Cancer care provider 21 Century Oncology Inc has reached a $34.7 million settlement with the U.S. government stemming from the improper use of a procedure that measures the level of radiation that leaves a patient’s body after treatment.

The U.S. Department of Justice announced the settlement on Tuesday. The oncology company, based in Fort Meyers, Florida, performed and billed for procedures that were not medically necessary, the Justice Department said.

Physicians and physicists who performed the procedure, known as “the Gamma function,” were not properly trained to interpret or use the results, the Justice Department said.