Rubidium-82 is a radioactive isotope of the element rubidium with a half-life of about 75 seconds. It is commonly used in nuclear medicine for cardiac imaging, specifically in positron emission tomography (PET) scans of the heart.
Rubidium-82 is produced by a generator system that allows for on-site production of the radioisotope. Once produced, it is administered intravenously to patients undergoing cardiac PET imaging. Rubidium-82 is taken up by the heart muscle in a manner proportional to blood flow, making it a valuable tracer for assessing myocardial perfusion and detecting areas of reduced blood flow in the heart.
During a Rubidium-82 PET scan, the radioisotope emits positrons that interact with nearby electrons, resulting in the production of gamma rays. These gamma rays are detected by the PET scanner, which creates detailed images of the heart’s blood flow and function. Rubidium-82 PET imaging can help diagnose coronary artery disease, evaluate myocardial viability, and assess the effectiveness of treatments in patients with heart conditions.
One of the advantages of Rubidium-82 PET imaging is its short half-life, which allows for rapid imaging with high-quality results. Additionally, Rubidium-82 has a low radiation dose, making it a safe and effective option for cardiac imaging.
Overall, Rubidium-82 is a valuable radioisotope used in nuclear medicine for cardiac imaging, providing important diagnostic information for patients with heart disease. Its ability to assess myocardial perfusion and function makes it a valuable tool in the evaluation and management of various cardiac conditions.
Properties:
Rubidium-82 (82Rb) is the direct decay product of 82Sr and has a half-life of only 76 sec. It decays with emission of positrons at an average intensity of 1,535 keV (83% – maximum at 3,379 keV) corresponding to a mean range of about 5.5 mm (2.8–12.4 mm), followed by annihilation producing two gamma rays at 511 keV. Additionally, about 13% of 82Rb nuclear decays are associated with a 776 keV prompt gamma emission which can be recorded as a coincidence with one of the 511 keV annihilation photons.
As a continuous infusion this radionuclide can be used for PET imaging in cardiology.
Manufacturing:
82Rb is simply extracted in a continuous manner from the 82Sr/82Rb generator.
Source and availability:
The availability of 82Rb is of course directly linked to the availability of the generator.
Derivatives – Applications:
82Rb chloride produced from the 82Sr/82Rb generator has such a short half-life that it is impossible to use it differently than as a direct application. It is a PET imaging agent used in myocardial perfusion imaging for the diagnosis of ischemia and necrosis. 82Rb behaves like the more conventional SPECT agent (201Tl and 99mTc imaging agents) with the advantages of higher quality images, fast procedure (less than 30 min compared to 4 hours) and the possibility to quantify. 82Rb also shows some significant advantages in obese patients and in women.
So far, the cardiac indication is the only one for which this product has received a marketing authorization, but very recently (2013) a new use has been discovered when imaging tumors. The mechanism and utility in oncology still need to be explored (conclusion pending).
Price:
The price of the 82Rb used per patient is directly linked to the number of patients that can be handled in an imaging center. Production of 82Rb is not a limiting factor as the generator can be ‘milked’ every ten minutes. Roughly the two injections given to a patient can be performed in less than 30 min, so theoretically one could expect a throughput of two patients per hour and up to 20 patients per day (if based on only 10 hours working day) and 400 patients a month (if based on 5 days a week).
In this almost maximum case, the cost of 82Rb would be in the range of EUR 60 (US$ 80) per patient. This is the cheapest cost of goods for a PET cardiology agent in comparison to any fluorinated compound, 15O-Water or 13N-Ammonia. It is even not that much more expensive than any 99mTc MPI agent. In fact, one should consider that a throughput of half the figure above is closer to standard, but the CoGs per dose would not be higher than EUR 120 (US$ 160) which is still very competitive compared to other fluorinated agents.
Issues:
- The major issues are the high upfront price of the generator and the availability of these generators.
- Access to the generator is limited by the worldwide capacity for producing 82Sr.
Comments:
82Rb’s applications are limited to cardiology. In terms of myocardiac infusion imaging, 82Rb competes with the marketed 99mTc SPECT agents (sestamibi, tetrofosmin), will compete with the fluorinated compounds that are under development (CardioPET, Flurpiridaz) and may compete with 15O and 13N. In terms of quality of images, the PET agents are definitely superior, but dedicated PET cameras are still rare. 15O and 13N need an important initial investment that has to be counted on top of the camera investment and limits the number of centers that can afford this technology. Finally, 18F-labeled PET agents will remain very expensive (incompressible bottom-line costs are in the range of EUR 80–90 (US$ 100–120) per patient and for this reason 82Rb becomes economically the best PET imaging agent. The 82Rb CoGs could even be improved in the future with the increase of competition.