Early Metabolic Changes Of Magnetic Resonance Spectroscopy In Evaluation Of Brain Gliomas Undergoing Gamma Knife Therapy

Keywords: glioblastoma multiforme, Imaging, gamma knife, magnetic resonance imaging, magnetic resonance spectroscopy

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     The aim of the study was to evaluate the use of magnetic resonance spectroscopy (MRS) in patients treated with stereotactic radiosurgery.
     From 2004 to 2005, 27 patients with Grade II~IV gliomas were treated with the Leksell Gamma Knife (LGK) and with the follow-up data until the end of 2008 were identified. In 18 patients partial resection had been conducted before LGK treatment. The rest 9 cases undergone stereotactic biopsy and all had been identified to be gliomas pathologically.
     They were treated with the margin dose 15~20 Gy, the treatment isodose 35~45 Gy. In all 27 patients, multivoxel MRS examinations were performed on a 3.0T MR scanner one day before and 15 days after radiosurgery. Spectral data for N-acetylaspartate (NAA), choline (Cho), creatine (Cr), and lactate (Lac) were analyzed. The tumor regrowth onset was established by comparing the results of control MRI with postoperative CT scans, and also on the basis of changes in clinical condition.
     Cho, Cr, and NAA peaks were obtained in 92.6% (25 cases). 16 patients suffered gliomas regrowth within 12 months after LGK treatment. 12 of them undergone surgical operations and the rest 4 went for another LGK. The one year, two year and three year survival rate were 43.6% (7 cases), 18.8% (3 cases), and 0% (0 cases), respectively. In these cases, Cho/NAA, Lac/Cr ratios increased and the NAA/Cr ratio decreased around the vicinity of the therapy area. The other 11 patients survived without gliomas regrowth within one year follow-up. 3 of them get lost in contact after then. 6 of them still survived on resent follow-up, and they survived more than 2 years. The rest 2 cases died from gliomas regrowth 17 and 22 months after LGK, respectively.
     This is a retrospective study.
     In these cases, Cho, Cr, and NAA peaks were totally decreased and no Lac peak was observed around the vicinity of the therapy area. The authors carried out the univariate analysis and found that an increase in Cho/NAA ratio was correlated with a shorter survival time.
     In conclusion, patients undergoing LGK may benefit from the postoperative MRS imaging in the prediction of glioma regrowth.


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