The scan uses magnetic resonance imaging to track the diffusion, or movement, of water through the brain.

Tumor cells block the flow of water, so as those cells die, water diffusion patterns change, and the new MRI technology can track it, the team at the University of Michigan Comprehensive Cancer Center said.

They studied 20 people with malignant brain tumors, and found that any change in the diffusion map showed if chemotherapy or radiation therapy was having any effect on the cancer.

It worked within three weeks — 10 weeks before traditional MRI techniques of assessing whether therapy is working, they reported in the Proceedings of the National Academy of Sciences.

Most primary brain tumors kill their victims, with patients surviving only 10 months after diagnosis on average.

Usually, patients get seven weeks of treatment, followed by a traditional MRI scan six weeks afterwards to see if the tumor shrank. If it did not, doctors may try a different approach, depending on the tumor.

Speeding up this process can save patients from often-uncomfortable treatments that may be a waste of time, said Brian Ross, a professor of radiology and biological chemistry who helped lead the study.

“Do you want to go through seven weeks of treatment only to find two months later that it had no effect?” he said in a statement.

“Using MRI tumor diffusion values to accurately predict the treatment response early on could allow some patients to switch to a more beneficial therapy and avoid the side effects of a prolonged and ineffective treatment,” he added.

Now the teams plans to test the technique with breast cancer, and head and neck cancer.

The University of Michigan said it holds a patent on the MRI diffusion technology and has licensed it to Molecular Therapeutics Inc. a privately held Michigan company, to develop into a product hospitals and doctors could use.