Below-the-Table System May Protect Against Scatter Radiation in the Cath Lab

PARIS, France—A new radiation protection system that replaces the traditional cath lab table mattress with a radiolucent carbon fiber platform and memory foam shows promise for protecting all personnel against harmful X-rays during procedures, according to a new study.

“We're taking a very holistic approach to reducing all the scatter radiation in the room, not just trying to protect one individual. By eliminating the scatter radiation in the whole room, we protect the entire team,” Robert Wilson, MD (University of Minnesota, Minneapolis), who presented the EggNest research findings here at EuroPCR on Wednesday, told TCTMD. Wilson is founder and CEO of Egg Medical, which makes the system.

The EggNest system consists of a carbon fiber sled-like platform that lays on top of the traditional cath lab table, integrated ECG wiring, internal shielding, and a quad-layer memory foam that can withstand chest compressions. The entire system conforms to the patient’s body and also has movable shoulder, arm, and leg shields, integrated rails that move with the patient, a mounted clear shield, and a built-in radial table with shield.

As Wilson explained in his presentation, he and his team measured scatter radiation during a simulated cath lab procedure at six different positions—echocardiographer, right neck access, left chest/biopsy, angiographer, assistant, and nurse—from 20 to 200 cm off the floor with no shielding, standard shielding (consisting of hanging and table shields with a 0.5-mm lead equivalent), and the EggNest.

Not surprisingly, the personnel positions near the patient’s head and chest receive the most scatter radiation. Yet, interestingly enough, the nurse position 1.5 m from the table receives more radiation than the assistant at the foot of the table. Notably, Wilson said, 69% of the scatter radiation comes from below the table.

Scatter Radiation Doses Around the Cath Lab

 

“If you’re not protecting below the table, you’re not reducing the scatter radiation in that room substantially,” Wilson said.

Compared with standard shielding, the EggNest system reduced the average scatter radiation dose by 82% for the assistant, 89% for the right neck access position, 90% for the angiographer, 92% for both the nurse and left chest/biopsy position, and 97% for the echocardiographer. Additionally, overall scatter radiation from angulated X-ray views was “markedly attenuated” by the EggNest system, Wilson said.

While standard shielding, especially table skirts, “works great,” it simply does not cover “enough of the area to be able to eliminate the amount of scatter radiation that we would like,” he said, adding that the EggNest does this “without compromising imaging flow.”

Quick Transition

Following Wilson’s presentation during the ‘Out of the Box Technologies’ session, panelist Hollis Call, CEO of MarketMonitors, Santa Barbara, CA, asked if there are any downsides to the EggNest.

Wilson replied that there aren’t any substantial ones. “You do have to flip the shields up in the middle of a case,” he said, but the overall learning curve for hospitals that install this is “about 2 days.”

Additionally, in response to an audience question about the effectiveness about simply adding more effective under-the-table protection instead of the full EggNest system, Wilson said that is how this idea began. “We said, ‘Oh, we'll just put a lead tablecloth basically. But here's what happens. The detector goes off 100% of the time whenever you move the X-ray C-arm, and the second thing is that the floppy lead thing drapes over the primary beam, which really increases the dose a lot and you can't see half the field.” His team “did a lot of trial and error,” Wilson assured.

Ryan D. Madder, MD (Spectrum Health Fred and Lena Meijer Heart Center, Grand Rapids, MI), who was not involved in the study, told TCTMD in an email that “considering the increasing awareness of radiation exposure hazards faced by physicians, nurses, and technologists in the cath lab, the EggNest represents promising technology that has the potential to significantly improve cath lab radiation safety for the entire cath lab team.”

However, while the “results are promising, additional studies are needed to determine the effectiveness of the EggNest in reducing physician and staff radiation doses in larger studies performed in real-world clinical settings among patients undergoing invasive cardiac procedures,” he added.

The New Reality

Making a more universal point about radiation exposure, session co-chair William Wijns, MD (Lambe Institute for Translational Medicine and Cúram, Galway, Ireland), said he doesn’t understand how the nurse position ended up receiving so much more radiation than he would expect.

Wilson said he “thought the same thing too. I’ve been told if you’re 6 feet away, don’t worry about it.” The measurements showed exposure rates of 250 to 300 µSv/h for posterior-anterior (PA) angulation for the nurse position, he explained. But “if you angulate, and if you do cine angulation, it can get up to 11,000 µSv/h,” which is almost as much as a patient can receive.

“The reality is that most of these measurements you see published are all PA, they are all completely minimized, and you're not doing PA projections most of the time. You're doing angulated projections,” Wilson continued. “A lot of that is coming from under the table.” Most cath lab personnel wear their meters on their chest where their exposure levels might seem reasonable under standard shielding.

“The nurse position was a big surprise for me,” he said. “You begin to see where a lot of the things that we have been taught about radiation scatter are technically true but not necessarily practically true.”

“If the nurses get to know this, what's going to happen in Europe is that the unions are going to get involved,” Wijns said.

Wilson reported that in fact at one hospital where he installed the EggNest, “the nurses and techs wrote a group letter to administration basically saying that they were being overradiated” and requested more protection.

It might be “strange” to ask for regulatory support for something like an EggNest, Call said, but perhaps it’s warranted.

Wilson said that strangely enough, besides the Occupational Safety and Health Administration’s “as low as reasonably achievable” (ALARA) policy, the only US agency that has been “super critical” about radiation exposure in the cath lab is the Environmental Protection Agency, “which really doesn't even have jurisdiction over this.”

“I bet everyone on this panel knows someone who likely had a hematologic malignancy,” Wilson concluded. “We need more regulatory push. Part of it is there hasn’t been a solution. Now that we have at least a partial solution, this might help.”

Wilson told TCTMD that they are done with the prototype phase and are now seeking distribution options. “We'd like to have this be the standard platform for angiography and X-ray labs worldwide,” he said.

Photo Credit: Egg Medical