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Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection
G Model BONSOI-4483; No. of Pages 5
ARTICLE IN PRESS Joint Bone Spine xxx (2016) xxx–xxx
Available online at
ScienceDirect www.sciencedirect.com
Original article
Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection Céline Cozic a , Fabien Audran b , Christophe Blanchard c , Christophe David d , Vincent Andre a , Michel Caulier a , Stéphane Varin a , Gilles Tanguy a , Jérôme Dimet e , Grégoire Cormier a,∗ a
Service de rhumatologie, CHD Vendée, boulevard Stéphane-Moreau, 85925 La Roche-sur-Yon cedex 9, France Unité de physique médicale, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France c Service de radiologie, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France d Unité de radioprotection, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France e Service de recherche clinique, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France b
a r t i c l e
i n f o
Article history: Accepted 18 May 2016 Available online xxx Keywords: Interventional rheumatology Radioprotection Patient radiation exposure Optimization of protection
a b s t r a c t Objectives: To decrease radiation exposure of patients undergoing interventional rheumatology procedures, without adversely affecting quality of care. Methods: The radiation dose received, assessed by the dose-area product (DAP), was measured during 283 intraarticular injections performed under fluoroscopic guidance between May and July 2013. Then, three steps were taken to decrease patients’ radiation exposure: a copper filter was added, the anti-scatter grid was removed, and exposure cell sensitivity was set at the highest value. DAP was measured during 158 intraarticular injections performed in 2014 with these measures in place. Results: Mean DAP before optimization was 175 Gray·m2 during facet joint injections (n = 4) and 43 Gray·m2 during hip injections but was less than 20 Gray·m2 for injections into the shoulders (15.7 Gray·m2 ), ankles (7.7 Gray·m2 ), wrists (3.7 Gray·m2 ), and fingers (3.3 Gray·m2 ). After optimization, DAP decreased markedly for all injection sites, by 52% (shoulders) to 87% (facet joints, 22.7 Gray·m2 ). Decreases occurred at all three steps of the procedure, i.e., patient installation, injection, and last image hold. Exposure during facet joint injections varied from 84 (54.5–108.5) Gray·m2 when body mass index (BMI) was < 25 kg/m2 to 228.9 (161.3–340.4) Gray·m2 when BMI was > 30 kg/m2 . Conclusion: Simple technical changes translate into large decreases in patient radiation exposure during fluoroscopically-guided injections, particularly at the facet joints and in obese patients. ´ e´ franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. © 2016 Societ
1. Introduction Fluoroscopy has been widely used in interventional rheumatology for decades to ensure that injections are performed intraarticularly. In recent years, concern has arisen about the risks associated with exposure to ionizing radiation during interventional rheumatology procedures. However, data on radiation protection of patients in this setting are scarce. In the European Union, patient radiation protection is regulated by Euratom directive 97/43, which was made a part of French
∗ Corresponding author. Service de rhumatologie, CHD Vendée, boulevard Stéphane-Moreau, 85925 La Roche-sur-Yon cedex 9, France. E-mail address: [email protected] (G. Cormier).
law by a decree issued on November 7, 2007. Radiation protection seeks to minimize or eliminate patient exposure to ionizing radiation by applying two principles, the principle of justification and the principle of optimization of protection to keep exposures as low as possible, while maintaining adequate image quality. Since 2004, regulations set diagnostic reference dose levels for each type of radiological procedure to serve as indicators for optimization. These levels are neither maximum doses that must not be exceeded nor radiological risk indicators. Instead, they are intended to help professionals assess the quality of radiological equipment and procedures, by providing a reference to which observed mean patient exposures can be compared. However, no diagnostic reference dose levels are available for interventional rheumatology. In France, a ministerial decree issued in September 2006 requires that the radiation dose to the patient during a fluoroscopy procedure be
http://dx.doi.org/10.1016/j.jbspin.2016.09.021 ´ e´ franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. 1297-319X/© 2016 Societ
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
G Model BONSOI-4483; No. of Pages 5
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recorded in the patient’s medical file. Doses delivered during fluoroscopy are measured as the dose-area product (DAP, in Gray·m2 defined as the mean absorbed dose to air in a cross-section of the Xray beam multiplied by the surface area of the same cross-section. DAP values are independent from the location of the cross-section along the beam, because the dose decreases, but the surface area increases, with the distance from the source to the cross-section. The primary objective of our work was to optimize our protection procedures by working jointly with radiophysicists and radiology technicians to decrease patient radiation exposure during rheumatology interventions under fluoroscopic guidance. The secondary objectives were to measure patient radiation exposure during these interventions and to evaluate whether this exposure varied with body mass index (BMI). 2. Method The study involved two phases. We first measured patient radiation exposure during intraarticular injections at any site, performed under standard conditions. The data were analyzed by consensus among the rheumatologists, a physicist, and radioprotection experts. Then, desirable changes in fluoroscopy settings were identified and implemented, and patient radiation exposure was measured with these new conditions. For all procedures, patients were on a Siemens Iconos R200 table. Collection of the data for the study was approved by the French Data Protection Authority (CNIL). 2.1. First phase (standard conditions) The study included consecutive patients who underwent an interventional rheumatology procedure between May and July 2013 at the regional hospital of La-Roche-sur-Yon, France. At the rheumatology department of this institution, two to three sessions of 9 to 12 interventional rheumatology procedures are performed under fluoroscopic guidance each week, for a total of about 1200 procedures annually. For each procedure, the patient’s BMI was recorded, and total DAP was computed for all three stages of the procedure, i.e., patient installation, the injection (Fig. S1 in the online-only supplement), and the last image hold. 2.2. Second phase (radiation dose optimization and its effects) A multidisciplinary meeting attended by the radiophysicists and radiology technicians was held to discuss measures that would decrease patient radiation exposure without adversely affecting image quality. Four measures were identified during experiments performed with a phantom: • a copper filter is a thin copper disk (0.1 to 0.3 mm) that can be positioned within the X-ray beam at the request of the operator to eliminate low-energy photons that increase the dose to the patient without contributing to image quality. We found that a copper filter decreased the dose by up to 60% (25 cm-thick phantom, 0.3 mm-thick copper filter, and 73 kV). A copper filter can be used for both radiography and fluoroscopy; • an anti-scatter grid is placed automatically between the patient and the image detector to eliminate radiation that has deviated from the direction of the primary beam, chiefly due to passage through the patient’s tissues. Removing the anti-scatter grid can decrease the patient radiation dose by up to 80% (for a radiograph taken in automatic exposure mode) but can adversely affect image quality. An anti-scatter grid can be used for both radiography and fluoroscopy; however, with fluoroscopy, the grid is
removed only if this does not impair the operator’s ability to perform the procedure; • in automatic exposure mode, adjusting generator voltage to the thickness of the patient can limit the charge. The dose decrease is particularly large for thick patients (who require higher voltages). This adjustment is possible only during radiography; with the radiology equipment used in our study, voltage is adjusted automatically during fluoroscopy; • finally, when taking radiographs, using the highest sensitivity setting for the exposure cell diminishes the amount of photons and, therefore, the exposure dose, by up to 49%. These parameters were set in the presence of the physicians to check that image quality was not unacceptably affected and remained sufficient to allow accurate intraarticular placement of the injections. All these parameters are set by the radiology technician, without requiring any intervention from the physician. The decision about whether to remove the anti-scatter grid is taken by the physician during the procedure according to image quality. Consecutive patients who underwent shoulder or facet joint injections under fluoroscopy guidance between April and July 2014 at the La-Roche-sur-Yon rheumatology department were included in the second phase of the study. These two injection sites were chosen for two reasons: they were the most common sites of injection in everyday practice, and our preliminary assessment showed that they were associated with the highest patient radiation exposures (see the Results section). All patients were informed that their BMI and the DAP delivered to them during the procedure would be recorded. 2.3. Statistical analysis Quantitative data were described as median (and ranges), and qualitative data as % (confidence interval). Student’s t test was chosen for comparisons of quantitative variables. 3. Results 3.1. Patient radiation exposure before optimization: 283 injections in 2013 The highest radiation exposure was for the facet joints, followed by the hip and shoulder. Median DAP values were as follows: • • • • • • •
175 Gray·m2 (76.4–180.1) for four facet joints (56 injections); 152.3 Gray·m2 (80.7–197.9) for two facet joints (60 injections); 43 Gray·m2 (32.1–50.3) for the hip (17 injections); 15.4 Gray·m2 (10.2–24.6) for the shoulder (71 injections); 7.7 Gray·m2 (4.8–12.4) for the ankle (17 injections); 3.7 Gray·m2 (2.77–4) for the wrist (17 injections); 3.3 Gray·m2 (1.65–8.85) for the fingers (45 injections) (Fig. 1).
When we analyzed the dose delivered during each of the three phases of each procedure, we found that the last image hold accounted on average for 62% of the total dose (at least 42% for the fingers and up to 77% for the hip). The percentage of the dose delivered was 8% during patient installation and 30% during the injection (Fig. 2). 3.2. Decreased patient radiation exposure after protection optimization In 2014, after implementing the changes, we studied 158 new injections, including 89 in the facet joints and 69 in the shoulder. The median DAP for four and two facet joints was
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
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Fig. 1. Median dose-area product delivered before optimization of protection, according to the injection site.
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Fig. 4. Decrease in dose-area product at each of the three phases of the procedure between 2013 and 2014.
(P < 0.01). Thus, the dose reduction was largest for the last image hold (−87%) (Fig. 4). 3.3. Association between body mass index (BMI) and patient radiation exposure
Fig. 2. Contribution of each of the three phases of the procedure to the radiation exposure, according to the injection site.
22.7 Gray·m2 (14.8–33.4) and 15.2 Gray·m2 (8.6–27.3), respectively, i.e., decreases of 83 and 87%, respectively. For the shoulder, mean DAP was 6.4 Gray·m2 (4–13.8), i.e., a significant 52% decrease (Fig. 3). The decrease in total DAP was due to decreases at all three phases of the procedure (installation, injection, and last image hold), for both the facet joint and the shoulder injections. When we pooled the facet joint injections (two and four), median DAP during installation decreased from 5.6 (2.5–10.7) Gray·m2 in 2013 to 1.6 (0.6–3.6) Gray·m2 in 2014 (P < 0.01), median DAP during the injection from 34.7 (13.8–63.4) Gray·m2 to 8.3 (4.4–11.6) Gray·m2 (P < 0.01), and DAP during the last image hold from 81.2 (48.7–116.5) Gray·m2 to 8.9 (5.7–15) Gray·m2
BMI was associated with DAP only for the facet joint injections before protection optimization. Among patients who received facet joint injections, 32 had BMI values < 25 kg/m2 , 37 had BMI values in the 25–30 kg/m2 range, and 32 had BMI values > 30 kg/m2 . Median DAP was 84 (54.5–108.5) Gray·m2 in the lowest BMI group, 143 (91.9–177.7) Gray·m2 in the intermediate BMI group, and 228.9 (161.3–340.4) Gray·m2 in the highest BMI group (Fig. 5). The difference across the three groups was statistically significant (P < 0.001). BMI was not significantly associated with DAP at other injection sites. After optimization, overweight or obese patients still received higher doses during facet joint injections, but the association with BMI was weaker (Fig. 5). Thus, median DAP was 16.1 Gray·m2 in the lowest BMI group (n = 36), 21.2 Gray·m2 in the intermediate BMI group (n = 37), and 28.6 Gray·m2 in the highest BMI group (n = 16). The difference across groups was statistically significant (P = 0.01). 3.4. Decreased physician radiation exposure after protection optimization During the study, we started to measure physician radiation exposure by having each physician wear an operational dosimeter
Fig. 3. A: significant 87% decrease in radiation exposure during injections into two facet joints; B: significant 52% decrease in radiation exposure during injection into the shoulder.
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
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Fig. 5. Variation in radiation exposure during facet joint injections, according to patient body mass index, in 2013 and 2014.
over the lead apron and another under the apron. The dose was measured as the total dose and not as a dose per unit surface area, i.e., was not comparable to the measurements in the patients. Before optimization, the mean dose was 15.4 Sv over and 0.4 Sv under the apron for a fluoroscopy-guided session with a mean duration of 2 hours 50 minutes. After optimization, for the same session duration, the mean dose was 6 Sv over and 0.4 Sv under the apron. Thus, optimization resulted in a 2.5-fold decrease in the dose that would be received by a physician without a lead apron. In contrast, no decrease occurred for the dose received while wearing a lead apron. This finding is ascribable to the very high attenuation factor of lead (here, 17 to 40), which made any difference undetectable. It is worth noting that the exposure due to natural radiation is 3 mSv per year and that the upper limit considered acceptable for workers is 6 mSv per year.
4. Discussion To comply with the optimization principle for radiation protection, the equipment, procedures, and work organization should be designed to keep patient radiation exposure as low as possible, while achieving the desired objective. Poor performance in the area of radiation protection indicates inadequate control of the safety of the process. Thus, optimization in radiation protection is a preventive approach aimed at decreasing the occurrence of adverse health effects in the long term. When optimization is not performed, patient radiation exposures remain unknown and may therefore cause harm. Radiation exposure can induce two types of health effects. Immediate or deterministic effects occur when an exposure threshold is exceeded. Thus, high doses of ionizing radiation produce immediate effects on living organisms, such as burns of varying severity. No such effects are expected to occur during fluoroscopyguided interventional rheumatology procedures. Long-term or random or stochastic effects are effects whose severity is independent of the dose, although their probability increases with the dose. They include the development of solid and hematological malignancies. Several years elapse between the exposure and the effect. The effects of low-dose exposures on human health are unclear. The associations that link ionizing radiation exposure to an excess of solid malignancies have not been demonstrated for very low radiation doses. At present, the effects on human health of exposure to doses less than 100 mSv are a focus of scientific debate. Nevertheless, several studies, including one reported recently [1,2], suggest that the risk of solid or hematological malignancies increases
linearly with the dose starting at low doses in workers exposed to ionizing radiation at the workplace. The results obtained in our study before the optimization measures indicate fairly low radiation exposures during rheumatology procedures (3.3 Gray·m2 to 177.7 Gray·m2 ). For purposes of comparison, the diagnostic reference dose levels in radiology are 25 and 100 Gray·m2 for an anterior-posterior and a lateral chest radiograph, respectively; 450 and 800 Gray·m2 for an anteriorposterior and a lateral radiograph of the lumbar spine, respectively; and 800 Gray·m2 for an anterior-posterior radiograph of the pelvis. Reference dosimetry levels are also available for interventional radiology procedures. For instance, the reference level is 4700 Gray·m2 for coronary angiography, 8000 Gray·m2 for follow-up brain angiography, and 35 000 Gray·m2 for embolization of an aneurysm [3,4]. The mean effective dose during the procedures performed in our study indicated a low level of radiation exposure compared to radiography, scintigraphy, or computed tomography (Table 1). However, radiation exposures measured in our study showed some degree of variability. The highest values were recorded during facet joint injections in patients with BMI > 30 kg/m2 . Some patients had DAP values of about 600 Gray·m2 , i.e., about one-tenth of the DAP associated with coronary angiography, for a procedure whose expected benefits are far less. This finding may indicate a need for caution in patients who require repeated injections, particularly those who exposed to high radiation doses during computed tomography, young patients (whose sensitivity to radiation is greater), or overweight/obese patients. Previous studies also found higher radiation exposures in patients with high BMI values. In addition, excess weight can increase the radiation exposure by making the procedure more difficult and therefore longer to perform. Nevertheless, radiation exposure is increased compared to patients with lower BMIs even when the duration of exposure is the same [7,8]. Another major finding from the first phase of our study is the major contribution of the last image hold to radiation exposure. On average, the last image hold contributed 62% of the patient radiation exposure. This finding suggests a need for evaluating the usefulness of the last image hold. We decided to optimize radiation protection in our everyday practice, to ensure that the lowest possible dose was delivered to our patients while maintaining sufficient image quality. Standardized implementation of new parameters by the radiology technicians resulted in large decreases in patient radiation exposure, even in the subgroup of patients with high BMI values. Thus, the mean dose now delivered during injections into four facet joints is comparable to the reference dose for an anterior chest radiograph (25 Gray·m2 ).
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
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Table 1 Mean effective dose for various investigations requiring exposure of the patient to ionizing radiation. Investigation
Code for the French health insurance system
Mean effective dose (mSv)
Source [5,6]
Arthrography of four facet joints after optimization of protection at our institution Facet joint arthrography Other investigations Whole-body dual energy X-ray absorptiometry Shoulder arthrography Full length spinal AP and lateral radiographs Radiographs of the cervical and lumbar spinal segments Single-phase whole-body scintigraphy (late phase) CT of a spinal segment without contrast injection EOS imaging, in an adult
LHQH001
0.04 mSv
Study at our institution
LHQH001
0.7 mSv
SFR procedure [5]
PAKQ009
0.001 mSv
Mettler, 2008 [5]
MEQH001 LHQK002
0.03 mSv 1.5 mSv
SFR procedure [5] SFR procedure [5]
LDQK005
1.8 mSv
SFR procedure [5]
PAQL003
4.4 mSv
LHQK001
11 mSv
IRSN evaluation of diagnostic reference dose levels [5] IRSN study in 2013 [5]
0.3 mSv
Damet et al. [6]
AP: anterior-posterior; CT: computed tomography; SFR: French Society for Rheumatology; IRSN: French Radiation Protection and Nuclear Safety Institute.
The exposure related to the last image hold diminished substantially. The quality of this last image is less important than the quality of the images taken during the injection. Therefore, the anti-scatter grid can be removed routinely just before the last image hold. In contrast, the grid may need to be left in place during the injection, particularly in overweight/obese patients, in whom image quality is always inadequate without the grid. The grid can be removed before the last image hold, which is stored in the patient’s file. It should be noted that the optimization measures were implemented on a table that did not offer all the options available for optimizing the dose/image quality ratio, such as a flat panel detector and pulsed mode. Nevertheless, the radiology technician could modify a sufficient number of parameters to ensure effective optimization of the dose delivered. The very low radiation doses delivered to patients, even during facet joint injections, warrant the continued performance of intraarticular injections under fluoroscopic guidance, as a complement to injections under ultrasound guidance. Finally, these changes in practice are also used for injections under computed tomography guidance, with different technical parameters and image reconstruction algorithms. Disclosure of interest The authors declare that they have no competing interest.
Appendix A. Supplementary data Supplementary data (Fig. S1) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.jbspin.2016.09.021. References [1] Richardson DB, Cardis E, Daniels RD, et al. Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS). BMJ 2015;351:h5359. [2] Leuraud K, Richardson DB, Cardis E, et al. Ionising radiation and risk of death from leukaemia and lymphoma in radiation-monitored workers (INWORKS): an international cohort study. Lancet Haematol 2015;2:e276–81. [3] Georges JL1, Belle L, Ricard C, et al., RAY’ACT investigators. Patient exposure to X-rays during coronary angiography and percutaneous transluminal coronary intervention: results of a multicenter national survey. Catheter Cardiovasc Interv 2014;83:729–38. [4] Kien N, Rehel JL, Etard C, et al. Patient dose during interventional neuroradiology procedures: results from a multi-center study. J Radiol 2011;92:1101–12. [5] IRSN. Exposition de la population franc¸aise aux rayonnements ionisants liée aux actes de diagnostic médical en 2012. Rapport PRP-HOM No 2014-6; 2012, 81 pages. [6] Damet J, Fournier P, Monnin P, et al. Occupational and patient exposure as well as image quality for full spine examinations with the EOS imaging system. Medical Physics 2014;41:063901. [7] Cushman D, Flis A, Jensen B, et al. The effect of body mass index on fluoroscopic time and radiation dose during sacroiliac joint injections. PM R 2015, http://dx.doi.org/10.1016/j.pmrj.2015.11.008. [8] Smuck M, Zheng P, Chong T, et al. Duration of fluoroscopic-guided spine interventions and radiation exposure is increased in overweight patients. PM R 2013;5:291–6.
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
ARTICLE IN PRESS Joint Bone Spine xxx (2016) xxx–xxx
Available online at
ScienceDirect www.sciencedirect.com
Original article
Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection Céline Cozic a , Fabien Audran b , Christophe Blanchard c , Christophe David d , Vincent Andre a , Michel Caulier a , Stéphane Varin a , Gilles Tanguy a , Jérôme Dimet e , Grégoire Cormier a,∗ a
Service de rhumatologie, CHD Vendée, boulevard Stéphane-Moreau, 85925 La Roche-sur-Yon cedex 9, France Unité de physique médicale, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France c Service de radiologie, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France d Unité de radioprotection, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France e Service de recherche clinique, CHD Vendée, 85925 La Roche-sur-Yon cedex 9, France b
a r t i c l e
i n f o
Article history: Accepted 18 May 2016 Available online xxx Keywords: Interventional rheumatology Radioprotection Patient radiation exposure Optimization of protection
a b s t r a c t Objectives: To decrease radiation exposure of patients undergoing interventional rheumatology procedures, without adversely affecting quality of care. Methods: The radiation dose received, assessed by the dose-area product (DAP), was measured during 283 intraarticular injections performed under fluoroscopic guidance between May and July 2013. Then, three steps were taken to decrease patients’ radiation exposure: a copper filter was added, the anti-scatter grid was removed, and exposure cell sensitivity was set at the highest value. DAP was measured during 158 intraarticular injections performed in 2014 with these measures in place. Results: Mean DAP before optimization was 175 Gray·m2 during facet joint injections (n = 4) and 43 Gray·m2 during hip injections but was less than 20 Gray·m2 for injections into the shoulders (15.7 Gray·m2 ), ankles (7.7 Gray·m2 ), wrists (3.7 Gray·m2 ), and fingers (3.3 Gray·m2 ). After optimization, DAP decreased markedly for all injection sites, by 52% (shoulders) to 87% (facet joints, 22.7 Gray·m2 ). Decreases occurred at all three steps of the procedure, i.e., patient installation, injection, and last image hold. Exposure during facet joint injections varied from 84 (54.5–108.5) Gray·m2 when body mass index (BMI) was < 25 kg/m2 to 228.9 (161.3–340.4) Gray·m2 when BMI was > 30 kg/m2 . Conclusion: Simple technical changes translate into large decreases in patient radiation exposure during fluoroscopically-guided injections, particularly at the facet joints and in obese patients. ´ e´ franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. © 2016 Societ
1. Introduction Fluoroscopy has been widely used in interventional rheumatology for decades to ensure that injections are performed intraarticularly. In recent years, concern has arisen about the risks associated with exposure to ionizing radiation during interventional rheumatology procedures. However, data on radiation protection of patients in this setting are scarce. In the European Union, patient radiation protection is regulated by Euratom directive 97/43, which was made a part of French
∗ Corresponding author. Service de rhumatologie, CHD Vendée, boulevard Stéphane-Moreau, 85925 La Roche-sur-Yon cedex 9, France. E-mail address: [email protected] (G. Cormier).
law by a decree issued on November 7, 2007. Radiation protection seeks to minimize or eliminate patient exposure to ionizing radiation by applying two principles, the principle of justification and the principle of optimization of protection to keep exposures as low as possible, while maintaining adequate image quality. Since 2004, regulations set diagnostic reference dose levels for each type of radiological procedure to serve as indicators for optimization. These levels are neither maximum doses that must not be exceeded nor radiological risk indicators. Instead, they are intended to help professionals assess the quality of radiological equipment and procedures, by providing a reference to which observed mean patient exposures can be compared. However, no diagnostic reference dose levels are available for interventional rheumatology. In France, a ministerial decree issued in September 2006 requires that the radiation dose to the patient during a fluoroscopy procedure be
http://dx.doi.org/10.1016/j.jbspin.2016.09.021 ´ e´ franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. 1297-319X/© 2016 Societ
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
G Model BONSOI-4483; No. of Pages 5
ARTICLE IN PRESS C. Cozic et al. / Joint Bone Spine xxx (2016) xxx–xxx
2
recorded in the patient’s medical file. Doses delivered during fluoroscopy are measured as the dose-area product (DAP, in Gray·m2 defined as the mean absorbed dose to air in a cross-section of the Xray beam multiplied by the surface area of the same cross-section. DAP values are independent from the location of the cross-section along the beam, because the dose decreases, but the surface area increases, with the distance from the source to the cross-section. The primary objective of our work was to optimize our protection procedures by working jointly with radiophysicists and radiology technicians to decrease patient radiation exposure during rheumatology interventions under fluoroscopic guidance. The secondary objectives were to measure patient radiation exposure during these interventions and to evaluate whether this exposure varied with body mass index (BMI). 2. Method The study involved two phases. We first measured patient radiation exposure during intraarticular injections at any site, performed under standard conditions. The data were analyzed by consensus among the rheumatologists, a physicist, and radioprotection experts. Then, desirable changes in fluoroscopy settings were identified and implemented, and patient radiation exposure was measured with these new conditions. For all procedures, patients were on a Siemens Iconos R200 table. Collection of the data for the study was approved by the French Data Protection Authority (CNIL). 2.1. First phase (standard conditions) The study included consecutive patients who underwent an interventional rheumatology procedure between May and July 2013 at the regional hospital of La-Roche-sur-Yon, France. At the rheumatology department of this institution, two to three sessions of 9 to 12 interventional rheumatology procedures are performed under fluoroscopic guidance each week, for a total of about 1200 procedures annually. For each procedure, the patient’s BMI was recorded, and total DAP was computed for all three stages of the procedure, i.e., patient installation, the injection (Fig. S1 in the online-only supplement), and the last image hold. 2.2. Second phase (radiation dose optimization and its effects) A multidisciplinary meeting attended by the radiophysicists and radiology technicians was held to discuss measures that would decrease patient radiation exposure without adversely affecting image quality. Four measures were identified during experiments performed with a phantom: • a copper filter is a thin copper disk (0.1 to 0.3 mm) that can be positioned within the X-ray beam at the request of the operator to eliminate low-energy photons that increase the dose to the patient without contributing to image quality. We found that a copper filter decreased the dose by up to 60% (25 cm-thick phantom, 0.3 mm-thick copper filter, and 73 kV). A copper filter can be used for both radiography and fluoroscopy; • an anti-scatter grid is placed automatically between the patient and the image detector to eliminate radiation that has deviated from the direction of the primary beam, chiefly due to passage through the patient’s tissues. Removing the anti-scatter grid can decrease the patient radiation dose by up to 80% (for a radiograph taken in automatic exposure mode) but can adversely affect image quality. An anti-scatter grid can be used for both radiography and fluoroscopy; however, with fluoroscopy, the grid is
removed only if this does not impair the operator’s ability to perform the procedure; • in automatic exposure mode, adjusting generator voltage to the thickness of the patient can limit the charge. The dose decrease is particularly large for thick patients (who require higher voltages). This adjustment is possible only during radiography; with the radiology equipment used in our study, voltage is adjusted automatically during fluoroscopy; • finally, when taking radiographs, using the highest sensitivity setting for the exposure cell diminishes the amount of photons and, therefore, the exposure dose, by up to 49%. These parameters were set in the presence of the physicians to check that image quality was not unacceptably affected and remained sufficient to allow accurate intraarticular placement of the injections. All these parameters are set by the radiology technician, without requiring any intervention from the physician. The decision about whether to remove the anti-scatter grid is taken by the physician during the procedure according to image quality. Consecutive patients who underwent shoulder or facet joint injections under fluoroscopy guidance between April and July 2014 at the La-Roche-sur-Yon rheumatology department were included in the second phase of the study. These two injection sites were chosen for two reasons: they were the most common sites of injection in everyday practice, and our preliminary assessment showed that they were associated with the highest patient radiation exposures (see the Results section). All patients were informed that their BMI and the DAP delivered to them during the procedure would be recorded. 2.3. Statistical analysis Quantitative data were described as median (and ranges), and qualitative data as % (confidence interval). Student’s t test was chosen for comparisons of quantitative variables. 3. Results 3.1. Patient radiation exposure before optimization: 283 injections in 2013 The highest radiation exposure was for the facet joints, followed by the hip and shoulder. Median DAP values were as follows: • • • • • • •
175 Gray·m2 (76.4–180.1) for four facet joints (56 injections); 152.3 Gray·m2 (80.7–197.9) for two facet joints (60 injections); 43 Gray·m2 (32.1–50.3) for the hip (17 injections); 15.4 Gray·m2 (10.2–24.6) for the shoulder (71 injections); 7.7 Gray·m2 (4.8–12.4) for the ankle (17 injections); 3.7 Gray·m2 (2.77–4) for the wrist (17 injections); 3.3 Gray·m2 (1.65–8.85) for the fingers (45 injections) (Fig. 1).
When we analyzed the dose delivered during each of the three phases of each procedure, we found that the last image hold accounted on average for 62% of the total dose (at least 42% for the fingers and up to 77% for the hip). The percentage of the dose delivered was 8% during patient installation and 30% during the injection (Fig. 2). 3.2. Decreased patient radiation exposure after protection optimization In 2014, after implementing the changes, we studied 158 new injections, including 89 in the facet joints and 69 in the shoulder. The median DAP for four and two facet joints was
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Fig. 1. Median dose-area product delivered before optimization of protection, according to the injection site.
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Fig. 4. Decrease in dose-area product at each of the three phases of the procedure between 2013 and 2014.
(P < 0.01). Thus, the dose reduction was largest for the last image hold (−87%) (Fig. 4). 3.3. Association between body mass index (BMI) and patient radiation exposure
Fig. 2. Contribution of each of the three phases of the procedure to the radiation exposure, according to the injection site.
22.7 Gray·m2 (14.8–33.4) and 15.2 Gray·m2 (8.6–27.3), respectively, i.e., decreases of 83 and 87%, respectively. For the shoulder, mean DAP was 6.4 Gray·m2 (4–13.8), i.e., a significant 52% decrease (Fig. 3). The decrease in total DAP was due to decreases at all three phases of the procedure (installation, injection, and last image hold), for both the facet joint and the shoulder injections. When we pooled the facet joint injections (two and four), median DAP during installation decreased from 5.6 (2.5–10.7) Gray·m2 in 2013 to 1.6 (0.6–3.6) Gray·m2 in 2014 (P < 0.01), median DAP during the injection from 34.7 (13.8–63.4) Gray·m2 to 8.3 (4.4–11.6) Gray·m2 (P < 0.01), and DAP during the last image hold from 81.2 (48.7–116.5) Gray·m2 to 8.9 (5.7–15) Gray·m2
BMI was associated with DAP only for the facet joint injections before protection optimization. Among patients who received facet joint injections, 32 had BMI values < 25 kg/m2 , 37 had BMI values in the 25–30 kg/m2 range, and 32 had BMI values > 30 kg/m2 . Median DAP was 84 (54.5–108.5) Gray·m2 in the lowest BMI group, 143 (91.9–177.7) Gray·m2 in the intermediate BMI group, and 228.9 (161.3–340.4) Gray·m2 in the highest BMI group (Fig. 5). The difference across the three groups was statistically significant (P < 0.001). BMI was not significantly associated with DAP at other injection sites. After optimization, overweight or obese patients still received higher doses during facet joint injections, but the association with BMI was weaker (Fig. 5). Thus, median DAP was 16.1 Gray·m2 in the lowest BMI group (n = 36), 21.2 Gray·m2 in the intermediate BMI group (n = 37), and 28.6 Gray·m2 in the highest BMI group (n = 16). The difference across groups was statistically significant (P = 0.01). 3.4. Decreased physician radiation exposure after protection optimization During the study, we started to measure physician radiation exposure by having each physician wear an operational dosimeter
Fig. 3. A: significant 87% decrease in radiation exposure during injections into two facet joints; B: significant 52% decrease in radiation exposure during injection into the shoulder.
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021
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Fig. 5. Variation in radiation exposure during facet joint injections, according to patient body mass index, in 2013 and 2014.
over the lead apron and another under the apron. The dose was measured as the total dose and not as a dose per unit surface area, i.e., was not comparable to the measurements in the patients. Before optimization, the mean dose was 15.4 Sv over and 0.4 Sv under the apron for a fluoroscopy-guided session with a mean duration of 2 hours 50 minutes. After optimization, for the same session duration, the mean dose was 6 Sv over and 0.4 Sv under the apron. Thus, optimization resulted in a 2.5-fold decrease in the dose that would be received by a physician without a lead apron. In contrast, no decrease occurred for the dose received while wearing a lead apron. This finding is ascribable to the very high attenuation factor of lead (here, 17 to 40), which made any difference undetectable. It is worth noting that the exposure due to natural radiation is 3 mSv per year and that the upper limit considered acceptable for workers is 6 mSv per year.
4. Discussion To comply with the optimization principle for radiation protection, the equipment, procedures, and work organization should be designed to keep patient radiation exposure as low as possible, while achieving the desired objective. Poor performance in the area of radiation protection indicates inadequate control of the safety of the process. Thus, optimization in radiation protection is a preventive approach aimed at decreasing the occurrence of adverse health effects in the long term. When optimization is not performed, patient radiation exposures remain unknown and may therefore cause harm. Radiation exposure can induce two types of health effects. Immediate or deterministic effects occur when an exposure threshold is exceeded. Thus, high doses of ionizing radiation produce immediate effects on living organisms, such as burns of varying severity. No such effects are expected to occur during fluoroscopyguided interventional rheumatology procedures. Long-term or random or stochastic effects are effects whose severity is independent of the dose, although their probability increases with the dose. They include the development of solid and hematological malignancies. Several years elapse between the exposure and the effect. The effects of low-dose exposures on human health are unclear. The associations that link ionizing radiation exposure to an excess of solid malignancies have not been demonstrated for very low radiation doses. At present, the effects on human health of exposure to doses less than 100 mSv are a focus of scientific debate. Nevertheless, several studies, including one reported recently [1,2], suggest that the risk of solid or hematological malignancies increases
linearly with the dose starting at low doses in workers exposed to ionizing radiation at the workplace. The results obtained in our study before the optimization measures indicate fairly low radiation exposures during rheumatology procedures (3.3 Gray·m2 to 177.7 Gray·m2 ). For purposes of comparison, the diagnostic reference dose levels in radiology are 25 and 100 Gray·m2 for an anterior-posterior and a lateral chest radiograph, respectively; 450 and 800 Gray·m2 for an anteriorposterior and a lateral radiograph of the lumbar spine, respectively; and 800 Gray·m2 for an anterior-posterior radiograph of the pelvis. Reference dosimetry levels are also available for interventional radiology procedures. For instance, the reference level is 4700 Gray·m2 for coronary angiography, 8000 Gray·m2 for follow-up brain angiography, and 35 000 Gray·m2 for embolization of an aneurysm [3,4]. The mean effective dose during the procedures performed in our study indicated a low level of radiation exposure compared to radiography, scintigraphy, or computed tomography (Table 1). However, radiation exposures measured in our study showed some degree of variability. The highest values were recorded during facet joint injections in patients with BMI > 30 kg/m2 . Some patients had DAP values of about 600 Gray·m2 , i.e., about one-tenth of the DAP associated with coronary angiography, for a procedure whose expected benefits are far less. This finding may indicate a need for caution in patients who require repeated injections, particularly those who exposed to high radiation doses during computed tomography, young patients (whose sensitivity to radiation is greater), or overweight/obese patients. Previous studies also found higher radiation exposures in patients with high BMI values. In addition, excess weight can increase the radiation exposure by making the procedure more difficult and therefore longer to perform. Nevertheless, radiation exposure is increased compared to patients with lower BMIs even when the duration of exposure is the same [7,8]. Another major finding from the first phase of our study is the major contribution of the last image hold to radiation exposure. On average, the last image hold contributed 62% of the patient radiation exposure. This finding suggests a need for evaluating the usefulness of the last image hold. We decided to optimize radiation protection in our everyday practice, to ensure that the lowest possible dose was delivered to our patients while maintaining sufficient image quality. Standardized implementation of new parameters by the radiology technicians resulted in large decreases in patient radiation exposure, even in the subgroup of patients with high BMI values. Thus, the mean dose now delivered during injections into four facet joints is comparable to the reference dose for an anterior chest radiograph (25 Gray·m2 ).
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Table 1 Mean effective dose for various investigations requiring exposure of the patient to ionizing radiation. Investigation
Code for the French health insurance system
Mean effective dose (mSv)
Source [5,6]
Arthrography of four facet joints after optimization of protection at our institution Facet joint arthrography Other investigations Whole-body dual energy X-ray absorptiometry Shoulder arthrography Full length spinal AP and lateral radiographs Radiographs of the cervical and lumbar spinal segments Single-phase whole-body scintigraphy (late phase) CT of a spinal segment without contrast injection EOS imaging, in an adult
LHQH001
0.04 mSv
Study at our institution
LHQH001
0.7 mSv
SFR procedure [5]
PAKQ009
0.001 mSv
Mettler, 2008 [5]
MEQH001 LHQK002
0.03 mSv 1.5 mSv
SFR procedure [5] SFR procedure [5]
LDQK005
1.8 mSv
SFR procedure [5]
PAQL003
4.4 mSv
LHQK001
11 mSv
IRSN evaluation of diagnostic reference dose levels [5] IRSN study in 2013 [5]
0.3 mSv
Damet et al. [6]
AP: anterior-posterior; CT: computed tomography; SFR: French Society for Rheumatology; IRSN: French Radiation Protection and Nuclear Safety Institute.
The exposure related to the last image hold diminished substantially. The quality of this last image is less important than the quality of the images taken during the injection. Therefore, the anti-scatter grid can be removed routinely just before the last image hold. In contrast, the grid may need to be left in place during the injection, particularly in overweight/obese patients, in whom image quality is always inadequate without the grid. The grid can be removed before the last image hold, which is stored in the patient’s file. It should be noted that the optimization measures were implemented on a table that did not offer all the options available for optimizing the dose/image quality ratio, such as a flat panel detector and pulsed mode. Nevertheless, the radiology technician could modify a sufficient number of parameters to ensure effective optimization of the dose delivered. The very low radiation doses delivered to patients, even during facet joint injections, warrant the continued performance of intraarticular injections under fluoroscopic guidance, as a complement to injections under ultrasound guidance. Finally, these changes in practice are also used for injections under computed tomography guidance, with different technical parameters and image reconstruction algorithms. Disclosure of interest The authors declare that they have no competing interest.
Appendix A. Supplementary data Supplementary data (Fig. S1) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.jbspin.2016.09.021. References [1] Richardson DB, Cardis E, Daniels RD, et al. Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS). BMJ 2015;351:h5359. [2] Leuraud K, Richardson DB, Cardis E, et al. Ionising radiation and risk of death from leukaemia and lymphoma in radiation-monitored workers (INWORKS): an international cohort study. Lancet Haematol 2015;2:e276–81. [3] Georges JL1, Belle L, Ricard C, et al., RAY’ACT investigators. Patient exposure to X-rays during coronary angiography and percutaneous transluminal coronary intervention: results of a multicenter national survey. Catheter Cardiovasc Interv 2014;83:729–38. [4] Kien N, Rehel JL, Etard C, et al. Patient dose during interventional neuroradiology procedures: results from a multi-center study. J Radiol 2011;92:1101–12. [5] IRSN. Exposition de la population franc¸aise aux rayonnements ionisants liée aux actes de diagnostic médical en 2012. Rapport PRP-HOM No 2014-6; 2012, 81 pages. [6] Damet J, Fournier P, Monnin P, et al. Occupational and patient exposure as well as image quality for full spine examinations with the EOS imaging system. Medical Physics 2014;41:063901. [7] Cushman D, Flis A, Jensen B, et al. The effect of body mass index on fluoroscopic time and radiation dose during sacroiliac joint injections. PM R 2015, http://dx.doi.org/10.1016/j.pmrj.2015.11.008. [8] Smuck M, Zheng P, Chong T, et al. Duration of fluoroscopic-guided spine interventions and radiation exposure is increased in overweight patients. PM R 2013;5:291–6.
Please cite this article in press as: Cozic C, et al. Decreased patient exposure to ionizing radiation during interventional rheumatology procedures after optimization of protection. Joint Bone Spine (2016), http://dx.doi.org/10.1016/j.jbspin.2016.09.021