Physicist finds meaning in numbers to enhance proton therapy treatment

I joined St. Jude Children’s Research Hospital in September 2015, just a few months before the first patient was treated in the St. Jude Proton Therapy Center.

In my previous role, I was a senior physicist. St. Jude offered me the opportunity to experience a management position for the first time in my career.

As chief of clinical medical physics in the Radiation Oncology Department, I oversee a team responsible for treatment planning, commissioning, calibrating and assuring quality of the treatment machines and patient treatment plans in Radiation Oncology, including the proton therapy center. The center is the only one of its kind dedicated to treating pediatric patients.

Our team includes five physicists, three dosimetrists, two medical physics assistants and one linear accelerator engineer. Their work includes a variety of daily, weekly and monthly quality-assurance checks, patient treatment planning, and research and development work with the goal of enhancing treatment techniques.

My work deals with precision. I have always been fascinated with math and numbers, which steered me toward the study of physics. My interest in helping others led me to the field of medical physics.

St. Jude has one of the most advanced proton therapy systems in the world, equipped with pencil-beam scanning and 3-D volumetric imaging guidance. During treatment, protons are highly accelerated and then deposit most of their energy at the tumors with no exit dose to surrounding healthy tissues. Patients, who can be sedated or not for the procedure, are positioned on robotic couches for treatment.

We can tailor the shape of the radiation according to where we want to treat the patient. Everything must be precise—within one millimeter of accuracy.

Medical physicists are an integral part of the radiation therapy team. Our team works closely with radiation oncologists, radiation therapists and nurses. We oversee the technical aspects of treatment to make sure patients are treated safely and accurately.

Physics plays a significant role in proton therapy and all types of radiation therapy. As technology evolves, there's a requirement for physicists to ensure all components of a system are working safely and efficiently. Much of that work involves the institution of safety measures.

The numbers have meaning, and their meaning can be easily translated to patient care because St. Jude is such a unique place. We are given the best resources to help challenge ourselves and express innovative ideas so that we can use this technology to provide the best treatment and care for patients.

Li Zhao, PhD, is chief of clinical medical physics in the Radiation Oncology Department at St. Jude.