“It was complex and we had a very large project team considering the small size of the facility. In addition to the traditional architects and engineers, we had shielding consultants, vibration consultants, air and effluent modeling people, radiation experts, and that was just on the design side,” says Trip Grant, project manager and architect with Flad & Associates.

The facility supports advanced imaging research critical to the early stages of drug discovery. As part of the process, radioactive isotopes tracers are blended with drug compounds and injected into subjects. Researchers track the isotopes using sophisticated PET imaging equipment then correlate this information with MRI and CT scans to create highly accurate multidimensional pictures of living tissue and biological processes as they relate to specific treatments.

The design team set out to create a highly functional lab that exceeded regulatory safety standards yet minimized the costs of conducting radiological imaging research. Because the research requires use of isotopes with very short half-lives, it became necessary that the isotopes be created on-site. Therefore, the center contains a cyclotron located in a chamber with two-foot-thick, high-density concrete walls. The lab’s MRI room utilizes a powerful magnet that is specifically designed to integrate with PET technology. In addition to resolving the complexities of incorporating radioactive materials, high magnetic fields, and vibration/radio-frequency sensitive equipment, the facility was developed in tight quarters with vivarium and research space on all sides that was highly sensitive to construction sound and vibration.

“Pfizer selected that site partly because there is vivarium space on both sides. So they couldn’t just go in there and dig up the slab with a jackhammer. They had to saw cut everything and carry it out piece by piece. It was very tedious work,” says Grant.

Design of the bioimaging center required a diverse team of consultants and experts. According to Grant, having a client project manager who understood the science and could translate it to contractors and consultants was critical to success. In addition to the project manager, Pfizer also provided their own facilities management, EH&S staff, and radiation safety official, as well as a consultant hired specifically to guide the permitting process with state officials.

Safety + Function

Due to the potential hazards associated with bioimaging technology, the team established that the primary driver for the project was safety. Functionality was the second most important priority, with schedule coming in third and cost fourth.

“When we were initially hired for the project, schedule was number one because they had ordered the MRI, hot cells, and cyclotron. As we started talking with the client, we realized that—with the radiation, hydrogen, and hazardous chemicals—this was not the right approach. So safety became the number one driver for all design decisions on the project,” says Grant.

In the initial feasibility design for the site, there were two MRI suites and a cyclotron room that required a large equipment holding area; the PET scanner rooms were very small, and there was no procedure space. The entire facility required all personnel to be radiation trained and equipped with radiation badges. Researchers were also subject to vivarium protocols including use of full gowns, gloves, and masks.

“The original plan blended all of the protocols into one space, which made it really difficult for the users. We dissected that plan and figured out where people needed to be and tried to understand what protocols were necessary for their studies so we could create a functional space that was still very safe,” says Grant.

To increase lab functionality, imaging and observation functions were separated and radiation protocol zones were established where workers wear dosimeters, have radiation safety training, and understand the hazards. Likewise, radiochemistry functions were removed from the vivarium so that researchers in the cyclotron room and radio-chemistry laboratory do not need to enter the animal protocol zone, and chemists don’t have to wear vivarium personal protective equipment.

“A key advantage to this design is that people in the control room don’t need to be radiation badged and trained. They can come to work wearing lab coats and safety glasses, and observe without having to go through all the protocols,” says Grant.

Higher Standards

The design team’s guiding principle for safety beyond code requirements was characterized with the acronym ALARA: “As Low As Reasonably Achievable.”

“The ALARA principle dictates that, when it comes to protecting workers, the environment, and the general public, the question is how much can you do? It doesn’t prescribe how many curies, or what dose is acceptable. It is basically your conscience sitting on your shoulder asking: are you doing the best you can?” says Grant.

In order to “design right without over-designing,” the team used regulatory maximum requirements for shielding calculations combined with conservative occupancy projections to establish specific shielding needs in various areas of the facility.

A measurement called “occupancy factor” was used to determine the amount of time per year that an individual works in a particular location. Determining occupancy factors for different areas of the lab required extensive discussion with users, the radiation safety officer, and shielding designer.

“We looked at how long researchers would be standing over things like the PET scanning equipment in the course of a year, then paired those figures with conservative assumptions of the number of studies per week and amount of exposure per subject that could be expected,” says Grant.

By identifying exactly what activities happen in the facility, designers were able to establish where to place the majority of shielding. Lead windows and concrete walls were used to provide protection between observation and imaging zones. The cyclotron chamber, where radiation levels reach as high as 40 millirem per hour, has two-foot-thick, high-density concrete walls and a lead-shielded door that weighs more than two tons and is mechanically operated.

“Despite being very expensive to install, it was deemed necessary due to the amount of radiation activity occurring in that particular area,” says Grant.

A key element of segregated lab design is the use of hot cells—large fume hoods with four-inch lead shielding and robotic arms for conducting procedures with radioactive materials.

“Strategic use of hot cells and shielding allowed us to provide sufficient safety without over-designing the entire facility,” says Grant.

Maximizing Public Safety

Pfizer wanted to be a good neighbor and maintain the flexibility to grow and change in the future. So when it came to designing the facility’s effluent exhaust system the company set out to achieve 10 percent of the maximum allowable contaminant release levels.

“We wanted to provide a 90 percent safety buffer for future growth, and increase neighborhood goodwill,” says Grant.

To achieve this, designers implemented a combined strategy of filtration, dilution, and delay to bring radioactive exhaust quantities to extremely low levels.

“Different kinds of radioisotopes are managed in different ways. So it was really incumbent on us during the design process to find out from the researchers exactly what they were doing and what kind of radioactivity is involved,” says Grant.

An essential part of the effluent system is time delay. Some elements deteriorate in less then two minutes while others can take up to two hours. Designers used time delay to the facility’s advantage by creating an elaborately routed duct work and filter system that slows release by a minimum of 3.5 hours. Another system explored but not utilized consisted of reinforced pressurized tanks that hold contaminated air captured from hot cells until isotope decay is complete. The idea for this solution was abandoned when it was revealed by the researchers that a byproduct of their radiochemistry processing was hydrogen.

As a result of the systems employed, “the facility emits such low levels that that Pfizer didn’t think their monitors were working. So they went back and re-commissioned them only to realize that, yes, the monitors are working and so is everything else. Background-level radiation is all that comes out the exhaust stack at the end of the day,” says Grant.

By Johnathon Allen