Last year, Cath Lab Digest published an interview covering alternative access for chronic total occlusions in critical limb ischemia. J.A. Mustapha, MD, interviewed Andrej Schmidt, MD, Department of Angiology, Leipzig Heart Center, Leipzig, Germany.
Read the full article below or click the link for the original publicaiton:
CLI PERSPECTIVES: Alternative Access for CTOs in CLI
CLI Perspectives is headed by section editor J.A. Mustapha, MD,
Metro Health Hospital, Wyoming, Michigan.
Critical limb ischemia
Chronic total occlusions (CTO)
Volume 23 – Issue 2 – February, 2015
J. Mustapha: What is your preferred access method for crossing complex superficial femoral artery (SFA) CTOs, with the exception of ostial SFA disease?
A. Schmidt: Most SFA CTO crossing is performed via ipsilateral antegrade approach.
J. Mustapha: Why do you prefer an ipsilateral antegrade approach?
A. Schmidt: For multiple beneficial reasons, including shortening the distance from the access site to the CTO, enhancement of pushability, and much better wire and catheter torque.
J. Mustapha: Do you ever perform a contralateral access approach for SFA CTOs?
A. Schmidt: Yes, mostly in patients who are not good candidates for antegrade access such as obese patients, those with proximal disease, ostial SFA disease, or CTOs. Mostly, I prefer antegrade access for SFA CTOs.
J. Mustapha: Many of us have seen you perform live cases and have witnessed your excellent techniques in retrograde popliteal and SFA access in complex CTO crossing. Why do you access these segments?
A. Schmidt: We access distal to the CTO cap of the SFA or popliteal CTO only when we fail to cross from antegrade approach first. The reason we access close to the CTO is similar to the reasoning of the antegrade access, close to the CTO cap, which in turns helps with retrograde pushability and torqueability.
J. Mustapha: What advice would you give practitioners who would like to perform similar retrograde access in the SFA/popliteal?
A. Schmidt: Proceed with caution, as this should only be attempted after an antegrade approach fails. Be sure to have a balloon across the occluded target lesion and the guidewire across the distal access before taking the access catheter out, so that in case a problem (dissection, occlusion) occurs at the distal entrance, balloon angioplasty can be done to fix it. Hemostasis is principally done by external compression.
J. Mustapha: What is the average time of your balloon inflation?
A. Schmidt: The time depends on the size of the access catheter or the sheath used. Most of the time, we use the smallest catheter possible, .018-inch to .035-inch. Therefore, we perform a three-minute balloon inflation followed by an angiogram.
J. Mustapha: Is this the same for a stick in a stent vs no stent?
A. Schmidt: Yes.
J. Mustapha: Do you worry about harming the stent after getting access in it?
A. Schmidt: No. So far, in our experience, we have not had any issues with stents in these situations. Keep in mind, we only get an access in the stent in extreme cases and place the smallest catheter possible.
J. Mustapha: Moving to retrograde tibial access, which access method do you use to enter the artery, angiogram-guided or ultrasound-guided?
A. Schmidt: We use angiogram-guided access.
J. Mustapha: Which is your preferred tibial artery for retrograde access and which part of the artery do you like to enter?
A. Schmidt: My preferred artery is the anterior tibial artery and I prefer to enter it proximally.
J. Mustapha: Why proximal versus distal?
A. Schmidt: Proximally, because the vessel diameter is larger and accommodates a 4 French sheath if needed.
J. Mustapha: How do you get the access?
A. Schmidt: First we position the foot supine and support it with a rolled-up towel, then perform an angiogram in left oblique 30° view, and enter the needle thru the skin into the artery. If no blood returns, we perform an oblique view with repeat angiogram which helps show the tip of the needle and artery.
J. Mustapha: How do you obtain hemostasis after the proximal tibial access?
A. Schmidt: Most of the time, we use an external blood pressure cuff. Occasionally, we use an intra-arterial balloon.
J. Mustapha: If needed, what are your tips and tricks for getting distal tibial access?
A. Schmidt: Starting with the dorsalis pedis access, foot positioning is important. First we position the foot supine and support it with a rolled-up towel, then the C-arm is positioned at about 15° ipsilateral and 10° cranial. We then use the quick access needle holder, followed with an angiogram. Also, we can puncture and perform contrast injection simultaneously, as needed.
J. Mustapha: Do you recommend road mapping for tibial access?
A. Schmidt: No, side movements of the artery due to puncture needles are not noticed, which may lead to accidental venous access and failed attempts. Also, I don’t recommend coming in from a lateral approach.
J. Mustapha: How do you know your needle is in line with the artery?
A. Schmidt: After angiogram is done, make the needle form one line with the artery (Figure 1A-B).
J. Mustapha: What do you do in the setting of no blood return?
A. Schmidt: Obtain oblique orthogonal views at 55-65°, load the guidewire into the needle, and perform contrast injection via the proximal sheath and pull back very slowly. Keep testing if the guidewire makes it through. Another method is to pull back slowly and inject contrast from the needle holder until you see contrast in the artery, then advance the guidewire (Figure 2A-G).
J. Mustapha: Any tips on how to get peroneal access?
A. Schmidt: Start with an anterior approach. Place the C-arm at ipsilateral LAO 30° (Figure 3A), perform antegrade angiogram, and position the needle in line with the artery. If no success, then move the C-arm to right anterior oblique (RAO) 70° (Figure 3B) and repeat angiogram. Redirect the needle toward the artery, puncturing the peroneal artery through the membrana interossea.
J. Mustapha: Which puncture site is safer?
A. Schmidt: The distal tibial access approach is safer, as it is not associated with compartment syndrome.
J. Mustapha: What needles to you use for proximal and distal tibial access?
A. Schmidt: For proximal anterior tibial, posterior tibial, and peroneal access, we use a 7cm, 21g needle. For distal tibials, we use a 4cm, 21g needle.
J. Mustapha: Please advise what NOT to do in infrapopliteal retrograde access.
A. Schmidt: One should not access communication arteries, especially those off of the peroneal artery, as shown in Figure 4.
J. Mustapha: How do you minimize radiation exposure?
A. Schmidt: My angiographical approach to retrograde pedal and tibial puncture is quick and precise, minimizing radiation exposure. I attribute this to experience and the right equipment (Figure 5A). I wear a ring dosimeter (Figure 5B) to measure my exposure.
Disclosure: Dr. Mustapha reports he is a consultant to Bard Peripheral Vascular, Covidien, Cordis, CSI, Spectranetics, and Boston Scientific. Dr. Schmidt reports occasional consulting for Bard and Medtronic.
Although women are more likely to experience vascular complications in the hospital, their one-year survival rate is more favorable than men. 11,808 women and 11,884 men were evaluated over two years and the one-year mortality rate was lower in women, although the in-hospital survival rate was about the same.
Read the full article below, or click the link to see the original posting:
SCAI: Women Undergoing TAVR Have a Different Risk Profile and Greater Survival Rate Than Men
May 6, 2016 — Orlando, Fla. – Data from one of the largest national registries of transcatheter aortic valve replacement (TAVR) patients shows that although women are more likely to experience vascular complications in the hospital, their one-year survival rate is more favorable than men. This STS/ACC TVT Registry™ analysis was presented today as a late-breaking clinical trial at the Society for Cardiovascular Angiography and Interventions (SCAI) 2016 Scientific Sessions in Orlando, Fla.
Investigators evaluated in-hospital and one-year outcomes for 23,652 TAVR patients, including 11,808 women (49.9 percent) and 11,844 men (51.1 percent), from 2012-2014. Compared to men, women were older, with lower GFR (kidney function) but higher prevalence of porcelain aorta and a higher mean STS adult cardiac surgery risk score (9 percent vs. 8 percent). However, women undergoing TAVR had a lower prevalence of comorbidities, such as coronary artery disease, atrial fibrillation and diabetes.
“Prior to this study, smaller analyses have suggested that men and women have different outcomes following TAVR procedures,” said Jaya Chandrasekhar, MBBS, MRCP, FRACP, a post-doctoral research fellow with Roxana Mehran, MD, FACC, FAHA, FSCAI, at the Icahn School of Medicine at Mount Sinai and the primary author of this report. “We wanted to gain in-depth understanding into the differences between men and women undergoing TAVR procedures from the US national registry and to evaluate the discrepancies by sex in longer-term outcomes.”
The study demonstrated that women were treated more often using non-transfemoral access (45 percent vs. 34 percent) with smaller sheath and device sizes but had a higher valve cover index than men. Post-procedure, women experienced more in-hospital vascular complications than men (8.27 percent vs. 4.39 percent, adj HR 1.70, 95 percent CI 1.34 – 2.14, P < 0.001) along with a trend for more bleeding (8.0 percent vs. 5.96 percent, adj HR 1.19, 95 percent CI 0.98 – 1.44, P = 0.08).
Despite these complications for women, the in-hospital survival rate was the same as men. Additionally, one-year mortality was lower in women (21.3 percent) than in men (24.5 percent).
“These findings are promising for women,” said Dr. Chandrasekhar. “There is a suggestion that the lower rate of coronary artery disease in women undergoing TAVR does put them at an advantage for longer-term survival, compared to men. The next step should be to study quality of life metrics and outcomes beyond one year including causes for death in both men and women. At the same time, frailty should be better defined to allow appropriate selection of patients for this procedure.”
Dr. Chandrasekhar reports no disclosures.
Dr. Chandrasekhar presented “Sex Based Differences in Outcomes With Transcatheter Aortic Valve Therapy: From STS/ACC TVT Registry” on Friday, May 6, 2016, at 9:00 a.m. ET.
The Society for Cardiovascular Angiography and Interventions is a 4,500-member professional organization representing invasive and interventional cardiologists in approximately 70 nations. SCAI’s mission is to promote excellence in invasive/interventional cardiovascular medicine through physician education and representation, and advancement of quality standards to enhance patient care. SCAI’s public education program, Seconds Count, offers comprehensive information about cardiovascular disease.
WORLDWIDE INNOVATIONS & TECHNOLOGIES, INC. (WIT)
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BRAIN Study Confirms Higher Radiation Dose to Cardiologists’ Left Side:
This study was conducted by Ethisham Mahmud, MD, of University of California, San Diego, along with 7cardiology fellows and 4 physicians as they performed diagnostic and interventional cardiovascular procedures to show the attenuation of radiation by using a lead-free cap. Dr. Mahmud discusses the significant amount of exposure the left time of the cranium receives compared to the right during these procedures. Dr. Mahmud says that we need to do a lot more to further understand the equipment being used and the dangers of radiation in the lab. He notes that lead-free caps are a great way to reduce scatter radiation.
BRAIN Study Confirms Higher Radiation Dose to Cardiologists’ Left Side
Single-center study looks at whether protective cap can limit radiation exposure during interventional procedures
Exposure consistently greater on left side of head; secondary operators receive more radiation than primary
By Yael L. Maxwell
Tuesday, August 18, 2015
Radiation exposure to the cranium is higher on the left than on the right side for cardiologists doing invasive procedures, though this difference can be attenuated by wearing a nonlead-based cap in the cath lab, according to a study published in the August 17, 2015, issue of JACC: Cardiovascular Interventions.
For the BRAIN (Brain Radiation Exposure and Attenuation During Invasive Cardiology Procedures) study, Ehtisham Mahmud, MD, of the University of California, San Diego (La Jolla, CA), and colleagues assessed 7 cardiology fellows and 4 attending physicians (mean age 38.4 years; all men) at their institution as they performed diagnostic and interventional cardiovascular procedures (mean 66.2 cases per operator; mean fluoroscopy time 14.9 minutes).
Each participant wore a lightweight XPF attenuating cap (BLOXR; Salt Lake City, UT) containing barium sulfate and bismuth oxide. All caps were fitted with 6 dosimeters to measure radiation exposure on the outside and inside of the cap.
A Little More on the Left
Total exposure on the outside of the cap was numerically higher on the left than center location (106.1 vs 83.1 mrad; P = .075), but exposure in both areas was higher than on the right side (50.2 mrad; P < .001 for both). Total exposure inside the cap was similar for all 3 locations—ranging from 41.8 to 42.3 mrad—and was only slightly higher than that measured by the ambient controls (38.3 mrad; P = .046).
After accounting for the ambient radiation, outside left exposure was 16 times higher than exposure on inside left and 4.7 times higher than that on the outside right (P < .001 for both). Exposure on the outside center was 11 times higher than on the inside center of the cap (P < .001), but no difference was seen between outside and inside doses on the right side.
Among a variety of factors—including patient weight, patient BMI, operator height, operator weight, percentage of radial cases, fluoroscopy time, and dose area product—only operator training level (fellow in training or attending cardiologist) predicted the extent of radiation exposure on the outside left and center locations.
Attending cardiologists—who tend to stand in the secondary position farther from the radiation source—received more outside left and center radiation than did fellows, who usually stand in the primary position (P = .002 and P = .01, respectively). “Despite the decreased exposure to the second operator as explained by the inverse square law, the optimal use of shielding in favor of the primary operator may overcome the protection offered by the increased distance,” Dr. Mahmud and colleagues suggest.
The Cap is Only the Beginning
In a telephone interview with TCTMD, Dr. Mahmud said the value of the study is “not as much about the cap as the concept.” Regardless of what protection operators may or may not use, “the most important message of this paper is that the left side of the brain gets tremendously greater exposure to radiation,” he said.
“We’re not doing a whole lot to protect ourselves… whether it’s in the primary or secondary position,” Dr. Mahmud continued. “One option is this cap, but the reality is we need to do a lot more to further understand and design equipment… or to look at alternative ways to do the procedure.”
Stephen Balter, PhD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview that the overall exposure reported outside the cap in the study is “reasonable” and well within the regulatory guidelines of 15,000 total mrad per year.
That said, using the cap “certainly doesn’t hurt,” he commented, and the fact that it can be used multiple times makes it less expensive than other options.
It is well known that radiation exposure is greater on the left than right side of cath lab operators, Dr. Balter explained. “It’s just how they stand and how they look at the monitors.” But “tracking people and understanding what’s happening is very relevant,” he said, adding that more specific results should come in time with theoretical modeling studies.
There will never be enough epidemiological research to show whether the XPF cap and other protections are increasing safety, Dr. Balter said. “There is a theoretical gain based on the radiobiology of models,” he added. “But it’s a small gain based on these numbers.”
All About Education
Dr. Mahmud said his team is planning another study, known as BRAIN 2, to further examine the phenomenon of how operator position affects radiation exposure. “The primary position is actually often better protected than the secondary position, where you’re a little bit further away but you might get more exposure to scatter,” he explained. “This is probably the first time this has ever been measured and ascertained.”
The second study will assess the validity of the difference between positions, Dr. Mahmud said. “We’re actually going to measure in a very systematic manner the radiation exposure for operators in the primary and secondary positions and behind and in front of shields.” BRAIN 2 will require the operators to stay in the same position throughout the course of each procedure, he explained.
But all of these studies, present and future, are meant to educate, Dr. Mahmud observed. “I am always shocked as to how few people seem to even admit that [radiation] is an issue. So I think it’s going to take more and more information, knowledge, and dissemination,” about the potential risk and any preventative options available, he said.
Reeves RR, Ang L, Bahadorani J, et al. Invasive cardiologists are exposed to greater left sided cranial radiation: the BRAIN study (Brain Radiation Exposure and Attenuation During Invasive Cardiology Procedures). J Am Coll Cardiol Intv. 2015;8:1197-1206.
Dr. Mahmud reports receiving clinical trial support from Boston Scientific, Corindus, and Gilead; serving as a consultant to The Medicines Company; and serving on the speakers bureau of Medtronic.
Dr. Balter reports no relevant conflicts of interest.
Unlike patients who are only exposed to ionized radiation during their procedure, cath lab technicians are exposed during every procedure they perform. This article discusses health effects associated with radiation exposure in the cath lab along with ways to protect the health of those technicians. Two of those ways are wearing a lead-based shield, and keeping a distance between the operator and the radiation source.
Wohns, David, and Ryan Madder. “Protecting the Provider: A Reexamination of Cath Lab Radiation Safety.” Cath Lab Digest. HMP Communications, Feb. 2015. Web. 26 May 2016.
Read the article in full below, or click the link to see the originally published article at Cath Lab Digest:
In the delivery of high-quality healthcare, patient safety is always a major concern of providers and the public. The safety of healthcare workers frequently receives significantly less attention. Recent events have highlighted this issue and are altering this perspective, with greater recognition of the sacrifices and risks that healthcare workers routinely take to perform their jobs. Patient safety remains the number-one concern of healthcare providers. However, the health and safety of providers should receive equal attention, particularly when novel techniques and strategies can be adopted to mitigate provider risk.
During 2014, the Ebola patients treated within U.S. borders caught the attention of the mainstream media and the public. Besides the public’s general concern for the patients, much attention was devoted to the healthcare workers who were exposed to the virus while caring for Ebola patients. These events raised the public’s awareness of healthcare worker safety and also caused many people to ask: “How do we ensure the safety of healthcare providers who put themselves in harm’s way to look after their patients’ health?”
This increased awareness is especially relevant to interventional cardiologists. Unlike patients, who are only exposed to ionizing radiation during their procedure, interventional cardiologists and other members of the cath lab team are repeatedly exposed to ionizing radiation, subjecting them to potentially serious long-term health issues. Additionally, the physical demands of performing their jobs while wearing heavy protective gear can lead to chronic orthopedic conditions that may prematurely end careers or force change into other fields of medicine.
With the increased interest in healthcare worker safety, it is an appropriate time to explore the risks associated with cath lab environments and novel technological solutions available to improve safety.
Assessing cath lab risks
Medical procedures performed in the cath lab are a leading source of occupational ionizing radiation exposure for medical personnel1, due to the use of fluoroscopy and cine angiography during these procedures. This occupational radiation exposure is of particular concern because today’s interventional cardiologists are spending significantly greater time in the cath lab doing more complex and lengthy procedures. Further, the performance of percutaneous coronary intervention (PCI) procedures in cath labs has increased more than 50 percent since 20002, potentially exposing interventional cardiologists to additional radiation.
Although research studies have demonstrated substantial variations in the amount of ionizing radiation to which interventional cardiologists are exposed, a look at the literature reveals the following:
One study showed that an interventional cardiologist’s head and neck area are generally exposed to approximately 20 to 30 millisieverts (mSv) per year3, which equates to 2 to 3 rems per year.
Another demonstrated that cumulative doses for the average interventional cardiologist after 30 years in the cath lab fall between 50 to 200 mSv, equivalent to 5 to 20 rems, or 2,500 to 10,000 chest x-rays.4
A third shows that interventionalists receive approximately 1 to 3 sieverts (Sv) to their head during their career (equivalent to 1,000 to 3,000 mSv, or 100 to 300 rems), which corresponds to about 500mSv to the brain5 (equivalent to 50 rems).
A separate study showed that interventional cardiologists have a radiation exposure rate documented to be two to ten times higher than that of diagnostic radiologists.4
Adverse health effects
Despite the availability and use of personal protective equipment (PPE), such as lead aprons, leaded glasses and thyroid collars, there are significant radiation exposure risks that have the potential to negatively impact the health of interventional cardiologists and their staff. Below are some findings from recent scientific literature:
Cataracts: The Occupational Cataracts and Lens Opacities in Interventional Cardiology (O’CLOC) study revealed that 50 percent of interventional cardiologists and 41 percent of cardiac cath nurses and technologists had significant posterior subcapsular lens changes, a precursor to cataracts, which is typical of ionizing radiation exposure.6
Thyroid disease: Studies have reported structural and functional changes of the thyroid as a result of radiation exposure.7 Structural changes such as malignant and benign thyroid tumors develop at a linear rate to dose exposure. Functional changes that would result in hyper- or hypo-thyroidism were noted at elevated doses of external and internal radiation exposure.7
Brain tumors and brain disease: A recent study focused on interventionalists who had been diagnosed with a variety of brain tumors. The study revealed that 86% of the brain tumors (where location is known) originated on the left side of the brain.8 This is significant, since interventional cardiologists typically stand with the left side of their body closest to the X-ray source and scattered radiation. In the general population, brain tumors originate with equal frequency on the left and right hemispheres.
Cardiovascular changes: Recent studies suggest evidence of a link between low- to moderate-dose radiation exposure and cardiovascular changes, despite personal protective wear.5
Reproductive health effects: For males, ionizing radiation has demonstrated a reduction in sperm.9 Additionally, cath lab staff members who may become pregnant while working in the cath lab must also take into consideration the effects that ionizing radiation can have on the developing fetus.
Additionally, there are orthopedic-related consequences from the heavy weight of lead gear worn by interventional cardiologists. The repeated standing and leaning over patients during procedures is fatiguing and commonly leads to chronic orthopedic conditions. A 2006 survey conducted by the Society for Cardiovascular Angiography and Interventions (SCAI) disclosed that interventional cardiologists suffer from a disproportionate amount of back, hip, and knee injuries leading to a significant amount of missed workdays.10 The weight of the personal protective gear is fatiguing, and a physician who is fatigued or experiencing discomfort may be more likely to be distracted or rush through a procedure.
Protecting the health of cath lab employees
There are two traditional techniques used to reduce radiation exposure. One is lead-based shielding, and the second is increasing the distance between the operator and the radiation source.
A relatively new approach to shielding includes devices that support lead aprons that hang from a boom, rather than being worn by clinicians. These hanging aprons provide effective radiation protection with a greater quantity of lead than is traditionally worn by operators. Since the operator is not physically supporting the lead, these devices have the potential to reduce orthopedic injuries and reduce overall operator fatigue.
The advent of robot-assisted percutaneous coronary intervention (PCI) represents another novel approach to reducing radiation exposure to operators. Robotic systems for PCI allow interventional cardiologists to perform procedures remotely, away from the patient’s bedside. Seated in a radiation-protected cockpit, the physician uses digital controls to robotically manage catheters, guide wires, angioplasty balloons, and stents to clear blockages and restore blood flow. These technologies are beneficial in reducing exposure by positioning operators further from the radiation source, but also have the potential to mitigate the impact that wearing PPE has on operators, such as orthopedic pain, missed work and disability.
The robotic-assisted PCI system being used at Spectrum Health is called CorPath (Corindus Vascular Robotics). The CorPath System allows physicians to perform PCI procedures from the comfort of a radiation-shielded cockpit that includes angiographic and hemodynamic monitors. Physicians using the system are able to take measurements, with sub-millimeter accuracy, of relevant anatomy, as well as advance or retract guide wires and/or balloon stent catheters with movements as small as a millimeter. A clinical trial has shown that using the robotic system reduced radiation exposure to the primary operator by more than 95 percent.11
Elevating healthcare worker safety
Interventional cardiology is a uniquely rewarding, highly innovative profession. The bulk of the innovation in our field over the past 3 decades has appropriately been focused on patient care. However, the manner and circumstances with which that care has been delivered in the cath lab has changed little over time. New approaches are now available to begin to mitigate the biomechanical, orthopedic, and radiation risks of working in the cath lab. The CorPath System is an example of a device with tremendous promise to reduce these hazards for interventional cardiologists, contributing to longer, healthier careers. We have been excited to bring this innovative technology to our cath labs as part of the evolution of our environment.
Sun Z, AbAziz A, Yusof AK. Radiation-induced noncancer risks in interventional cardiology: optimisation of procedures and staff and patient dose reduction. Biomed Res Int. 2013; 2013: 976962. doi: 10.1155/2013/976962.
Best PJ, Skelding KA, Mehran R, Chieffo A, Kunadian V, Madan M, et al; Society for Cardiovascular Angiography & Interventions’ Women in Innovations (WIN) Group. SCAI consensus document on occupational radiation exposure to the pregnant cardiologist and technical personnel. Catheter Cardiovasc Interv. 2011 Feb 1; 77(2): 232-241. doi: 10.1002/ccd.22877.
L Renaud. A 5-y follow-up of the radiation exposure to in-room personnel during cardiac catheterization. Health Phys. 1992 Jan; 62(1): 10-15.
Picano E, Andreassi MG, Piccaluga E, Cremonesi A, Guagliumi G. Occupational risks of chronic low dose radiation exposure in cardiac catheterisation laboratory: the Italian Healthy Cath Lab study. EMJ Int Cardiol. 2013; 1: 50-58.
Picano E, Vano E, Domenici L, Bottai M, Thierry-Chef I. Cancer and non-cancer brain and eye effects of chronic low-dose ionizing radiation exposure. BMC Cancer. 2012 Apr 27; 12: 157. doi: 10.1186/1471-2407-12-157.
Vano E, Kleiman NJ, Duran A, Romano-Miller M, Rehani MM. Radiation-associated lens opacities in catheterization personnel: results of a survey and direct assessments. J Vasc Interv Radiol. 2013 Feb; 24(2): 197-204. doi: 10.1016/j.jvir.2012.10.016.
Ron E, Brenner A. Non-malignant thyroid diseases after a wide range of radiation exposures.Radiat Res. 2010 Dec; 174(6): 877-888. doi: 10.1667/RR1953.1.
Roguin A, Goldstein J, Bar O, Goldstein JA. Brain and neck tumors among physicians performing interventional procedures. Am J Cardiol. 2013 May 1; 111(9): 1368-1372. doi: 10.1016/j.amjcard.2012.12.060.
Burdorf A, Figà-Talamanca I, Jensen TK, Thulstrup AM. Effects of occupational exposure on the reproductive system: core evidence and practical implications. Occup Med (Lond). 2006 Dec; 56(8): 516-520.
Heavy Lead Aprons Causing Pain for Cath Lab Professionals
A survey was published in March of 2015 exhibiting musculoskeletal pain caused by work-related stress due to lead aprons. In order to protect from scatter radiation, cath lab professionals are required to wear heavy lead aprons. A survey was emailed to 2,682 cardiology and radiology employees at 6 Mayo Clinic facilities in the U.S. and received responses from 57%. Of these responses, 62% of techs, 60% of nurses, 44% of attending physicians and 19% of trainees reported work-related pain. Dr. Singh recommends that these employees be rotated out of the cath lab suites more frequently to reduce stress. Additionally, he recommends lighter-weight or non-lead-based protective wear.
Dalton, Kim. “Survey Puts Spotlight on Physical Stress of Working in a Cath Lab.” Tctmd: Cardiovascular Research Foundation, 23 Feb. 2015. Web. 26 May 2016.
Read the full article below, or click the link to read the original article:
Survey Puts Spotlight on Physical Stress of Working in a Cath Lab
By Kim Dalton
Monday, February 23, 2015
Cath lab personnel who spend long hours wearing heavy lead aprons to protect against radiation exposure are more likely to experience musculoskeletal problems than colleagues who work in other hospital settings, according to the results of a survey published in the March 3, 2015, issue of the Journal of the American College of Cardiology. Cath lab staffers did not report more radiation-related cataracts and cancers, although the low prevalence of such conditions and the study’s cross-sectional design may have hampered its ability to detect a difference.
According to an accompanying editorial by James A. Goldstein, MD, of the Beaumont Health System (Royal Oak, MI), years of such physical stress can result in “missed days of work, surgery, and, in some cases, curtailed careers.”
Investigators led by Mandeep Singh, MD, of the Mayo Clinic (Rochester, MN), emailed surveys to 2,682 cardiology and radiology department employees at 6 Mayo Clinic facilities across the country and received responses from 57% (n = 554 in cardiology and 989 in radiology; average age 43 years; 33% male). Respondents were divided into cath lab workers (n = 1,042) and controls (n = 499) based on whether they reported being engaged in procedures involving radiation.
The most common occupations of respondents were:
Technician/technologist: 54.3% (mean 15.5 years in position)
Registered nurse: 18.3% (mean 16.1 years)
Physician: 13.4% (mean 18.8 years)
Other: 9.3% (mean 11.3 years)
Resident/fellow: 4.7% (mean 4.0 years)
Clinical employees with exposure to procedures involving radiation that required wearing a lead apron were more likely to have experienced work-related pain and to have sought medical care for it than the control group. In addition, they were more likely to report pain at the time of the survey (table 1).
However, there was no difference between the groups in objective assessment scores for current pain, recent use of pain medication, missed workdays, or use of disability.
The association between work-related pain and lead apron wearing remained after adjustment for age, sex, body mass index, preexisting musculoskeletal conditions, years in the profession, and job description (adjusted OR 1.67; 95% CI 1.32-2.11).
Cath lab employees who reported a history of work-related pain were more likely to be female, spent more time each week exposed to radiation, and wore a lead apron more often than controls (all P < .001). Tactics aimed at reducing musculoskeletal pain were also more common in those who reported work-related pain and included:
Prompt removal of the lead apron after procedures
Stretching/exercising before or after procedures
Wearing soft-soled shoes
There was no relationship between risk of injury and the type of lead apron worn (1 piece vs 2 pieces) or use of a glass shield or eye protection.
The likelihood of experiencing work-related pain varied by job description, with the highest incidence reported by techs (62%) and nurses (60%), followed by attending physicians (44%) and trainees (19%; P for trend < .001). Although techs and nurses were more likely than attending physicians to be female, the findings were similar when the analysis was restricted to men or women.
Cath lab workers exposed to radiation did not report more cancers, cataracts, hypothyroidism, or nephrolithiasis than employees not so exposed and showed no difference in rates of a composite endpoint including these conditions and musculoskeletal pain (P = .26).
Focus on Relieving Physical Stress
According to the authors, this is the first study to show that techs and nurses have a higher prevalence of work-related musculoskeletal pain than attending physicians despite being younger and having fewer years in the cath lab.
One reason for the discrepancy may be that physicians regularly rotate out of the cath lab while nurses and tech personnel do not, they suggest. Another possible contributor is that staff perform physically stressful tasks, like transferring patients on and off the table and applying compression after sheath removal.
According to Dr. Singh and colleagues, ongoing efforts should be made to provide regular ergonomic evaluations, periodic rotations out of the cath lab suite, and lighter-weight, non–lead-based protective wear. In addition, they say, robotic interventional equipment and remote monitoring technologies may help reduce both the number of personnel needed to care for the patient and their proximity to the radiation source, thereby diminishing the time spent wearing a lead apron.
The researchers acknowledge that these data cannot resolve questions about cancer risk from radiation exposure, in part because the incidence of the disease in younger cath lab personnel is low. Moreover, staffers diagnosed with cancer may transfer to a job that does not expose them to radiation or retire, and thus their cases would not be captured in this cross-sectional survey.
In the editorial, Dr. Goldstein calls the findings “alarming and sobering.” But, he adds, given the growth in the volume, complexity, and length of interventional procedures, the “escalating epidemic of occupational-induced orthopedic afflictions” should not be surprising.
Dr. Goldstein observes that innovative equipment that facilitate quality imaging with lower doses is helping to minimize radiation exposure, and measures like ceiling-suspended lead aprons, shielded gloves and scrub caps for cranial protection, and vascular robotic technology can help reduce orthopedic problems.
‘Take Care of Yourself’
But in a telephone interview with TCTMD, Craig St. George, RT, director of online education for the American Society of Radiologic Technologists (Albuquerque, NM), said that over 6 years working at the Mayo Clinic in Jacksonville, FL, he cannot recall anyone complaining of a work-related injury.
However, he noted, many of his colleagues exercised, stretched, and practiced yoga, which likely helped counter the stress of wearing a lead apron day after day. Another important factor in minimizing aches and pains, he suggested, was that each person was custom-fitted for an apron. And they could choose from different versions, including a wraparound model with a waist belt that took much of the weight off the shoulders. They also stood on ergonomic pads near the table to help cushion their feet during long hours. In addition, the strain of transferring patients to and from the table was mitigated by working in teams.
As for any radiation concerns, Mr. St. George said he relied on his training—making sure he was properly shielded and standing in the right place to minimize exposure—and oversight by the hospital’s radiation safety officer.
“I know people who have been technologists for 20 or 30 years, and I’ve never heard anyone say, ‘This is really wearing on me,’ he commented, adding, “You go into the profession because you want to take care of patients, and to do that you have to take care of yourself.”
Sources: 1. Orme NM, Rihal CS, Gulati R, et al. Occupational health hazards of working in the interventional laboratory: a multisite case control study of physicians and allied staff. J Am Coll Cardiol. 2015;65:820-826.
2. Goldstein JA. Orthopedic afflictions in the interventional laboratory: tales from the working wounded [editorial]. J Am Coll Cardiol. 2015;65:827-829.
Dr. Singh reports no relevant conflicts of interest.
Dr. Goldstein reports owning equity in a company developing radiation shielding equipment.
Mr. St. George reports no relevant conflicts of interest.
This article discusses a study comprising 466 hospital staff members, including interventional cardiologists, electrophysiologists, nurses and technicians who are exposed to radiation regularly. Additionally, 280 staffers who were not exposed to radiation in the cath lab were interviewed. This study gathered work-related and lifestyle information, current medications and health status for these workers. Almost three percent of interventional cardiology staff had a history of cancer, compared to less than one percent of the unexposed group. Eight percent of lab workers had experienced skin lesions, 30 percent experienced orthopedic illness and five percent had cataracts, compared to two, five, and less than one percent of the unexposed group.
See the full article below or read the original by clicking the link below:
Cath Lab Workers May Be Harmed by Radiation
Wednesday, 13 Apr 2016 08:53 AM
Healthcare workers in labs where patients undergo heart procedures guided by X-rays may be at higher risk for cataracts, skin lesions, bone disorders or cancer than other healthcare workers, according to a new study.
Procedures in the “cath lab” – named for the catheters threaded into the heart – are done for all forms of cardiac disease, like congenital heart defects, ischemic heart disease or heart arrhythmias, said lead author Maria Grazia Andreassi of the CNR Institute of Clinical Physiology in Pisa, Italy.
“These procedures, highly effective and often life-saving, require substantial radiation exposure to patients,” Andreassi told Reuters Health by email.
But staff members, too, are exposed to radiation. In particular, for the cardiologists and electrophysiologists who work near the patient and the radiation source, “the cumulative dose in a professional lifetime is not negligible,” Andreassi said.
The researchers used questionnaires to gather work-related and lifestyle information, current medications and health status for 466 exposed hospital staff, including interventional cardiologists, electrophysiologists, nurses and technicians, half of whom had been working for at least 10 years. They also surveyed 280 staffers who had not been exposed to radiation in the cath lab.
Almost 3 percent of interventional cardiology staff had a history of cancer, compared to less than 1 percent of the unexposed comparison group. Eight percent of lab workers had experienced skin lesions, 30 percent had an orthopedic illness and five percent had cataracts, compared to two percent, five percent and less than one percent of the unexposed group, respectively.
Doctors had higher risks than nurses or technicians, and risk was higher for those who had been working more than 16 years, as reported in Circulation: Cardiovascular Interventions.
Stroke and heart attack risk were similar in the radiation and non-radiation exposure groups.
“Compared to healthcare professionals not exposed to radiation, workers with more than 16 years of occupational work are approximately 10 times more likely to experience cataracts and eight times more likely to have cancer after adjusting for other confounders,” like age and smoking status, Andreassi said.
Protective measures like leaded aprons, thyroid collars, leaded glasses, and overhead radiation shields can reduce the radiation dose to the operators, but are still not used regularly in every laboratory, Andreassi said.
Healthcare workers in the cath lab “sort of know there is a risk but it’s typically presented to young people as something to know about and not to worry about,” said Dr. Lloyd Klein of Advocate Illinois Medical Center in Chicago, who coauthored an editorial accompanying the new study.
“Everyone wears lead aprons, and increasingly, lead caps,” Klein told Reuters Health by email. “We are careful about unnecessary exposure.”
But wearing lead creates orthopedic problems and doesn’t completely protect against the effects of radiation, he said.
The Occupational Safety and Health Administration and federal and state agencies probably need to get more involved than they already are, he said.
Interventional cardiologist Dr. John Wang, chief of the Cardiac Catheterization Lab at MedStar Union Memorial Hospital in Baltimore, Maryland demonstrates a new technique to cardiac catheterization procedure by using transradial access.
Patients may need a cardiac catheterization if they are experiencing cholesterol narrowing’s in the blood vessels which may result in chest pain or even a heartattack. This procedure is typically performed through the femoral artery, but there is sufficient collateral blood flow to the hand to make the wrist an accessible location for catheterization. There is no risk of bleeding complications where the catheter is inserter so this technique is used to increase patient comfort and experience a quicker recovery. If the patient is in need of a stent, this can be placed through the wrist as well.
Link to demonstration video:
Dr. John Wang also discusses the benefits of transradial cardiac catheterization:
“Chronic total occlusions are difficult to treat and only a small number of patients receive percutaneous treatment due to risks including time, complications, and amount of scatter radiation.”
Cath Lab Digest recently published an article regarding the difficulties in treating chronic total occlusions. One of the challenges in the procedure is the level of scatter radiation, which is why our team at RADPAD® found the article so relevant:
Despite advances in wire and stent technology, chronic total occlusions (CTOs) remain a difficult lesion subset to treat. CTOs are present in about 20% of patients undergoing cardiac catheterization; however, only a small percentage are offered percutaneous treatment.1,2 There are several reasons for this. Time and resource constraints, complications risk, and variations in technical expertise are some of the reasons for inconsistent attempt rates. The current hybrid algorithm approach to CTO percutaneous coronary intervention (PCI) uses a combination of antegrade and retrograde techniques to facilitate wire crossing and procedural success.3 In the early stages of adopting this approach, some operators may use an antegrade-only approach.4 The use of specialty catheters and wires may facilitate engagement and crossing of the proximal cap. We present two case examples using the SuperCross microcatheters (Vascular Solutions) to perform CTO revascularization via an antegrade approach.
This is a 62-year-old male with recent admission to another outside hospital with positive troponins, and cardiac catheterization revealing a CTO of the circumflex artery and right coronary artery (RCA). He had ventricular tachycardia and had a subsequent revascularization at the hospital twice which was unsuccessful. He was then referred to our institution for bypass. Given that there was no involvement of the left anterior descending coronary artery (LAD), he was referred by surgery for possible CTO revascularization. Repeat angiography revealed a CTO of the circumflex artery (left-left collaterals) with a CTO of the RCA as well, with what appeared to be filling via right-to-right collaterals (Figures 1-2). Based on the angiogram and his clinical presentation, it was decided to fix the circumflex CTO first.
The right radial was accessed with a 6/7 GlideSheath Slender (Terumo) and the left radial was accessed with a 6 French sheath. A Q 3.5 guide catheter (Boston Scientific) was used to engage the left coronary system and an Amplatz right (AR) mod guide catheter (Cordis) was used to engage the RCA in order to perform dual angiography.
The left main was calcified and bifurcated into the LAD and circumflex artery. The LAD was patent with mild angiographic disease and no focal obstructions. It gave rise to a diagonal and there was some evidence of left-to-left collaterals. The circumflex artery was 100% occluded after what appeared to be a high atrioventricular (AV) groove. It was a short occlusion and then reconstituted into obtuse marginal branches (OM)1 and a large OM2. There is calcification noted in the occlusion. The RCA was a large-caliber artery. It was occluded distally at the crux, and had some late right-to-right collaterals.
Heparin was administered, and using a Turnpike Gold catheter (Vascular Solutions) and a Runthrough wire (Terumo), we got into the circumflex and then exchanged out for a Gaia guidewire (Asahi Intecc) to penetrate the proximal cap. The Turnpike Gold catheter, unfortunately at this point, was downward and therefore, did not allow engagement of the proximal cap (Figure 3). The catheter was changed for a SuperCross 90-degree catheter (Vascular Solutions), which pointed the wire up towards the blunt cap of the CTO and away from the bifurcation (Figure 4). We then used the Gaia wire to penetrate the proximal cap and gain some purchase. We advanced the 90-degree SuperCross catheter, but it would not penetrate the cap. We were able to get the guidewire to gain some more purchase and then switched out for the Turnpike Gold catheter. Using the Turnpike Gold in a clockwise manner permitted advancement into the proximal cap and advancement of the guidewire distally. Once we confirmed it was luminal, we tried to advance the Turnpike Gold to switch out the wire, but we could not advance completely without the guide catheter backing out. well as the calcification of the vessel. We switched the wire out to a Pilot 200 wire (Abbott Vascular) and were able to wire both branches, OM1 and OM2, to confirm there was no subintimal wire placement. Given that OM2 was a larger branch, we placed the wire distally, confirmed that we were luminal (Figure 5), and then, in a counter-clockwise manner, removed the Turnpike Gold catheter. A 0.9 mm laser (Spectranetics) was used to perform laser athrectomy at the setting of 40/60 initially, then at 60/80, as multiple passes were made to create a pilot channel (Figure 6). A 2.0 x 15 mm AngioSculpt balloon (Spectranetics) was successfully advanced and predilated the lesion (Figure 7). After significant predilation at 10 atmospheres for 1 minute, we were able to wire a Runthrough wire into the OM1. We ballooned with a 2.25 x 20 mm balloon and switched out the Pilot wire for a second Runthrough wire (Figure 8). We advanced a 2.5 x 26 mm Resolute stent (Medtronic) favoring the OM2, which was a larger branch, and inflated at nominal pressure. We removed the Runthrough wire from the OM1 and using the Turnpike Gold as support, rewired the OM with a Sion wire (Asahi Intecc). We ballooned with a 2.0 x 20 mm balloon in the OM1 and in the ostium, and predilated the OM2 circumflex stent with a 2.5 mm Quantum balloon (Boston Scientific). A low-pressure inflation of the OM1 was performed with a 2.0 mm balloon at 4 atmospheres, and after intracoronary nitroglycerin (NTG), final angiography revealed TIMI-3 flow without dissection, embolization, or perforation, with an excellent angiographic result (Figure 9). The patient was staged for the RCA CTO 4 weeks later and had successful PCI using a SuperCross catheter and a Twin-Pass catheter (Vascular Solutions) to complete the procedure.
A 70-year-old male with a history of coronary artery bypass graft surgery (CABG) x 3 in 2000 and an implantable cardioverter defibrillator (ICD) (for inducible ventricular tachycardia [VT] in 2006) presented with chest pain and precordial ST depression and positive troponins. He was taken to the lab urgently for ongoing chest pain and a left heart catheterization was performed, revealing a patent left internal mammary artery-left anterior descending coronary artery (LIMA-LAD), occluded saphenous vein graft-right coronary artery (SVG-RCA) (with collateral filling of the native RCA via left-to-right collaterals) and an occluded SVG to the obtuse marginal (OM) (Figures 10-11). The SVG-OM was the culprit based on the angiogram, electrocardiogram (EKG), and clinical presentation.
It was decided to revascularize the native OM instead of an occluded 16-year old graft. Given the patient’s height (6 feet, 9 inches), it was decided to access the right brachial for secondary access (guide length can be an issue from the radial). The femoral sheath was upsized to an 8 French with an Extra Backup (EBU) 3.75 guide (Medtronic). From the brachial approach, an Amplatz left (AL) 1 was used to engage the SVG-OM, and a wire passed distally to mark and control the distal vessel (Figure 12). The proximal cap was defined, but the branch came off at an angle. Initial attempts were made to wire with a Turnpike catheter (Vascular Solutions), and Fielder XT (Abbott Vascular) and Pilot wire (Abbott Vascular). The angle made it difficult to engage the cap (Figure 13) and a SuperCross 120 catheter allowed us to engage with a Fielder XT and maintain the “CTO bend” on the wire (Figure 14). The wire was “knuckled” and advanced through the occlusion into the true distal lumen (Figures 15-16). Excimer laser, intravascular ultrasound (IVUS), and stenting were performed on the native vessel with placement of a 2.5 x 38 mm and a 3.0 x 16 mm Synergy stent (Boston Scientific) (Figure 17). There was a wire perforation noted of no hemodynamic or clinical consequence. The patient was discharged home the following morning.
There are several factors that favor an antegrade-only approach to CTO revascularization (for those not adopting the hybrid algorithm):
1) Well-visualized proximal cap;
2) Presence of a microchannel;
3) Minimal calcification;
4) Occlusion <20 mm;
5) No angulation >45 degrees; and
6) A good distal target.4
In addition to wire selection, microcatheter support can enhance “pushability” and facilitate lesion crossing. There are several microcatheters available and the most commonly used ones in the United States include the Corsair (Asahi Intecc), Finecross (Terumo), and Turnpike (Vascular Solutions). These are straight-tip catheters and therefore, may not provide the best approach for an angled proximal cap.
The SuperCross catheters are a series of microcatheters used for guidewire support and directional wiring. In addition, they can be utilized for subselective delivery of diagnostic and therapeutic agents. The coronary catheters are available in straight, flexible, and angled versions (Figures 18-19). The angled-tip catheters are available in a 45, 90, 120 and 90 XT (extended degree tip for secure cannulation). The inner layer is PTFE and the outer layer is hydrophilic. They have a 0.71 mm outer diameter (OD) and 0.43 mm inner diameter (ID), and are 6 French compatible. We have used these catheters to access side branches, as wire support for an angulated left circumflex off the left main, and, as in the above cases, to engage a difficult proximal cap. Once we have gained purchase into the CTO, the microcatheter is usually changed to a Corsair, Turnpike, or Finecross to navigate the remainder of the occlusion. When the wire is able to cross, but the microcatheter cannot follow, a catheter such as the Tornus (Asahi Intecc) or Turnpike Gold may be able to advance through the occlusion (other options, if available, include laser atherectomy or exchanging the wire for rotational atherectomy). A full discussion about antegrade crossing of CTOs is beyond the scope of this article. For more information, visit ctofundamentals.org.
Fefer P, Knudtson ML, Cheema AN, Galbraith PD, Osherov AB, Yalonetsky S, et al. Current perspectives on coronary chronic total occlusions: The Canadian Multicenter Chronic Total Occlusions Registry. J Am Coll Cardiol. 2012; 59:991-997.
Grantham JA, Marso SP, Spertus J, House J, Holmes DR Jr., Rutherford BD. Chronic total occlusion angioplasty in the United States. JACC Cardiovasc Interv. 2009; 2: 479–486.
Brilakis ES, Grantham JA, Rinfret S, Wyman RM, Burke MN, Karmpaliotis D, et al. A percutaneous treatment algorithm for crossing coronary chronic total occlusions. JACC Cardiovasc Interv. 2012; 5: 367– 379.
Rinfret S, Joyal D, Spratt JC, Buller CE. Chronic total occlusion percutaneous coronary intervention case selection and techniques for the antegrade-only operator. Catheter Cardiovasc Interv. 2015 Feb 15; 85(3): 408-415.
Disclosures: Orlando Marrero reports he is a consultant for Boston Scientific.
Dr. Zaheed Tai reports the following: Terumo (proctor for transradial course), Spectranetics (proctor for laser course, speaker, advisory board member), and Boston Scientific (CTO proctor).
We would like to share a compelling piece from CX about the endovascular pioneers who moved the field forward, but also illuminated the dangers of X-ray scatter radiation.
CX acknowledges “huge debt” owed to endovascular pioneers affected by radiation
Since its introduction in the late 80s, endovascular therapy has become increasingly widespread and important. A mini-symposium held yesterday brought to the fore the radiation damage that has occurred to pioneering operators in the field. It also focused on currently available methods to reduce radiation exposure during endovascular procedures.
The list of names reads like a who’s who of pioneers in the endovascular world, and you would surely have read about and heard about these legends whose work has broken new ground, time and time again. Yesterday at CX, Roger Greenalgh, London, UK, read out that list of names for a very different reason; he was outlining how these pioneers had personally been affected by working with ionising radiation.
First on the list was renowned cardiovascular surgeon, Edward Diethrich. After being diagnosed with cataracts in both eyes, calcified plaque in a carotid artery, a brain tumour (oligodendroglioma), he has been instrumental in taking the message of the dangers of radiation exposure to the medical community. Working in collaboration with The Organization for Occupational Radiation Safety in Interventional Fluoroscopy (ORSIF), he has released a documentary film focusing on the impact that chronic, low-level exposure to ionising radiation has on physicians that practice interventional medicine in fluoroscopy labs.
Then, Allan Reid, consultant interventional radiologist, Glasgow, UK, and a disciple of Ted Diethrich was remembered. Sadly, Reid died of a brain tumour (glioblastoma) in September 2015. His brother, Donald Reid, a consultant vascular surgeon, Edinburgh, UK, was seated in the front row.
The list of eminents goes on: Krassi Ivancev, who has led the way in interventional radiology procedures in Sweden and Bulgaria and is a member of the CX Advisory Board, has been diagnosed with cataracts, as has world-class interventional radiologist Lindsay Machan from Vancouver, Canada, a frequent speaker at CX.
Greenhalgh’s presentation ended in remembering Roy Greenberg, pioneering vascular surgeon from Cleveland Clinic, USA, and a disciple of Krassi Ivancev. Greenberg is remembered as a physician who was instrumental in pushing forward the field of endografting for complex aortic disease. He died of widespread malignant tumour of the peritoneum in December 2013, aged 49.
It is important to note that when the endovascular revolution began, the dangers of working with radiation were not the first concern in physicians’ minds; they set out to help their patients using every new tool and procedure at their disposal including performing long procedures of endovascular abdominal aneurysm repair, and thoracic endovascular aortic repair. Yet, this meant that they were often putting themselves at risk in the process, and this is why, Greenhalgh emphasised, that we owe these pioneers a huge debt of gratitude.
The message resonated with physicians practising in the endovascular field.
Timothy Resch, Malmo, Sweden, explained that EVAR and TEVAR are now well-established for infrarenal aortic aneurysms and descending thoracic aortic pathologies.
“Endovascular repair of areas including aortic branch vessels, such as iliac bifurcation, visceral aorta, and the aortic arch is evolving rapidly. The proper use and evaluation of preoperative imaging for planning is vital to minimise contrast and radiation exposure during complex cases. It is important that X-ray equipment and X-ray protection are properly used and understanding fundamental principles of minimising radiation exposure is critical to minimising the risk. Advanced imaging using fusion technology and intraoperative cone beam CT has the possibility of reducing exposure and improving outcome,” he said.
Reducing radiation during endovascular procedures
There is increasing awareness developing regarding occupational hazards of endovascular therapy, most importantly long-term radiation exposure, said Barry Katzen, Miami, USA.
“A number of very practical steps can be taken to reduce radiation exposure to patients, operator and staff. Awareness itself can be an effective first step in reducing exposure as operators and teams start paying attention to this important topic. Radiation reduction can be focused on reducing the amount of radiation being produced (flouroscopy dose, time, X-ray dose times and frame rates), as well as steps to provide protection to operators and staff including the use of lead aprons, eye protection, and maintaining distance. Simple methods can be surprisingly effective, such as reducing frame rates. In our institution, robotic catheterisation has been very effective at reducing dose, by both positioning operators and staff further from the source, and by reducing fluoroscopy and procedure time,” he said.
Training oneself to apply the ALARA principle
Stephan Haulon, Lille, France, then told delegates that every effort is being made to reduce radiation exposure whilst doing complex aortic endovascular reconstruction.
“Complex aortic endovascular repair procedures can be technically challenging and require fluoroscopy guidance with sometimes prolonged exposure. This has an important effect on vascular physicians, who perform these procedures each day, and are therefore at risk of exposure to high doses X-rays. However, X-rays are well-known for the biological hazards they can induce, such as skin/lenses injuries or cancer occurrence. As the benefit/risk ratio must prevail in medicine, it is mandatory to carefully evaluate the risk of radiation exposure, for the patients, but also for the medical staff—this is known as the As Low As Reasonably Achievable (ALARA) principle,” he said.
Haulon shared some tips and tricks that should be implemented in routine practice to reduce radiation exposure. For example, it is highly recommended to work with the “half or low dose modes”, available in most of the imaging systems, or to use the “pulse mode” rather than the continuous fluoroscopy. All imaging controls should be available to scrubbed physicians at the tableside. “Digital Subtraction Angiography (DSA) mode should be avoided and limited to diagnostic purposes, every time this is possible, and fluoroscopy should be preferred. Collimation must be optimised, distance between the captor and the patient minimised and distance between the tube and the patient maximised. Magnification should be avoided if not necessary, as lateral or cranio-caudal angulations.
Haulon explained that that new generation imaging systems available in the most recent hybrid rooms provide the newest technologies to successfully achieve good image quality with low exposure. “Old image intensifiers have been replaced by flat panel detectors that achieve a high level of radiographic performance. They are equipped with 3D workstations that allow a fine pre-operative analysis —useful to avoid unnecessary exposures —and advanced imaging applications, such as fusion imaging or cone beam computed tomography that also allow consequent dose savings,” he said.
“Dose awareness and training in radiation protection are also fundamental to optimise dose reduction. One should train oneself to apply the ALARA principle in daily practice by implementing all the tips and tricks to reduce exposure, but this should also be stressed during every vascular surgeon initial formation, as during its whole practice. Radiation awareness can be raised by monitor staff occupational exposure and patients’ exposure in the operating room, and then compare it to reference levels or published evidence. Specific attention must be paid to the application of dose reduction in routine practice to ensure safety and efficiency, for both patients and staff, during EVAR procedures,” Haulon emphasised.
Importance of simulation
Lars Loenn, Copenhagen, Denmark, made the case for radiation protection training in a simulated setting and stated that this makes a difference regarding radiation awareness. “To learn to use radiation exposure wisely, learners should be trained to undertake the task almost without thinking,” Loenn noted. This is a challenge in a classical training situation with radiation exposure to the team and patient in the angiosuite. “The simulated setting is however an incredible learning opportunity since it is radiation free and allows the trainee to try different approaches and learn how to reduce the radiation exposure while receiving dynamic and instant feedback on delivered radiation in the form of a ‘heat map’. In fact, you can train on radiation aspects at the same time as you train on procedural skills in the simulator. Additionally, certain radiation safety skills needed to be obtained in specific procedure related situations can easily be created in a simulator scenario. Simulated radiation protection training could possibly even be used in credentialing new interventional operators based on a proficiency standard in the future,” he said.
“We need a new way of thinking and merge ergonomics, image management and radiation safety training into one package will bring essential value to training. Health professionals should be provided with the means to successfully do their jobs and I strongly believe this is the way to do it,” he said.
Key to safe application of radiation is awareness of potential risks
Then, Fiona Rohlffs, Hamburg, Germany, said that modern hybrid-operating rooms improve the endovascular workflow, but noted that this development is also associated with increased exposure to radiation for staff and patients. That is why, it is vital, she said, that it demands more awareness of, and knowledge about dose and protective measures. Rohlffs set out that this is especially important for complex aortic procedures involving the aortic arch or the thoracoabdominal aorta.
Rohlffs and team compared reported dose values for branched or fenestrated-EVAR and present values for complex TEVAR procedures, while explaining that the comparison of dose values especially for complex procedures still remains challenging because of unequal reporting standards and acquisition system differences.
Data from the team in Hamburg showed that a comparison between fenestrated and branched EVAR shows a significant difference to the personal dose of first operator, which increased for branched procedures and seems to be due to different operating positions.
Rohllfs told delegates that dose reduction is possible if several protective measures are applied. “To achieve this, CT-fusion techniques are increasingly used for complex fenestrated or branched procedures. System improvements can significantly reduce the amount of radiation,” she noted.
Concluding, Rohllfs said that the key to safe application of radiation is the awareness of potential risks and a good knowledge of how to achieve maximal protection for patients and staff.
Interventionalists are accustomed to extensive regulations in nearly all aspects of their field, and so are very surprised to discover that the protective quality of their lead aprons is very loosely regulated, resulting in great variation between similarly labeled products. Especially when buying a lightweight non-lead apron, they don’t know what they are getting without complicated laborious in-house testing which is usually beyond their reach. This article outlines the problems and provides some practical tips to avoid the pitfalls that lead to years of silent overexposure.
By Chet R. Rees, MD, Victor Weir, PhD., DABR, Andrew Lichliter, MD, and Evans Heithaus MD
About 40-50% of interventionalists have switched to lightweight “lead” aprons (usually non-lead in reality) to deal with the musculoskeletal problems and fatigue that plague the profession and result in pain, injury, and limitation causing decreased quality of life, and reduction of case-load or disability (1,2). Most are not aware that several studies demonstrate that lightweight aprons don’t fully protect, and they may be receiving radiation exposures several times higher than if wearing standard non-lightweight aprons, despite indistinguishable labels and manufacturer-provided information. For example, one study showed that 73% of 41 aprons tested were outside tolerance levels (4), and there are many others showing the inadequacies of products, standards, and regulations in this industry (3-10). The following example may help frame the problem and its magnitude (Fig 1).
Fig 1. Two aprons are both labeled “0.5 mm Pb equivalent”, with corroboration by their product brochures, websites, and salesmen. They are from different manufacturers but are the same configuration and are almost indistinguishable except by their weights (and color patterns). Yet operator exposure when wearing the lightweight apron on the left was 12 times the operator exposure when wearing the one on the right (appendix A).
How can two aprons with the same label differ so remarkably in their protection? It is due to a combination of loose regulations, optional and outdated standards for testing, and the difference in physical properties for lead and non-lead materials which are often not accounted for in the tests. These problems include:
The radiation attenuation (blocking power) of non-lead materials is very energy dependent (fig 2) (3,5,7-9,13,14). Vendor-reported testing is frequently at only one beam quality (related to energy spectrum), while protection at other important unreported energies to which the operator is being exposed may be lower than expected by label interpretation (9). Think of two pairs of sunglasses which both appear equally dark and protective, but one doesn’t block damaging invisible UV rays, whereas the other pair does. If the labels reported only the ability to block visible light, or red light, or blue light, or any color, the user could not know which pair to buy and could receive UV damage with the first pair. Fortunately, consumers are now protected by sunglass labels which report the UV blockage values. But apron labeling is still outdated and paradoxically aprons have gotten less protective overall than the older ones (which contained lead) because the outdated standards worked well for lead, but not for the more recent non-leads which are often used in lightweight aprons.
Fig 2.The intensity of radiation behind a tungsten layer shows the high energy-dependency of its attenuation powers. If tested with a beam quality predominantly above 80keV, its Pb equivalency would be far better than if tested in a beam quality predominating in the lower energies. For this reason such non-leads should not be used alone in a protective garment. Filtration properties of the testing beam importantly affect beam quality and must be known.
Attenuating materials, particularly non-leads of lower atomic number, actually emit secondary radiation (or fluorescence) when exposed to radiation. This new radiation reaches the operator and is of biologically damaging energies (19), however is not well detected with the most commonly used testing methods (narrow beam geometry). Use of more appropriate, but not required, testing methods (broad beam or inverse broad beam) would expose the poor protection of the lightweight aprons, despite their labels (5,8-10,13-15).
Fig 3. Narrow beam geometry (left or top). Fluorescent radiation emitted by non-lead test material is not detected by detector so results are falsely favorable. Broad beam geometry (right or bottom) permits detection of the fluorescent radiation which would expose the wearer of the apron, giving more accurate results.
The methods recommended by standards bodies are not required, and are mostly outdated and inadequate. ASTM does not require broad beam geometry and does not provide for Pb equivalency though used on the label. The effects of somewhat improved IEC-616331-1:2014 are unknown and have yet to be realized in commercial products. Manufacturer’s labels continue to be poorly representative of protection, especially for non-leads.
The labels of some vests and skirts specify lead equivalencies that may correspond only to a double layer (overlap zone) without being clear (3). This creates confusion and may lead the user to believe the entire garment is twice its actual thickness.
Fig 4. Apron vest is only 0.25 mm Pb, but is labeled as “0.5” because it overlaps to 0.5 in the blue shaded area. However most of the area is not overlapped so radiation transmits through the other areas where the user thought the thickness was twice it’s actual.
Fig 5. Cross-section views of 2 overlapping aprons. Very different aprons are labeled the same, confusing the buyer who will purchase the lighter one (A) on the left believing they are equal. In fact A is half as thick in front and sides, and user gets more radiation inside apron. “Front” Pb equivalency on label depends on overlap for apron on left, but not for apron B on the right. Although misleading, it is not illegal to label as on the left (A). Other variations occur such as 0.5 on sides with .25 in front giving 0.5 in overlap and sides. Notice scatter often originates eccentrically, so frontal overlap may be less effective. Apron A is non-lead and B contains lead.
Fig 6. Side-by-side fluoroscopy of the two aprons A and B shown above in Fig 5. Single thickness of apron B attenuates much better than A although both labelled “0.5 mm Pb equiv”.
Fig 7. Aprons A (from Figs 5 and 6) and a new apron C are labeled “0.5 mm Pb” and 0.25 mm Pb” respectively, yet are fairly close in attenuation on a quick fluoroscopy examination. Interestingly, C attenuates slightly better than A, opposite of what one would expect from the labels, and this difference was confirmed on tests performed as described in Fig 6. Both are non-lead. Fluoroscopy of C confirms that is labeled appropriately with regard to “Front” value not relying on overlap.
Substantial weight reductions with equivalent protection have not been achieved for commercial Non-Pb garments, and protection depends largely on weight of the apron for lead and non-lead. Materials that attenuate similarly to Pb over the relevant energy range are still heavy, especially when secondary radiation is measured. Commercial claims of great weight reductions without compromise of protection are made without supporting documentation. This is more recently noted even by manufacturers, such as the statements from one company website that “…there are miniscule differences in the weights of the powders used to produce radiation protection materials…there are no secret formulas…the bottom line here is, it’s lighter weight, it is not offering the same protection levels…Plus or minus a very small percentage, a true 0.5mm [lead equivalent] LE apron is going to weight the same from one manufacturer to the next” (21). Although these facts are becoming more widely understood, under protective aprons are still on the market and need to be avoided.
An excellent study by Pasciak, et al. (22), shows this relationship nicely in their figure 8, where 5 aprons materials were tested along with different thickness of lead foil. Lead foil offered the best protection per weight, and 4 of the 5 aprons fell on a separate line of weight vs. protection which paralleled the pure lead, owing to extra weight due to matrix and fabric. The fifth apron was an outlier; a non-lead with very poor protection per weight. Two aprons met their labels of 0.5 mm equiv (1 non-lead and 1 lead), and the other 3 failed to varying degrees, with as much as ~3X as much exposure to operator. The best protection was provided by the sole lead-based apron. In another study by Lichliter, et al (23), exposure to a phantom operator “wearing” several test aprons was measured while positioned realistically near a phantom patient creating scatter. It had several advantages over previous studies because it tested actual scattered radiation, used a clinically realistic setup, and accounted for differences in the form of the apron (such as open-back vs. closed-back, and differences in how overlap is treated as outlined in Fig 4) rather than just testing scraps of fabric. As seen in Fig 5, weight correlates very well with 1/exposure creating an almost straight line. Data fell along two lines; one for closed-back models and the other for open-back, showing that it is not necessary to cover the back when it is not turned to the patient during fluoroscopy, and that open-back designs are lighter in weight for equivalent protection since they don’t have heavy material in the back. In fact the best protection was provided by an open-back design, Zero-Gravity ™ due to it’s 1.0 mm Pb thickness. Exposures in it were 9.8% of the mean for all aprons, and 37.5% of the best apron. The most protective apron was quite heavy and worn very infrequently in the department.
Fig 6. Exposure-1 (1/operator-exposure) correlates closely with weight of apron, with most protective aprons being higher on Y axis. There are two main lines; one corresponding to closed-back aprons (skirts and vests), and the other to open-backed aprons (butcher style). Note that the open-backed aprons are lighter for equivalent protection, and the most effective model was the open-backed Zero-Gravity ™ which is shown as 0 weight since it is suspended and can’t be weighed. It is also evident that the lead aprons performed better overall than the non-leads in this group, although with some overlap. Test set-up is pictured on the right, with acrylic stack (phantom patient) producing scatter, and phantom operator on a wood frame with dosimeter inside the chest/abdomen region, standing in a typical position for vascular procedure.
HOW TO BUY AN APRON:
The easiest way to safely buy an apron with reasonable assurance of its protection is to buy a lead or lead-composite apron labeled 0.5 mm Pb equiv which does not feel lightweight, and if it is an overlapping design, check it with fluoroscopy to make certain it is not labeled misleadingly as shown in Figs 4-5. This is done in two ways. First, look for transition points between the back panel and the higher attenuating front panel, which if present, means the frontal Pb equivalency may not depend on overlap (e.g. Apron B in figure 5). If the apron is the same all the way around, as in Apron A of Fig 5, and the label suggests the front is twice the thickness of the back, then the apron is labeled misleadingly and it is probably best to avoid the apron and its manufacturer and vendor. Second, place the new apron side by side under fluoroscopy with an old trusty lead apron that has been tested in the past, and is labeled with the same Pb equivalency. They must be side to side due to the automatic brightness control (separate exams will not work). This test is crude and only under one beam quality but can help to distinguish large differences or misleading labeling based on overlap only.
If you need to cut a little weight, consider an open back “butcher” style apron with a good waist band to take weight off the shoulders. Get lead-based material and make sure it does not feel lightweight. Consider the fluoro test against a trusty known apron to look for gross problems.
If you insist on non-lead, insist on a label designating testing using IEC-616331-1: 2014-05 and IEC-616331-3:2014-05 (they must say 2014 in the titles) and look for the following information: Broad beam geometry (or with inverse broad beam, but NOT with narrow beam) indicated on label. Results of tests at 5 energies ranging from 30-150 kVp or wider using the beam qualities specified in Table 1 of the IEC document. The document is vague on exactly what beam qualities must be used and how to report it, so it is important to check carefully. If not on label, request source documentation which specifies the beam qualities in Table 1 of the IEC document. Unfortunately this document is copyrighted and must be purchased in their web store. It may be nearly impossible to obtain all of this information from the vendor, and as of late 2015 most manufacturers can’t provide all of it even on request (24). Ultimately, the garment should be tested in house by a physicist with a copy of the IEC-616331-1:2014 who has the set-up and knowledge to do this. This will be unavailable at most institutions. Until things change considerably with good validation in the literature, this author strongly advises against lead-free materials, especially since they do not save significant weight even when offering similar protection, and are more likely to be poorly represented by their labels.
If your back or neck is killing you and you can’t do your job without a lightweight apron, be aware that you are probably making a trade-off between weight and radiation protection. It would still be wise to test it against other options in-house using acceptable methods to make certain it is not one of the worst. Even a simple side by side fluoroscopic evaluation may be better than nothing, but the value of this has not been established.
Regulations are unlikely to change soon, and the standards are not preventing high variability of products. The only way to remedy these problems are to police the manufacturers and vendors ourselves by demanding copious technical information, making careful choices, and testing and rejecting aprons and vendors who can’t provide information or who provide misleading information.
About the author: Chet R. Rees, MD is a practicing interventional radiologist and Clinical Professor in Dallas, TX at the Baylor Scott and White Hospital. He discloses no conflict of interest in the protective apron industry. He discloses a financial interest with CFI Medical Solutions, who makes shielding products including the Zero-Gravity ™ suspended radiation protection system.
Q: Do substantially lightweight aprons provide adequate protection? A: No, not even when the label implies they can. There is no miracle material which dramatically cuts weight without making sacrifices in protection. The literature has shown that modest weight reductions may be achieved by mixing metals compared to using pure lead, but substantial weight reductions for same protection has been an elusive goal, despite the appearances of labels and manufacturer’s claims.
Q: Does the “0.5 mm Pb equivalent” label on my apron mean I am protected? A: If your apron contains lead and it is not lightweight, it probably does mean you are getting the protection close to what you were expecting based on the label. But if your apron is non-lead, such labels usually do not guarantee such protection.
Q: Is there any type of label I can trust for non-leads? A: Maybe, time will tell. The IEC-616331-1:2014 (it must say 2014 in the title) standards have incorporated some improved methods including inverse broad beam geometry and suggestion for multiple energies. However whether these are used, followed as intended, or how the results compare to independent tests are a still unknown. This author has never seen a full IEC-616331-1:2014 label on any product despite frequent checks at vendors booths.
Q: Are all non-lead aprons terrible? A: No. Some models are not lightweight, use a good mixture of metals to provide attenuation over a spectrum of energies, and include enough to be effective. Based on reports, this seems to be the minority. Current labeling and marketing information are not very helpful, but picking them up and feeling their weight is a pretty good indicator. Unfortunately again, studies have shown that some non-lead aprons provide less protection even on a per weight basis, in addition to the loss of protection due to being lightweight, thereby being especially poor (22,23).
Q: How do I test my apron to be sure I am okay? A: If your apron contains lead and is not lightweight, it is probably okay, but you can test at a couple beam qualities using narrow or broad beam geometry which may be available to your physicist and compare results to the attenuation tables and Pb equivalency tables, or test against a known standard. Fluoroscope any overlapping models to make sure the labeled attenuation does not correspond to overlap zone only. If your apron is non-lead, it may be difficult or impossible for you to get it done in house. Set up a broad beam geometry, and use 5 beam qualities ranging from 30-150 kVp with the beam filtration values shown in the tables in IEC-616331-1:2014. Compare results to the attenuation tables and Pb equivalency tables. Fluoroscope any overlapping models to make sure the labeled attenuation does not correspond to overlap zone only.
This stuff scares me. How can we fix this? A: Major changes in regulations could help but will not happen anytime soon. Rapid change is possible through user awareness and demands made upon vendors. If physicians and other workers refuse to buy from vendors whose aprons haven’t been tested in rigorous ways with test values and conditions indelibly attached to the garment, then some vendors will provide the necessary information, it will be more accurate, and the quality of their aprons will have to improve since under-performing models will be exposed. Vendors who don’t do this will probably continue but at least the user will have a choice they do not have right now.
Q: Why do manufacturers use non-leads to make lightweight aprons if non-leads aren’t really significantly more protective per weight? Why not just use thinner lead preparations? A: We can’t know the intentions, but we can state a couple things which might lead to this. First, commonly used testing such as with narrow beam geometry and use of one or two beam qualities are reasonably accurate for lead but not for non-leads; a poorly protective lightweight non-lead apron could slip through the cracks and get a 0.5 mm Pb label much more easily than a poorly protective lightweight lead apron. Second, lightweight aprons sell, they are in demand, and can command higher prices which may lead to higher profit margins. The buyer may easily believe that non-leads are lighter than lead and so can therefore make lighter aprons (when in fact aprons can easily be made to any weight using any substance in different amounts). Taken all together, the users can easily go down the intuitive, but incorrect, path that lighter materials are more efficient and make protective lightweight aprons which they should pay more money to obtain. And the sellers are simply offering what the people want, without violating any regulations or laws. The cycle can only be broken by user awareness and demands made upon vendors so that profits come to those providing good solid protection with complete and appropriate test results, not from well marketed lightweight aprons which protect worse than evident from label.
Q: Is there any use for a lightweight apron? A: Probably yes. Some personnel don’t get very close to the patient (source of scatter radiation) during procedures, such as a circulating technologist who is usually behind the control panel. The inverse square law reduces the field in their location enough such that 0.5 mm Pb equivalency is not required. However, they should still be able to assess their purchases by label and brochure without taking wild guesses as to actual protection. For example, settling for 0.25 mm Pb equivalency but getting something less is not acceptable. Interventionalists standing near the patient should be using 0.5 mm Pb equiv without deficiencies.
Q: Weren’t there studiesthat showed that non-lead bilayers could substantially lower weight without loss of attenuation? A: Two studies raised hopes of 25% weight reduction with equivalent attenuation, however these were experimental, included non-commercial metals and computer-based simulations (13,15). The authors noted that actual attenuating capabilities must be measured in the final product since it is influenced by the matrix materials and other manufacturing factors which they did not account for. Such findings in commercially available aprons have not been demonstrated to our knowledge.
1. Klein, LW, Tra Y, Garratt KN, et al. Occupational health hazards of interventional cardiologists in the current decade. Catheterization and Cardiovascular Interventions 2015. 86 (5) 913-924, November 1.
2. Ross AM, Segal J, Borenstein D, Jenkins E, Cho S. Prevalence of spinal disc disease among interventional cardiologists. Am J Cardiol. 1997 Jan 1;79(1):68-70.
3. Muir S, McLeod R, Dove R. Light-weight lead aprons—light on weight, protection, or labeling accuracy? Australas Phys Eng Sci Med 2005 Jun;28(2):128-30.
4. Finnerty M, Brennan PC. Protective aprons in imaging departments: manufacturer stated lead equivalence values require validation. Eur Radiol 2005 Jul;15(7):1477-84.
5. Eder H, Panzer W, Schofer H. Is the lead-equivalent suited for rating protection properties of lead-free radiation protective clothing? Rofo 2005 Mar;177(3):399-404.
7. Eder H, Schlatt H, Hoeschen C. X-ray protective clothing: does DIN 6857-1 allow an objective comparison between lead-free and lead-composite materials? Rofo 2010 May;182(5):422-8. doi: 10.1055/s-0028-1110000.
8. Christodoulou EG, Goodsitt MM, Larson SC, Darner KL, Satti J, Chan HP. Evaluation of the transmitted exposure through lead equivalent aprons used in a radiology department, including the contribution from backscatter. Med Phys 2003 Jun;30(6):1033-8.
9. Jones AK, Wagner LK. On the futility of measuring the lead equivalence of protective garments. Med Phys 2013 Jun;40(6):063902-2:063902-9. doi: 10.1118/1.4805098.
10. Pichler T, Schopf T, Ennemoser O. Radiation protection clothing in X-ray diagnostics – comparison of attenuation equivalents in narrow beam and inverse broad-beam geometry. Rofo 2011 May;183(5):470-476. doi: 10.1055/s-0029-1245996.
13. McCaffrey JP, Mainegra-Hing E, Shen S. Optimizing non-PB radiation shielding materials using bilayers. Med Phys 2009 Dec;36(12):5586-5594.
14. Schlattl H, Zankl M, Eder H, Hoeschen C. Shielding properties of lead-free protective clothing and their impact on radiation doses. Med Phys 2007 Nov;34(11):4270-80.
15. McCaffrey JP, Tessier F, Shen H. Radiation shielding materials and radiation scatter effects for interventional radiology (IR) physicians. Med Phys 2012 Jul;39(7):4537-4546. doi: 10.1118/1.4730504.
16. McCaffrey JP, Shen H, Downton B, Mainegra-Hing E. Radiation attenuation by lead and nonlead materials used in radiation shielding garments. Med Phys 2007 Feb;34(2):530-537. doi: 10.1118/1.2426404.
17. ASTM International (West Conshohocken, PA). Standard test method for determining the attenuation properties in a primary X-ray beam of materials used to protect against radiation generated during the use of X-ray equipment. Designation F2547-06. Available through http://www.astm.org/Standards/F2547.htm.
19. Schmid E, Panzer W, Schlattl H, Eder H. Emission of fluorescent x-radiation from non-lead based shielding materials of protective clothing: a radiobiological problem? J Radiol Prot 2012 Sept;32(3):129-139. doi: 10.1088/0952-4746/32/3/N129.
20. Akber SF, Das IJ, Kehwar TS. Broad beam attenuation measurements in lead in kilovoltage X-ray beams. Med Phys 2008;18:197–202. doi: 10.1016/j.zemedi.2008.04.008.