In conventional imaging diagnosis, an external energy source (e.g., X-rays, magnetic fields or ultrasound) is used to generate internal images of bones and tissues. In nuclear medicine and molecular imaging procedures acknowledged as nuclear molecular diagnosis, the energy source is introduced into the body by means of radiopharmaceuticals specifically targeting a concrete tissue, organ or molecular process. The nuclear signal is then detected by means of an external device such as a gamma chamber, SPECT or PET system in order to obtain and display information about the target organ’s function and its cellular activity.
Since disease begins in the form of microscopic cellular changes, nuclear molecular diagnosis is able to detect the disorder in a very early stage, when treatment may be more effective, and often long before conventional imaging techniques or other tests are able to detect anomalies.
The exploratory methods involved are non-invasive and cause no patient discomfort. They have only minimal side effects since the emitted radiation is equal to or less than that which is used in routine radiological studies. Consequently, nuclear molecular diagnosis delivers the possibility of changing patient care from reactive to proactive care.
Nuclear molecular diagnosis can now be used to study practically all the main body organs and systems. Indeed, it is now a key element in the medical care of patients with cancer, heart disease and brain disorders.
Positron emission tomography
One of the most significant tools ever developed in nuclear molecular diagnosis is positron emission tomography (PET) using the radiopharmaceutical fludeoxyglucose (FDG). Most PET studies are currently combined with computed tomography (CT or CAT) in order to locate areas of abnormal cellular activity more easily.
Fludeoxyglucose is a compound similar to glucose that accumulates in the parts of the body characterized by increased metabolic activity. Once FDG has been injected into the patient’s bloodstream, it is distributed to all tissues, and the PET-CT chamber reveals the distribution of FDG throughout the body for the purpose of identifying possible anomalies. By way of example, cancer cells usually exhibit an important FDG uptake, while brain cells affected by dementia consume less glucose and therefore present a diminished FDG uptake.
Apart from FDG, there are many other PET radiotracers that can be used to perform a broad variety of highly useful morphological, functional and analytical studies in medical practice.