de Fatima Vasco Aragao M, Law M, Batista de Almeida D, Fatterpekar G, Delman B, Bader A S, Pelaez M, Fowkes M, Vieira de Mello R, Moraes Valenca M
From the Departments of Radiology (M.d.F.V.A., D.B.d.A., B.D., A.S.B., M.P.)Centro Diagnóstico Multimagem (M.d.F.V.A.), Recife, BrazilDepartment of Neuropsychiatry and Behavioral Studies (M.d.F.V.A., M.M.V.), Federal University of Pernambuco, Recife, Brazil
Department of Radiology (M.L.), University of Southern California, Los Angeles, California.
AJNR Am J Neuroradiol. 2014 Aug;35(8):1495-502. doi: 10.3174/ajnr.A3905. Epub 2014 Apr 3.
The differentiation of pilocytic astrocytomas and high-grade astrocytomas is sometimes difficult. There are limited comparisons in the literature of the advanced MR imaging findings of pilocytic astrocytomas versus high-grade astrocytomas. The purpose of this study was to assess the MR imaging, PWI, DWI, and MR spectroscopy characteristics of pilocytic astrocytomas compared with high-grade astrocytomas.
Sixteen patients with pilocytic astrocytomas and 22 patients with high-grade astrocytomas (8-66 years of age; mean, 36 ± 17 years) were evaluated by using a 1.5T MR imaging unit. MR imaging, PWI, DWI, and MR spectroscopy were used to determine the differences between pilocytic astrocytomas and high-grade astrocytomas. The sensitivity, specificity, and the area under the receiver operating characteristic curve of all analyzed parameters at respective cutoff values were determined.
The relative cerebral blood volume values were significantly lower in pilocytic astrocytomas compared with the high-grade astrocytomas (1.4 ± 0.9 versus 3.3 ± 1.4; P = .0008). The ADC values were significantly higher in pilocytic astrocytomas compared with high-grade astrocytomas (1.5 × 10(-3) ± 0.4 versus 1.2 × 10(-3) ± 0.3; P = .01). The lipid-lactate in tumor/creatine in tumor ratios were significantly lower in pilocytic astrocytomas compared with high-grade astrocytomas (8.3 ± 11.2 versus 43.3 ± 59.2; P = .03). The threshold values ≥1.33 for relative cerebral blood volume provide sensitivity, specificity, positive predictive values, and negative predictive values of 100%, 67%, 87%, and 100%, respectively, for differentiating high-grade astrocytomas from pilocytic astrocytomas. The optimal threshold values were ≤1.60 for ADC, ≥7.06 for lipid-lactate in tumor/creatine in tumor, and ≥2.11 for lipid-lactate in tumor/lipid-lactate in normal contralateral tissue.
Lower relative cerebral blood volume and higher ADC values favor a diagnosis of pilocytic astrocytoma, while higher lipid-lactate in tumor/creatine in tumor ratios plus necrosis favor a diagnosis of high-grade astrocytomas.
毛细胞型星形细胞瘤与高级别星形细胞瘤的鉴别有时存在困难。关于毛细胞型星形细胞瘤与高级别星形细胞瘤的先进磁共振成像（MR）表现，文献中的比较有限。本研究的目的是评估毛细胞型星形细胞瘤与高级别星形细胞瘤的MR成像、灌注加权成像（PWI）、扩散加权成像（DWI）及磁共振波谱（MR spectroscopy）特征。
使用1.5T MR成像设备对16例毛细胞型星形细胞瘤患者和22例高级别星形细胞瘤患者（年龄8 - 66岁；平均36±17岁）进行评估。采用MR成像、PWI、DWI及MR波谱来确定毛细胞型星形细胞瘤与高级别星形细胞瘤之间的差异。测定了各分析参数在各自临界值时的敏感度、特异度及受试者工作特征曲线下面积。
与高级别星形细胞瘤相比，毛细胞型星形细胞瘤的相对脑血容量值显著更低（1.4±0.9对3.3±1.4；P = 0.0008）。与高级别星形细胞瘤相比，毛细胞型星形细胞瘤的表观扩散系数（ADC）值显著更高（1.5×10⁻³±0.4对1.2×10⁻³±0.3；P = 0.01）。与高级别星形细胞瘤相比，毛细胞型星形细胞瘤的肿瘤内脂质 - 乳酸/肿瘤内肌酸比值显著更低（8.3±11.2对43.3±59.2；P = 0.03）。相对脑血容量≥1.33的临界值，对于鉴别高级别星形细胞瘤与毛细胞型星形细胞瘤，其敏感度、特异度、阳性预测值及阴性预测值分别为100%、67%、87%及100%。ADC的最佳临界值≤1.60，肿瘤内脂质 - 乳酸/肿瘤内肌酸≥7.06，肿瘤内脂质 - 乳酸/对侧正常组织脂质 - 乳酸≥2.11。
相对脑血容量较低及ADC值较高有利于毛细胞型星形细胞瘤的诊断，而肿瘤内脂质 - 乳酸/肿瘤内肌酸比值较高且伴有坏死则有利于高级别星形细胞瘤的诊断。
