Specially-adapted scanners can be used to help physicians during brain surgery, a study shows.
MRI scanners helped surgeons in one in four cases
Magnetic Resonance Imaging (MRI) scanners are generally used to screen the body for diagnosing cancer.
The German study in Radiology said scanning found extra tissue that needed to be removed in a quarter of cases, meaning repeated surgery was avoided.
A UK expert said such scans would be beneficial - but he warned the cost of the machines could be prohibitive.
There are two types of MRI scanner; low and high field.
While low-field scanners - which provide lower clarity images - have been used for some operations, the adapting of high-field scanners has proved hard due to technological restraints.
The first open low-field scanners were developed and used during surgery in the mid 1990s.
But high-field scanners which produce better images are now available. This is the type of MRI scanner used in the German research.
Their design means it is difficult for a surgeon to operate while they are being used.
During the study by the team at the University Erlangen-Nurnberg, patients, aged from seven to 84, had to be manoeuvred in and out of the MRI scanner.
The researchers assessed the size of the tumour by scanning the patient's brain during the operation, and then decided if their plans for the surgery needed to change.
In just over a quarter of the 200 cases, the surgeons found more cancerous tissue needed to be removed.
Dr Christopher Nimsky, the lead author of the report, said he hoped technological advancements would allow open high-field scanners to be built and placed underneath operating tables.
"Imaging during surgery provide intraoperative quality control," he said.
"It presents valuable information during the procedure that allows the surgeon an opportunity to adjust the strategy."
However, Professor Wladyslaw Gedroyc, a radiologist at St Mary's Hospital in London, said even if the open high-field scanners were developed the cost of them may prove prohibitive.
"In the UK we have already used low-field scanners for abdominal surgery.
"But high-field scanners do allow a substantial improvement in brain surgery. The images are very clear and I think this study shows they are beneficial.
"However, it is a question of technology and expense."