- Email: [email protected]
Radiation exposure to eye lens and operator hands during endovascular procedures in hybrid operating rooms
Radiation exposure to eye lens and operator hands during endovascular procedures in hybrid operating rooms Nicolas Attigah, MD,a Kyriakos Oikonomou, MD,b Ulf Hinz, MSc,c Thomas Knoch, MSc,d Serdar Demirel, MD,a Eric Verhoeven, MD, PhD,b and Dittmar Böckler, MD,a Heidelberg and Nuremberg, Germany Objective: The purpose of this study was to evaluate the radiation exposure of vascular surgeons’ eye lens and fingers during complex endovascular procedures in modern hybrid operating rooms. Methods: Prospective, nonrandomized multicenter study design. One hundred seventy-one consecutive patients (138 male; median age, 72.5 years [interquartile range, 65-77 years]) underwent an endovascular procedure in a hybrid operating room between March 2012 and July 2013 in two vascular centers. The dose-area product (DAP), fluoroscopy time, operating time, and amount of contrast dye were registered prospectively. For radiation dose recordings, single-use dosimeters were attached at eye level and to the ring finger of the hand next to the radiation field of the operator for each endovascular procedure. Dose recordings were evaluated by an independent institution. Before the study, precursory investigations were obtained to simulate the radiation dose to eye lens and fingers with an Alderson phantome (RSD, Long Beach, Calif). Results: Interventions were classified into six treatment categories: endovascular repair of infrarenal abdominal aneurysm (n [ 65), thoracic endovascular aortic repair (n [ 32), branched endovascular aortic repair for thoracoabdominal aneurysms (n [ 17), fenestrated endovascular aortic repair for complex abdominal aortic aneurysm, (n [ 25), iliac branched device (n [ 8), and peripheral interventions (n [ 24). There was a significant correlation in DAP between both lens (P < .01; r [ 0.55) and finger (P < .01; r [ 0.56) doses. The estimated fluoroscopy time to reach a radiation threshold of 20 mSv/y was 1404.10 minutes (90% confidence limit, 1160, 1650 minutes). According to correlation of the lens dose with the DAP an estimated cumulative DAP of 932,000 mGy/m2 (90% confidence limit, 822,000, 1,039,000) would be critical for a threshold of 20 mSv/y for the eyes. Conclusions: Radiation protection is a serious issue for vascular surgeons because most complex endovascular procedures are delivering measurable radiation to the eyes. With the correlation of the DAP obtained in standard endovascular procedures a critical threshold of 20 mSv/y to the eyes can be predicted and thus an estimate of a potential harmful exposure to the eyes can be obtained. (J Vasc Surg 2015;-:1-6.)
Endovascular procedures have emerged in vascular surgery over the past decades and represent a proportion up to 80% of vascular interventions.1 Endovascular treatment of infrarenal aortic aneurysms became first-line treatment with increasing evidence.2 The introduction of branched From the Department of Vascular and Endovascular Surgery,a and Unit of Documentation and Statistics, Department of Surgery,c Ruprecht-Karls University, Heidelberg; the Department of Vascular and Endovascular Surgery, Paracelsus Medical University, Nurembergb; and the Unit of Radiation Protection, Department of Surgery, Ruprecht-Karls University of Heidelberg, Heidelberg.d Author conflict of interest: D.B. is a proctor for Siemens AG (Siemens, Germany). The institution in Heidelberg receives a research grant from Siemens for different research projects. E.V. is a consultant for Cook and Siemens, and he has received educational grants from both Cook and Siemens. Correspondence: Dittmar Böckler, MD, Department of Vascular and Endovascular Surgery, University of Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2015.08.051
and fenestrated grafts has extended endovascular treatment options towards more complex anatomies to treat juxtarenal aneurysms, thoracoabdominal aneurysms and aortic dissections.3-8 Since the advent of hybrid operating rooms and a proendovascular approach in many indications, exposure to radiation for vascular surgeons and interventionalists in general has increased significantly.9,10 The risk of radiation injury is quite well investigated in patients, but not in operators/interventionalists.11 There is an increasing interest in the personal professional radiation risk.9,12 Whereas the trunk is most likely well enough protected by lead garments, eye lens and hands are at risk of unprotected exposure. For the eye lens in particular, the mechanism of radiation injury is not fully understood, and both deterministic or stochastic mechanisms could induce early cataract.13 Referring to occupational health radiation to hands is of minor clinical relevance. However, there exist data that chronic low-dose exposure might have an effect on the microvascular structure and probably induces radiodermatitis.14,15 The aim of this study was to determine prospectively the cumulative radiation exposure of eye lens and finger doses among vascular surgeons working in a hybrid operating room environment performing complex endovascular procedures and to estimate critical radiation thresholds. 1
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2 Attigah et al
METHODS Between March 2012 and July 2013, 171 consecutive patients underwent an endovascular procedure in two vascular centers, the Department of Vascular and Endovascular Surgery of the University of Heidelberg, and the Department of Vascular and Endovascular Surgery in Nuremberg, Germany. All patients were treated in a similar Hybrid-OR (Artis-Zeego, Siemens, Forchheim, Germany). From the procedure the operating time, the fluoroscopy time, and the dose-area product (DAP) was recorded. The detector field of view was 48 cm2. To estimate eye lens and finger doses, preliminary simulations of an endovascular procedure were conducted with a female Alderson-phantome (RSD, Long Beach, Calif). The Alderson phantome mimics scatter radiation generated under in vivo conditions. The radiation doses for eye lens and fingers during simulation were measured with a Dose Rate Meter 6150AD4 (Automess, Ladenburg, Germany) in a typical distance between the radiation field and the eye lens (86 cm) and fingers (40 cm) during an endovascular procedure, with the person being approximately 178 cm tall and standing right-sided to the operating table (Fig 1). For the dose estimation of the surgeons during the endovascular procedures, thermoluminescent eye lens and finger dosimeters for single use (AWST-TL-TD, type W Hemholtz-Zentrum Munich, German research center for environmental health) were attached to the front part of the forehead and dorsally to the ring finger of the right hand of the operating surgeon. According to the International Council for Radiation Protection, a threshold of 20 mSv/y was judged critical for operators’ lens exposure.16 All operating surgeons were board-certified vascular surgeons with a mandatory basic and special course in radiation physics and radiation protection. The whole staff was encouraged to use all available protection measures such as lead screens, undertable lead aprons, optimum source-toobject distance, and fade-in of the region of interest. Additionally, a dosimeter was placed at the anesthesia working place approximately 2.5 m from the radiation source. The dose recordings were measured by an independent certified institution (Hemholtz-Zentrum Munich, Germany). Patients gave their informed consent to the operation and their consent to use clinical data for quality control purposes and clinical research. Study approval was waived by the institutional review board given that all data were anonymous and no patient identifiers were obtained. Statistical analysis. SAS software (Release 9.1; SAS Institute, Inc, Cary, NC) was used. Age at operation was presented as median with interquartile range. Quantitative parameters such as operating time (minutes), fluoroscopy time (minutes), DAP (milligray per square meter [mGy/m2]), the use of contrast dye (mL), lens doses (mSv), and finger doses (mSv) are expressed as mean values 6 standard deviation. The Kruskal-Wallis test was used as overall test to compare these quantitative parameters between treatment groups. Categorical parameters are presented as absolute
Fig 1. Preliminary dose estimation for eye lens and fingers. Simulation was performed with an Alderson-phantome (female; RSD, Long Beach, Calif). Radiation doses for eye lens and fingers were calculated with a Dose Rate Meter 6150AD4 (Automess, Ladenburg, Germany) for an 178-cm tall person in a typical position during an endovascular procedure standing right-sided next to the table with a distance of 40 cm distal to the irradiated field (measuring points A and B).
numbers and as relative frequencies. The Spearman correlation coefficient, with its corresponding P value, was used to examine the relationship of operating time, fluoroscopy time, DAP, the use of contrast dye, lens doses, and finger doses. Scatter plots with a regression line were used to present a correlation between two quantitative parameters. Mean values with 90% confidence limits (CLs) of fluoroscopy time and DAP for a radiation threshold of 20 mSv/y lens dose were estimated using the values of each operation. Twosided P values were computed and a difference was considered significant at P # .05. RESULTS Precursory investigations. The preliminary simulation of an endovascular aortic procedure showed that with a 10 seconds period of fluoroscopy in DSA modus the eye lens received a radiation dose of 0.02 mSv/s and the fingers of 0.41 mSv/s (Fig 1). Demographic data. A total of 171 patients were operated on in a hybrid operating room in both vascular centers (n ¼ 88 in Heidelberg [center 1], n ¼ 83 in Nuremberg [center 2]). One hundred thirty-eight (81%) patients were male, with a similar distribution in both centers. The median patient age was 73 years (interquartile range,
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Table. Procedural results of the six treatment categories Variable
EVAR
TEVAR
BEVAR
FEVAR
IBD
Peripheral
No. 65 32 17 25 8 24 OR time, minutes 111 6 38 124 6 78 317 6 131 219 6 94 148 6 55 114 6 109 Fluoroscopy time, 19 6 10 19 6 19 89 6 52 62 6 36 29 6 7 12 6 11 minutes 2 DAP, mGy/cm 23,000 6 25,000 23,000 6 20,000 48,000 6 38,000 39,000 6 33,000 28,000 6 21,000 13,000 6 23,000 Contrast dye, mL 124 6 50 130 6 77 226 6 69 164 6 72 138 6 34 71 6 48 Lens dose, mSv 0.47 6 0.34 0.57 6 0.41 0.70 6 0.65 0.69 6 0.46 0.78 6 0.60 0.52 6 0.38 Finger dose, mSv 0.62 6 0.62 0.76 6 0.74 1.31 6 1.58 1.02 6 1.53 0.75 6 0.76 0.79 6 0.61
P d <.01 <.01 <.01 <.01 .28 .46
BEVAR, Branched endovascular aortic repair; DAP, dose-area product; EVAR, endovascular aortic repair; FEVAR, fenestrated endovascular aortic repair; IBD, iliac branched device; OR, operating room; TEVAR, thoracic endovascular aortic repair. All values are presented as means 6 standard deviation.
Fig 2. Scatter plots with regression line indicating correlation of eye lens radiation doses with dose-area product (DAP).
65-77 years). The performed endovascular operations were split into six treatment categories (endovascular aortic repair, thoracic endovascular aortic repair, fenestrated endovascular aortic repair, branched endovascular aortic repair, iliac branched device, and peripheral interventions). Baseline characteristics of categories and radiation doses are reported in the Table. There was a significant correlation between the DAP and both the lens and the recorded finger doses, as well there was a correlation between doses for eyes and fingers (P < .01 [r ¼ 0.55]; P < .01 [r ¼ 0.56]; and P < .01 [r ¼ 0.75]; Figs 2-4). The estimated fluoroscopy time to reach a radiation threshold of 20 mSv was 1400 minutes (90% CL, 1160,
1650). According to correlation of the lens dose with the DAP an estimated cumulative DAP of 932,000 mGy*cm2 (90% CL, 822,000, 1,039,000) would be critical to reach a threshold of 20 mSv for the eyes. Additionally a dosimeter was placed at the anesthesiology working place and the radiation dose was recorded for 110 days, approximately 2.5 m away from the radiation source. The recorded irradiation dose was 3.1 mSv. DISCUSSION This study shows that radiation exposure to eye lens and fingers is detectable in relevant amounts and therefore cannot be neglected. The average eye lens radiation dose for the
4 Attigah et al
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Fig 3. Scatter plots with regression line indicating correlation of finger radiation doses with dose-area product (DAP).
surgeon in this study was 0.78 mSv during iliac branched device procedures. The finger dose in the branched endovascular aortic repair category was 1.31 mSv. There was a significant correlation between the DAP and the recorded doses for both eyes and fingers. The doses of eyes and fingers hereby correlated significantly with each other. According to this study, a fluoroscopy time of 1401.1 minutes (23.40 hours) is considered to be critical to reach a lens dose of approximately 20 mSv/y. Although the federal law in Germany sets the dose maximum for eye lens at 150 mSv/y, a recent statement of the International Commission on Radiation Protection recommended to reduce the limit to 20 mSv/y.16,17 There is evidence that radiation to the surgeon’s eye can be attenuated considerably by wearing radiation protection glasses. However, best protection is achieved by a frontal position to the radiation source. With the head turned to the side relative to the patient as the source of scatter, as in most interventional clinical settings, the protective effect is markedly decreased and makes the additional use of a ceiling suspended lead screen mandatory to achieve full protection levels.18 A recent approach to reduce radiation to both patients and staff could be the use of disposable radiation-absorbing drapes.19 Two limitations of this study are that radiation doses of the assisting surgeons were not obtained and that no differentiation was made between fluoroscopy and digital subtraction mode. Radiation protection is a serious issue not only because of the cataract risk, but also because there is emerging evidence that ionizing radiation could be
responsible for brain tumors in interventional cardiologists and physicians performing interventional procedures.20,21 Therefore, all measures for radiation attenuation should be carefully applied. These are maximum shielding, distance from the radiation source, and optimum collimator positioning.22-24 In this regard, education for vascular surgeons is an increasingly important factor and should be mandatory, because there is evidence that training improves the radiation doses of patients and surgeons at the same time.25-27 A dosimeter was also placed at the working place of anesthesia, approximately 2.5 m away from the radiation source. The recording over 110 days showed a dose of 3.1 mSv. This emphasizes the need for protection of the whole room personnel. In the case of anesthesiologists, this is best accomplished by the means of moveable lead walls in addition to lead aprons.28 Because there is no clear evidence so far whether radiation injury to the eye lens is deterministic rather than stochastic, maximum eye protection should be implemented with caution and care.29 Furthermore, data exist showing that chronic exposure to the eyes may cause dry eye condition and radiation retinopathy, both chronic conditions with few treatment options.30-32 Compared with the eyes, radiation to the fingers is of minor clinical relevance. However there is evidence that chronic exposure to hands changes microvascular structure and might induce radiodermatitis.14,15
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Fig 4. Scatter plots with regression line indicating correlation of finger radiation doses with eye lens radiation doses.
CONCLUSIONS Radiation protection is a serious issue of increasing importance for interventionalists such as vascular surgeons, because most complex endovascular procedures impart measurable radiation doses to the eye lens. With a positive correlation of the DAP to the detected doses of lens and fingers in standard endovascular procedures, a critical threshold of 20 mSv/y can be roughly estimated and thus give the surgeon an index of the risk overtime as the DAP can be easily obtained from any fluoroscopy device. In this study the threshold of 20 mSv would be reached in approximately 1400 minutes of fluoroscopy time per year. AUTHOR CONTRIBUTIONS Conception and design: NA, TK Analysis and interpretation: NA, TK, EV, DB Data collection: NA, KO, SD Writing the article: NA Critical revision of the article: NA, UH, TK, EV, DB Final approval of the article: NA, KO, SD, EV, DB Statistical analysis: UH Obtained funding: Not applicable Overall responsibility: DB REFERENCES 1. Veith FJ. Metamorphosis of vascular surgeons to endovascular specialists: must vascular surgery have an independent board and can we get there? J Endovasc Ther 2005;12:269-73.
2. Bockler D, Riambau V, Fitridge R, Wolf Y, Hayes P, Silveira P, et al. Worldwide experience with the Endurant Stent graft: review of the literature. J Cardiovasc Surg 2011;52:669-81. 3. Solomon H, Chao AB, Weaver FA, Katz SG. Change in practice patterns of an academic division of vascular surgery. Arch Surg 2007;142: 733-6; discussion: 736-7. 4. Cowan JA Jr, Dimick JB, Henke PK, Rectenwald J, Stanley JC, Upchurch GR Jr. Epidemiology of aortic aneurysm repair in the United States from 1993 to 2003. Ann N Y Acad Sci 2006;1085:1-10. 5. Larzon T, Lindgren R, Norgren L. Endovascular treatment of ruptured abdominal aortic aneurysms: a shift of the paradigm? J Endovasc Ther 2005;12:548-55. 6. Mani K, Lees T, Beiles B, Jensen LP, Venermo M, Simo G, et al. Treatment of abdominal aortic aneurysm in nine countries 20052009: a Vascunet report. Eur J Vasc Endovasc Surg 2011;42: 598-607. 7. Chuter T. Branched stent grafts for endovascular repair of the aortic arch: a work in progress. Gefässchirurgie 2009;3:191-7. 8. Verhoeven EL, Vourliotakis G. Thoracic endovascular aortic repair for aortobronchial or aortoesophageal fistulas: permanent or temporary salvage or not an option at all? J Endovasc Ther 2009;16:441-2. 9. Ketteler ER, Brown KR. Radiation exposure in endovascular procedures. J Vasc Surg 2011;53(1 Suppl):35S-8S. 10. Panuccio G, Greenberg RK, Wunderle K, Mastracci TM, Eagleton MG, Davros W. Comparison of indirect radiation dose estimates with directly measured radiation dose for patients and operators during complex endovascular procedures. J Vasc Surg 2011;53: 885-94.e1; discussion: 894. 11. Picano E, Vano E, Rehani MM, Cuocolo A, Mont L, Bodi V, et al. The appropriate and justified use of medical radiation in cardiovascular imaging: a position document of the ESC Associations of Cardiovascular Imaging, Percutaneous Cardiovascular Interventions and Electrophysiology. Eur Heart J 2014;35:665-72. 12. Brown KR, Rzucidlo E. Acute and chronic radiation injury. J Vasc Surg 2011;53(1 Suppl):15S-21S.
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13. Walsh SR, Cousins C, Tang TY, Gaunt ME, Boyle JR. Ionizing radiation in endovascular interventions. J Endovasc Ther 2008;15:680-7. 14. Wild P, Gauron C, Derock C, Champion K, Cohen P, Menez C, et al. 0024 Effects of chronic low-dose exposure to ionising radiation on physician micro-vascular structure revealed by nail fold capillaroscopy. Occup Environ Med 2014;71(Suppl 1):A60. 15. Artignan S, Conso F, Hazebroucq V. [Radiodermatitis in interventional radiology (hand dose measurement, screening and compensation)]. J Radiolog 2003;84:317-9. 16. Stewart FA, Akleyev AV, Hauer-Jensen M, Hendry JH, Kleiman NJ, Macvittie TJ, et al; ICRP. ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organsethreshold doses for tissue reactions in a radiation protection context. Ann ICRP 2012;41:1-322. 17. Ainsbury EA, Bouffler S, Cocker M, Gilvin P, Holt E, Peters S, et al. Public Health England survey of eye lens doses in the UK medical sector. J Radiol Protect 2014;34:15-29. 18. van Rooijen BD, de Haan MW, Das M, Arnoldussen CW, de Graaf R, van Zwam WH, et al. Efficacy of Radiation Safety Glasses in Interventional Radiology. Cardiovasc Intervent Radiol 2014;37:1149-55. 19. Kloeze C, Klompenhouwer EG, Brands PJ, van Sambeek MR, Cuypers PW, Teijink JA. Editor’s choiceeUse of disposable radiationabsorbing surgical drapes results in significant dose reduction during EVAR procedures. Eur J Vasc Endovasc Surg 2014;47:268-72. 20. Roguin A. Brain tumours among interventional cardiologists: a call for alarm? Eur Heart J 2012;33:1850-1. 21. Roguin A, Goldstein J, Bar O. Brain tumours among interventional cardiologists: a cause for alarm? Report of four new cases from two cities and a review of the literature. EuroIntervention 2012;7:1081-6. 22. Bashore TM. Radiation safety in the cardiac catheterization laboratory. Am Heart J 2004;147:375-8.
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23. Vano E. Radiation exposure to cardiologists: how it could be reduced. Heart 2003;89:1123-4. 24. Ullery BW, Landau B, Wang GJ, Faifrman RM, Woo EY. Radiation dose to the interventionalist is directly affected by the operating position. Vascular 2014;22:149-53. 25. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Chung J, Anderson JA, et al. Surgeon education decreases radiation dose in complex endovascular procedures and improves patient safety. J Vasc Surg 2013;58:715-21. 26. Shaw PM, Vouyouka A, Reed A. Time for radiation safety program guidelines for pregnant trainees and vascular surgeons. J Vasc Surg 2012;55:862-8.e2. 27. Chambers CE. Mandatory radiation safety training for fluoroscopy imaging: a quality improvement priority or unnecessary oversight? JACC Cardiovasc Intervent 2014;7:391-3. 28. Mohapatra A, Greenberg RK, Mastracci TM, Eagleton MJ, Thornsberry B. Radiation exposure to operating room personnel and patients during endovascular procedures. J Vasc Surg 2013;58:702-9. 29. Hamada N, Fujimichi Y, Iwasaki T, Fujii N, Furuhashi M, Kubo E, et al. Emerging issues in radiogenic cataracts and cardiovascular disease. J Radiat Res 2014;55:831-46. 30. Parsons JT, Bova FJ, Fitzgerald CR, Mendenhall WM, Million RR. Severe dry-eye syndrome following external beam irradiation. Int J Radiat Oncol Biol Phys 1994;30:775-80. 31. Hempel M, Hinkelbein W. Eye sequelae following external irradiation. Recent Results Cancer Res 1993;130:231-6. 32. Kurien BT, Mathews SA, Scofield RH. Can low dose diagnostic dental radiation trigger Sjogren’s syndrome? Med Hypotheses 2007;69: 995-1000. Submitted Sep 15, 2014; accepted Aug 2, 2015.
Endovascular procedures have emerged in vascular surgery over the past decades and represent a proportion up to 80% of vascular interventions.1 Endovascular treatment of infrarenal aortic aneurysms became first-line treatment with increasing evidence.2 The introduction of branched From the Department of Vascular and Endovascular Surgery,a and Unit of Documentation and Statistics, Department of Surgery,c Ruprecht-Karls University, Heidelberg; the Department of Vascular and Endovascular Surgery, Paracelsus Medical University, Nurembergb; and the Unit of Radiation Protection, Department of Surgery, Ruprecht-Karls University of Heidelberg, Heidelberg.d Author conflict of interest: D.B. is a proctor for Siemens AG (Siemens, Germany). The institution in Heidelberg receives a research grant from Siemens for different research projects. E.V. is a consultant for Cook and Siemens, and he has received educational grants from both Cook and Siemens. Correspondence: Dittmar Böckler, MD, Department of Vascular and Endovascular Surgery, University of Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2015.08.051
and fenestrated grafts has extended endovascular treatment options towards more complex anatomies to treat juxtarenal aneurysms, thoracoabdominal aneurysms and aortic dissections.3-8 Since the advent of hybrid operating rooms and a proendovascular approach in many indications, exposure to radiation for vascular surgeons and interventionalists in general has increased significantly.9,10 The risk of radiation injury is quite well investigated in patients, but not in operators/interventionalists.11 There is an increasing interest in the personal professional radiation risk.9,12 Whereas the trunk is most likely well enough protected by lead garments, eye lens and hands are at risk of unprotected exposure. For the eye lens in particular, the mechanism of radiation injury is not fully understood, and both deterministic or stochastic mechanisms could induce early cataract.13 Referring to occupational health radiation to hands is of minor clinical relevance. However, there exist data that chronic low-dose exposure might have an effect on the microvascular structure and probably induces radiodermatitis.14,15 The aim of this study was to determine prospectively the cumulative radiation exposure of eye lens and finger doses among vascular surgeons working in a hybrid operating room environment performing complex endovascular procedures and to estimate critical radiation thresholds. 1
JOURNAL OF VASCULAR SURGERY --- 2015
2 Attigah et al
METHODS Between March 2012 and July 2013, 171 consecutive patients underwent an endovascular procedure in two vascular centers, the Department of Vascular and Endovascular Surgery of the University of Heidelberg, and the Department of Vascular and Endovascular Surgery in Nuremberg, Germany. All patients were treated in a similar Hybrid-OR (Artis-Zeego, Siemens, Forchheim, Germany). From the procedure the operating time, the fluoroscopy time, and the dose-area product (DAP) was recorded. The detector field of view was 48 cm2. To estimate eye lens and finger doses, preliminary simulations of an endovascular procedure were conducted with a female Alderson-phantome (RSD, Long Beach, Calif). The Alderson phantome mimics scatter radiation generated under in vivo conditions. The radiation doses for eye lens and fingers during simulation were measured with a Dose Rate Meter 6150AD4 (Automess, Ladenburg, Germany) in a typical distance between the radiation field and the eye lens (86 cm) and fingers (40 cm) during an endovascular procedure, with the person being approximately 178 cm tall and standing right-sided to the operating table (Fig 1). For the dose estimation of the surgeons during the endovascular procedures, thermoluminescent eye lens and finger dosimeters for single use (AWST-TL-TD, type W Hemholtz-Zentrum Munich, German research center for environmental health) were attached to the front part of the forehead and dorsally to the ring finger of the right hand of the operating surgeon. According to the International Council for Radiation Protection, a threshold of 20 mSv/y was judged critical for operators’ lens exposure.16 All operating surgeons were board-certified vascular surgeons with a mandatory basic and special course in radiation physics and radiation protection. The whole staff was encouraged to use all available protection measures such as lead screens, undertable lead aprons, optimum source-toobject distance, and fade-in of the region of interest. Additionally, a dosimeter was placed at the anesthesia working place approximately 2.5 m from the radiation source. The dose recordings were measured by an independent certified institution (Hemholtz-Zentrum Munich, Germany). Patients gave their informed consent to the operation and their consent to use clinical data for quality control purposes and clinical research. Study approval was waived by the institutional review board given that all data were anonymous and no patient identifiers were obtained. Statistical analysis. SAS software (Release 9.1; SAS Institute, Inc, Cary, NC) was used. Age at operation was presented as median with interquartile range. Quantitative parameters such as operating time (minutes), fluoroscopy time (minutes), DAP (milligray per square meter [mGy/m2]), the use of contrast dye (mL), lens doses (mSv), and finger doses (mSv) are expressed as mean values 6 standard deviation. The Kruskal-Wallis test was used as overall test to compare these quantitative parameters between treatment groups. Categorical parameters are presented as absolute
Fig 1. Preliminary dose estimation for eye lens and fingers. Simulation was performed with an Alderson-phantome (female; RSD, Long Beach, Calif). Radiation doses for eye lens and fingers were calculated with a Dose Rate Meter 6150AD4 (Automess, Ladenburg, Germany) for an 178-cm tall person in a typical position during an endovascular procedure standing right-sided next to the table with a distance of 40 cm distal to the irradiated field (measuring points A and B).
numbers and as relative frequencies. The Spearman correlation coefficient, with its corresponding P value, was used to examine the relationship of operating time, fluoroscopy time, DAP, the use of contrast dye, lens doses, and finger doses. Scatter plots with a regression line were used to present a correlation between two quantitative parameters. Mean values with 90% confidence limits (CLs) of fluoroscopy time and DAP for a radiation threshold of 20 mSv/y lens dose were estimated using the values of each operation. Twosided P values were computed and a difference was considered significant at P # .05. RESULTS Precursory investigations. The preliminary simulation of an endovascular aortic procedure showed that with a 10 seconds period of fluoroscopy in DSA modus the eye lens received a radiation dose of 0.02 mSv/s and the fingers of 0.41 mSv/s (Fig 1). Demographic data. A total of 171 patients were operated on in a hybrid operating room in both vascular centers (n ¼ 88 in Heidelberg [center 1], n ¼ 83 in Nuremberg [center 2]). One hundred thirty-eight (81%) patients were male, with a similar distribution in both centers. The median patient age was 73 years (interquartile range,
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Table. Procedural results of the six treatment categories Variable
EVAR
TEVAR
BEVAR
FEVAR
IBD
Peripheral
No. 65 32 17 25 8 24 OR time, minutes 111 6 38 124 6 78 317 6 131 219 6 94 148 6 55 114 6 109 Fluoroscopy time, 19 6 10 19 6 19 89 6 52 62 6 36 29 6 7 12 6 11 minutes 2 DAP, mGy/cm 23,000 6 25,000 23,000 6 20,000 48,000 6 38,000 39,000 6 33,000 28,000 6 21,000 13,000 6 23,000 Contrast dye, mL 124 6 50 130 6 77 226 6 69 164 6 72 138 6 34 71 6 48 Lens dose, mSv 0.47 6 0.34 0.57 6 0.41 0.70 6 0.65 0.69 6 0.46 0.78 6 0.60 0.52 6 0.38 Finger dose, mSv 0.62 6 0.62 0.76 6 0.74 1.31 6 1.58 1.02 6 1.53 0.75 6 0.76 0.79 6 0.61
P d <.01 <.01 <.01 <.01 .28 .46
BEVAR, Branched endovascular aortic repair; DAP, dose-area product; EVAR, endovascular aortic repair; FEVAR, fenestrated endovascular aortic repair; IBD, iliac branched device; OR, operating room; TEVAR, thoracic endovascular aortic repair. All values are presented as means 6 standard deviation.
Fig 2. Scatter plots with regression line indicating correlation of eye lens radiation doses with dose-area product (DAP).
65-77 years). The performed endovascular operations were split into six treatment categories (endovascular aortic repair, thoracic endovascular aortic repair, fenestrated endovascular aortic repair, branched endovascular aortic repair, iliac branched device, and peripheral interventions). Baseline characteristics of categories and radiation doses are reported in the Table. There was a significant correlation between the DAP and both the lens and the recorded finger doses, as well there was a correlation between doses for eyes and fingers (P < .01 [r ¼ 0.55]; P < .01 [r ¼ 0.56]; and P < .01 [r ¼ 0.75]; Figs 2-4). The estimated fluoroscopy time to reach a radiation threshold of 20 mSv was 1400 minutes (90% CL, 1160,
1650). According to correlation of the lens dose with the DAP an estimated cumulative DAP of 932,000 mGy*cm2 (90% CL, 822,000, 1,039,000) would be critical to reach a threshold of 20 mSv for the eyes. Additionally a dosimeter was placed at the anesthesiology working place and the radiation dose was recorded for 110 days, approximately 2.5 m away from the radiation source. The recorded irradiation dose was 3.1 mSv. DISCUSSION This study shows that radiation exposure to eye lens and fingers is detectable in relevant amounts and therefore cannot be neglected. The average eye lens radiation dose for the
4 Attigah et al
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Fig 3. Scatter plots with regression line indicating correlation of finger radiation doses with dose-area product (DAP).
surgeon in this study was 0.78 mSv during iliac branched device procedures. The finger dose in the branched endovascular aortic repair category was 1.31 mSv. There was a significant correlation between the DAP and the recorded doses for both eyes and fingers. The doses of eyes and fingers hereby correlated significantly with each other. According to this study, a fluoroscopy time of 1401.1 minutes (23.40 hours) is considered to be critical to reach a lens dose of approximately 20 mSv/y. Although the federal law in Germany sets the dose maximum for eye lens at 150 mSv/y, a recent statement of the International Commission on Radiation Protection recommended to reduce the limit to 20 mSv/y.16,17 There is evidence that radiation to the surgeon’s eye can be attenuated considerably by wearing radiation protection glasses. However, best protection is achieved by a frontal position to the radiation source. With the head turned to the side relative to the patient as the source of scatter, as in most interventional clinical settings, the protective effect is markedly decreased and makes the additional use of a ceiling suspended lead screen mandatory to achieve full protection levels.18 A recent approach to reduce radiation to both patients and staff could be the use of disposable radiation-absorbing drapes.19 Two limitations of this study are that radiation doses of the assisting surgeons were not obtained and that no differentiation was made between fluoroscopy and digital subtraction mode. Radiation protection is a serious issue not only because of the cataract risk, but also because there is emerging evidence that ionizing radiation could be
responsible for brain tumors in interventional cardiologists and physicians performing interventional procedures.20,21 Therefore, all measures for radiation attenuation should be carefully applied. These are maximum shielding, distance from the radiation source, and optimum collimator positioning.22-24 In this regard, education for vascular surgeons is an increasingly important factor and should be mandatory, because there is evidence that training improves the radiation doses of patients and surgeons at the same time.25-27 A dosimeter was also placed at the working place of anesthesia, approximately 2.5 m away from the radiation source. The recording over 110 days showed a dose of 3.1 mSv. This emphasizes the need for protection of the whole room personnel. In the case of anesthesiologists, this is best accomplished by the means of moveable lead walls in addition to lead aprons.28 Because there is no clear evidence so far whether radiation injury to the eye lens is deterministic rather than stochastic, maximum eye protection should be implemented with caution and care.29 Furthermore, data exist showing that chronic exposure to the eyes may cause dry eye condition and radiation retinopathy, both chronic conditions with few treatment options.30-32 Compared with the eyes, radiation to the fingers is of minor clinical relevance. However there is evidence that chronic exposure to hands changes microvascular structure and might induce radiodermatitis.14,15
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Fig 4. Scatter plots with regression line indicating correlation of finger radiation doses with eye lens radiation doses.
CONCLUSIONS Radiation protection is a serious issue of increasing importance for interventionalists such as vascular surgeons, because most complex endovascular procedures impart measurable radiation doses to the eye lens. With a positive correlation of the DAP to the detected doses of lens and fingers in standard endovascular procedures, a critical threshold of 20 mSv/y can be roughly estimated and thus give the surgeon an index of the risk overtime as the DAP can be easily obtained from any fluoroscopy device. In this study the threshold of 20 mSv would be reached in approximately 1400 minutes of fluoroscopy time per year. AUTHOR CONTRIBUTIONS Conception and design: NA, TK Analysis and interpretation: NA, TK, EV, DB Data collection: NA, KO, SD Writing the article: NA Critical revision of the article: NA, UH, TK, EV, DB Final approval of the article: NA, KO, SD, EV, DB Statistical analysis: UH Obtained funding: Not applicable Overall responsibility: DB REFERENCES 1. Veith FJ. Metamorphosis of vascular surgeons to endovascular specialists: must vascular surgery have an independent board and can we get there? J Endovasc Ther 2005;12:269-73.
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23. Vano E. Radiation exposure to cardiologists: how it could be reduced. Heart 2003;89:1123-4. 24. Ullery BW, Landau B, Wang GJ, Faifrman RM, Woo EY. Radiation dose to the interventionalist is directly affected by the operating position. Vascular 2014;22:149-53. 25. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Chung J, Anderson JA, et al. Surgeon education decreases radiation dose in complex endovascular procedures and improves patient safety. J Vasc Surg 2013;58:715-21. 26. Shaw PM, Vouyouka A, Reed A. Time for radiation safety program guidelines for pregnant trainees and vascular surgeons. J Vasc Surg 2012;55:862-8.e2. 27. Chambers CE. Mandatory radiation safety training for fluoroscopy imaging: a quality improvement priority or unnecessary oversight? JACC Cardiovasc Intervent 2014;7:391-3. 28. Mohapatra A, Greenberg RK, Mastracci TM, Eagleton MJ, Thornsberry B. Radiation exposure to operating room personnel and patients during endovascular procedures. J Vasc Surg 2013;58:702-9. 29. Hamada N, Fujimichi Y, Iwasaki T, Fujii N, Furuhashi M, Kubo E, et al. Emerging issues in radiogenic cataracts and cardiovascular disease. J Radiat Res 2014;55:831-46. 30. Parsons JT, Bova FJ, Fitzgerald CR, Mendenhall WM, Million RR. Severe dry-eye syndrome following external beam irradiation. Int J Radiat Oncol Biol Phys 1994;30:775-80. 31. Hempel M, Hinkelbein W. Eye sequelae following external irradiation. Recent Results Cancer Res 1993;130:231-6. 32. Kurien BT, Mathews SA, Scofield RH. Can low dose diagnostic dental radiation trigger Sjogren’s syndrome? Med Hypotheses 2007;69: 995-1000. Submitted Sep 15, 2014; accepted Aug 2, 2015.