Leaders of some large academic medical centers and community hospitals called for Massachusetts Gov. Deval Patrick to examine how Massachusetts General Hospital, Brigham and Women's Hospital, Children's Hospital, and a few other institutions are able to obtain higher payments from health insurers even though there is often no demonstrated difference in the quality of the care delivered by those hospitals. Hospital executives and state officials say the practice of insurers paying substantially higher fees to a handful of Boston medical centers is imperiling some rival hospitals and distorting the greater Boston healthcare market.