Biospectral scan

A biospectral scan is a procedure used by the Trill to examine Trill symbionts that are joined with a host.

In 2371, Doctor Renhol and other Trill Symbiosis Commission doctors ran a biospectral scan on Jadzia Dax to investigate why her isoboramine levels were falling. To scan, an incision was made in Jadzia's abdomen to insert the scanner. 

In an alternate timeline in which the USS Defiant (NX-74205) (I) and its crew were sent back in time thousands of years, Julian Bashir ran biospectral scans on Dax and kept records of the results.