TEXAS CENTER FOR PROTON THERAPY

Location:  Irving, TX
Client:  Texas Oncology and Baylor Health Enterprises
Completed:  October 2015
Size:  65,000 SF, including three treatment vaults
Architect:  CallisonRTKL 
General Contractor:  Linbeck
Project Cost:  $32 million ($105 million including proton equipment)

Update March 2017: The Texas Center for Proton Therapy won the Eminent Conceptor Award — the highest honor bestowed for Engineering Excellence in Texas — from the American Council of Engineering Companies Texas Chapter (ACEC Texas). The project also won a Gold Medal (top honor) in its category, Structural Systems. 

The Texas Center for Proton Therapy (TCPT) is one of only 15 proton therapy centers in the United States. Its mission is to treat patients using state-of-the-art cancer-fighting technologies while providing patient-centered care in a welcoming environment. The Center uses advanced technology to treat the most challenging cancers with a precise “pencil beam” of protons delivered at 2/3 the speed of light from an accelerator located half a football field away. Pencil-beam technology uses sub-millimeter precision to deliver high-energy proton beams to distinct areas of the tumor, allowing the radiation to be delivered directly to the tumor while minimizing the dose to surrounding healthy tissue.

Prior to the Center’s completion, patients within the 6.5 million population of the Dallas/Fort Worth Metroplex had to repeatedly travel an approximate 400-mile round trip to receive comparable treatment. The new Center allows patients to remain near their homes, families, jobs, and schools while they receive the typically six- to eight-week-long course of often life-saving treatment.

In creating a bespoke structure for the TCPT, which gives hope where despair too often reigns, Walter P Moore creatively overcame a number of challenges to meet the demanding and very specific criteria of this crucial new facility. They exhibited excellence in engineering in two key ways: by developing an innovative, high-performing hybrid foundation system and by serving as a fulcrum between the technical requirements of the physicist and equipment suppliers and the practical requirements of the builder.

Completed three months ahead of schedule in the fall of 2015, the TCPT was the first LEED®-certified stand-alone proton therapy center in the United States.

Original / Innovative Application of New or Existing Techniques

The tiny and powerful cancer-killing proton beams are created inside a 220-ton particle accelerator called a cyclotron, which is located almost a half football field away and connected to the operating suite via a tunnel structure. The cyclotron separates hydrogen into protons and electrons and injects the protons into an accelerator that shoots them toward the operating suite at 2/3 the speed of light. To be effective, the proton beams must be delivered with pinpoint accuracy; the accuracy of the beam depends largely on the ability of the structural engineer to create a highly stable support structure.

The structural team first drew on the lessons they learned while performing structural forensics on a previous proton beam therapy center that had been forced out of operation due to malfunctions. Their investigation concluded that long-term creep movements in the foundations had shifted the beamline of the cyclotron out of tolerance, rendering the equipment useless. An understanding of what went wrong on that prior project led to better decisions by the team on the TCPT project. They knew that even very small differential movements — experienced due to one or more of a variety of possible structural behaviors including settlement, long-term creep, or shrinkage — could undermine the entire mission of the facility. Armed with this urgency, the team set out to ensure the needed structural stability.

The first technical challenge lay in the ground. The soils of the D/FW area are highly plastic, meaning they are prone to both volumetric shrinkage and swell. This challenge was exacerbated by the site that had been built up with the excavated clay from a nearby freeway embankment project, increasing the possibility of long-term soil settlement. Typical methods used in the Metroplex to control movements due to subgrade movements include building atop void forms or with a fully structured slab. Both of these techniques proved impractical due to the varying elevations of the floors and the extreme weight of the equipment and maze walls, some up to 13 feet thick.

Instead, Walter P Moore collaborated with the geotechnical engineer to develop a hybrid mat-on-pier foundation. First, straight drilled concrete piers on 8’ by 8’ spacing were founded in a solid shale bearing layer at 40 feet below grade. A 30”-thick concrete mat was then poured atop the piers to distribute loads to the piers without differential movements. The piers and the mat work integrally to provide a highly stable base for the 220-ton cyclotron and the thick maze walls.

Social, Economic, and Sustainable Issues

The opening of this specialized treatment center brought a new crucial capability in cancer care to the Dallas/ Fort Worth Metroplex. For adult patients, pencil-beam proton therapy generally means fewer side effects and a better quality of life. For the pediatric patient, the benefits are even more striking, reducing the risks of secondary cancer over the patient’s lifespan.

The overall design team combined efforts to reduce the carbon footprint of construction materials and operations, leading to designation as the first LEED® certified stand-alone proton therapy center in the United States.

Most importantly, the Metroplex is no longer America’s largest metropolitan area without a proton therapy center. Thanks to the success of this facility, resident patients and their loved ones don’t have to travel to Houston or Oklahoma City; they can get this often life-saving treatment locally, benefitting both individual patients and the overall health of the community.

Complexity

The Texas Center for Proton Therapy presented a complex, inter-woven set of criteria that the structural engineer had to tackle simultaneously and interactively, developing concepts that were repeatedly tested against the needs of each constituent as well as the budget and schedule. The structure (including maze walls) is geometrically complex in three dimensions. To properly model and clearly understand the stress and movement interactions of the heavy equipment and maze walls atop the hybrid foundation system and the supporting soils presented a complex technical soil-structure interaction challenge.

Protecting users and patients from stray proton beams demanded a shielding system of concrete walls and strategically located steel plates that were designed by the physicist, tuned by the structural engineer, and integrated throughout the facility. In addition to the normal coordination and interaction with the owner, architect, MEP engineer, and civil engineer, Walter P Moore repeatedly interfaced with the geotechnical engineer, the physicist, the equipment manufacturer, and the contractor to work out solutions at both grand and micro scales.

Outcomes

By carefully listening to the project stakeholders and responding with integrated, well-considered solutions, the structural engineer was key to the successful completion of this important project. The cyclotron was installed and calibrated with a minimum of unexpected challenges and in turn, the Center became operational several months earlier than planned, almost unheard of for this type of complex facility. It was delivered on budget and has met or exceeded every project goal. The facility has been welcomed by the community and is operating near its capacity of 100 patients per day.