BQ5: How can physics research improve the practice of medicine?

Before you can treat a disease or disorder, you have to detect it; and if you are trying to treat a tumor, you have to find it. All modern imaging methods rely on the interaction of radiated light or sound with tissue, and all of them originated in fundamental physics. Today, ultrasound, radiowaves and X-rays produce stunning high resolution images deep in tissue, antimatter (in the form of positron emission tomography or PET) is used daily at Duke Hospital to diagnose cancer, and X-ray/γ ray/ charged particle beams are used to kill diseased cells. Duke physicists play important role in the development of next-generation techniques, and in refining these techniques to make them clinically useful.

The role of physics in medical imaging and treatment falls into two broad categories. At one extreme, physicists develop next-generation techniques, applying quantum mechanics to extract molecular information is not commonly present in existing modalities. For example, at near infrared wavelengths, humans are not opaque; light can penetrate many centimeters into tissue (this is the basis of the finger clamp in a doctor’s office, which measures blood oxygenation and hemoglobin by transmission of light). If you put your hand in front of a light bulb, you will see the bones, but they will be blurred and distorted by light scattering. New optical methods which remove the effects of scattering, or compensate for its effects, have powerful and broad applications. Next-generation microscopes, using highly controlled laser light (such as shaped ultrafast laser pulses) can monitor biochemical reactions in vivo as they happen, or improve diagnosis in the pathologist’s office. Another example is nuclear magnetic resonance (NMR), which relies on once-esoteric nuclear physics (the existence of spin energy levels). Today NMR is the premier structural tool in chemistry, and its cousin magnetic resonance imaging (MRI) is an extremely important method for probing soft matter (including the human body). In addition, next-generation beam sources and detectors developed for fundamental nuclear physics often find their next application in medical imaging, for example to deliver targeted energy to a cancer deep inside the body without killing surrounding tissue; TUNL has had an active program for years in this direction.

This work is of course highly interdisciplinary; in fact, one Duke Radiology professor and one BME professor are Duke Physics PhD graduates. Duke faculty are leaders in magnetic resonance hyperpolarization technologies which promise to drastically alter this field over the next decade; for example, an MRI in an ambulance, powered by a car battery, no longer looks crazy. We also pioneer in development of new methods for optical imaging (such as in the ALIS@Duke facility mentioned earlier). Researchers at TUNL have been developing next-generation neutron imaging methods, which could provide a nice complement to X-ray approaches, as neutron scattering cross-sections are different from X-ray scattering cross-sections. Many faculty members in biomedical engineering work on closely related ideas, including device development for resource-limited (Third World) healthcare.

The gap between producing an image which is useful to physicists (who usually have well-defined, controlled, and reproducible samples) and producing an image useful to clinicians (who do not) is vast; so is the gap between producing a particle beam and safely applying it to a patient. For this reason, at the other extreme, Duke Physics works closely with the Medical Physics program (centered in School of Medicine), where a major thrust is validation, refinement, and coregisteration of existing imaging and treatment modalities to make them clinically useful. Thus medical physics provides the technical foundations of radiology, radiation oncology, and nuclear medicine; it is built on a foundation of physics, but with distinct body of knowledge and scholarship. It is the largest degree-granting Medical Physics program in the country, and currently is one only four degree-granting programs as part of Duke-Kunshan University.

Experimental approaches overlap significantly between medical imaging, biophysics, and materials science. These approaches also provide the core underpinning of newly evolving fields, such as molecular imaging and theranostics (the combination of diagnostics and therapy at the same time).

Research at Duke University