Nuclear Medicine

Nuclear Medicine is the practice of medical imaging that uses small amounts of radioactive material (referred to as radiopharmaceuticals) during its procedures to diagnose and determine the severity of, and to treat a variety of diseases by providing pictures of the inside of a body’s cellular level. These tests are useful in helping physicians diagnose and detect many different types of cancers, endocrine, gastrointestinal, heart disease, neurological, and other maladies inside the body during their early stages.


Nuclear medicine is the byproduct of numerous contributions over several decades from the result of various scientists that are skilled in the fields of physics, chemistry, engineering and medicine. Because of the multiple disciplines utilized in nuclear medicine, it is difficult to trace the actual origin of nuclear medicine, though it is credited between the years of 1934 and 1946, due to the discoveries of artificial radioactivity and the production of radionuclides for medicine related use. Nuclear medicine became publicly recognized on December 7, 1946 after a published article in the Journal of the American Medical Association. 

Nuclear medicine scans are considered a noninvasive procedure, and outside of intravenous injections, the tests themselves are relatively painless, usually conducted by technicians called Radiographers. Nuclear medicine has been called “radiology done inside out” or “endoradiology” because the process records the radiation that emits internally from within the body as opposed to the radiation that is created from external sources such as X-rays. 

In cases of performing nuclear medicine imaging, radiopharmaceuticals are given internally, either presented in an intravenous or oral format, or inhaled as gas.  Once in place, special imaging devices referred to as gamma cameras (external detectors) take the radiation emitted by the radiopharmaceuticals (or radiotracers) and use them to create images and provide molecular information.  This is similar in practice to a diagnostic X-ray, where the external radiation passes through the body to create its image.

In many specialized medical centers, nuclear medicine images can be superimposed via computed tomography (CT) or magnetic resonance imaging, which can be used to produce specialized views as part of an image fusion or co-registration process.  These two views allow information from two different exams for study to lead to more precise information and accurate diagnoses.

As changes in technology become more and more imminent, medical imaging manufacturers also provide single photon emission computed tomography/computed tomography (SPECT/CT) and positron emission tomography/computed tomography (PET/CT) units.  Both of these devices are able to perform both imaging exams simultaneously.

There are several types of diagnostic nuclear medicine that are used:

In the two-dimensional (2D) realm, Scinigraphy (“scint”) uses internal radionuclides to create its imagery.

Some of the related two-dimensional nuclear medicine scans are:

  • Whole body bone scan
  • Myocardial perfusion scan
  • Parathyroid scan
  • Normal hepatobiliary scan (HIDA scan)
  • Normal pulmonary ventilation and perfusion (V/Q) scan
  • Thyroid scan with iodine-123

Three-dimensional scans (“SPECT”) are 3D techniques that use the data from gamma camera projections, and can be reconstructed in different planes.  A third-dimensional type of scan that is not quite as readily available is known as the PET (positron emission tomography)/MRI scan. These scans use coincidence detection for their processes.

Some of the related two-dimensional nuclear medicine scans are:

  • SPECT liver scan with technetium-99m labeled autologous red blood cells.
  • Maximum intensity projection (MIP) of a whole body positron emission tomography.

There are also hybrid scanning techniques where nuclear medicine scans can be superimposed, using software or hybrid cameras for CT or MRI to highlight the parts of the body where the radiopharmaceutical is concentrated.

Types of hybrid scans are:

  • Normal whole body PET/CT scan with FDG-18.
  • Abnormal whole body PET/CT scan with multiple metastases from a cancer.

There are also therapeutic procedures that can be taken from nuclear medicine. For example, radioactive iodine (I-131) therapy uses small amounts of radioactive material against cancers and other medical conditions that affect the thyroid gland.

Non-Hodgkin’s lymphoma patients that do not respond positively to chemotherapy may undergo radioimmunotherapy (RIT), which is a personalized cancer treatment combining radiation therapy in conjunction with the immunotherapy and its targeting abilities, as it is able to mimic the cellular activity found in the body’s immune system.

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