SWI对星形细胞瘤分级及与单发转移瘤鉴别诊断的价值

目的应用磁敏感加权成像(susceptibility weighted imaging,SWI)对脑肿瘤瘤体实质的血管及微出血状态进行量化分析,探讨其对星形细胞瘤分级及其与单发脑转移瘤鉴别诊断的价值。材料与方法对42例经手术及病理证实的脑肿瘤患者行常规MRI序列及SWI检查,包括星形细胞瘤Ⅰ级3例、Ⅱ级8例、Ⅲ级9例、Ⅳ级8例及转移瘤14例。SWI原始数据经处理得到滤过后相位图(CPI)、SWI最小密度投影图(SWIM i n I P)。将S W IM i n I P上肿瘤实质内线状或点状低信号结构定义为肿瘤内磁敏感信号(ITSS),计数肿瘤内所有层面ITSS数。星形细胞瘤不同级别之间、星形细胞瘤与转移瘤之间的ITSS差异用Wilcoxon检验进行分析。对于肿瘤之间有统计学差异的参数,采用ROC曲线分析其诊断敏感度、特异度。应用Spearman相关性分析星形细胞瘤级别与ITSS关系。结果Ⅰ级星形细胞瘤瘤内实质的ITSS数目均值为(3.00±2.65),Ⅱ级为(4.12±0.64),Ⅲ级为(18.11±2.15),Ⅳ级为(18.75±2.48)。Ⅱ级与Ⅲ级星形细胞瘤之间ITSS数目有显著差异(H=7.835,P0.01);Ⅲ级与Ⅳ级之间ITSS无显著差异(H=0.021,P=0.885)。低级别(Ⅰ级与Ⅱ级)星形细胞瘤的ITSS明显小于高级别星形细胞瘤(Ⅲ级与Ⅳ级;H=13.156,P0.01)。星形细胞瘤级别与ITSS呈正相关(r=0.746,P=0.000)。以7.5为鉴别高、低级别星形细胞瘤的ITSS阈值,敏感度为88.2%,特异度为81.8%,ROC曲线下面积(AUC)为0.912;以6.0为阈值鉴别Ⅱ级与Ⅲ级星形细胞瘤,敏感度为100%,特异度为87.5%,AUC为0.903。高级别星形细胞瘤瘤内实质的ITSS均值(18.41±1.58)明显高于转移瘤(6.14±1.56,P=0.001);以6.5为鉴别阈值,敏感度为94.1%,特异度为71.4%,AUC为0.861。结论肿瘤实质ITSS数量反映了肿瘤的微血管异质性,有助于星形细胞瘤的分级及其与转移瘤的鉴别诊断。

SWI study on astrocytoma grading and differential diagnosis of astrocytoma and solitary metastases

Objective: The purpose of this study is to explore the value of the intratumoral susceptibility signal intensity (ITSS) in grading of astrocytoma and in differential diagnosis of astrocytomas and metastases. Materials and Methods:Forty-two recruited patients with brain tumors conifrmed pathologically, including 14 solitary metastases and 28 astrocytomas(WHO grade Ⅰ=3, grade Ⅱ=8, grade Ⅲ=9 and gradeⅣ=8) underwent conventional MRI examinations and susceptibility weighted imaging (SWI). Intratumoral susceptibility signal intensity(ITSS)in tumor parenchyma was obtained. The ITSS values were further compared between different grades of astrocytoma and between astrocytomas and metastases by Wilcoxon test. Receiver operating characteristic curve (ROC) was used to determine the differentiation ability of ITSS number for astrocytoma grading and brain tumors differential diagnosis. Spearman coefficient correlation analysis was used to analyze the relation between ITSS and astrocytoma grade. Results: The mean values of ITSS in grade Ⅰ, Ⅱ,Ⅲ, Ⅳ astrocytomas and metastases were respectively (3.0±2.67), (4.12±0.64),(18.11±2.15), (18.75±2.48) and (6.14±1.56). Significant difference was observed in high-grade (ⅢandⅣ) and low-grade (ⅠandⅡ) astrocytomas (H=13.156, P<0.01), and even between the gradesⅡandⅢastrocytomas (H=7.835, P<0.01), while no signiifcant difference was found between grade ⅢandⅣastrocytomas(H=0.021, P=0.885). Positive correlation was observed between ITSS and astrocytoma grade (r=0.746,P=0.000). Area under the ROC curve (AUC) was 0.912 in differentiation of the high-grade and low-grade astrocytomas when the cutoff value was set as 7.5, and the sensitivity and speciifcity were 88.2% and 81.8%. AUC was 0.903 in differentiation of the gradeⅡand gradeⅢastrocytomas when the cutoff value was set as 6.0, and the sensitivity and speciifcity were 100% and 87.5%. Signiifcant differences of ITSS were observed between the metastases (mean rank=9.89) and high-grade astrocytomas(mean rank=21.06) (H=11.679, P=0.001), while no signiifcant difference was observed between the metastases and low-grade astrocytomas. AUC in differentiation of the high-grade astrocytomas and metastases was 0.861 when the cutoff value of ITSS was set as 6.5, and the sensitivity and speciifcity were 94.1% and 71.4%. Conclusion:ITSS is helpful to determine the grade of astrocytoma and differentiate the high grade astrocytoma and metastates, which relfects the microhemorrhage and tumor vessels in the tumor parenchyma.