Imaging Technique Measures Brain Tumor Sodium Levels

BALTIMORE, May 1 -- In what is believed to be a first-of-its-kind study, Johns Hopkins University researchers have used magnetic resonance imaging (MRI) to measure sodium concentrations in the cells of malignant brain tumors. Because growth of such cancers are linked to elevated sodium levels, an easy way to measure them could improve diagnosis and treatment monitoring. The study is published in the today's edition of Radiology.

"Determining precise sodium concentrations has been a problem, but MRI can do it at the same time it identifies possible malignant lesions," said Ronald Ouwerkerk, PhD, an instructor of radiology at the Johns Hopkins Department of Radiology, MRI Research Division. Using proton MRI after injecting contrast agents to enhance areas containing many small blood vessels, the researchers found 50 percent more sodium in lesions that turned out to be malignant tumors than in normal brain tissue.

"Using MRI noninvasively in a single examination to get information about tumor metabolism and physiology improves identification of tumor malignancy and is a big step forward," said Ouwerkert.

In the Johns Hopkins study, 20 patients with brain malignancies confirmed by biopsy and nine subjects with no brain tumors underwent sodium MRI. Sodium concentrations were determined in malignant tumors, gray brain matter, white brain matter, cerebrospinal fluid and vitreous humor (fluid within the eye). The image intensities in the sodium images were compared with the signals from a sample with known sodium content. The special scan method the researchers use for 3-D sodium MRI makes it possible to directly calculate sodium concentrations.

The researchers found sodium concentrations in cancer cells were elevated by an average of 50 percent compared to the other noncancerous tissues or those tissues in subjects with no tumors.

The study was funded by the National Health, Lung and Blood Institute; the National Center for Research Resources; and the American Cancer Society.

For more information, visit: www.mri.jhmi.edu