Radiologists say "very concerned" patients may not be cured of serious illnesses when demand for services increases, due to a lack of imaging equipment in the UK.
The president of the Royal College of Radiologists warned that the service was "woefully underfunded".
She said that cleaning requirements because of the coronavirus would reduce capacity.
The British Department of Health and Welfare said it was investing £ 200 million in imaging equipment.
"Radiology is one of those services that people use all the time, but that they don't always think about, it's not sexy like surgery," said Dr. Jeanette Dickson, president of the Royal College of Radiologists.
"The image affects virtually all patients who enter the hospital.
"If you look at us in a European average, we are certainly one of the countries with the lowest number of scanners per head of the population."
A comparison carried out by the OECD, the Organization for Economic Cooperation and Development, in 2014 – the last set of comparable figures – showed that there were only 9.5 scanners per million head of the population, well below the values of Spain, Germany, France and Italy. .
The BBC was informed that some trusts had only one scanner operating in the UK.
Dickson said that normal service before the outbreak was "woefully underfunded and underfunded" and that they were "coping, but badly".
She said the whole picture was insufficient before the Covid-19 crisis. The latest figures from the Royal College of Radiologists show that 11% of posts funded by radiologists across the UK were vacant.
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In April, Cancer Research said that a drop in screening and referrals meant that approximately 2,700 people were diagnosed each week.
Sara Hiom, director of early diagnosis at Cancer Research UK, said CT scanners to diagnose cancer "were already at a breaking point before the pandemic."
The BBC believes that more than 30 CT scanners were obtained from the independent sector during the coronavirus crisis, with at least 35 more orders.
"The capacity will be much, much less than the demand," even with the equipment ordered, said Dickson.
She warned that even when all images are resumed, and the NHS is fully functional, it would take "at least 30 to 45 minutes" for deep cleaning scanners after Covid-19 patients and "more attention" would be paid to cleaning of equipment among all patients. patients. Patients need to distance themselves socially in the waiting room.
"I am very concerned that we may find that patients are undergoing unnecessary treatments or damaging unnecessarily and missing out on the opportunity to cure cancer or other serious illness due to the lack of images," said Dickson.
Sara Hiom added: "The government needs to invest in the necessary equipment, employing and training more staff to enable the NHS to handle the portfolio of patients awaiting cancer care.
"Immediate diagnosis and treatment remain crucial to offer patients greater chances of survival."
The British Department of Health and Social Care said in a statement that it is "committed to increasing our capacity for early cancer diagnosis and has provided £ 200 million for new, state-of-the-art diagnostic machines to improve the quality and speed of diagnosis and replace any outdated machines ".
He added that cancer services would be "among the first of many NHS services to return to normal" during the coronavirus outbreak.
An NHS England spokesman said: "Further cleaning of CT scanners and additional infection control measures are being implemented across the pandemic to protect staff and patients.
"The NHS is making full use of the additional scanning capacity in the independent sector, in addition to purchasing additional scanners so that testing can proceed normally."
The Welsh government said it was "increasing the diagnostic capacity in radiology, including a new National Academy of Images, and doubling the radiology training program".
In the meantime, the Scottish government has said it expects all health councils "to continue to prioritize radiology capabilities for patients referred with an urgent suspicion of cancer during and after the Covid-19 outbreak."
"Most cancer radiology diagnoses and treatments have continued, however, treatment plans for some patients will change to minimize individual risk," he added.