McCarthy Lifts 30

McCarthy Lifts 30,000 Pound Accelerator into Place for Mercy Proton Therapy Center


The centerpiece of the new Mercy Proton Therapy Center currently under construction at the David C. Pratt Cancer Center, a MEVION S250iTM gantry-mounted proton accelerator, was positioned into place by McCarthy Building Companies, Saturday, July 17, at the site located at 607 S. New Ballas Road in Creve Coeur.

After a journey across seven states, the accelerator was placed through an opening in the vault’s 7-foot, 6-inch thick concrete lid using a 350-ton capacity crane, the same day it arrived.

“This major milestone in construction puts us one step closer to making the Mercy Proton Therapy Center a reality for our patients,” said Steve Mackin, Mercy executive vice president and Mercy’s East Communities president. “Seeing the equipment before it’s enclosed in the concrete vault shows just how massive an undertaking this project has been. It’s remarkable to think of the many people who will survive – and thrive – because of this technology.”

A small crowd of leaders from Mercy, McCarthy and Mevion took turns signing the equipment and then watched as the accelerator unit was placed. It was secured inside a three-story high, 42-foot-by-47-foot “vault” treatment room featuring concrete walls ranging from three to seven and a half feet thick located within the new 17,000-square-foot, three-story addition to the David C. Pratt Cancer Center. Because being as little as one inch off in thickness would result in less radiation shielding, the center was designed and built with extreme precision, with tolerances less than three-quarters-inch wall-to-wall and one-inch floor-to-ceiling.

Construction began in July 2020; the center’s opening is planned for summer 2022.

The world’s only gantry-mounted proton accelerator, the MEVION S250i, features the HYPERSCAN® pencil beam scanning technology and Adaptive Aperture® pMLC that delivers a highly stable, fast, precise and uniform proton therapy beam. The complete unit weighs 300,000 pounds, including the 30,000-pound accelerator, 85,000-pound housing and 72,000 pounds of arms and counterweights.

Currently, there are only 41 proton centers in the United States. Proton therapy, which has fewer side effects than traditional cancer treatments and can be used for many types of cancer, uses high-energy beams of protons to precisely deliver radiation to a tumor, reducing or eliminating unwanted radiation exposure to surrounding, healthy tissue. Mercy will make this option available for patients pursuing both research options and traditional clinical care.

About Mercy

Mercy, named one of the top five large U.S. health systems for four consecutive years by IBM Watson Health, serves millions annually. Mercy is one of the nation’s most highly integrated, multi-state health care systems, including more than 40 acute care, managed and specialty (heart, children’s, orthopedic and rehab) hospitals, convenient urgent care locations, imaging centers and pharmacies. Mercy has 900 physician practices and outpatient facilities, more than 4,000 Mercy Clinic physicians and advanced practitioners and 40,000-plus co-workers serving patients and families across Arkansas, Kansas, Missouri and Oklahoma. Mercy also has clinics, outpatient services and outreach ministries in Arkansas, Louisiana, Mississippi and Texas. In addition, Mercy’s IT division, Mercy Technology Services, and Mercy Virtual commercially serve providers and patients from coast to coast.

About McCarthy

McCarthy Building Companies, Inc. is the oldest privately held national construction company in the country – with more than 150 years spent collaborating with partners to solve complex building challenges on behalf of its clients. With approximately 5,000 salaried employees and craft professionals, the firm has offices in St. Louis, Atlanta; Collinsville, Ill.; Kansas City, Kan.; Omaha, Neb.; Phoenix; Las Vegas; Denver; Dallas, Houston; and San Diego, Newport Beach, San Francisco, San Jose and Sacramento, Calif. McCarthy is 100 percent employee owned. More information about the company is available online at or by following the company on FacebookTwitterLinkedIn and Instagram.