Detailed information regarding health requirements for visa applicants is explained thoroughly on the Immigration website
Medical examinations conducted overseas are generally only acceptable if conducted by Panel doctors. A Panel doctor is a doctor or a radiologist who has been appointed by the Australian Government to perform medical examinations on visa applicants who have applied from outside Australia.
For a list of Australian Embassy approved Panel Doctors.
When do I visit a Panel doctor?
You should not have your visa medical examination until you have been formally requested to do so by the office processing your visa application.
Do I visit both a Panel doctor and a radiologist?
In most cases, you should attend a Panel doctor first and, if an x-ray is required, the Panel doctor will refer you to a Panel radiologist. In some cases, however, you will be advised by the department that only a radiological examination is required for your visa application. In these instances, the department will supply you with a list of Panel radiologists.