The FDA has notified the public and the medical imaging community about the potential for inadvertent, increased radiation exposure in patients who underwent or will be undergoing cardiac PET scans with rubidium-82 (Rb-82) chloride injection from CardioGen-82 (Bracco Diagnostics).

A CardioGen-82 PET scan is one of a variety of nuclear medicine scans and uses Rb-82 chloride injection to evaluate the heart. The 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, according to the agency.

The FDA said that currently, the risk of harm from this exposure is believed to be “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, according to the agency, which added that it would take much more radiation to cause any severe adverse health effects in patients.

Healthcare professionals should follow the required testing and quality control procedures 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.

The FDA said it is investigating the root cause of this failure with CardioGen-82 and will promptly notify the public with updates.

For healthcare professionals, the agency is advising these options:

• 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, which 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 uCi Sr-82/mCi Rb-82 or 0.02 uCi 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 uCi/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 uCi/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 and notify Bracco.

More information is available online on the FDA webste.