Nuclear medicine
Nuclear medicine is the medical field that uses small amounts of radioactive materials, called radiotracers or radiopharmaceuticals, to image body function, diagnose disease, guide treatment, and deliver targeted radiation therapy in selected conditions.
What nuclear medicine is
Nuclear medicine uses radioactive materials in very small, carefully controlled amounts to diagnose or treat disease. Instead of only showing anatomy, many nuclear medicine studies show how tissue is working: metabolism, blood flow, receptor activity, organ function, bone turnover, inflammation, or cancer-specific targets. This functional view can reveal problems that may not be obvious on structural imaging alone.
Radiotracers
A radiotracer is a molecule labeled with a radioactive isotope. After it is injected, swallowed, or inhaled, it follows a biological pathway in the body. A scanner detects radiation coming from the tracer and a computer turns those signals into images or measurements. The choice of tracer depends on the clinical question, such as cancer staging, heart perfusion, bone disease, thyroid function, infection, or brain activity.
PET and SPECT
PET stands for positron emission tomography, and SPECT stands for single-photon emission computed tomography. Both create images from radioactive signals, but they use different tracer physics and detector methods. Hybrid scanners such as PET/CT or SPECT/CT combine functional nuclear medicine data with anatomic CT images so clinicians can locate abnormal activity more precisely.
Diagnosis and staging
Nuclear medicine can help diagnose, stage, or monitor many conditions. PET imaging is widely used in oncology to find active cancer, assess treatment response, or look for recurrence. Nuclear cardiology can evaluate blood flow to the heart. Bone scans, thyroid scans, kidney studies, hepatobiliary scans, lung scans, and other procedures answer specific questions about organ function or disease activity.
Theranostics and therapy
Some nuclear medicine pairs diagnosis and treatment through theranostics. A diagnostic tracer can show whether a target is present, and a related therapeutic radiopharmaceutical can deliver radiation to cells with that target. This approach is used in selected cancers and other diseases, with growing interest in patient-specific dosimetry and treatment selection.
Radiation safety
Nuclear medicine uses radiation, so safety practices matter. Staff calculate administered activity, verify patient identity, handle radioactive materials carefully, monitor exposure, follow storage and disposal rules, and give patients instructions when needed. The goal is to use enough radioactivity to answer the medical question or treat the target while avoiding unnecessary exposure.
Limits and interpretation
A nuclear medicine image is not a simple yes-or-no answer. Tracer uptake can reflect cancer, healing, inflammation, infection, normal physiology, medication effects, timing, technical artifacts, or patient preparation. Interpretation depends on the clinical question, other imaging, lab results, symptoms, prior treatment, and knowledge of how each tracer behaves.
Why it matters
Nuclear medicine matters because disease is often functional before it is structural. By following molecules inside the body, the field can show where biology is active, not only where anatomy looks different. That makes nuclear medicine valuable for cancer, heart disease, endocrine disease, infection, bone disorders, brain conditions, and increasingly targeted treatment.