Common Radionuclides Used in Medical Imaging
The most commonly used radionuclides in medical imaging include technetium-99m, thallium-201, rubidium-82, fluorine-18, nitrogen-13, and indium-111, each with specific decay characteristics, half-lives, and production methods that determine their clinical applications. 1
Table of Common Radionuclides in Medical Imaging
| Radionuclide | Type of Decay | Half-life | Production Method | Common Applications |
|---|---|---|---|---|
| Technetium-99m | Gamma (140 keV) | 6 hours | Generator-produced (from Mo-99) | Myocardial perfusion, bone, renal, hepatobiliary imaging [1] |
| Thallium-201 | X-ray/Gamma (68-80 keV) | 73 hours | Cyclotron-produced | Myocardial perfusion and viability assessment [1] |
| Rubidium-82 | Positron (511 keV) | 75 seconds | Generator-produced | Myocardial perfusion PET imaging [1] |
| Fluorine-18 (FDG) | Positron (511 keV) | 110 minutes | Cyclotron-produced | Metabolic imaging, myocardial viability, inflammation [1] |
| Nitrogen-13 | Positron (511 keV) | 10 minutes | Cyclotron-produced | Myocardial perfusion PET imaging [1] |
| Indium-111 | Gamma | 67 hours | Cyclotron-produced | Labeled antibodies (Myoscint), inflammation imaging [1] |
SPECT Imaging Radionuclides
Technetium-99m
- Emits gamma rays at 140 keV energy level 1
- 6-hour half-life allows sufficient time for imaging while limiting radiation exposure 1
- Generator-produced from molybdenum-99, making it widely available in nuclear medicine departments 2
- Forms various complexes with different chelators for specific organ targeting:
Thallium-201
- Emits X-rays and gamma rays primarily in the 68-80 keV range 1
- Long half-life of 73 hours limits injectable dose 1
- Cyclotron-produced 3
- Redistributes over time, allowing viability assessment without additional radiation exposure 1
- Higher radiation dose to patients compared to technetium-99m agents 1
PET Imaging Radionuclides
Rubidium-82
- Positron emitter (511 keV annihilation photons) 1
- Ultra-short half-life of 75 seconds 1
- Generator-produced, making it more accessible than cyclotron-produced agents 1
- Allows for lower radiation exposure (3.3-3.8 mSv for rest-stress study) 1
- Cannot be used with exercise stress due to short half-life 1
Nitrogen-13 Ammonia
- Positron emitter (511 keV) 1
- 10-minute half-life 1
- Cyclotron-produced, requiring on-site or nearby cyclotron 1
- Excellent for quantification of myocardial blood flow 1
- Very low radiation dose (2.2 mSv for rest-stress study) 1
Fluorine-18 FDG
- Positron emitter (511 keV) 1
- 110-minute half-life allows transport from production site to imaging facility 1
- Cyclotron-produced 1
- Used for metabolic imaging, myocardial viability, and inflammatory conditions 1
Special Considerations
- PET radionuclides emit higher energy photons (511 keV) compared to conventional SPECT tracers, requiring different detection systems 1
- PET imaging typically requires attenuation correction using CT, adding a small additional radiation dose 1
- The choice between radionuclides involves balancing image quality, radiation exposure, and logistical considerations 1
- Newer generation SPECT and PET systems have improved detection efficiency, allowing for lower administered doses 1
Clinical Applications
- Myocardial perfusion imaging: Tc-99m agents, Tl-201, Rb-82, N-13 ammonia 1
- Myocardial viability: F-18 FDG, Tl-201 1
- Ventricular function: Tc-99m for first-pass and gated equilibrium studies 1
- Inflammation/infection: In-111 labeled antibodies, F-18 FDG 1
- Bone imaging: Tc-99m diphosphonates 3
The selection of a specific radionuclide depends on the clinical question, available technology, and patient-specific factors that affect radiation exposure and image quality 1.