One in 13 NHS hospital body scanners reviewed are "obsolete", a new report suggests.
A survey found that 8% of magnetic resonance imaging (MRI) scanners used in the NHS across the UK are deemed to be not fit for purpose.
Experts have warned that the health service must "future proof" its fleet of MRI machines, which are used to produce detailed images of the inside of the body.
The new report, which includes data on 42% of the UK's MRI systems or 171 scanners, found that half had plans in place to update old machines.
And for systems that were more than seven years old, only two in five hospitals had renewal plans in place.
Experts recommend that radiotherapy machines as well as MRI and CT scanners should be scrapped after 10 years.
But the review found that 29% of MRI scanners were 10 or more years old.
The report says this compares "unfavourably" to other European countries.
The authors warn the situation is "unlikely to improve" given the financial climate in the NHS.
The Clinical Imaging Board - a collaboration between The Royal College of Radiologists (RCR), the Society and College of Radiographers and the Institute of Physics and Engineering in Medicine - surveyed NHS radiology departments across the UK to gauge the state of MRI equipment.
When asked to judge the technical quality of their systems, the review found that 90% of systems were deemed to be state of the art or adequate but 8% were thought to be obsolete.
Dr Nicola Strickland, president of the RCR, said: "While many hospitals have MRI replacement plans in place, it is concerning to see others do not appear to be planning for the future, especially when it comes to those working with older machines.
"That nearly 40% of MRI scanners that are seven or more years old are not destined for replacement any time soon is a real worry.
"Radiology departments are already struggling with ever-growing workloads and not enough staff, and many now face working with outdated equipment.
"The NHS needs to invest in the future of imaging and help radiology teams plan ahead, regardless of whether their MRI systems are two, five or 10-years-old, hospital managers must ensure they have appropriate plans in place to replace scanners as they age and technology continues to improve."