min] (minemax), SD
Mean fluoroscopy time [min] (minemax), SD
Distance to the central beam of X-ray system [cm]
Gastroenterologist (P1) Assisting staff (P2) Nurse (P3) Anesthesiologist (P4)
15.5 6.7 26.1 20.4
838.2 456.6 699.2 1220.0
2.6 0.2 5.9 2.1
3.8 3.4 7.9 2.3
50e80 80e100 65e80 30e40
(1.5e46.7), 14.5 (0.5e17.5), 6.6 (2.6e111.5), 29.7 (7.8e47.5), 12.0
(264.7e1264.0), (187.3e1068.0), (327.7e1384.0), (659.5e2906.0),
position. The highest mean eye lens dose was measured at position P3, while for the anesthesiologist (position P4) and gastroenterologist (position P1) the mean values were lower, and the lowest mean value was in position P2 (Table 2). The highest mean eye dose per procedure estimated in position P3 is explained by the highest mean fluoroscopy time for procedures measured in this position, while the mean values of FT for the procedures involving measurements in positions P1, P2, P4 were significantly lower (Table 1). This approach for assessment of eye dose was found to be strongly biased by fluoroscopy time, and for this reason the annual doses were estimated from the mean dose rates in each position, multiplied by the mean fluoroscopy time from all 49 procedures, and the typical workload for each member of staff. The highest mean dose rate of 1220.0 mSv h1 was measured in the anesthesiologist's typical position P4, followed by 838.2 mSv h1 in the gastroenterologist's typical position P1, 699.2 mSv h1 in the nurse position P3, and 456.6 mSv h1 in the position P2 of the assisting staff. The highest dose rates for the anesthesiologist and gastroenterologist are due to their positions close to the patient and the X-ray beam (Table 1, Fig. 1). The lowest dose rate for the assisting staff is because they usually stand behind the gastroenterologist and far from the X-ray beam. Measuring the eye lens dose directly is sometimes not possible which is why some authors have proposed predicting the eye dose levels from data available for other dose quantities, e.g. KAP. The results from the present study did not demonstrate good correlation between KAP and dose equivalent to the eye. Data from more ERCP procedures are needed to improve the statistical power of the correlation analysis. The difference between the mean FT and ET can be attributed to the fact that during part of the procedure the dose reaching the detector is below the detectable level. Good Spearman's correlation between FT and ET was found for the anesthesiologist (P4), with r ¼ 0.693, p < 0.05 (0.01). This is explained by the closest position relative to patient and radiation source, compared to other staff members. The calculated mean eye dose per procedure in the different positions varied between 34.9 mSv and 93.3 mSv when using FT for calculation, and between 26.4 mSv and 70.6 mSv when using ET (Table 2). The estimated annual doses based on average FT and average ET from all 49 procedures are presented in Fig. 2. The estimations predict that the highest annual dose will be received by the anesthesiologist, 37.3 mSv and 28.3 mSv when using FT and ET for the calculation, respectively. Regardless of the
304.5 288.6 298.1 565.5
(0.6e6.0), 1.7 (0.0e0.7), 0.2 (0.8e27.0), 7.2 (0.9e5.6), 1.3
(1.0e11.1), 2.6 (1.3e10.9), 3.4 (1.2e28.8), 8.8 (1.0e5.7), 1.3
calculation model, the estimated annual dose exceeded the annual dose limit by a factor of 1.9 when using FT and by a factor of 1.4 when using ET. In position P1 (main operator-gastroenterologist) the estimated annual dose values were above or around the annual dose limit. For position P3 these values were estimated to be less than annual dose limit by a factor of 1.9 for FT and 2.5 for ET. For position P2 the estimated doses were respectively 2.9 and 3.8 times less than the annual limit. These results are explained with different distance from the X-Ray beam and patient (Table 1). The use of FT for estimation of annual dose is a conservative approach overestimating the real doses [13]. Another source of overestimation was the assumption of only therapeutic ERCP procedures in estimation of annual dose. In real clinical situation, diagnostic procedures are also performed, usually associated with lower doses. The analysis of the occupational doses requires familiarity with the specificity of the procedures and working habits of the staff members. ERCP procedures are usually performed by a team of four staff members working in close proximity to the patient. The distance between the operator and patient is defined by the length of the duodenoscope. The operator is positioned next to the patient couch and facing the monitors, with his left side facing the x-ray source. As a result, the gastroenterologist's left eye is more exposed. The duration of the ERCP depends on the complexity of the procedure, patient characteristics, training and experience of the gastroenterologist. The professional exposure depends on clinical practice, including procedure technique and distance to the X-ray beam [6]. Radiation protection measures to reduce eye doses were recommended to the staff, including routine use of protective eye glasses. To be efficient, the eyewear should be shielded for side exposure, using either side shields or a wraparound design. Protective eyewear must fit properly to ensure that the lenses and side shields adequately protect the eyes and minimize exposure, as well as to minimize discomfort from the increased weight [14]. Alternatively or additionally, eye protection can be achieved by ceilingsuspended shields [15,16]. They provide shielding to the whole head and neck of the operator, allowing good visualization of the patient, adaptive positioning according to the clinical situation, and reduction of scatter to other staff located within the shadow of the barrier [15]. A second ceiling-suspended shield can be used to provide protection to both assisting staff and anesthesiologist.
Table 2 Estimated mean eye dose per procedure and annual doses for different staff member's positions.
Position Position Position Position
1 2 3 4
Mean eye dose per procedure [mSv]
Estimated annual eye dose [mSv]
FT ¼ 4.6 min 64.1 34.9 53.5 93.3
FT ¼ 4.6 min 25.6 7.0 10.7 37.3
ET ¼ 3.5 min 48.5 26.4 40.4 70.6
ET ¼ 3.5 min 19.4 5.3 8.1 28.3
Figure 2. Extrapolation of annual doses according to the position of medical staff and in comparison with the annual eye lens dose limit of 20 mSv.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
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A. Zagorska et al. / Physica Medica xxx (2015) 1e4
Conclusions The present study demonstrated that doses to the eye lens of the gastroenterologist performing procedure and of the anesthesiologist can exceed the annual dose limit. Radiation protection measures to reduce eye doses were recommended to the staff, including routine use of protective eye glasses and ceiling-suspended shields. The study demonstrated that close collaboration between the medical physicist and medical staff is very effective in improving the radiation protection practice in the department. Acknowledgments The authors express sincere gratitude to the staff members of Gastroenterology department for the provided valuable information and their cooperation which ensured efficient work during the study. References [1] Buls N, Pages J, Mana F, Osteaux M. Patient and staff exposure during endoscopic retrograde cholangiopancreatography. Br J Radiol 2002;75:435e43. [2] Olgar T, Bor D, Berkmwn G, Yazar T. Patient and staff doses for some complex X-ray examinations. J Radiol Prot 2009;29:393e407. [3] Martin CJ, Magee JS. Assessment of eye and body dose for interventional radiologists, cardiologists, and other interventional staff. J Radiol Prot 2013;33: 445e60. [4] Vanhavere F, Carinou E, Domienik J, Donadille L, Ginjaume M, Gualdrinif G, et al. Measurements of eye lens doses in interventional radiology and cardiology: final results of the ORAMED project. Radiat Meas 2011;46:1243e7.
[5] O'Connor U, Gallagher A, Malone L, O'Reilly G. Occupational radiation dose to eyes from endoscopic retrograde cholangiopancreatography procedures in light of the revised eye lens dose limit from the international commission on radiological protection. Br J Radiol 2013 Feb;86(1022):20120289. http:// dx.doi.org/10.1259/bjr.20120289. [6] International Atomic Energy Agency TECDOC 1731. Implications for occupational radiation protection of the new dose limit for the lens of the eye. 2013. [7] International Commission on Radiological Protection. Statement on tissue reactions approved by the commission on April 21. 2011. ICRP; 2011. [8] European Commission. Council directive 2013/59/euroatom. 2014. L13/1. [9] International Organization for Standardization. X and gamma reference radiation for calibrating dosemeters and dose rate meters and for determining their response as a function of photon energy. Calibration of area and personal dosemeters and the measurement of their response as a function of energy and angle of incidence. 1999. ISO 4037-3. [10] International Electrotechnical Commission. IEC 61526. Radiation protection instrumentation - measurement of personal dose equivalents Hp(10) and Hp(0,07) for X, gamma, neutron and beta radiations - direct reading personal dose equivalent meters. 2010. [11] ICRP 103 ICRP. The 2007 recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37. 2007. p. 2e4. [12] Vanhavere F, Carinou E, Gualdrini G, Clairand I, Sans Merce M, Ginjaume M, et al. ORAMED: optimization of radiation protection of medical staff. EURADOS Report. 2012-02. [13] European Commission. Technical recommendations for monitoring individuals occupationally exposed to external radiation. Radiat. Prot. 160. 2009. [14] Koukorava C, Farah J, Sturelens L, Clairand I, Donadille L, Vanhavere F, et al. Efficiency of radiation protection equipment in interventional radiology: a systematic Monte Carlo study of eye lens and whole body doses. J Radiol Prot 2014;34:509e28. [15] Scheler B. Operators shielding: how and why. tech vasc. Interv Rad 2010;13: 167e71. [16] Radiological Protection Institute of Ireland. The design of diagnostic medical facilities where ionising radiation is used. 2009.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
Contents lists available at ScienceDirect
Physica Medica journal homepage: http://www.physicamedica.com
Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography A. Zagorska a, b, *, K. Romanova c, J. Hristova-Popova a, J. Vassileva a, K. Katzarov c a
National Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria Medical University, Sofia, Bulgaria c Military Medical Academy, Sofia, Bulgaria b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 December 2014 Received in revised form 18 March 2015 Accepted 20 March 2015 Available online xxx
The paper presents a study of the radiation doses to eye lens of medical staff during endoscopic retrograde cholangiopancreatography (ERCP) procedures performed in a busy gastroenterology department. For each procedure the dose equivalent to the eye, exposure time, dose rate, Kerma Area Product and fluoroscopy time were recorded. Measurements were performed for a period of two months in four main positions of the operating staff, and then extrapolated to estimate annual doses. The fluoroscopy time per ERCP procedure varied between 1.0 min and 28.8 min, with a mean value of 4.6 min. The calculated mean eye dose per procedure varied between 34.9 mSv and 93.3 mSv. The results demonstrated that if eye protection is not used, annual doses to the eye lens of the gastroenterologist performing the procedure and the anesthesiologist can exceed the dose limit of 20 mSv per year. © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Keywords: Eye lens exposure Medical staff Endoscopic retrograde cholangiopancreatography
Introduction Endoscopic retrograde cholangiopancreatography is a common interventional image guided procedure performed to diagnose conditions of the biliary and/or pancreatic systems, in which the bile and pancreatic ducts are visualized using radiocontrast medium [1]. When carried out with therapeutic intent, it plays an important role in reducing the number of surgeries. ERCP is most often performed in gastroenterological departments by staff with insufficient knowledge on the radiation protection measures for patient and staff dose reduction, and not necessarily in the presence of a radiologist [1]. The procedure requires the operator and other medical staff to stand in close proximity to the patient, resulting in possible higher radiation doses to the whole body and particularly to the lens of the eye. Published data for eye lens doses during the ERCP are scarce. These studies show wide variations in terms of dose, fluoroscopic time, equipment, workload, applied working practices and measurement methods [2e6]. The topic became of increased importance after the International Commission on Radiological Protection recommended the annual dose limit for equivalent dose to the lens of the
* Corresponding author. Medical University, Sofia, Bulgaria. E-mail address: [email protected] (A. Zagorska).
eye to be reduced to 20 mSv [7]. The recently published International Atomic Energy Agency (IAEA) report recommended investigations to be performed to identify whether workers receive significant dose to the lens of the eye [6]. According to the new EURATOM Directive 2013/59, all members of staff who can potentially receive an equivalent dose to the eye lens greater than 15 mSv per year should be under occupational dose monitoring [8]. The purpose of this work is to collect data on the radiation doses to eye lens of medical staff working in a busy gastroenterology department during ERCP procedures, to compare them with the new annual limit for the lens of the eye, and to explore the potential for optimization of clinical practice. Materials and methods The study was performed in the procedure room of a busy gastroenterology department. ERCP procedures were performed using a C-arm fluoroscopy system Arcadis Varic, Siemens Healthcare, with a 23 cm diameter image intensifier. The half value layer of the system was 3.1 mm Al at 80 kV. A standard vascular mode with continuous fluoroscopy, and vertical X-ray beam with a X-ray tube under the patient couch were used for all procedures. ERCP procedures involved the following medical specialists: one or two gastroenterologist, one or two nurses and an anesthesiologist.
http://dx.doi.org/10.1016/j.ejmp.2015.03.011 1120-1797/© 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
2
A. Zagorska et al. / Physica Medica xxx (2015) 1e4
Only therapeutic procedures using a duodenoscope were performed. The patient was placed on a coach in left lateral decubitus position. During the procedure all images were obtained using injection of contrast medium and under local anesthesia. An overview of the staff positions relative to the patient is shown in Fig. 1. During the procedure the main operator-gastroenterologist stands in position P1, facing the patient, or facing the monitors. The monitors are situated above the patient's head and to the right of the operator. The assistant, who can be either a second gastroenterologist or nurse, stands in position P2 behind the operator. The nurse in position P3 stands near the head of the patient to guide the duodenoscope. The anesthesiologist stands in position P4, next to the head of the patient to monitor the patient's breathing, and may occasionally he leaves his position to administer anesthesia. All members of the team wear apron and thyroid shields with 0.50 mm lead equivalent. No ceiling suspended shields or radiation protection couch drapes were available. Patient doses were measured with an integrated Air kerma-area product (KAP) meter. Eye-dose to the medical staff was measured with EDD-30 active electronic dosimeter (Unfors, Sweden), calibrated in terms of operational quantity personal dose equivalent Hp(0.07) in mSv, using N-80 X-ray beam [9] and traceable to Secondary Standards Dosimetry Laboratory e Sofia, Bulgaria. In addition, EDD 30 was tested for angular response in laboratory conditions using N-60 X-ray beam. The response of the dosimeter was within the range 0.80e0.97 for angles up to 60 and as required in the IEC 61526 standard [10,12]. Due to the specific nature of the work the readings of the EDD-30 were not corrected for angular response. The detector was placed at the level of the eye closest to the X-ray tube side. For the main operator and nurse this was the left eye, and for anesthesiologist - the right eye. All measurements were performed without any protective eye shielding. As only one active dosimeter was available, the measurements for different staff members were performed consecutively, i.e. for different procedures. Trial version SPSS Statistics desktop for Windows software was used for the statistical analysis. A Spearman's test was used due
to number of measurements in each position and a lack of normal distribution of the data. For each procedure the following information was recorded: dose equivalent to the eye, dose rate and exposure time (ET) from the EDD-30 dosimeter, and patient dose in terms of Kerma Area Product (KAP), fluoroscopy time (FT) and tube voltage, as displayed on the fluoroscopy system console. Using the departmental records, the total annual workload was estimated to be 800 procedures in 200 working days, and this value was used to estimate the annual dose to the eye lens. All procedures were performed by two gastroenterologists acting as main operators. The workload for the anesthesiologist was assumed to be the same as for the gastroenterologists, and for the nurses e half that of the gastroenterologist, as they change their position to operate monitoring equipment or to assist in other medical procedures not involving X-ray. Additionally, the daily workload was assumed to be two ERCP procedures for the gastroenterologist and anesthesiologist, and one for the nurses. Results Data collection was performed during a period of two months. Forty-nine therapeutic ERCP procedures were included. In each of these the eye lens dose was measured for one of the available positions (P1eP4). The eye lens dose was measured in position P1 (main gastroenterologist) for 15 procedures, in position P4 (anesthesiologist) for 14 procedures, in position P3 (nurse) for 13 procedures, and in position P2 (nurse or second gastroenterologist) for 7 procedures. The results for dose, dose rate, exposure time to the eye lens per procedure and FT for the main positions of the staff members in endoscopic room are presented in Table 1. For each quantity, mean values, minimum and maximum (in parentheses) and standard deviation (SD) are presented. The first, third and fourth columns in Table 1 show the mean eye dose, exposure time and fluoroscopy time respectively, averaged from the measurements in each position. The fluoroscopy time per ERCP procedure varied between 1.0 and 28.8 min, with a mean value of 4.6 min. Table 2 presents mean eye lens dose per procedure calculated by multiplying the mean dose rate in each position by the mean FT and ET respectively, obtained by averaging all measurements. The annual dose was calculated as the product of the mean eye dose per procedure and the typical workload of 400 procedures for the main operator and anesthesiologist and 200 procedures for the assisting staff and nurses. The real exposure time measured by the EDD 30 varied between 0.0 and 27.0 min, with a mean value of 3.5 min. Discussion
Figure 1. Patient and staff positions, Position 1: gastroenterologist (P1), Position 2: gastroenterologist or nurse (P2), Position 3: nurse (P3), Position 4: anesthesiologist (P4).
The equivalent dose Hp(3) is considered to be the most accurate method for monitoring the equivalent dose to the eye lens [6,11]. It is recommended that dosimeters should be type tested and calibrated in terms of Hp(3) using an appropriate phantom. At the time of this study methodology for calibration in terms of Hp(3) was not available. According to the IAEA recommendations, if a dosemeter calibrated in Hp(3) is not available, a dosemeter calibrated in terms of Hp(0.07) can be used to assess the eye dose from photon radiation with sufficient accuracy [6]. A limitation of this study was that measurements in different positions were performed during different procedures, due to the availability of only one direct dosimeter. Because of the variation in complexity of different ERCP procedures, resulting from the individual patient's pathology, the fluoroscopy time varied from 1.0 min to 28.8 min. Estimated mean eye dose per procedure in Table 1 was performed on the base of measurements in each
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
A. Zagorska et al. / Physica Medica xxx (2015) 1e4
3
Table 1 Results from measurements for different positions of medical staff. Medical staff
Mean eye dose per procedure [mSv] (minemax), SD
Mean dose rate at the level of the eye [mSv/h ] (minemax), SD
Mean exposure time [min] (minemax), SD
Mean fluoroscopy time [min] (minemax), SD
Distance to the central beam of X-ray system [cm]
Gastroenterologist (P1) Assisting staff (P2) Nurse (P3) Anesthesiologist (P4)
15.5 6.7 26.1 20.4
838.2 456.6 699.2 1220.0
2.6 0.2 5.9 2.1
3.8 3.4 7.9 2.3
50e80 80e100 65e80 30e40
(1.5e46.7), 14.5 (0.5e17.5), 6.6 (2.6e111.5), 29.7 (7.8e47.5), 12.0
(264.7e1264.0), (187.3e1068.0), (327.7e1384.0), (659.5e2906.0),
position. The highest mean eye lens dose was measured at position P3, while for the anesthesiologist (position P4) and gastroenterologist (position P1) the mean values were lower, and the lowest mean value was in position P2 (Table 2). The highest mean eye dose per procedure estimated in position P3 is explained by the highest mean fluoroscopy time for procedures measured in this position, while the mean values of FT for the procedures involving measurements in positions P1, P2, P4 were significantly lower (Table 1). This approach for assessment of eye dose was found to be strongly biased by fluoroscopy time, and for this reason the annual doses were estimated from the mean dose rates in each position, multiplied by the mean fluoroscopy time from all 49 procedures, and the typical workload for each member of staff. The highest mean dose rate of 1220.0 mSv h1 was measured in the anesthesiologist's typical position P4, followed by 838.2 mSv h1 in the gastroenterologist's typical position P1, 699.2 mSv h1 in the nurse position P3, and 456.6 mSv h1 in the position P2 of the assisting staff. The highest dose rates for the anesthesiologist and gastroenterologist are due to their positions close to the patient and the X-ray beam (Table 1, Fig. 1). The lowest dose rate for the assisting staff is because they usually stand behind the gastroenterologist and far from the X-ray beam. Measuring the eye lens dose directly is sometimes not possible which is why some authors have proposed predicting the eye dose levels from data available for other dose quantities, e.g. KAP. The results from the present study did not demonstrate good correlation between KAP and dose equivalent to the eye. Data from more ERCP procedures are needed to improve the statistical power of the correlation analysis. The difference between the mean FT and ET can be attributed to the fact that during part of the procedure the dose reaching the detector is below the detectable level. Good Spearman's correlation between FT and ET was found for the anesthesiologist (P4), with r ¼ 0.693, p < 0.05 (0.01). This is explained by the closest position relative to patient and radiation source, compared to other staff members. The calculated mean eye dose per procedure in the different positions varied between 34.9 mSv and 93.3 mSv when using FT for calculation, and between 26.4 mSv and 70.6 mSv when using ET (Table 2). The estimated annual doses based on average FT and average ET from all 49 procedures are presented in Fig. 2. The estimations predict that the highest annual dose will be received by the anesthesiologist, 37.3 mSv and 28.3 mSv when using FT and ET for the calculation, respectively. Regardless of the
304.5 288.6 298.1 565.5
(0.6e6.0), 1.7 (0.0e0.7), 0.2 (0.8e27.0), 7.2 (0.9e5.6), 1.3
(1.0e11.1), 2.6 (1.3e10.9), 3.4 (1.2e28.8), 8.8 (1.0e5.7), 1.3
calculation model, the estimated annual dose exceeded the annual dose limit by a factor of 1.9 when using FT and by a factor of 1.4 when using ET. In position P1 (main operator-gastroenterologist) the estimated annual dose values were above or around the annual dose limit. For position P3 these values were estimated to be less than annual dose limit by a factor of 1.9 for FT and 2.5 for ET. For position P2 the estimated doses were respectively 2.9 and 3.8 times less than the annual limit. These results are explained with different distance from the X-Ray beam and patient (Table 1). The use of FT for estimation of annual dose is a conservative approach overestimating the real doses [13]. Another source of overestimation was the assumption of only therapeutic ERCP procedures in estimation of annual dose. In real clinical situation, diagnostic procedures are also performed, usually associated with lower doses. The analysis of the occupational doses requires familiarity with the specificity of the procedures and working habits of the staff members. ERCP procedures are usually performed by a team of four staff members working in close proximity to the patient. The distance between the operator and patient is defined by the length of the duodenoscope. The operator is positioned next to the patient couch and facing the monitors, with his left side facing the x-ray source. As a result, the gastroenterologist's left eye is more exposed. The duration of the ERCP depends on the complexity of the procedure, patient characteristics, training and experience of the gastroenterologist. The professional exposure depends on clinical practice, including procedure technique and distance to the X-ray beam [6]. Radiation protection measures to reduce eye doses were recommended to the staff, including routine use of protective eye glasses. To be efficient, the eyewear should be shielded for side exposure, using either side shields or a wraparound design. Protective eyewear must fit properly to ensure that the lenses and side shields adequately protect the eyes and minimize exposure, as well as to minimize discomfort from the increased weight [14]. Alternatively or additionally, eye protection can be achieved by ceilingsuspended shields [15,16]. They provide shielding to the whole head and neck of the operator, allowing good visualization of the patient, adaptive positioning according to the clinical situation, and reduction of scatter to other staff located within the shadow of the barrier [15]. A second ceiling-suspended shield can be used to provide protection to both assisting staff and anesthesiologist.
Table 2 Estimated mean eye dose per procedure and annual doses for different staff member's positions.
Position Position Position Position
1 2 3 4
Mean eye dose per procedure [mSv]
Estimated annual eye dose [mSv]
FT ¼ 4.6 min 64.1 34.9 53.5 93.3
FT ¼ 4.6 min 25.6 7.0 10.7 37.3
ET ¼ 3.5 min 48.5 26.4 40.4 70.6
ET ¼ 3.5 min 19.4 5.3 8.1 28.3
Figure 2. Extrapolation of annual doses according to the position of medical staff and in comparison with the annual eye lens dose limit of 20 mSv.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
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Conclusions The present study demonstrated that doses to the eye lens of the gastroenterologist performing procedure and of the anesthesiologist can exceed the annual dose limit. Radiation protection measures to reduce eye doses were recommended to the staff, including routine use of protective eye glasses and ceiling-suspended shields. The study demonstrated that close collaboration between the medical physicist and medical staff is very effective in improving the radiation protection practice in the department. Acknowledgments The authors express sincere gratitude to the staff members of Gastroenterology department for the provided valuable information and their cooperation which ensured efficient work during the study. References [1] Buls N, Pages J, Mana F, Osteaux M. Patient and staff exposure during endoscopic retrograde cholangiopancreatography. Br J Radiol 2002;75:435e43. [2] Olgar T, Bor D, Berkmwn G, Yazar T. Patient and staff doses for some complex X-ray examinations. J Radiol Prot 2009;29:393e407. [3] Martin CJ, Magee JS. Assessment of eye and body dose for interventional radiologists, cardiologists, and other interventional staff. J Radiol Prot 2013;33: 445e60. [4] Vanhavere F, Carinou E, Domienik J, Donadille L, Ginjaume M, Gualdrinif G, et al. Measurements of eye lens doses in interventional radiology and cardiology: final results of the ORAMED project. Radiat Meas 2011;46:1243e7.
[5] O'Connor U, Gallagher A, Malone L, O'Reilly G. Occupational radiation dose to eyes from endoscopic retrograde cholangiopancreatography procedures in light of the revised eye lens dose limit from the international commission on radiological protection. Br J Radiol 2013 Feb;86(1022):20120289. http:// dx.doi.org/10.1259/bjr.20120289. [6] International Atomic Energy Agency TECDOC 1731. Implications for occupational radiation protection of the new dose limit for the lens of the eye. 2013. [7] International Commission on Radiological Protection. Statement on tissue reactions approved by the commission on April 21. 2011. ICRP; 2011. [8] European Commission. Council directive 2013/59/euroatom. 2014. L13/1. [9] International Organization for Standardization. X and gamma reference radiation for calibrating dosemeters and dose rate meters and for determining their response as a function of photon energy. Calibration of area and personal dosemeters and the measurement of their response as a function of energy and angle of incidence. 1999. ISO 4037-3. [10] International Electrotechnical Commission. IEC 61526. Radiation protection instrumentation - measurement of personal dose equivalents Hp(10) and Hp(0,07) for X, gamma, neutron and beta radiations - direct reading personal dose equivalent meters. 2010. [11] ICRP 103 ICRP. The 2007 recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37. 2007. p. 2e4. [12] Vanhavere F, Carinou E, Gualdrini G, Clairand I, Sans Merce M, Ginjaume M, et al. ORAMED: optimization of radiation protection of medical staff. EURADOS Report. 2012-02. [13] European Commission. Technical recommendations for monitoring individuals occupationally exposed to external radiation. Radiat. Prot. 160. 2009. [14] Koukorava C, Farah J, Sturelens L, Clairand I, Donadille L, Vanhavere F, et al. Efficiency of radiation protection equipment in interventional radiology: a systematic Monte Carlo study of eye lens and whole body doses. J Radiol Prot 2014;34:509e28. [15] Scheler B. Operators shielding: how and why. tech vasc. Interv Rad 2010;13: 167e71. [16] Radiological Protection Institute of Ireland. The design of diagnostic medical facilities where ionising radiation is used. 2009.
Please cite this article in press as: Zagorska A, et al., Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography, Physica Medica (2015), http://dx.doi.org/10.1016/j.ejmp.2015.03.011
