Diagnostic nuclear medicine

Thyroid gland scintigraphy Source: Technical University of Munich, Clinic and Policlinic of Nuclear Medicine, Klinikum rechts der Isar

Patients in diagnostic nuclear medicine are given radioactive pharmaceuticals (radiopharmaceuticals) accumulating in organs and tissues in varying concentrations, depending on the pharmacological properties of the compound administered. Due to their radioactivity, the spatial and time distribution of the radiopharmaceutical in the body is detectable using proper measuring equipment, and thus can be visualised.

Which technology is used?

Basically there are three different technologies:

• conventional scintigraphy

• two tomography procedures:

  • single photon emission computerized tomography (SPECT)
  • positron emission tomography (PET).

When are diagnostic nuclear medicine procedures applied?

Malignant melanoma of the forehead; Two soft tissue metastases right shoulder / left hip. Source: Technical University of Munich, Clinic and Policlinic of Nuclear Medicine, Klinikum rechts der Isar

Diagnostic nuclear medicine enables almost all organ systems of man to be examined. It provides information on the function of organ systems in question as to both general dysfunctions (for example renal function scintigraphy) and localised foci in individual organs (for example, detection of foci of inflammation). Diagnostic nuclear medicine is a valuable extension of so-called morphologic imaging procedures used to visualise the form and structure of organs or tissues under examination (for example, X-ray diagnostics).

How often are diagnostic nuclear medicine procedures applied?

During the years 2016 to 2021, the frequency of nuclear medicine examinations slightly decreased. The annual mean number of nuclear medicine examinations carried out in Germany between 2019 and 2021 was about 2.1 million, corresponding to a mean annual frequency of applications of about 25 examinations per 1,000 inhabitants. The mean annual effective dose per inhabitant and year was about 0.05 millisievert (mSv).

Three procedures predominate

The following three procedures contribute most to the total frequency of nuclear medicine examinations as well as to the associated collective effective dose, that is, scintigraphy or SPECT of

Relative contribution of different examination types to total frequency in 2015

• the thyroid gland,
• the skeleton, and
• the heart

(see figure).

Note that in the figure, heart examinations during rest and during exercise are counted separately, even if they are performed in the course of one examination (during one day or two consecutive days).

Examinations of the thyroid and the skeleton decreased by approximately 25 % between 2016 and 2021, but heart examinations increased. Due to the high diagnostic value as a nuclear medical examination procedure, the frequency of PET examinations is also continuously increasing. Today, PET is mainly performed together with CT as a so-called hybrid imaging procedure. In 2016 to 2021, more than 85 % of all PET examinations in the inpatient sector were already performed using a PET/CT system.

Mean effective dose per procedure

Averaged over all examinations carried out, the mean effective dose per procedure is 2.2 mSv (excluding dose from CT in PET/CT examinations). Thyroid scintigraphy or SPECT is most frequently used and is associated with a quite low mean effective dose of 0.7 mSv per examination. Renal examinations are relatively frequently applied in children, and are also characterized by low radiation exposure (0.4 mSv per examination). Adding the doses for heart examinations during rest and during exercise, the resulting dose is relatively high: ca. 5-6 mSv per examination (2-day or 1-day protocol).

Relative contribution of different examination types to total collective effective dose in 2016

Magnitude of radiation exposure from nuclear medicine diagnostics

Nuclear medicine examinations are considerably less frequent than X-ray examinations. Despite the higher dose per examination, the average radiation exposure per inhabitant from nuclear medicine diagnostics is therefore - compared to the radiation exposure from diagnostic X-rays - relatively low.