Indications for Scintigraphy

When to Use Scintigraphy?

The nuclear medicine physician must choose the appropriate marker product for the examination. The marker must associate with the desired part of the body in a highly specific manner.

We can use:

• A simple radioactive atom, an unstable isotope of an element that exists naturally in the body. This is the case for several isotopes of iodine, which are known to concentrate in the thyroid gland, making them an excellent marker for this gland. We can also use atoms that are metabolized in the body in a similar way to a natural substance, if the latter does not have a radioactive isotope that emits usable radiation. For example, thallium-201 behaves like potassium, which is widely captured by muscles, particularly the heart muscle.
• A labeled molecule. It is essential to ensure that the labeling is stable during the various phases of normal human metabolism and that the degradation of the new molecule does not lead to the appearance of toxic components. For example, diphosphonates labeled with technetium-99m have an elective affinity for bone tissue in remodeling (areas of inflammation or cancer metastases). However, we can also link a radioactive atom to a hormone or an antibody.
• A set of cells, taken from the subject, kept alive, and labeled with the radioactive tracer, then reinjected into the patient to follow their behavior. For example, red blood cells labeled with technetium-99m allow us to visualize the cardiac cavities and calculate various important parameters in the study of cardiac dysfunction.

It is evident that all the manipulations required for the preparation of injections must be performed with great care, and strict controls are present at each stage.

Currently, almost all medical specialties can use radioisotopes, whether for diagnostic (imaging or biological assays) or therapeutic purposes. However, certain areas are particularly privileged, and there are even areas where nuclear medicine represents the only means of obtaining the desired information quickly and safely.

Among the main indications in our country, we can mention:

• First and foremost, bone and joint disorders (a little more than a third of scintigraphies performed in France), with a large number of searches for bone metastases (breast cancer, prostate cancer), but also many less severe pathologies (assessment of various pains and infections affecting bone tissue).
• Cardiovascular exploration (25%), grouping examinations of the myocardium (coronary pathology) and imaging of the cardiac cavities (isotopic ventriculography and ejection fraction calculation).
• Pulmonology, particularly searches for pulmonary embolisms (15%), the only area where scintigraphy is used in emergency and is a first-line examination that can orient diagnosis and adapted therapy.
• Thyroid, the first and largest indication of nuclear markers, now less explored in nuclear medicine (10-12% of examinations), given the highly performant ultrasound techniques also used in this field.
• Finally, a set of scintigraphies dedicated to renal, digestive, and neurological explorations.

There is also a vast domain of applications in biology that concerns all immuno-assays using antibody-antigen reactions labeled with radioisotopes. These techniques, although largely competed by advances in immunofluorescence, remain sometimes the reference (hormone assays, drug assays, various pathogen assays). In the field of hematology, radioisotopic techniques remain irreplaceable for the study of the functionality of different organs and blood cells involved in hemopathies.