NOVEMBER 2003

SMI conference report

By: Catherine Carrington

Proton MR spectroscopy noninvasively provides highly sensitive and specific information about the prognosis of children with brain tumors, according to a study led by Aria A. Tzika, Ph.D., director of the NMR Surgical Laboratory at Massachusetts General Hospital and the Shriners Burn Institute in Boston. The study was reported at the Society for Molecular Imaging meeting in August.

Investigators performed 50 MRS exams using a 1.5T MR scanner in 27 children undergoing therapy for neuroglial brain tumors. The best predictor of disease progression was the percent change in the ratio of choline to N-acetylaspartate (NAA) (p < 0.001).

Using a 20% increase in the choline/NAA ratio as the cutoff, MRS correctly identified 16 of 18 patients with progressive disease (89% sensitivity) and 28 of 32 patients with stable disease (88% specificity). The odds of tumor progression were approximately 55 times higher if the change in the choline/NAA ratio was at least 20%.

Normalized relative cerebral blood volume (rCBV) was measured in 11 of the 27 patients as well. It was able to distinguish between progressing and stable tumors (p = 0.03) but was not as consistent as MRS in yielding usable data.

Future work with higher field strength magnets will more finely separate various components of the choline spectra, as well as enable examination of a larger number of metabolites.