Wu Liu, clinical physicist who developed imaging techniques and treatments for cancer, dies at 51

Wu Liu, PhD, an associate professor of radiation oncology at Stanford Medicine who spent his career creating new imaging techniques and radiation treatments for cancer, died May 14 after a diagnosis of brain cancer last year. He was 51.

“Though Liu’s time with Stanford Medicine was far too short, his impact will be enduring,” said Lloyd Minor, MD, dean of the Stanford School of Medicine and vice president for medical affairs at Stanford University. “He was a gifted clinician and an indispensable part of our cancer radiology program, developing new treatments for cancers of the eye.”

Liu’s clinical focus was developing and improving cancer treatments for patients using radioactive sources. These treatments, called brachytherapy, involve placing radioactive materials near tumors to damage cancer cells. He was especially instrumental at the Stanford Cancer Center, where he designed treatment plaques tailored to each patient with an optimal distribution of radioactive materials, his colleagues said. This treatment substantially improved patient comfort and treatment accuracy.

“He was a national expert in brachytherapy, the go-to person for eye plaque brachytherapy,” said Lei Xing, PhD, a professor of radiation oncology. “I appreciated his high standard of work and strong ability to take on responsibilities and initiatives. He was an ideal colleague to have around any clinic.”

During his career as a medical physicist, Wu published more than 42 peer-reviewed papers in leading journals. He also taught medical physics residents and helped develop the curriculum for the radiation physics residency program.

“Wu accomplished a lot. During his time as a postdoc in my lab, he spearheaded several projects to track the tumor motions in real time and made significant contributions to radiation therapy techniques,” said Xing, the Jacob Haimson and Sarah S. Donaldson Professor. “His work sparked significant research and clinical activities in radiation oncology, leading to much-improved patient care.”

Not only was Liu an excellent, patient-focused researcher, but he was also “an easygoing, sociable, family-focused person,” his friend and colleague Ruijiang Li, PhD, associate professor of radiation oncology, said of Liu, who leaves behind a wife and daughter. “He was open-minded, generous, humble and true to himself. Wu is known for his sense of humor and optimism.”

A dear friend and close colleague

Liu’s family said he combined modesty and ambition with a strong intellect. He appreciated that his research helped others and cared deeply for his family and friends.

“We lost a dear friend and a close colleague,” Li said. “His death gives us another personal reason, as cancer researchers, to find better ways to detect cancer early and treat cancer.”

Born in Beijing, China, on July 23, 1972, Liu was the youngest of the family by a long stretch — 18 years from his next-youngest sibling. His father was a magazine editor, and his mother was a book proofreader.

Liu attended high school in Beijing, then earned a bachelor’s degree in astronomy from Nanjing University and a master’s degree in astrophysics from the Chinese Academy of Sciences in Beijing.

He switched to medical physics when he moved to the University of Wisconsin-Madison, where he earned a master’s degree in computer science in 2006 and a PhD in medical physics in 2007. Shortly after, he joined Stanford Medicine as a postdoctoral scholar in Xing’s lab.

There, Liu developed new ways to deal with patient movement during image-guided radiation therapy, including using artificial intelligence to improve the cancer treatment.

“He was a postdoc who every lab would like to have,” Xing said. “He was a highly motivated and great team player. He made his mentors look good and made me proud.”

After his postdoctoral studies, Liu took a position at Yale-New Haven Hospital as an assistant professor of radiation oncology. In 2019, Liu returned to California as an associate professor of radiation oncology at Stanford Medicine. His work in the clinic included planning, checking and delivering brachytherapy and external beam radiation treatments and performing checks, calibration and quality assurance evaluations on radiation machinery.

Liu went on leave after his diagnosis of glioblastoma in August 2023 but kept up with his collaborators to discuss their projects and offered guidance to his trainees.

Soccer enthusiast and family man

In graduate school, Liu was an extroverted, talkative and popular person, his wife, Nina Hsieh, said. He liked to be the center of the conversation. They met at a party in a student apartment complex and married in May 2003.

He wooed her with his astronomy, poetry and literature knowledge, especially a Chinese epic tale, “The Romance of the Three Kingdoms.”

His decency and integrity as a human being served as a model for us all.

Hsieh said Liu enjoyed making people laugh and had a positive attitude toward life, even during the most challenging times.

“Wu was humble, dedicated and true to himself, and he would stand up for what he believed in,” Li said. “I will miss our late-night beers, the hourlong chats during hikes, and how we were equally bad at tennis.”

Besides playing tennis badly, Liu’s hobbies included studying history and traveling the world. Hsieh said that during his travels, he liked to visit universities and walk around their campuses. They also took regular family ski trips to Lake Tahoe, where Liu spent his time on the slopes conquering black diamonds. He also liked to hike, visiting state parks and coastal areas with his daughter.

He was well known for his love of soccer: “I felt that his passion toward soccer was only slightly less than his passion toward his research and clinical responsibilities,” Xing said.

Liu and Hsieh’s daughter, Sienna, was born in 2013. Sienna was Liu’s favorite person to share his love of soccer with, whether kicking the ball in the park behind their house or taking her to Stanford women’s soccer games.

“Although he was very busy with his job, he liked to spend time with family. He never forgot a birthday, anniversary or holiday and liked to celebrate them,” Hsieh said. “His decency and integrity as a human being served as a model for us all.”

Liu was a member of the American Association of Physicists in Medicine and the American Society for Radiation Oncology. He was on the board of editors for the Journal of Applied Clinical Medical Physics, served on the physics committee for the American Brachytherapy Society, and was a member of the science council and research grants evaluation subcommittee for ASTRO.

Liu is survived by his wife, Nina Hsieh, and daughter, Sienna Liu, of Palo Alto, California. His mother, Xingguang Gan; brother, Xiaoxin Liu; and sister, Xueqing Liu, all of Beijing, survive him, along with multiple nieces and nephews. His father, Tai Liu, preceded him in death.