** Shares of Australia's Mach7 Technologies M7T.AX rise as much as 17.5% to A$0.335, set for their best trading day since March 31, if gains hold

** The medical imaging systems provider signs a new customer contract with leading U.S.-based tele-radiology provider American Radiologist Network

** Adds that initial contract value is A$1.7 million ($1.21 million)

** Stock down over 45% this year, including the day's move

($1 = 1.4081 Australian dollars)