More and more obese patients are unable to be scanned in X-ray and MRI machines because they are too big.
Traditional MRI machine
Even if big patients can fit into scanners, the machinery will not work because X-ray beams and soundwaves cannot penetrate deep fat.
With 60 per cent of Australians either overweight or obese, radiologists say the problem is becoming more common in hospital patients.
Royal Melbourne Hospital head of radiology Prof Brian Tress said standard X-rays, CT scans, MRI scans and ultrasounds were sometimes ineffective when used on obese people, making diagnosis extremely difficult.
"The more flesh there is, the more the X-ray beam gets attenuated or scattered and produces grey results," Prof Tress said. This is one of many methods doctors and clinicians use to measure adipose tissue (fat).
"This is just another indication of the extent of the obesity problem."
Royal Australian and New Zealand College of Radiologists spokeswoman Dr Liz Carter said X-ray images became blurry when used on a patient weighing 100kg (220lb) or more.
Ultrasounds were virtually impossible on these patients, but Dr Carter said CT scans and MRI scans could often be used as a last resort.
As well as the personal health risks of obesity, large patients also posed risks to medical staff. "There is the risk to the equipment, of it being broken, and to the staff if they have to move the patients," Dr Carter said.
X-rays, CT scans, ultrasounds and MRI scans are used to look for broken bones, fetuses, blood clots, tumours, diseased organs and other internal abnormalities.
Most scanning equipment can hold patients up to 250kg (550lb).
But those who cannot fit into a scanner must be referred to hospitals with open-sided MRI equipment, such as Sunshine and Goulburn Valley.
Open MRI machine