Proton therapy pioneer James M. Slater died last Wednesday, December 26. He was 89.

A longtime radiologist at Loma Linda University Medical Center in California, Slater is credited with overseeing the creation of the world’s first proton treatment center, the LLUMC Proton Treatment Center, in 1990.

Born in 1929 in Salt Lake City, Utah, the young doctor-to-be grew up fascinated by the world of science, a passion which led him to pursue and graduate with a bachelor’s degree in physics in 1955 from the University of Utah.

Initially working as a California junior high school math teacher, Slater soon decided to combine his love for physics with medicine and applied to Loma Linda University School of Medicine, which he graduated from in 1963.

He then trained as a resident at LDS Hospital in Utah and White Memorial Medical Center in Los Angeles before moving to Texas to complete a National Institutes of Health Fellowship at the University of Texas MD Anderson Cancer Center. It was here that his interest in heavy-charged particle therapy emerged, leading him to choose radiology as his specialty.

“[It] was a shocking experience to see how ill we made our patients. During treatment they became very, very sick,” he said in a documentary, The Convergence of Disciplines. “Some of them had to stop treatment and recuperate for a week or so before they could come back. This reduced their chance for a cure and caused misery for them as an individual and for their family.”

Returning to Loma Linda University Health in 1970, Slater set to work on advancing the field of radiation medicine, delving into computer-assisted radiotherapy planning for the development of CT-based treatment. His first system was introduced in 1971, earning him a first-place award from the European Association of Radiology in 1975 and an invitation to speak at the U.N. International Atomic Energy Agency in Vienna. He also received the first-place award from the American Society of Therapeutic Radiologists in 1978.

Wanting to find more ways to target and eliminate tumors without damaging surrounding healthy tissue, his attention turned to proton therapy, leading him to request and gain permission, in 1986, from the Loma Linda University and Loma Linda University Medical Center boards of trustees to partner with the Fermi National Accelerator Laboratory (Fermilab) in the planning of the LLUMC Proton Treatment Center.

Constructing the $100 million facility was not without its challenges. The high costs for the project led Slater to testify before a congressional hearing with U.S. Congressman Jerry Lewis to request funds of up to $25 million.

“After the hearing, we went to the committee session with the Senate and got $25 million. And it was a direct result of the presentation of Dr. Slater,” Lewis later remarked in The Convergence of Disciplines.

The new treatment also became a contentious subject in 1989, the same year the first synchrotron components were shipped from Fermilab to Loma Linda University Health campus, with a Wall Street Journal article referring to the particle accelerator as a “contraption.”

Many feared that the treatment would be ineffective or instill false hope in cancer patients, and took issue with the fact that it was funded with millions of dollars from Congress and the U.S. Department of Energy.

The three-story facility, nonetheless, opened its doors in 1990, equipped with an accelerator and proton guidance system weighing 400 tons and capable of producing up to 250 million electron volts of radiation. It has since treated more than 18,000 patients and was the only institute of its kind up until 2003. In recognition of Slater’s work, the hospital renamed the facility, in 2007, the James M. Slater, M.D. Proton Treatment and Research Center.

In addition to the center, Slater’s legacy also includes his son, Jerry D. Slater, who chairs the department of radiation medicine at Loma Linda University Health.

A service is scheduled to take place in Salt Lake City Utah.