动态对比增强磁共振灌注成像在脑肿瘤诊断中的应用价值

Evaluation of clinical application in diagnosis of brain tumor with dynamic contrast-enhanced perfusion MR imaging

目的探讨磁共振灌注成像对脑肿瘤尤其是胶质瘤分级及与其他颅内肿瘤的鉴别诊断价值。方法对127例经病理检查证实为脑肿瘤患者的手术前对比增强磁共振灌注成像结果进行回顾分析,其中胶质瘤76例(包括Ⅰ、Ⅱ级36例,Ⅲ级20例,Ⅳ级20例);转移瘤20例;脑膜瘤20例;脑原发性淋巴瘤8例;血管外皮细胞瘤3例。于局部脑血容量图中确定肿瘤最大灌注区,绘制信号强度-时间曲线,比较不同类型肿瘤灌注曲线的特点;并计算最大局部脑血容量,经与对侧正常脑白质参考点校正获得最大相对局部脑血容量,比较各级别胶质瘤、转移瘤、淋巴瘤瘤内最大相对局部脑血容量,以及Ⅲ、Ⅳ级胶质瘤和转移瘤瘤周水肿区最大相对局部脑血容量。结果(1)胶质瘤Ⅰ、Ⅱ级,Ⅲ级和Ⅳ级患者最大相对局部脑血容量测值分别为1.38±0.74、2.65±1.07和3.22±1.57,三者间差异存在高度统计学意义(H=36.688,P<0.001);灌注量以Ⅰ、Ⅱ级胶质瘤最低,Ⅳ级最高。(2)脑原发性淋巴瘤内呈低或等灌注,最大相对局部脑血容量测值(1.50±1.05)与Ⅲ、Ⅳ级胶质瘤(间变性胶质瘤+胶质母细胞瘤)相比,差异有高度统计学意义(P<0.01)。(3)虽然转移瘤最大相对局部脑血容量测值(2.34±1.97)与Ⅲ、Ⅳ级胶质瘤间差异无统计学意义(P>0.05),但两类肿瘤瘤周水肿区最大相对局部脑血容量测值差异具有统计学意义,Ⅲ、Ⅳ级胶质瘤高于转移瘤(u=2.538,P<0.05)。(4)轴外肿瘤(脑膜瘤及血管外皮细胞瘤)于脑血容量图中呈明显高灌注,于对比剂首过信号强度-时间曲线上显示为首过期后MRI信号强度-时间曲线不易回到基线水平,提示其微循环血管因缺乏血-脑屏障导致对比剂快速渗漏进入组织间隙。结论动态对比增强磁共振灌注成像可以揭示肿瘤内血管分布状况,量化病变部位的血管生成,为临床提供病理生理学信息。肿瘤内和肿瘤周围最大相对局部脑血容量变化可对胶质瘤分级及胶质瘤与转移瘤、淋巴瘤和轴外肿瘤的鉴别诊断提供帮助,具有较高的临床应用价值。

Objective Our study was to explore the value of dynamic contrast-enhanced perfusion MR imaging in diagnosing brain tumor, especially the grading of glioma and in differentiating various intracranial tumors. Methods Reviewed and analysed the data of 127 brain tumor patients who underwent conventional MR imaging and dynamic contrast-enhanced perfusion MR imaging before surgical resection or stereotactic biopsy and were confirmed by pathological examination. There were 76 cases of glioma including 36 low grade glioma （WHO grade Ⅰ,Ⅱ ）, 20 anaplastic glioma （grade Ⅲ）, and 20 glioblastoma （grade Ⅳ）, and 51 cases with intracranial tumors including 20 metastatic carcinoma, 20 meningioma, 8 lymphoma and 3 hemangiopericytoma. Maximum tumor perfusion area was defined in the regional cerebral blood volume （rCBV） mapping. A signal intensity-time curve was drawn. Compared the characteristics of various tumor perfusion curves, and calculated the maximum rCBV. The maximum relative regional cerebral blood volume （rrCBV） was obtained by comparing with that in the normal contralateral white matter of brain as reference point. Compared the rrCBV in various grade of glioma, metastatic carcinoma, and lymphoma, and the rrCBV at the peritumoral area of Ⅲ, Ⅳ grade glioma and metastatic carcinoma. Results The maximum rrCBV of grade Ⅰ, Ⅱ, Ⅲ and Ⅳ glioma were 1.38±0.74, 2.65±1.07 and 3.22±1.57, respectively, and there were statistically significant differences among them （H=36.688, P〈0.001）. The perfusion volume was the lowest in grade Ⅰ , Ⅱ glioma and the highest in grade Ⅳ. There was significant difference between the maximum rrCBV in primary cerebral lymphoma with low-or iso-perfusion （1.50±1.05） and grade m, IV glioma （anaplastic glioma group and glioblastoma group） （P〈0.01）. The rrCBV in peritumoral edoma area of grade i1I, IV glioma was significantly higher than that in metastatic tumor （u=2.538, P〈0.05）, although there was no statistical difference between the rrCBV in metastatic tumor （2.34：1：1.97） than that in grade Ⅲ, Ⅳ glioma （P〉0.05）. The perfusion of extra-axial tumors （meningiorna and hemangiopericytoma） was significantly high in cerebral blood volume mapping, and the MRI signal intensity-time curve could not return to baseline level in the contrast first pass signal intensity-time curve, suggesting that due to the absence of blood-brain barrier contrast effused rapidly to the interstitial space from microcireulatory vessels. Condusion Dynamic contrast-enhanced perfusion MR imaging can reveal the lesion vascular distribution and quantity angiogenesis of tumor and provide valuable physiopathologie information. The maximum rrCBV in tumor and peri-tumor is helpful and valuable for the grading of glioma and differentiating glioma from metastatic carcinoma, lymphoma, and extra-axial tumors.