| Purpose: To explore the multivoxel ~1H-MRS characteristics and metabolic changes in radiation-induced brain injury or tumor recurrence after radiotherapy or radiosurgery and the value of ~1H-MRS in differentiating one from the other. Materials and methods: 32 patients with astrocytic or metastatic tumors, which were previously treated with radiotherapy or gamma knife radiosurgery, had new contrast-enhancing areas in the perilesional brain. There were 20 men and 12 women, 16-76 years old, mean age 46. 9±15.2 years. 19 cases of astrocytic tumors had undergone partial surgical resection, including 2 of glioblastomas, 6 of anaplastic astrocytomas, 10 of diffuse astrocytomas and 1 of pilocytic astrocytoma. 13 cases of metastatic brain tumors had the primary cancer located in the lungs (11 cases), ovary (1 case) and ureter (1 case). Multivoxel ~1H-MRS examinations were performed with PRESS sequence on a GE Signa Excite 1. 5T MR scanner. Results: Significant decrease of NAA peak was observed in the cases of radiation-induced brain injury while significant increase of Cho peak in the cases of tumor recurrence. The Cho/Cr and Cho/NAA ratios were significantly higher in recurrent tumor than in radiation injury (P < 0.01). The cutoff value as tumor criteria for Cho/Cr was 1.781, and the resulting sensitivity, specificity and diagnostic accuracy were 87%, 100%, and 93.5% respectively. The cutoff value as tumor criteria for Cho/NAA was 1.540, and the resulting sensitivity, specificity and diagnostic accuracy were 87%, 100%, and 93.5% respectively. Conclusion: Multivoxel ~1H-MRS is an effective diagnostic modality for the differentiation between radiation-induced brain injury and tumor recurrence. |
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