Dave Fornell, editor of DAIC Magazine
14 Ways to Reduce Radiation Exposure in the Cath Lab
One radiation protection technology that often has operators packed around displays at some conference expos waiting to try it out is the ZeroGravity system. It is a ceiling suspended suit that offers more protection than standard aprons, including full body protection including the face. It allows operators to shed their lead aprons and eliminate any weight on the operator’s back, helping alleviate orthopedic back pain.
In the past, there was not much that could be done to mitigate the X-ray radiation exposure of interventional cardiologists or cath lab staff. Also years ago, the subspecialty of interventional cardiology was new and few people had experience with what happens to cath lab staff exposed to X-rays for 25-30 years over their career. Today, 30 years after interventional cardiology became a subspecialty, the impact of that exposure is coming to light. This has spurred discussions about radiation safety and caused a demand for new ways to reduce staff exposure.
“This is an area where everyone has some anxiety about it, but there are not a lot of people who are doing anything about it. People are now much more conscious about radiation safety than in the past," explained Emmanouil Brilakis, M.D., Ph.D., director, Center for Complex Coronary Interventions, Minneapolis Heart Institute. He said concern has increased in recent years as interventional procedures have become more complex and last longer, increasing the exposure to staff.
“The No. 1 thing that has to be done is education,” said Sunil Rao, M.D., professor of medicine at Duke University Medical Center, and section chief, cardiology, at the Durham VA Medical Center. “People who work in the cath lab usually like the environment and are working every day to help really sick patients." He said very often, operators are more concerned about the patients than they are about their own exposure to an invisible health hazard that might take 20 years to manifest as a health issue later in life.
“Getting staff to understand radiation safety has been a very big challenge,” Rao said. “The first step in lowering staff exposure is creating a comprehensive education program. When people understand the risks, then the education becomes about how to reduce the risks.”
Both of these experts offered the following ideas of things interventional labs can do to lower their exposure.
9 Simple Things Labs Can Do Now:
• If everyone takes two steps back from the table during imaging it can cut their dose exposure in half.
• Use proper positioning of the C-arm in relation to the patient. Brilakis said the X-ray generator should be as far away from the patient as possible and the detector needs to be as close to the patient as possible. This both optimizes image quality and reduces the amount of scatter radiation. Rao said he has been in several labs where this is not standard practice.
• The X-ray source of the C-arm should be placed under the patient table. This helps reduce scatter radiation. Scatter from under the table also will need to pass through the table and patient before hitting staff, which will reduce the amount of overall staff exposure.
• Lower the frame rate on the imaging system. The old standard was 30 frames per second (FPS), and today it is usually 15 FPS. Brilakis said most operators can lower this to 10 FPS without a major impact on the imaging. Rao reduced his rate to 7.5 FPS, which he said takes some getting used to because images can appear more jerky, but it results in big dose savings.
• Use more supplemental imaging like ultrasound, optical coherence tomography (OCT), intravascular ultrasound (IVUS) and transesophageal echo (TEE) instead of fluoro.
• Use the "fluoro save" feature of newer systems. This allows operators to save the last image acquired to aid procedural guidance, rather that using additional X-ray imaging.
• Use vessel road mapping technologies if available on your angiography imaging system. This can help reduce the need for additional fluoro.
• Use lead drapes under the patient table. These can help cut scatter from under the table. Rao said some labs complain that these get in the way of C-arm travel around the patient, but he said careful placement of the drapes can help avoid C-arm contact.
• Use tubing extensions on manual manifold contrast injectors to allow the operator to stand several feet further back from the table during contrast injection imaging.
5 New Technologies That Can Reduce Dose in the Cath Lab
There are several new technologies available that can help reduce scatter radiation by creating a barrier between the operators and the imaging system, or removing the operator entirely from the radiation field. Brilakis offered the following list of ideas and new technologies to help lower staff exposure:
• RadPads offers a series of drapes, table skirts and wearable protection pads to reduce scatter radiation exposure.
• The ZeroGravity system from Tidi Products enables the operators to shed their lead aprons in favor of a ceiling or boom suspended protective suit with a face shield that the operator can walk up to and place their arms through. It offers several times more protection than standard lead aprons and is easier on the operator’s back, since the boom suspension supports all the weight.
• The Corindus Corpath robotic system is another technology that allows operators to shed their lead aprons. Instead, they sit in a lead-lined booth away from the radiation field to remotely control catheters.
• Egg Medical recently introduced the EggNest cath lab table, which has built in radiation shielding. The company has data showing it can reduce scatter radiation by 90 percent. It provides protection to the entire medical team, regardless of their location in the lab. The system also moves with the patient table and as the C-arm rotates, providing passive protection.
• Use of the newer generation angiography systems that utilize lower-dose imaging technologies.
New Angiography Technologies Helping to Lower Dose
The newest generation of angiography systems offered by all vendors on the U.S. market have made great strides in the past few years toward reducing the doses needed to get high-quality images. “The development has been really rapid for new technologies to reduce dose on these systems,” Rao said. “I am really jealous of labs that are able to buy the newer systems.”
If hospitals are looking for new imaging systems, Rao noted they should consider the dose reduction features and what these might mean for staff dose exposure savings over the decade the equipment will likely be in service.
Brilakis said the dose lowering capabilities of the Philips AlluraClarity and recently released Siemens systems are great. He said GE has also made strides to lower dose, but feels the other two vendors went further in optimizing the dose.
But even with a new imaging system, cath labs still need to make sure all the settings that enable lower-dose imaging are actually used. "You have to optimize the machine," Brilakis said. "It is not enough to just buy a new machine." He explained this includes making sure to set the FPS speeds and use of the available filters on the machines. Labs also need to make sure all operators understand what the features are and how they can be customized and optimized by each user. It is also important to have frank discussions with the engineers who help set up these systems so they understand what cath lab operators need.
"If someone is a medical physicist or if they are involved with radiation protection, they will have much different views on the settings than the interventional cardiologist," Brilakis explained. "So, you need to walk through the lab with them and discuss your workflow. You actually need to take them in the cath lab and show them how you work."
It is also important to be on the same page when using descriptions and nomenclature. Everyone needs to standardize on the same taxonomy and units of measure, he said. This includes how radiation dose is measured, either using milligray (mGy) or miliSieverts (mSv), so everyone is speaking the same language.
Brilakis said there also is the question of how to calculate estimated exposures using various methods and measuring points. This too needs to be agreed upon. "In my mind, air kerma should be used," Brilakis said. "There is more confusion than there needs to be about measuring radiation doses."
Supplemental Imaging to Reduce X-ray Use in the Cath Lab
Rao said use of supplemental imaging in the cath lab can help reduce the reliance on X-ray imaging. He has seen coronary procedures guided largely by OCT with very little fluoro. Ultrasound, TEE and IVUS can also play a role in many procedures to cut use of angiographic imaging.
“Most labs already have these technologies available, but the biggest challenge is just getting people to use this technology,” Rao explained.
Several vendors offer road mapping technology to create overlays of the coronary vessels on live fluoro that can help reduce the need for contrast and X-ray use. This can include overlays of anatomical images from computed tomography (CT) or rotational angiography.
Robotics Helps Remove Staff From the Radiation Field
“Robotic PCI has a lot of promise," Rao said. “I think robotics will help realize a lot of radiation reduction because it takes the operator out of the radiation field and they do not need to wear lead. Techs can also see dose reduction because they can load the wires when there is no imaging and then step back a safe distance when fluoro or cine is used.”
Standard Radiation Protection May Not Have Much Effect
Brilakis and Rao said there is some data showing the standard radiation protection glasses and skull caps worn in the lab may offer little protection. He said it is due to the scatter radiation bouncing up from the table at a steep angle, which actually travels under the glasses and the caps, rather than hitting those protective barriers head on where they would be more effective.
"The glasses we wear and the caps we wear really don't protect us," Brilakis said.
Preventing Back Pain Due to Heavy Aprons
“The orthopedic problems are a real issue,” Rao said. “I think there is a failure in where to position screens so operators do not need to strain and lean over to see the screen.”
Rao added that strength training is important for operators and cath lab staff. He sees a lot of emphasis by his peers on proper diet and endurance training, but something that would really help them prevent back issues is exercises to strengthen their back muscles so they can stand for hours each day supporting the lead. The problems with straining the back comes from staff not having the muscle support they need to hold the weight and move, he said.
Read more about interventional lab radiation safety and more thoughts from Rao and Brilakis in the blog "Defining the Cath Lab Workplace Radiation Safety Hazard."
For more on new technologies to help reduce dose in the cath lab, read the article "5 Technologies to Reduce Cath Lab Radiation Exposure."