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Accelerator for 2nd Mevion Proton Therapy System Delivered to Siteman Cancer Center at Barnes-Jewish Hospital, St. Louis MO

The proton accelerator arrived at Barnes-Jewish Hospital on Friday, July 26, 2019.

LITTLETON, Mass., July 29, 2019 – Mevion Medical Systems has delivered the accelerator for a second Mevion proton therapy system to the S. Lee Kling Proton Therapy Center at Siteman Cancer Center, based at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, Missouri.

The addition of the second proton therapy system will feature Mevion’s HYPERSCAN Pencil Beam Scanning (PBS) technology, coupled with the industry’s only proton multi-leaf collimator, the Adaptive Aperture. This powerful duo improves on older scanning technologies by delivering conformal fields of therapeutic radiation to tumors faster and with more precision – making it the most advanced form of PBS available today.

In addition, the new proton therapy system will feature the latest imaging modalities with a ceiling rail-mounted, cone-beam CT system and an integrated Siemens Somatom diagnostic CT system. With these new capabilities, Washington University physicians and scientists at Siteman will research new approaches to adaptive re-planning and hypofractionation, aiming to advance the field of proton therapy. Siteman and the Mevion Advanced Development team are currently collaborating on research studies into ultra-high dose rate, or “FLASH,” treatment modalities on Mevion systems.

The proton accelerator module arrives at the underground treatment vault on Friday, July 26th, 2019.

In 2013, Washington University physicians at Siteman Cancer Center treated the first patient in the world using a Mevion compact proton therapy system. Siteman treats adult cancer patients with proton therapy and partners with St. Louis Children’s Hospital, also located on the Washington University Medical Campus, to treat pediatric cancer patients.

“We’re excited to see our first installation grow into our first 2-room facility. A staged proton system expansion is a pragmatic approach for any hospital considering this advanced treatment modality,” said Tina Yu, chief executive officer of Mevion Medical Systems. “Siteman has taken the time to fully develop its proton therapy program and are now expanding with the latest technology.”

The second Mevion system will be located directly next to the first. This will be the first cancer center with two Mevion systems. Several other proton therapy centers with Mevion systems are following this approach, having planned a second room at the time of the first to accommodate expansion as needed.

The proton accelerator module, prior to installation in the treatment vault.

About Mevion Medical Systems

Mevion Medical Systems, Inc. is the leading provider of compact proton therapy systems for use in radiation treatment for cancer patients. Mevion is based in Littleton, Massachusetts, with a presence in Europe and China. For more information, please visit

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