US diva Jennifer Lopez visited a children\'s hospital in Panama to which she has donated telemedicine equipment at the start of a series of South American concerts. \"As a mother, children are the most important thing for me,\" she said on Tuesday at a hospital for poor children in the capital, where she was accompanied by her sister Lynda and Panamanian officials. Lopez, 42, will kick off a new tour here on Thursday, with upcoming concerts in Brazil, Argentina, Chile, Venezuela, Canada and the United States. Last month, Lopez was named the world\'s most powerful celebrity by Forbes magazine, which based its rankings on earnings, press coverage and Internet presence. After taking time off to become a mother in 2008, Lopez returned to the public eye last year with a star turn as one of three talent judges on \"American Idol\".