Engineers from Germany were yesterday setting up the scanner at Lake Imaging in St John of God Hospital.

The scanner and the refurbishment of rooms to accommodate it cost more than $2 million.

Lake Imaging manager Craig Lightfoot said the scanner was used for the diagnosis of cancer and was 25 per cent more effective at determining correct treatment than a CT scan alone.

He said the scanner was able to determine the level of activity in a tumour during treatment even if its size had not changed.

"It works as a really high end CT," he said.

"Tumours will change their activity during treatment before they change their size.

"It will enable us to tell if the tumour is responding before you used to be able to."

Mr Lightfoot said there were only three other PET scanners available in Victoria, all of which were located in Melbourne.

He said there was currently a four-week wait for tests.

"Having this service available in the Ballarat region will save patients the anxious wait, which leads to unnecessary stress, and means that the doctors and specialists can get instant results on the diagnosis," he said.

"This leads to a quicker turn-around time for patient treatment if needed."

Mr Lightfoot said the new scanner was a massive step forward for Ballarat and could also be used for research.

"We'll be able to treat more complex cases," he said.

Lake Imaging will conduct staff training in the next couple of weeks. The scanner is expected to available for use from June 30.