Radiation Safety in the Catheterization Laboratory: Current Perspectives and Practices

Abstract: Background. There is great variability in radiation safety practices in cardiac catheterization laboratories around the world. Methods. We performed an international online survey on radiation safety including interventional cardiologists, electrophysiologists, interventional radiologists, and vascular surgeons. Results. A total of 570 responses were received from various geographic locations, including the United States (77.9%), Asia (7.9%), Europe (6.8%), Canada (2.8%), and Mexico and Central America (2.1%). Most respondents (73%) were interventional cardiologists and 23% were electrophysiologists, with 14.4 ± 10.2 years in practice. Most respondents (75%) were not aware of their radiation dose during the past year and 21.2% had never attended a radiation safety course; 58.9% are “somewhat worried” and 31.5% are “very worried” about chronic radiation exposure. Back pain due to lead use was reported by 43.0% and radiation-related health complications including cataracts and malignancies were reported by 6.3%. Only 37.5% of respondents had an established radiation dose threshold for initiating patient follow-up. When comparing United States operators with the other respondents, the former were more likely to attend radiation safety courses (P<.001), wear dosimeters (P<.001), know their annual personal radiation exposure (P<.001), and have an established patient radiation dose threshold (P<.001). They were also more likely to use the fluoro store function, under-table shields, leaded glasses, ceiling lead glass, and disposable radiation shields, and were more concerned about the adverse effects of radiation. Conclusions. Radiation safety is of concern to catheterization laboratory personnel, yet there is significant variability in radiation protection practices, highlighting several opportunities for standardization and improvement.

J INVASIVE CARDIOL 2018;30(8):296-300. Epub 2018 June 15.

Key words: radiation safety, catheterization laboratory

The adverse health risks of radiation exposure include cancer, skin injury, cataracts, thyroid disease, and reproductive effects. Moreover, radiation protective equipment, such as lead aprons, can cause back pain and orthopedic injuries.¹ As a result, radiation safety for patients, operators, and catheterization laboratory staff has been the focus of several quality-improvement efforts. In 1992, the Society of Cardiovascular Angiography and Interventions (SCAI) published guidelines for radiation safety in the cardiac catheterization laboratory, which were updated in 2011.^2,3 Similar guidelines have been developed by the Cardiovascular and Interventional Radiology Society of Europe and the Society of Interventional Radiology.^4-7 These guidelines aim to increase awareness of the side effects of radiation exposure and promote training and education for utilization of techniques and equipment to minimize radiation exposure. 

No large-scale survey has assessed radiation safety perspectives among operators from around the world and whether the differing perspectives and education are associated with differences in the use of radiation safety equipment and techniques. The goal of the present international survey was to examine current practices and perceptions about radiation safety in the cardiac catheterization laboratory.

Methods

We developed an online questionnaire (Appendix S1) to assess operator demographics, radiation safety education, utilization of radiation safety equipment/techniques, assessments and knowledge of patient/operator radiation dose, personal complications of chronic radiation exposure or lead use, and current level of concern about chronic radiation exposure. 

Questionnaire

The survey was designed using SurveyMonkey software. The preliminary set of questions was sent to 7 experienced catheterization laboratory operators to assess the comprehensiveness of the survey and relative ease of use of the software, with a goal of survey completion in under 10 minutes. After their input and subsequent revisions, the survey was made live on the internet on January 27, 2016 to operators around the world. One reminder email was sent to recipients 1 month after the survey went live. The online survey was then closed on April 20, 2016. The identity of all respondents was kept anonymous, allowing each individual to complete the survey just once. The SurveyMonkey software allowed real-time monitoring of the results while the survey was live, as well as exporting descriptive data after closure. Values were reported as percentages of total responses.

Study findings were analyzed using JMP 11.0 (SAS Institute). Continuous data are presented as mean ± standard deviation or median (interquartile range) and were compared using t-test or Wilcoxon rank-sum test, as appropriate. Categorical data are presented as percentages and compared using the Chi-square or Fisher’s exact test, as appropriate. A P-value of <.05 was considered statistically significant.

Results

A total of 570 responses were received from various geographic locations, including the United States (US; 77.9%), Asia (7.9%), Europe (6.8%), Canada (2.8%), and Mexico and Central America (2.1%). Most respondents (73%) were interventional cardiologists and 23% were electrophysiologists (Figure 1). Most respondents (92%) were men, mean age was 48.2 ± 10.0 years, and the mean duration of medical practice since the end of fellowship was 14.4 ± 10.2 years. 

Among respondents, 21.2% had never attended a radiation safety education course, 33.5% had attended 1 course in their careers, 27.6% attended safety courses annually, and 17.7% had attended these courses more than once, but not annually. Most operators wore dosimeters to measure their personal radiation exposure dose: 48.2% wore 1 dosimeter, 41.8% wore 2 dosimeters, and 4.2% wore >2 dosimeters. Only 5.8% of operators indicated that they did not wear any radiation dosimeters. Most dosimeters (88.1%) were worn on the thyroid collar or vest pocket (externally), followed by the waist or internal pocket underneath the lead (49.1%); 3.9% of operators wore a dosimeter on their fingers, while the remaining 3.9% listed “other location,” which included shoulder, wrist, ankles, and leaded glasses. Most operators (75.4%) who answered the survey did not know how much radiation they had received during the past year; 21.0% indicated that they had limited time in the catheterization laboratory and were unlikely to surpass the operator radiation exposure limits imposed by their institutions. Some operators (8.3%) limited the number of cases they performed and 8.2% had not worn radiation dosimeters in the catheterization laboratory for the same reason.

The frequency of use of various radiation sparing measures is shown in Table 1. Lead aprons were almost universally used, x-ray machine features (such as low frame count/sec fluoroscopy and use of the “fluoro store” function) were used routinely by approximately one-third of operators, whereas advanced equipment, such as the Zero Gravity system and robotic PCI, was used by very few operators. The frequency of x-ray equipment type was as follows: Philips Allura (40.3%), GE Innova (29.4%), Philips Clarity (19.1%), Siemens Artis Zee (19.1%), Siemens Artis One (16.2%), Toshiba Infinix Elite (5.0%), Toshiba Infinix Select (3.1%), and Shimadzu Trinias (1.5%). Most operators (60.6%) believed that the type of x-ray system had a significant impact on radiation dose received by both patient and operator.

Most respondents (76.3%) used fluoroscopy time as a measure of patient radiation dose, 39.0% used dose-area product (DAP; mGy•cm²), and 41.5% used air kerma (AK; Gy), with 11.7% not reporting patient radiation dose. Only 37.5% of respondents had an established dose threshold for initiating patient follow-up. The most commonly reported threshold was 5 Gy (38.5%), although reported thresholds were as low as 1 Gy and as high as 10 Gy. Other common measures of patient radiation dose threshold included 60 minutes of fluoroscopy time (9.6%).

Back pain as a result of long-term use of lead aprons was reported by 43.0% of respondents, while 1.9% had undergone spine surgery. Health complications believed to be related to radiation use (such as cataracts, thyroid disease, and malignancies) were reported by 6.3% of respondents. Overall, 58.9% of operators reported being “somewhat worried” about chronic radiation exposure, while 31.5% were “very worried.” 

Attendance of radiation safety courses, use of radiation dosimeters, and the “fluoro store” function were more common among US vs non-US operators (Figure 2). Attendance of radiation safety courses was also associated with higher likelihood of using shields, knowledge of personal radiation dose, and establishment of patient radiation dose threshold (Figure 3). 

Discussion

Our survey provides several novel insights on radiation safety practices around the world: (1) attendance at radiation safety courses is highly variable and was associated with higher use of radiation sparing measures; (2) only 1 in 4 respondents was aware of his/her radiation dose during the past year, although concern for radiation-related adverse effects was high; (3) the prevalence of radiation-related adverse effects was high; and (4) use of radiation safety measures was highly variable, and use of radiation dose limits was infrequent and variable.

Education can improve radiation safety practices. Kuon et al measured patient radiation exposure before and 3.7 months after a 90-minute minicourse in lower-irradiating cardiac invasive techniques in 154 interventionalists. Median DAP decreased by 48% and fluoroscopy time decreased by 21%, likely reflecting improved collimation or reduced-irradiation angulations.⁸ Simulator-based radiation safety training has also been developed and tested among 20 interventionalists whose radiation safety scores significantly increased.⁹ At a large tertiary-care institution, implementation of various clinical practices and technical changes, such as compulsory radiation safety training for cardiology fellows and intraprocedure dose announcements, resulted in 40% reduction in cumulative skin dose.¹⁰ Our survey suggests that radiation safety training is infrequently performed in the real world; more than half of the participants have never had radiation safety training or had only attended 1 course, and only 1 in 4 received annual training. This has been acknowledged by international organizations including the International Atomic Energy Agency and International Commission on Radiological Protection (ICRP); the latter recommends a second level of training for interventional cardiologists (in addition to training recommended for physicians who use x-rays). Such training should be accompanied by a certifying examination, and should be structured to include initial training and regular retraining.¹¹ Emphasizing the practical aspects of improving radiation safety (minimizing fluoroscopy time, using low frame rate/sec fluoroscopy, avoiding steep angles, and optimizing the image intensifier position), especially using simulation technology, could increase participant interest and translate into lower patient and operator radiation doses. 

Although it is impossible to adjudicate whether all reported side effects were truly associated with radiation exposure, the reported frequency was high; 46% reported back pain and 6.3% reported another adverse health outcome including cataracts, thyroid dysfunction, joint pain, neck pain, radiculopathy, hematologic disease, and skin lesions. These findings are consistent with prior reports. Andreassi et al performed a survey of 466 catheterization laboratory personnel and 280 unexposed subjects, and found significantly higher prevalence of skin lesions (8.6% vs 2.0%; P<.01), orthopedic problems (30.2% vs 5.4%; P<.001), and cataracts (4.7% vs 0.7%; P<.01) in the former group.¹² Compared with unexposed controls, interventional cardiology personnel have been shown to have a higher rate of cataract and precataract lens changes, with a prevalence as high as 79%.^13,14 Leraud et al followed a large cohort of radiation-monitored workers with low-dose, protracted radiation exposures on par with those sustained by interventional cardiologists (mean, 1.1 mGy/year), and found an excess relative risk for death from chronic myeloid leukemia of 10.45/Gy.¹⁵ Roguin et al found a propensity for brain and neck tumors in interventional cardiology personnel to occur on the left side (22 of 26 cases; 86%), which receives higher doses as compared with the right side.¹⁶ Hence, the heightened concern about radiation adverse effects among study participants (over 90% were somewhat or very worried) is understandable.

Despite these concerns and the recommendation of international bodies to use 2 dosimeters (1 over the apron at collar level or the left shoulder, and 1 under the apron on the trunk)¹¹ 48.2% of respondents wore only 1 dosimeter, and 6.8% did not wear any. Moreover, >75% of respondents did not know how much radiation they had received during the past year. Improving recording and awareness of radiation dose could benefit from centralized radiation-dose tracking and reporting, for example, with monthly or quarterly email communications. Moreover, avoiding a “punitive” approach to radiation-dose tracking (such as withdrawal of privileges upon reaching an annual radiation threshold) could help alleviate concerns of operators who do not wear their radiation dosimeter to prevent reaching the radiation limit, despite the personal health risks.

Use of radiation safety measures was highly variable among study participants, with basic personal protective equipment being most commonly used; over 90% of respondents use lead aprons and thyroid collar with every case in the cath lab, with leaded glasses, under-table shields, and ceiling-suspended transparent lead glass also being used consistently by most operators. Lead caps were infrequently utilized, possibly because they are heavy, hence uncomfortable. Alternatives made from barium sulphate and bismuth oxide are much lighter (approximately 50-150 g), and have been shown to substantially reduce dose to the head.^17,18 Disposable radiation drapes placed over the patient’s abdomen can help reduce operator dose, but were infrequently utilized.^19,20

Utilization of radiation-sparing operator behaviors was less consistent than use of personal protective equipment. Low-frame-rate fluoroscopy (eg, 7.5 frames/sec) is a simple way to reduce patient radiation and scatter radiation dose to the personnel, especially when used in combination with other radiation-sparing operator behaviors, such as avoidance of radiation-intensive steep beam angles,²¹ tight collimation,²² and use of spectral filters.^23-25 However, it was used in every procedure by only 34.1% of respondents in our study. Similarly, the fluoroscopy store functionality can be used as an alternative to cine acquisition to reduce radiation in some parts of the procedure, such as balloon inflations, but was used infrequently in our study.²⁶ Use of real-time audio/visual feedback systems was also low.^27,28

We found significant variability in patient radiation dose reporting; >75% use fluoroscopy time, even though it is not a reliable measure of radiation dose, as it does not include cine acquisitions. A surprising 11.7% of respondents do not report patient radiation dose at all, and 62.5% do not have a set radiation dose threshold to initiate patient follow-up. In the US, the National Council on Radiation Protection and Measurements (NCRP) advises patient notification, chart documentation, and communication with the primary care provider after procedures exceeding the substantial radiation dose limit (defined as fluoroscopic time >60 min, peak skin dose >3 Gy, AK >5 Gy, or DAP >500 Gy•cm²).²⁹ 

Radiation safety practices of US and non-US operators are different. US operators are more likely to have attended >1 radiation safety course in their career, indicating a stronger emphasis on education and staying up to date on radiation safety practices. US operators are also more likely to wear radiation dosimeters than their non-US counterparts; however, non-US operators are more likely to know their annual radiation dose. Finally, US operators use the fluoro store function more frequently as a means of minimizing radiation exposure.

The frequency of radiation safety course attendance also appears to have a significant impact on radiation safety practices. More frequent attendance was associated with higher use of the fluoro store function and under-table shields. Operators who attend safety courses more frequently are also more likely to know their own personal radiation exposure dose and to have a patient dose threshold for following up with patients to detect adverse sequelae. 

Study limitations. Among 6831 survey recipients, a total of 570 (8.3%) responded and some did not answer all survey questions. Most respondents were from the US. Finally, this survey included adult catheterization laboratory practitioners and did not include pediatric operators.

Conclusion

Our survey demonstrates great variability in radiation safety practices among operators around the world. Most operators are not aware of their own radiation exposure despite significant concerns about the sequelae of chronic radiation exposure. More frequent attendance of radiation safety courses was associated with more frequent use of dose-reducing techniques and knowledge of exposure dose; however, many operators had attended ≤1 course during their career. Expanding education and x-ray system improvement could help reduce the potential adverse effects of radiation for both patients and cath lab personnel. 

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From the ¹VA North Texas Healthcare System and UT Southwestern Medical Center, Dallas, Texas; ²Cleveland Clinic, Cleveland, Ohio; ³UC San Diego, San Diego, California; ⁴Penn State University, Hershey, Pennsylvania; and ⁵Minneapolis Heart Institute, Minneapolis, Minnesota. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Kumbhani reports research support and honoraria from the American College of Cardiology. Dr Rangan reports grant support from Spectranetics and InfraRedX. Dr Banerjee reports research support from Boston Scientific, Merck, and Abbott Vascular; honoraria from Medtronic, Astra Zeneca, and Janssen Pharmaceuticals. Dr Brilakis reports research support from Boston Scientific and Osprey; consulting/speaker honoraria from Abbott Vascular, Acist, Amgen, CSI, Elsevier, GE Healthcare, Medicure, and Nitiloop; he serves on the Board of Directors for the Cardiovascular Innovations Foundation and the Board of Trustees of the Society of Cardiovascular Angiography and Interventions; spouse is an employee of Medtronic. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript submitted March 26, 2018, final version accepted April 5, 2018.

Address for correspondence: Emmanouil S. Brilakis, MD, PhD, Minneapolis Heart Institute, 920 E. 28th Street, #300, Minneapolis, MN 55407. Email: esbrilakis@gmail.com