Background on 81mKr-Krypton:
Krypton-81m (81mKr) is a radioactive isotope of the noble gas krypton. It is a metastable isotope, meaning it exists in an excited state before decaying to a stable state. 81mKr emits gamma radiation during its decay process, which allows it to be detected and tracked using imaging techniques.
Application to Lung Ventilation:
81mKr has found significant application in the field of lung ventilation imaging. When inhaled by a patient, 81mKr distributes itself evenly in the lungs based on the air distribution, providing a clear image of the ventilation pattern within the lungs. This makes it a valuable tool for assessing lung function and diagnosing respiratory conditions.
The use of 81mKr for lung ventilation imaging offers several advantages over traditional imaging methods such as xenon-133 ventilation scans. These advantages include:
- Shorter Half-life: 81mKr has a shorter half-life compared to xenon-133, allowing for quicker imaging procedures and reducing radiation exposure to patients.
- High Resolution Imaging: The gamma radiation emitted by 81mKr enables high-resolution imaging of the lung ventilation pattern, providing detailed information about regional lung function.
- Non-Toxicity: Krypton is a noble gas and is non-reactive, making it safe for inhalation and imaging procedures.
Overall, the use of 81mKr in lung ventilation imaging offers a safe and effective method for assessing lung function, diagnosing respiratory disorders, and monitoring treatment responses in patients with lung diseases.
Description
The 81mKr Krypton gas is produced from an 81Rb/81mKr generator. 81mKr has a very short half-life of only 13 seconds. The parent isotope 81Rb has a physical half-life of about 4.5 hours, limiting the use of the generator to usually one working day (expiration 20 hours post-calibration, with ART at noon the day after production). Generators have a capacity of 2 to 20 mCi.
Clinical applications
The short half-life of 81mKr limits its application to lung ventilation. Images are usually recorded immediately after a 99mTc perfusion without moving the patient, allowing an exact comparison of ventilation and perfusion. Abnormal ventilation areas are identified as areas with limited radiation activities.
Sources
The product was on the US and EU markets under the name Kryptoscan™, but due to the limited interest from customers, was withdrawn from the US market and is available only from one single manufacturer in Europe (BV Cyclotron VU) under Mallinckrodt Pharma license. Nihon Medi-Physics sells the generator in Japan.
In Europe the generator’s price is in the range of EUR 400-500 based on yearly contracts remaining below a total of EUR 100,000. Reimbursement of one scan is in the range of EUR 330-350 (including tracer cost) which tells that profitability for a center can be reached only when more than 3-4 patients are screened per day. Customers who have yearly contracts do not necessarily have access to that number of patients and prefer to limit their purchase to 1 or 2 generators per week and regroup patients.
Competition
This product has limited applications and can easily be replaced by 99mTc-Technegas or 127Xe/133Xe for ventilation purposes when available. Its use is also cumbersome and more practical solutions are preferred. However, there are still some physicians who see advantages.
Comments
Compared to other radionuclides (e.g., 99mTc) the very short half-life of 81mKr turns to its advantage when it comes to decay products. 81mKr is not considered an environmental hazard and storage/collecting devices are not required.
Due to the low energy of the radionuclide, the quality of image is not as good as for 99mTc labeled ventilation tracers (chest side imaging is more difficult with 81mKr). In the past ten years the number of pulmonary ventilation scans was divided almost by 10, replaced by CT scans, which is not as specific and has a lower quality of diagnostic, but is readily available. This product will probably disappear within the next 10 years, replaced by new 99mTc labeled tracers.