Philips explores quantitative MR to boost precision

May 20, 2007

Unlike tests that provide thresholds such as good or bad cholesterol levels, MR scans are open to interpretation. Early steps toward quantitation have focused on measuring tumor size and volume as indicators of cancer progression or patient response to therapy. Philips is going further.

Unlike tests that provide thresholds such as good or bad cholesterol levels, MR scans are open to interpretation. Early steps toward quantitation have focused on measuring tumor size and volume as indicators of cancer progression or patient response to therapy. Philips is going further.

The company is looking at physiological changes in tumors that occur earlier than size changes, then quantifying them in hopes of providing definitive answers to a raft of questions now facing physicians and researchers.

Quantitation could help stage cancers, identify and monitor the progression of cancers and other diseases, and gauge the effects of therapy. It could even aid in the development of new drugs by helping to determine their effectiveness.

The company brought to its booth at the International Society for Magnetic Resonance in Medicine meeting in Berlin the results of research aimed at developing the means for making such measurements. The objective is to add precision without extending the MR exam by more than a few minutes, said Hannes Dahnke, Ph.D., senior scientist for medical imaging systems at Philips.

Philips displayed color-coded images exemplifying how quantitative measures might indicate the status of liver cancer. Those numbers came from measurements of the organ's ability to take up the MR contrast agent Resovist. Special MR acquisition sequences and postprocessing algorithms provide the basis for quantitating perfusion, which might be used as a very precise means of judging early response to therapy.

"Today the only quantitative measure of tumor response is to look at its size," Dahnke said. "Changes in size can be seen roughly after four weeks of radiotherapy or chemotherapy. In the meantime, physicians are blind to disease progression and whether the therapy is having an effect."

The increased precision possible with Philips' approach promises much earlier guidance. Dahnke emphasized that the software at this time is only a research tool. He noted, however, that the potential exists to turn this software into a clinical tool within one to three years.

Its commercialization could have significance beyond liver cancer, he said. Early successes at Philips have led the company to explore the measurement of iron in the liver as an indicator of hemachromatosis, a genetic disease that destroys the organ's ability to regulate iron content. Definitive diagnosis can currently be done only with liver biopsy. Software in development at Philips may ultimately be able to measure iron content in vivo and, consequently, provide a means for determining patient response to therapy.

The company is also looking into how heart disease and stroke could be similarly quantitated. Further down the road, novel contrast agents may be developed to improve the sensitivity of these measurements. This progress could come from work already under way as part of research involving Philips and funded by the German government.

The research is part of a broader goal within Philips to make MR easier to use and its results less vulnerable to misinterpretation.

"It fits into the idea of doing automated, one-push-button MR," said Franklin H. Schuling, Ph.D., sector head for molecular medicine at Philips Research. "This is our vision for the future."