A shortage of senior radiologists around the UK is causing delays for patients, and affecting cancer and other medical care.
Radiologists' leaders say the situation is unacceptable and must be tackled by ministers.
Figures suggest their workload of reading and interpreting scans has increased by 30% between 2012 and 2017.
But the number of consultant radiologists in England has gone up by just 15% in that time.
The figures, given to the BBC by the Royal College of Radiologists, also suggest the number of these senior posts in Scotland, Wales and Northern Ireland has remained static over that period.
'Brick wall'
Carol Johns is worried about her mother Maria, who is in constant pain because of swollen feet and ankles.
Over a six-month period there has been been a series of delays with scans and follow-up appointments, and Maria has still not been told the results or what the problem might be.
"You just can't get through to people – it's answer phones – you're just banging your head against a brick wall most of the time.
"I just want to see some light at the end of the tunnel, really, to get her some treatment and hopefully get a bit more quality of life," Carol said.
Dr Nicola Strickland, president of the Royal College of Radiologists said: "I can't overestimate how worrying it is.
"I do really feel the entire service will collapse if something isn't done about training more radiologists in the UK to fill all the vacant consultant posts, so we have to get imaging properly staffed – and right – and enough radiologists trained to make up this deficit."
More trainees needed
The Royal College of Radiologists says NHS hospitals have increasingly had to outsource analysis of complex scans to private companies or pay for existing staff to do overtime.
The total annual bill for this across the UK has doubled over the five-year period to £116 million.
The vacancy rate for consultant posts in the UK has increased from 9% to over 10% in just two years, with Northern Ireland seeing the highest rate at more than 18%.
The Royal College says more trainee radiologists are needed – with extra funding required for training and a "concerted effort" to retain staff.
The workload has increased significantly with more sophisticated technology available.
Some doctors, known as interventional radiologists, carry out complex procedures using image guidance to facilitate precisely targeted therapy.
This includes treating cancer tumours and dealing with blocked veins using small catheters.
Treating a higher number of elderly patients with complex conditions has also added to the workload.
Radiologists argue that their work is central to much of what the NHS does, so staff shortages are having a serious impact on patients by prolonging waits.
International shortage
The new figures highlighting workforce shortages come the week after news that a Scottish health board has no interventional radiologists after the departure of the last remaining specialist in that field.
The NHS Highland health board said patients needing emergency care by these experts, which was usually provided at Raigmore Hospital in Inverness, would be sent to Aberdeen or Dundee.
The Scottish Cabinet Secretary for Health, Jeane Freeman, said there had been "an international shortage of radiologists affecting health services worldwide".
But she said 50 specialist training places for clinical radiologists would be created over the next five years.
A Welsh Government spokesperson said it had nearly doubled the size of the radiology training programme in Wales.
"We have also created a new National Imaging Academy to provide state-of-the-art facilities for training more radiologists."
A Department of Health and Social Care spokesperson said the number of clinical radiologists in England had gone up by 29% since 2010.
"We want to see numbers continue to rise and over the next three years we are also putting in place more training for doctors to specialise in clinical radiology."
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