The Gillard government is under pressure to remedy the problem in next year's budget.
An Access Economics report to be released this week shows the price Medicare pays for bulk-billed scans is $26 less than it costs to deliver the service. For non-bulk-billed services, the Medicare rebate is $53 less than it costs the practice to provide the service, the report shows.
To stay afloat, diagnostic imaging businesses have to charge non-bulk-billed patients an average $74 out-of-pocket expense to cross-subsidise losses they make on bulk-billed scans.
Some newer scans have out-of-pocket expenses as high as $400 or $800, and prolonged radiotherapy treatments can set back patients by up to $16,000.
Health Minister Nicola Roxon last year raised the Medicare rebates for bulk-billed services by 10 per cent after diagnostic imaging services in rural areas threatened to close down.
An inquiry called by Ms Roxon is due to report by the end of the year and the sector hopes the government will respond by indexing the Medicare rebates to inflation.
Economist Ian Harper, who carried out the Access Economics study, said the government's failure to index the Medicare rebates for inflation left the industry with a funding shortfall of $570 million.
Cancer Voices of Australia chairman Ian Roos said growing out-of-pocket expenses was a huge issue for breast-cancer patients.
Women with breast cancer had to find $8000 to pay for radiotherapy treatment before Medicare refunded them $6000.
Women in northeastern Victoria were having mastectomies because they could not afford radiotherapy treatment, he said.