What Is Nuclear Medicine?
Nuclear medicine is a branch of medicine that uses small amounts of radioactive substances to diagnose and treat diseases. Unlike conventional imaging, which looks at the structure of organs, nuclear medicine looks at how organs and tissues are functioning. This makes it particularly useful for detecting problems at an early stage, sometimes before structural changes become visible on a regular scan.
The field covers both diagnostic imaging (such as PET CT scans, SPECT scans, and bone scans) and therapeutic procedures (such as radioactive iodine therapy for thyroid disease and radioligand therapy for cancer).
How Nuclear Medicine Differs from Radiology
In conventional radiology, X-rays or magnetic fields pass through the body from outside, creating images of internal structures. In nuclear medicine, the radiation source is inside the patient. A radioactive tracer is injected, swallowed, or inhaled, and it travels to the part of the body being studied. Special cameras then detect the radiation emitted by the tracer and produce images.
This inside-out approach means nuclear medicine can show how well an organ is working, not just what it looks like. A thyroid scan, for instance, reveals whether parts of the gland are overactive or underactive. A bone scan shows areas of increased bone turnover, which can indicate cancer spread, infection, or fracture healing.
Nuclear Medicine in Cancer Diagnosis
Cancer diagnosis is one of the most important applications of nuclear medicine. PET CT scanning, which combines metabolic imaging with anatomical detail, has become a standard tool in oncology. It helps doctors stage cancers, plan treatments, and monitor how well a treatment is working.
Different tracers are used for different cancers. FDG is the most common and works for a wide range of cancers. PSMA targets prostate cancer specifically. FAPI targets a protein found around many tumour types. Ga-68 DOTANOC is used for neuroendocrine tumours. The choice depends on the cancer type and what the doctor needs to know.
Learn more about the diagnostic scans available at our nuclear oncology practice.
Nuclear Medicine in Cancer Treatment
Beyond diagnosis, nuclear medicine also plays a direct role in treating cancer. This is where the field of theranostics comes in. The concept is straightforward: first, a diagnostic scan checks whether the cancer cells carry a specific target. If they do, a therapeutic version of the same molecule, now carrying a treatment dose of radiation, is administered to deliver radiation directly to the cancer cells.
Examples include Lu-177 PSMA therapy for prostate cancer and Lu-177 DOTATATE therapy for neuroendocrine tumours. Radioactive iodine therapy for thyroid cancer is another well-established nuclear medicine treatment that has been used for decades.
These targeted treatments are designed to deliver radiation primarily to cancer cells while limiting exposure to surrounding healthy tissue. The suitability of any treatment depends on the individual case, which is why eligibility is always confirmed through scans and tests before treatment begins.
The Role of a Nuclear Medicine Physician
A nuclear medicine physician is a doctor who has completed specialised training in using radioactive materials for both diagnosis and treatment. They interpret scans, administer therapies, and work closely with oncologists, surgeons, and other specialists to guide patient care.
In cancer care, the nuclear medicine physician often bridges the gap between imaging and treatment, particularly in theranostics where the same molecular target is used for both diagnosis and therapy.
Is Nuclear Medicine Safe?
The radioactive materials used in nuclear medicine are carefully measured and selected to provide the necessary diagnostic or therapeutic effect with the lowest reasonable radiation exposure. For diagnostic scans, the tracer dose is small and leaves the body within hours to a couple of days. For therapeutic procedures, the doses are higher and targeted, and patients receive specific safety instructions about precautions to follow.
Nuclear medicine procedures are carried out under strict regulatory standards by trained professionals. If you have questions about a specific procedure, discuss them with your doctor or the nuclear medicine team.