Based on a study performed at the University of Michigan Health System in Ann Arbor, Mich. researchers found that MR spectroscopy enables patients to avoid invasive procedures and treatments by helping physicians to differentiate between recurrent tumors and changes in the brain tissue due to radiation treatments. The study appeared in the February issue of the American Journal of Roentgenology. It involved 33 patients receiving radiation treatment for brain tumors and also undergone MRI examinations that showed new lesions; either a recurrent tumor or radiation changes. Ratios of three metabolites, choline (Cho), creatine (Cr) and n-acetylaspartate (NAA) were calculated in patients who underwent MR spectroscopy and researchers created an ROC curve and prediction model, which showed the post-test probability of a patient having a recurrent tumor. Number of patients with recurrent tumors was 20 and those with post-radiation change were 13. The authors concluded that an elevated Cho/NAA ratio has correlation with evidence of tumor recurrence and allowed creation of a prediction rule to aid in lesion classification.