On a day-to-day basis, radiation shielding is probably not something that is on the top of a healthcare provider’s list of concerns, but these massive projects are crucial to any facility.
Whether it’s an imaging department or a radiotherapy treatment center, having a basic knowledge of shielding will help you make sure the right decisions are made when shielding projects or issues arise. A few experts in the field shared their insight with HCB News on these matters.
What information should providers share with their shielding partners?
Shielding a diagnostic imaging facility and shielding a radiotherapy facility are two completely different tasks. Both require the facility to share certain information with the shielding company, but radiotherapy takes things to a whole other level.
“Radiotherapy is a lot more complicated because you're dealing with much higher levels of radiation,” said Cliff Miller, director of marketing and IT at NELCO Worldwide. “If you're above a 10 megavolts machine, you're not just dealing with gamma but you're also dealing with neutrons to shield for.”
Because of that, it’s beneficial to engage with the company early on in the planning phase regarding planning for the space requirements, the ancillary space around the room and fitting feasibility. All of that can have a large impact on the budget and schedule for completing the project.
“A radiation therapy vault may need four or eight feet of concrete on four- or eight-foot-thick walls and that obviously takes up a lot of room,” said Miller. “We can incorporate other materials to make the thickness of the rooms smaller so that maybe you can fit an extra treatment room in or fit it into a space that you didn't think could fit one before.”
Although shielding for the diagnostic setting is much simpler, there still is pertinent information that needs to be relayed. Andrew Martin, director of physics at Veritas Medical Solutions, said that facilities should identify the brand, model and features of the equipment they have selected, the maximum available dimensions, any obstructions within the area or logistics to the work space, the treatment types, dose per patient, the maximum treatment capacity they intend to offer and their local radiation protection regulations.
Paul Rochus, business development executive at MarShield Radiation Shielding, stressed the importance of knowing what sort of attenuation they need as well as the lead thickness. To determine that, they can consult with a health physicist or may have someone on staff in their radiation safety department.
But one thing every facility should always make sure to have is a good set of architectural drawings, according to Thomas Petrone, chief executive officer and chief medical physicist at Petrone Associates.
“These would have been created through a good working process between the owner, the equipment manufacturer, the technical staff who will utilize the equipment and the medical physicist,” he said. “The physicist must provide a good shielding requirements analysis before the shielding company can adequately bid the job.”
In the analysis, alternative shielding materials such as normal and high-density concrete can be considered for higher energy machines. On the lower-end side, such as mammography, gypsum board can be used in place of some lead.
To lead or not to lead?
For the diagnostic setting, lead is the shielding material of choice, but is it always the best choice? NELCO’s Miller definitely thinks so — citing that “it's the most cost-effective, easy to install, quickest to install, it's flexible and gives a finished product that the customers are happy with.”
The downside of lead is that it’s toxic and requires special manufacturing, handling, transportation and working restrictions. The WHO stated that lead negatively affects the development of the brain and nervous system in children, and may also lead to high blood pressure and kidney damage in adults.
The Institute for Health Metrics and Evaluation found that lead exposure was responsible for an estimated 540,000 deaths in 2016. It accounted for nearly 64 percent of the global burden of idiopathic developmental intellectual disability as well as 3 percent and 3.1 percent of the global burden of ischemic heart disease and stroke, respectively.
A few of the shielding companies have developed products and come up with strategies to mitigate the risk of lead exposure. MarShield sells lead bricks so that they can be painted to enclose the lead as well as rolling barriers, which encase lead in a metal frame.
NELCO has a comprehensive environmental health and safety program to address all of the safety concerns that their customers have with lead.
“We limit the amount of cutting and what we bring on to a job site,” said Miller. “We're not going to be cutting on a job site, because that can spread the lead throughout a building and we control the area where the lead is being installed so no one can access it.”
Lead is less expensive than other materials, like tungsten, but it’s still not considered to be inexpensive. To prevent waste, NELCO cuts lead with a knife instead of a saw so there is no dust.
According to Veritas’ Martin, lead is not a structurally sound material on its own and is subject to a phenomenon called Lead Creep. In those cases, a structural cage will typically be required to ensure the lead does not creep over time and collapse.
“You can use concrete instead of lead but need a much, much greater thickness,” said Petrone. “In a new building construction and where land is not expensive, that could be okay and is often a choice, but in a city that becomes problematic.”
But Petrone added that the ultimate solution is to involve all stakeholders upfront in the process. By doing that, you can minimize lead or other shielding by working with architects and physicists to come up with the ideal placement of the radiology equipment.
Rolling shields from MarShield
“A good shielding design by a qualified physicist should occur at the beginning of the process,” said Petrone. “An inexperienced physicist may incorrectly calculate the shielding needs and cost you down the line if there needs to be more shielding places.”
What about radiotherapy?
When it comes to radiotherapy, choosing the right material isn’t as clean cut. NELCO and Veritas don’t have a material of choice because they take into account each project’s unique needs.
“We'll use a myriad materials to meet the customer's needs and budget requirements,” said Miller. “We don't try to jam a product into every project and just say this is what we have and you live with it.”
If the customer has space constraints, then they may use lead since it has the highest shielding value of any material. In other cases, they may use a combination of lead and concrete or lead and the high-density concrete.
“As with most things, there is no one-size-fits-all solution,” said Martin. “The best shielding material depends on a number of factors including raw material cost, project logistics, difficulty handing and especially the nature of radiation being shielded.”
For radiotherapy, Veritas usually uses its VeriShield system, which involves dry, stacked shielding modules that interlock to form a leak-free therapy room. It’s structural in terms of load bearing, consistent in composition, shape and density, uses space efficiently, attenuates a wide range of ionizing radiation and is modular in nature to provide design flexibility.
Shield for existing or future throughput?
“Some may argue to shield for the existing workload and if the workload increases, add more shielding,” said Petrone. “Even if this would be possible, it is a dangerous selection, analogous to being penny wise and pound foolish.”
He added that the likelihood that a facility will forget to redo their shielding design, leaves them open to a noncompliance situation, which could be dangerous for the surrounding areas.
To prevent all of that, he recommends projecting how the caseload may increase over the lifetime of the unit before installing any radiation equipment. By doing that, the initial design will never have to be revisited.
“Most professionals would advise to project the absolute maximum steady state average workload that would ever be reached during the life of the machine,” said Petrone.
Martin agrees that new and/or growing facilities should always be looking 10 years down the road to anticipate future growth. That can range from considering additional future patients in a single space to including extra space adjacent to the current bunker in a design to easily add treatment rooms in the future.
“Adding extra layers of material to a room during initial construction is much more cost-effective than having to add shielding later,” he said. “Existing facilities with multiple treatment spaces in operation are usually adding equipment for more strategic reasons and should consider the extra shielding costs in conjunction with their ability to split additional workload over multiple treatment spaces.”