Fowler's research has led to new fundamental knowledge, development of important scientific tools, and has broad impacts in the application of nuclear medicine to diagnostics and health. She has worked for much of her career developing radiotracers for brain imaging to understand the mechanisms underlying drug addiction. Most recently, she has been engaged in developing methods to understand the relationship between genes, brain chemistry, and behavior.
In 1976, Fowler and her colleagues designed and synthesized a radioactively "tagged" form of sugar that is now used widely to study brain function and also to diagnose and plan treatment for cancer. She also developed another radiotracer, as these "tagged" molecules are called, that first showed that cocaine's distribution in the human brain parallels its effects on behavior.
Fowler played a central role in the development of a fluorine-18-labeled glucose molecule (FDG) enabling human brain glucose metabolism to be measured noninvasively. This positron-emitting molecule, together with positron emission tomography (PET) imaging, has become a mainstay for brain-imaging studies in schizophrenia, aging and cancer.
Another of her major accomplishments was the development of the first radiotracers to map monoamine oxidase (MAO), a brain enzyme that regulates the levels of other nerve-cell communication chemicals and one of the two major enzymes involved in neurotransmitter regulation in the brain and peripheral organs. Using these radiotracers, she discovered that smokers have reduced levels of MAO in their brains and lungs. This may account for some of the behavioral and epidemiological features of smoking, such as the high rate of smoking in individuals with depression and drug addiction, two conditions involving poor nerve-cell communication, and has led to many studies on reduced MAO and smoking.
Fowler holds eight patents for radiolabeling procedures.