In interviews, doctors at several other hospitals said they also used Burst’s products and expressed surprise that the F.D.A. Dr. Sandhu said he had used the product on at least 50 patients, thought it worked well and hadn’t detected any problems. He recalled that for some patients, insurance covered Burst treatment, which typically cost thousands of dollars. He said he would have notified patients had the F.D.A. He said he got off to a good start working for Dr. Härtl, but their standoff over the Burst research soured their relationship.

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Persons: Faheem, Sandhu, ”, Gadjradj, Härtl Organizations: Georgetown University Hospital, Weill Cornell Locations: New York