Cath Lab Radiation Shielding Protects Whole Team

Neil Osterweil

May 29, 2018

PARIS — A radiation shielding system reduces the amount of scatter radiation exposure to cath lab personnel by more than 80% compared with no shielding and better protects every position around the table than do conventional shielding systems.

In a new study, investigators examined exposures to scatter radiation in the cath lab and then compared exposure risk between standard shielding and use of the EggNest system (Egg Medical Inc).

"The majority of x-ray scatter radiation in any angiographic projection comes from below the table mattress top, and angulated views substantially increase staff radiation exposure," said Robert F. Wilson, MD, an interventional cardiologist at the University of Minnesota in Minneapolis and founder and chief executive officer of Egg Medical Inc. 

"Standard shielding provides limited protection for the angiographer positioned at the radial/femoral access sites, and no significant protection for the remainder of the heart team or for procedures with head access," he said here at the European Association of Percutaneous Cardiovascular Interventions (EuroPCR) 2018.

But they found a marked reduction in radiation exposure for both the physician and those at all positions around the table with the new system, as well as in all angiographic views tested, Wilson reported.

Interventional radiologists have the highest radiation exposure of any occupation, and a significant increase in risks for outcomes such as cancer, cataracts, skin lesions, hypertension, and neurodegenerative disease has been seen despite standard screening, the researchers note.

The EggNest system comprises a carbon fiber platform that replaces a patient mattress on a standard cath lab table, internal shielding, integrated electrocardiography wiring, and a patient mattress made of four layers of memory foam that can support chest compressions.

The system has a movable clear shield, integrated internal shields, a foldable arm shield, a shoulder shield, adjustable leg and femoral shields, integrated rails that move with the patient, and an integrated radial table shield.

It also has a specially contoured flexible shield below the table that conforms to the x-ray gantry and protects team members from radiation that comes from below.

Phantom Testing

To estimate radiation exposures to various members of the catheterization team, Wilson and colleagues created an experimental set-up using a Toshiba Infinix fixed-arm x-ray system for performing 70-keV fluoroscopy at 15 frames per second, 12 in field. The "patient" was a US Department of Energy calibrated human anthropometric phantom. The researchers measured scatter radiation with a RaySafe X2 radiation detector (Unfors RaySafe).

Scatter radiation was assessed at six positions around the cath lab in five angiographic views. The researchers measured scatter at both 20 cm and 200 cm from the floor for each position, with no shield, with standard shielding (hanging shield and table shield, each 0.5 Pb equivalent), and with the EggNest system.

They found that positions near the patient's head and chest receive the most scatter radiation and that the nurse positioned 1.5 m from the table actually receives more radiation than the assistant positioned at the table pedestal.

Table. Scatter Radiation Doses for Each Cath Lab Position Without Shielding

Position Average Dose (μSv/hour) Maximal Dose (μSv/hour)
Echocardiographer 1327 2060
Right head and chest 859 1180
Biopsy 1774 3310
Angiographer 644 1210
Assistant 296 560
Nurse 389 483

 

They also found that 69% of scatter radiation comes from below the table.

For positions on the right side of the table, the new system was associated with marked reductions in scatter radiation compared with standard shielding, including a 92% reduction at the biopsy position, a 90% drop at the radial/femoral position, and 82% decline at the assistant position.

For all heights and positions around the table, the average scatter radiation for the heart team in angulated x-rays was markedly attenuated compared with no shielding or standard shielding, Wilson said.

"The EggNest provides markedly more protection for both physician and the entire heart team, without compromising imaging flow, better protection at all positions around the table, and better protection at all angiographic views tested." Wilson said.

Peter J. Fitzgerald, MD, from Stanford University in California, a panelist for the session, told Wilson that "Siemens, Phillips, they all have radiation sensitivity programs, so I think that there clearly is a need, and I like the fact that you're covering everybody.

"You're protecting the whole environment. These echocardiographers really get horribly exposed," he added.

Fitzgerald also remarked, however, that getting hospitals to accept the shielding may require some shrewd salesmanship.

"I've been involved in this field and it's frustrating, because the hospital administrators don't care," he said. "The docs do, the nurses, the healthcare providers, but the hospital administrators don't necessarily care about protecting somebody unless there's a lawsuit."

"It's About Protecting Everybody"

Co-moderator William J. Wijns, MD, an interventional cardiologist from the Lambe Institute for Translational Medicine and Curam in Galway, Ireland, asked how it could be that the nurse's position should get more scatter radiation than the assistant's position right at the foot of the table.

"The nurse position was a big surprise for me," Wilson said, "and you begin to see where a lot of the things we have been taught about radiation scatter are technically true, but they're not, say, practically true."

Panelist Hollis Call, CEO of MarketMonitors Inc, Santa Barbara, California, asked whether in the United States the Occupational Safety and Health Administration (OSHA) had policies regarding radiation scatter in the cath lab. Wilson acknowledged that OSHA has guidelines regarding excess radiation exposure and calling for use of the lowest doses possible, "but in reality, at the end of the day, they say these are life-saving procedures and we basically don't want to get in the way."

Wilson and the panelists all agreed that they know interventional cardiologists with malignancies, including cancers on the left side of the brain.

Wilson said he also knows two interventionalists from the same city who developed hairy-cell leukemia, a rare hematologic malignancy.

Asked by theheart.org / Medscape Cardiology, whether he would demand a similar shielding system for his cath lab, Fitzgerald said that "there are some administrative challenges, and the business model in my opinion is most complex, but absolutely. And it's not just about protecting the docs; it's about protecting everybody."

The study was supported by EggNest. Wilson is founder and CEO of the company. Fitzgerald, Wijns, and Hollis reported no conflicts of interest relevant to the study.

Congress of the European Association of Percutaneous Cardiovascular Interventions (EuroPCR) 2018. Out-of-the-box technology session. Presented May 23, 2018.

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