[7-15-2011] The U.S. Food and Drug Administration (FDA) is alerting the public; in particular, the medical imaging community; about the potential for inadvertent, increased radiation exposure in patients who underwent or will be undergoing cardiac positron emission tomography (PET) scans with rubidium (Rb)-82 chloride injection from CardioGen-82 (manufactured by Bracco Diagnostics, Inc.). A CardioGen-82 PET scan is one of a variety of nuclear medicine scans that use radioactive drugs to evaluate the heart.
Facts about CardioGen-82
FDA has received reports of two patients who received more radiation than expected from CardioGen-82; the excess radiation was due to strontium isotopes which may have been inadvertently injected into the patients due to a “strontium breakthrough” problem with CardioGen-82.
At this time, FDA believes that the risk of harm from this exposure is minimal, although any unnecessary exposure to radiation is undesirable. The estimated amount of excess radiation the two patients received is similar to that other patients may receive with cumulative exposure to certain other types of heart scans; it would take much more radiation to cause any severe adverse health effects in patients.
FDA is actively investigating the root cause of this failure with CardioGen-82 and will promptly notify the public with updates.
Healthcare professionals should closely follow the required testing and quality control procedures essential to help detect strontium breakthrough from CardioGen-82. Other types of heart scans provide information very similar to CardioGen-82 and professionals are encouraged to consider these alternatives while FDA completes its investigation of the reported cases of excess radiation exposure.
Patients who have recently had heart scans should talk to their healthcare professional if they have any questions. Many heart scans do not involve use of CardioGen-82. Patients who are planning to undergo a heart scan should talk to the healthcare professional if they are unsure of the type of planned heart scan and the radiation risks associated with the scan. If a Cardio-Gen-82 scan is planned, patients may wish to delay this scan or use alternatives until the radiation issue is resolved.
- Patients who recently had a heart scan should talk to their healthcare professional if they have any questions or concerns.
- Patients who are planning to undergo a heart scan should talk to their healthcare professional if they have questions about the radiation risks associated with the planned heart scan. Patients who are planning to undergo a CardioGen-82 scan may wish to delay their procedure until the radiation issue is resolved.
- Adverse events experienced after a heart scan should be reported to the FDA MedWatch program, using the information in the "Contact Us" box at the bottom of the page.
While the investigation is ongoing, healthcare professionals should consider alternatives to the CardioGen-82 generator when planning nuclear medicine cardiac scans.
If CardioGen-82 is used, apply special attention to the steps that help to minimize the risk for strontium breakthrough, as outlined below and in the prescribing information.
Healthcare professionals should follow the prescribing information to determine the eluate Rb-82 content and Sr-82 and Sr-85 breakthrough using an ionization chamber-type dose calibrator. This should be done daily prior to the administration of Rb-82 chloride injection to any patients.
If results from strontium Sr-82/Sr-85 breakthrough testing exceed one-tenth (1/10) of the specification limit (1/10 of specification limit = 0.002 μCi Sr-82/mCi Rb-82 or 0.02 μCi Sr-85/mCi Rb-82), then perform the Rb-82 assay and Sr-82/Sr-85 breakthrough testing at least twice daily (i.e., the beginning and the middle of day). This additional test should be initiated on the day the Sr-82/85 levels exceed 1/10 of the specification limit indicated above and each day thereafter.
The Sr-82 content must not be more than 0.02 μCi/mCi of Rb-82 at end of elution. If the Sr-82 breakthrough exceeds these specified limits, discontinue use of the generator and notify Bracco.
The Sr-85 content must not be more than 0.2 μCi/mCi of Rb-82 at end of elution. If the Sr-85 breakthrough exceeds these specified limits, discontinue use of the generator and notify Bracco.
Use only additive-free Sodium Chloride Injection USP to elute the CardioGen-82 generator.
- Report product problems or adverse events involving CardioGen-82 to the FDA MedWatch program using the information in the "Contact Us" box at the bottom of this page. Also notify Bracco.
FDA has received reports of two patients who underwent PET myocardial perfusion imaging scans with CardioGen-82 and had detectable levels of radiation several months after their PET scans. Both patients were crossing the border to/from the United States when radiation detectors identified radiation originating from the patients. The radiation was found to originate from strontium (Sr-82 and Sr-85). A PET scan had been performed in each patient approximately 2 and 4 months earlier, respectively. Since Rb-82 has a half-life of 75 seconds and both patients reported that they had no other exposure to radioactive substances, the residual radiation is likely due to undetected strontium breakthrough. The total number of patients who have received doses from CardioGen-82 generators with strontium breakthrough is currently unknown.
The radiation exposure that a patient would typically receive from an injection of Rubidium-82 chloride (approximately 2.8 mSv) is generally less than that associated with other radionuclide cardiac diagnostic scans. The radiation exposure that the two patients received due to strontium isotope exposure appears to substantially exceed that typically associated with CardioGen-82. This assessment is based upon modeling performed by the Los Alamos National Laboratory. This modeling suggests that the excessive radiation exposure (approximately 90 mSv) associated with the strontium isotopes appears similar to the amount of cumulative radiation exposure some patients receive during cardiac diagnostic evaluations with other radionuclides. Multiple assumptions are involved in estimating the extent of this radiation exposure and efforts are ongoing to refine these estimates, including discussion with the Nuclear Regulatory Commission.
At this time, it is unknown whether this safety issue is due to a product problem involving generator failure or due to user error, or a combination of both factors. FDA is actively investigating the root cause of this issue and will take appropriate regulatory actions as warranted. FDA will promptly notify the public when a conclusion is made.
FDA Drug Safety Communication: FDA alerts healthcare professionals to stop performing heart scans with CardioGen-82 due to potential for increased radiation exposure in patients[ARCHIVED]
FDA Drug Safety Podcast for Healthcare Professionals: Increased radiation exposure due to undetected strontium breakthrough when using CardioGen-82 for cardiac positron emission tomography (PET) scans[ARCHIVED]