Peri-tumoural Magnetic Resonance Spectroscopy to Differentiate Solitary Primary Intra-axial High-grade Glioma and Brain Metastasis: a Pilot Study

CS Wong, TYC Chu, JKF Ma

Hong Kong J Radiol 2010;13:195-8

Objective: To determine whether the peri-tumoural choline/N-acetyl-aspartate ratio can be used to differentiate solitary primary intra-axial brain tumour and metatasis.

Methods: In this retrospective study, 18 treatment-naïve adults presenting with a solitary intra-axial mass underwent conventional contrast-enhanced and proton spectroscopic magnetic resonance imaging. The images were interpreted retrospectively by an experienced neuroradiologist and a radiology fellow with 6 years' experience. The radiologists were blinded to the clinicopathological and demographic data. The choline/N-acetylaspartate ratio was measured over the area of peri-tumoural oedema, which was defined by T2 hyperintensity and non-enhancing areas immediately adjacent to the enhancing portion of the tumour. A peri-tumoural choline/ N-acetyl-aspartate ratio of >1 was classified as positive, meaning primary brain tumour. Statistical analysis was performed using a 2 x 2 contingency table. The interclass correlation coefficient (alpha) was calculated as the index of concordance exceeding chance for inter-rater reliability.

Results: Of 18 patients, four were excluded from the study owing to absence of peri-tumoural cerebral oedema. Of the remaining 14 patients, nine had a solitary intra-axial high-grade gliomas confirmed pathologically, of whom eight had a peri-tumoural choline/N-acetyl-aspartate ratio of >1. The remaining five patients were classified as having a solitary brain metastasis with no known primary. A choline/N-acetyl-aspartate ratio of >1 in peritumoural region can be used as a parameter predicting a primary brain tumour; respective values for sensitivity, specificity, positive and negative predictive values were 90%, 100%, 100% and 83%, respectively.

Conclusion: The peri-tumoural choline/N-acetyl-aspartate ratio of >1 can be used as a parameter to differentiate the intra-axial primary brain tumour from metastasis.

中文摘要

瘤周區磁共振波譜對孤立原發性顱內高級別膠質瘤及腦轉移瘤的鑒別診斷：初步研究結果

黃鎮昇、朱曉青、馬嘉輝

目的：探討胆碱化合物/N-乙酰冬氨酸峰的比值（Cho/NAA比值）是否可以分辨出孤立原發性顱內腫瘤及腦轉移瘤。

方法：本回顧研究對象為18位孤立顱內腫瘤但未接受治療的患者。他們接受常規的造影增強及質子磁共振波譜檢查，得出的影像由一位經驗豐富的腦神經放射科醫生和另一位有六年經驗的放射治療師審閱，他們審閱前並未知道病人的病理及其他臨床資料。按著在腫瘤信號增強部分的附近位置，利用T2高信號及無強化區域來介定瘤周區，從而量度此區的cho/NAA比值。如果瘤周區的cho/NAA比值大於1，表示病人有原發性腦腫瘤（陽性反應）。用2行2列表作統計學上的分析。一致性指數超越評分者信度，即得組內相關系數（alpha）。

結果：18位病人中，4位因瘤周區沒有腦水腫的情況而未被納入研究。餘下的14人中，9人經病理學資料證實為孤立性顱內高級別膠質瘤，其中8人瘤周區的cho/NAA比值大於1。另外5人有腦轉移瘤但未發現其原發性腫瘤。瘤周區的cho/NAA比值大於1可作為原發性腦腫瘤的一個預測指標；其敏感性為90%、特異性100%、陽性預測值100%和陰性預測值83%。