In an independent medical exam (IME), one party, frequently the insurer, pays a fee for your services. An Impartial Physician has no relationship with, nor allegiance to, either party. The DIA retains you to serve as the judge's medical expert. You are neutral to the parties' dispute. Your report goes into evidence. The Supreme Judicial Court has said that the examiner, "…as to the prescribed medical issues, stands in the position of a master or arbitrator who has considered medical evidence from both parties and whose determination of the medical issues the administrative judge reviews…" at hearing. O'Brien's Case 424 Mass. 16, 23 (1996). MGL 152 § 11A
In short, an independent medical exam is conducted by a medical provider at the request of, and paid for by, the insurance company. The impartial examiner is paid for by the Department of Industrial Accidents.