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Nuclear medicine is the name given to tests and techniques that use a type of substances known as radiopharmaceuticals to identify diseases in early stages. There are many types of tests such as scintigraphy/SPECT, positron emission tomography (PET) or sentinel lymph node testing. The technique or the radiopharmaceutical is chosen depending on the part of the body that is to be observed, or the illness to be treated.

These tests provide unique information that cannot be obtained from other diagnostic imaging techniques and therefore offer the chance of identifying diseases in their early stages.

What is involved?

The procedures used in nuclear medicine are non-invasive and, apart from the intravenous injection of some radiopharmaceuticals, painless medical examinations. The subspecialty encompasses many different types of test: scintigraphy/SPECT, positron emission tomography (PET) or sentinel lymph node identification. The technique or radiopharmaceutical selected depends on the area of the body to be examined or the disease in question.

The radiopharmaceuticals, depending on the type of examination, may be injected into a vein or taken orally and subsequently accumulate in the organ or area under examination. They then emit a small amount of radiation from the point where they accumulate; this is detected with a special camera called a gamma camera. The signal detected is processed by a PC to produce detailed images of the structure and function of the organs and tissues.

What is it used for?

Nuclear medicine techniques are used to diagnose and treat a wide variety of oncological, neurological and cardiovascular diseases, etc. The tests mean different organs, tissues or bones can be examined, physiological processes occurring inside the body identified and molecular changes tracked in real-time.

How is it performed?

Firstly, the radiopharmaceutical is administered; depending on the type of test it is either injected intravenously or taken orally. It may take from several seconds up to days to accumulate in the area being studied. Hence the diagnosis will be carried out instantaneously or after hours or evens days.

During the test, a healthcare professional will help position the patient on the gamma camera’s bed. The camera will either rotate around them or remain in a fixed position. Although the patient will be asked to change position between images, it is important to remain perfectly still while images are being taken so the machine can record a good signal. The healthcare professional performing the test will instruct and monitor the patient at all times.

A PET scanner consists of a machine similar to the one used for computerised tomography (CT scans) or magnetic resonance, and is equipped with internal detectors that capture the signal from the radiopharmaceutical. In the case of a SPECT unit, the camera revolves around the patient’s body to produce three-dimensional images.

The test can last from 20 minutes up to several hours and may be carried out over the course of several days.

How do I prepare for a nuclear medicine test?

This group of tests does not require any special preparation.

Special situations

In the case of both scintigraphy/SPECT and PET tests, you must always inform the healthcare professional if:

  • Pregnancy. They will need to confirm your pregnancy and then assess whether the examination is appropriate;
  • Breastfeeding. You will need to stop breastfeeding for the period indicated by the healthcare professional so your body can eliminate the radiopharmaceutical.

Furthermore, for the PET test, you must also inform the healthcare professional if you have diabetes.

Who performs the test?

Healthcare professionals will guide and assist the patient throughout the test.

Who interprets the results?

A specialist in nuclear medicine. 

What can I expect to feel during the test?

You will not feel anything. Apart from the intravenous injections, the tests are completely painless and there are no associated side effects or complications. 

Substantiated information by:

Francisco Lomeña Caballero

Published: 20 February 2018
Updated: 20 February 2018


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