Shields is a recognized leader in the use of molecular imaging with positron emission tomography/computed tomography (PET/CT), which provides a detailed look at what is happening in the body at the cellular level. She is also well regarded for her expertise in the radionuclide treatment of various cancers. This therapy uses a radioactive drug to target cancer cells.

Shields has had a longstanding interest in evaluating patient response to cancer treatments like these and others. Her research interests include investigating new radiopharmaceutical therapies of cancer directed by molecular imaging, and ways to integrate them into an individualized cancer management plan. Shields sees a wide range of patients from oncology, cardiology and neurology, among other specialties.