The TGA website contains a excellent summary of the regulations relating to medical devices. In particular the approach taken by the TGA to risk assessment is summarised. 

The level of scrutiny by the TGA of a device before it is placed on the ARTG and supplied in Australia depends on the risk posed by the device. The TGA has adopted a classification system for devices, based on the level of risk. The lowest risk medical devices, Class 1 devices, are not assessed by the TGA prior to inclusion on the ARTG.

The extent of regulation therefore depends on:
• the intended purpose of the device
• the degree of risk the device poses to the patient
• the degree of risk the device poses to the user and those in the vicinity
• whether the device is used internally or externally to the patient
• the duration of use.

 For the full article use this link medical device regulation to be directed to the TGA website