Nuclear Medicine

Nuclear Medicine is a medical specialty that uses radioactive drugs, called radiopharmaceuticals, to diagnose, stage, treat and monitor diseases. Radiopharmaceuticals are comprised of either a radioisotope on its own, or a radioisotope bonded to a molecule.

Quick links: Nuclear Medicine Diagnostics, Nuclear Medicine Therapeutics

Molecular Nuclear Medicine: making personalized treatment a reality (a 22-minute documentary on Molecular Nuclear Medicine from the history of radioactivity and cancer to the most modern theragnostic techniques).

Copyright 2013 AAA. All rights reserved. Produced by AAA with the support of AIPES and CERN.

An illustrated introduction made by AIPES (Association of Imaging Producers & Equipment Suppliers). Reproduced with the permission of the owner.

The process of attaching a radioisotope to a molecule is known as labeling or radiolabeling. Radioisotopes emit different types of radiation, such as gamma, alpha, or beta, each of which has different properties and is used in different clinical settings.

Nuclear medicine can be divided into two basic categories, nuclear medicine diagnostics and nuclear medicine therapeutics.

According to research by MEDraysintell, the nuclear medicine market is projected to reach US$26 billion by 2030. While nuclear medicine diagnostics have historically accounted for over 80% of the nuclear medicine market, nuclear medicine therapeutics are projected to drive growth in the sector and represent over 60% of the market by 2030.

Nuclear Medicine Diagnostics

Nuclear Medicine Diagnostics often enable physicians to accurately diagnose complex diseases – including cancer, cardiovascular and neurological disorders in their early stages – and improve follow-up.

Also referred to as molecular imaging or functional imaging, these diagnostic procedures provide detailed pictures of what is happening inside the body at the molecular and cellular level. Where other diagnostic imaging procedures (such as x-rays and computed tomography (CT)) offer pictures of physical structure, molecular imaging allows physicians to see how the body is functioning and to evaluate its chemical and biological processes.

In these nuclear medicine diagnostics procedures, patients are injected with a radiopharmaceutical agent and imaged with PET (Positron Emission Tomography) or SPECT (Single Photon Emission Computed Tomography) cameras.

PET is a state-of-the-art molecular imaging technique that involves detection of a pair of gamma rays emitted from a patient’s body following administration of a radiopharmaceutical that binds to target cells. PET is used to diagnose a wide range of conditions within:

  • oncology
  • neurology
  • cardiology
  • infectious & inflammatory diseases 

Historically, PET scans with fluorodeoxyglucose (FDG) have been used in oncology to accurately:

  • determine the precise stage of many tumors,
  • localize unknown metastases, and
  • monitor therapeutic efficacy or the recurrence of the disease.

In FDG PET, a short-lived radioisotope called fluorine 18 (F 18) is attached to glucose (sugar) molecules to form FDG. Following injection into a patient, the drug is quickly absorbed by cancer or inflammatory disease cells, which are hyperactive and hungry for sugar.

Once inside the cells, FDG releases positron particles that collide with the electrons in the body and produce energy in the form of gamma rays. These rays are detected by the PET camera, which produces a high quality metabolic image of the tumor or lesion.

The same principle applies to other nuclear medicine diagnostics that use different targeting molecules. Recently, additional radioisotopes, such as gallium 68 (Ga 68) have been attached to molecules targeting specific receptors in tumors.

SPECT is another molecular imaging technique with a long history. Technetium 99m (Tc 99) is a commonly used radioisotope in SPECT imaging. SPECT imaging involves detection of single gamma ray emissions from a patient’s body following administration of a radiopharmaceutical that often binds to a target cell. SPECT is used to diagnose a wide range of conditions within:

  • oncology
  • cardiology
  • neurology
  • infectious diseases

Both PET and SPECT techniques are used broadly in nuclear medicine today. Various factors may determine which imaging modality is used for a specific patient or disease, including availability of a PET or SPECT camera and/or the associated radiopharmaceuticals required to perform the procedures, as well as individual physician or facility practice and preference.

Nuclear Medicine Therapeutics

Nuclear Medicine Therapeutics combine two approaches: tumor targeting and radiation. Tumor targeting allows drugs to selectively target cells associated with disease due to the affinity between the drug and certain receptors expressed by the relevant cells.

RadioLigand Therapy (RLT) is a form of nuclear medicine therapeutics which involves the systemic administration of a radiopharmaceutical comprised of a targeting compound (i.e. the ligand) that is coupled with a radioisotope. The RLT is injected into the patient’s bloodstream and binds to a specific receptor expressed on the the surface of tumor cells delivering small doses of radiation.

Peptide Receptor Radioisotope Therapy (PRRT) is a form of RadioLigand Therapy which involves the systemic administration of a radiopharmaceutical comprised of a targeting peptide that is coupled with a radioisotope emitting radiation. The peptide-radioisotope complex is injected into the patient’s bloodstream and binds to specific receptors expressed on the surface of tumor cells.