Why Should I Study Physics if I Want to be a Doctor?

“What have you learned by taking physics?” This final homework assignment completely stymied my AP student. “What should I say?” she asked, imploringly.

She had had to work really hard to do well in this class. Nothing about physics had been intuitively obvious to her. As her tutor, I had patiently explained and re-explained the material until she became comfortable with it.

I thought fast. Whatever I said would need to validate her experiences AND try to leave her open to the idea that physics could be an interesting subject for her in the future. So first I said, “I know that physics isn’t your cup of tea,” and then I asked, “What do you want to be when you grow-up?” She answered, “Something with biology. Maybe a doctor.” That was all the opening I needed. Here we go.

Modern physics has made remarkable contributions to the field of medicine for over 100 years. X-rays have been used by doctors to identify things like fractured bones, gun shots, and kidney stones, nearly since their 1895 discovery by the physicist Wilhelm Conrad Röntgen. He won the 1901 Nobel Prize in Physics for this work. After successfully treating cancer patients with x-rays in 1896, the physician Emil Herman Grubbe founded the first radiation therapy treatment center in Chicago. Research on radioactive elements by scientists like Henri Becquerel, Pierre Curie, and Marie Curie led to new medical imaging techniques and treatment therapies. It also garnered all of them Nobel Prizes. By the 1920’s, doctors began to understand how radiation therapy administered over multiple sessions – instead of just once – more effectively treated cancer and caused fewer side effects.

The history of nuclear medicine began in 1930, when Ernest Orlando Lawrence built the first cyclotron – a charged particle accelerator – at the University of California at Berkeley. This research won him the Nobel Prize in Physics in 1939. Ernest’s brother, the physician John Lawrence, investigated the medical uses of radioisotopes – unstable versions of radioactive elements – and subatomic particles, both produced by the cyclotron. As the father of nuclear medicine, John Lawrence lead the first research laboratory “devoted to nuclear medicine, diagnosis and treatment”. Nuclear medicine is used today to treat cancer and other diseases.

The research performed by the United States during World War II continued to advance human understanding of particle physics, and paved the way for additional medical advances after the war. Nuclear medicine is now a “specialized area of radiology that uses very small amounts of radioactive materials … to examine organ function and structure.” Radiology itself has three specialties: diagnostic radiology, which uses imaging to assess and diagnose medical conditions; interventional radiology, which uses image guided techniques to diagnose and treat patients; and oncological radiology, which oversees treatment plans for cancer patients.

Most likely, you have come in contact with some of the amazing medical devices made possible by physics. Modern medical imaging tools provide noninvasive and painless methods for diagnosis and treatment, but they must be used judiciously. Most of us have had an x-ray, which remains the most commonly prescribed imaging test. The x-ray has been joined over the last hundred years by other imaging inventions, such as:

1. Computed Tomography (CT), a “diagnostic imaging test … [which creates] detailed images of internal organs, bones, soft tissue and blood vessels”, typically employed for cancer detection, and in emergency rooms to diagnose internal injuries and bleeding;

2. Magnetic Resonance Imaging (MRI), a technique which employs a “powerful magnetic field, radio waves and a computer to produce detailed pictures of the body’s internal structures that are clearer, more detailed and more likely in some instances to identify and accurately characterize disease than other imaging methods”;

3. Positron Emission Tomography (PET), a tool which relies on “small amounts of radioactive materials…, a special camera and a computer to evaluate organ and tissue functions”, and is capable of detecting disease at very early stages; and

4. Ultrasound, the imaging method of choice for the pregnant woman and her fetus, which uses sound waves to produce images of soft tissues.

After talking about all this for a few minutes, I’d almost forgotten that my student was there. She now had a strange expression on her face. I turned to her and said, almost apologetically, “Did that make sense?” “It certainly did,” she replied. After a brief delay, she added, “Physics is cool.”

Some days, it’s really nice to be a STEM specialist.