MR弥散加权成像在星形细胞肿瘤诊断的价值
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摘要
目的：评价脑弥散成像（diffusion-weighted imaging,DWI）及表观弥散系数（apparent diffusion coefficient,ADC）在星形细胞肿瘤诊断中的作用。
材料与方法：采用Siemens 1.5T symphony扫描仪，对40例经手术病理证实的星形细胞肿瘤进行常规T1WI、T2WI、增强MR扫描及脑弥散成像，弥散敏感系数b值取b=0s/mm2及b=1000s/mm2，正常组测量基底节，脑白质，脑皮质及脑脊液的ADC值和ADC图值；病变组计算肿瘤组织区，肿瘤坏死、囊变区及水肿区的ADC值及ADC图值。良性肿瘤与恶性肿瘤组织区的ADC值的变异度,采用MR扫描仪的工具栏（Freehand）测量并计算。计算基底节、脑皮质、脑白质及脑星形细胞肿瘤的各个方向（read，phase，slice，3trace）ADC图值并比较。统计应用方差分析或t检验。应用图像分析软件计算40例肿瘤组织细胞构成密度，同时测出相应区域的ADC值,行线性相关分析,并计算相关系数。
结果：40例星形细胞肿瘤病理证实结果为毛细胞星形细胞瘤7例，星形细胞瘤13例，间变性星形细胞瘤9例、多形性胶质母细胞瘤10例。正常组与病变组ADC值相比有显著性差异（F=253.643，P<0.001）；在病变组，肿瘤组织区ADC值与肿瘤坏死、囊变区ADC值相比有显著性差异（P<0.01）；肿瘤水肿区与肿瘤坏死、囊变区ADC值有显著性差异（P<0.05）；恶性肿瘤组织区与水肿区ADC值有显著性差异；良性肿瘤与恶性肿瘤ADC值有显著性差异（P<0.05）。良性肿瘤肿瘤组织间ADC值的变异度与恶性肿瘤肿瘤组织间ADC值的变异度有显著性差异（P<0.05）；正常脑白质三方向ADC值之间存在显著性差异；而脑皮质、基底节及星形细胞肿瘤三方向ADC值之间无显著性差异。肿瘤细胞构成密度与ADC值之间呈逆相关，相关系数为-0.848。
结论: ADC值的测定能鉴别肿瘤的不同成分(如星形细胞肿瘤的肿瘤组织、瘤周水肿、瘤内坏死、囊变)及正常组织。良性肿瘤与恶性肿瘤ADC值及良性肿瘤
组织之间与恶性肿瘤组织之间ADC值的变异度是鉴别良恶性病变的一个非常有价值的指标。正常脑白质弥散呈各向异性，而脑皮质及基底节弥散呈各向同性，星形细胞肿瘤肿瘤组织弥散呈各向同性的特点。肿瘤细胞构成密度越高，ADC值越小，肿瘤细胞构成密度越低，ADC值越大，良性肿瘤细胞密度低，平均ADC值大，恶性肿瘤生长活跃，细胞密度高，ADC值小。DWI能用于肿瘤生长方式的评估。另外，脑弥散成像在星形细胞肿瘤与脑梗塞、脑脓肿、脑转移瘤和星形细胞肿瘤的复发鉴别诊断中具有重要的作用。
objective:To evaluate the usefulness of diffusion-weighted imaging (DWI)and apparent diffusion coefficients（ADC） in the diagnosis of cerebral astrocytic tumors.
Materials and Methods: Using a 1.5-T superconducting MR unit(Magnetom Symphony;Siemens,Germany),Forty pathologically confirmed cerebral astrocytic tumors underwent conventional T1-weighted imaging, T2-weighted imaging, contrast-enhanced MR imaging and diffusion-weighted imaging,we used two different b values(b=0s/mm2 and b=1000s/mm2).In the normal group,We calculated ADC values and ADC maps values of normal ganglion basilare,cerebral cortex,brain white matter and CSF,In the abnormal group,we calculated ADC values and ADC maps values of tumorous areas,necrotic or cystic areas of tumors and surrounding edematous areas,The coefficient of variation (CV) of benign tumors and malignant tumors were measured and computed with toolbar(Freehand) of MR unit, ADC values of every direction(read、phase、slice、3trace) were calculated in brain ganglion basilare,cerebral cortex,brain white matter and astrocytic tumors,statistical significance was determined using one-way ANOVA or t test to compare them.In 40 cases,tumor cellularity of tumorous areas was computed with imaging anlaysis software, At the same time, ADC values of tumorous areas were measured in corresponding areas, statistical comparisons of the ADC values with tumor cellularity were made linear regresion analysis and Pearson`s correlation coefficient.
Results: 40 astrocytic tumors with pathologically-proved brain tumor included pilocytic astrocytomas (n=7),astrocytomas(n=13) ,anaplastic astrocytomas (n=9), glioblastoma multiformes (n=11).In our study, the apparent diffusion coefficient
values of the normal group had significantly different from that of the abnormal group (F=253.643，P<0.001),In abnormal group,A significant difference was found between the ADC values of tumorous areas and tumorous necrotic or cystic areas (P<0.01),between the ADC values of edematous areas and tumorous necrotic or cystic areas (P<0.05),between the ADC values of malignant tumorous areas and surrounding edematous areas (P<0.05),but not between benign tumorous areas and surrounding edematous areas(P>0.05). The CV of benign tumorous ADC values was statistically different from that of malignant tumorous ADC values, significant difference existed among the ADC values of read ,slice,phase directions in brain white matter(P<0.05),but not among in cerebral cortex,in ganglion basilare and in astrocytic tumors(P>0.05).The ADC values were inversely correlated with tumor cellularity,pearson`s correlation coefficient was –0.848.
Conclusion： Measuring ADC values enabled us to differentiate various components of the tumor (e.g. tumorous portion,cystic or necrotic portion,surrounding edematous portion )and normal tissue;ADC values and CV of ADC values had great clinical value in distinguishing benign tumor from malignant tumor；In brain white matter,diffusion is anisotropic,in cerebral cortex and ganglion basilare,diffusion is isotropic,in astrocytic tumors, diffusion had the characterization of isotropic；Tumor cellularity was higher,ADC value was lower, vice verse.Benign tumor cellularity was low,mean ADC values were high, malignant tumorous cells reproducted rapidly and tumor cellularity was high,ADC values were low.Diffusion-weighted imaging can be used to evaluate the ways of tumorous reproduction. In addition,cerebral diffusion- weighted imaging played a important role in differentiating astrocytic tumors from acute ischemic stroke,brain abscesses, brain matastasis and recurrent astrocytomas.
材料与方法：采用Siemens 1.5T symphony扫描仪，对40例经手术病理证实的星形细胞肿瘤进行常规T1WI、T2WI、增强MR扫描及脑弥散成像，弥散敏感系数b值取b=0s/mm2及b=1000s/mm2，正常组测量基底节，脑白质，脑皮质及脑脊液的ADC值和ADC图值；病变组计算肿瘤组织区，肿瘤坏死、囊变区及水肿区的ADC值及ADC图值。良性肿瘤与恶性肿瘤组织区的ADC值的变异度,采用MR扫描仪的工具栏（Freehand）测量并计算。计算基底节、脑皮质、脑白质及脑星形细胞肿瘤的各个方向（read，phase，slice，3trace）ADC图值并比较。统计应用方差分析或t检验。应用图像分析软件计算40例肿瘤组织细胞构成密度，同时测出相应区域的ADC值,行线性相关分析,并计算相关系数。
结果：40例星形细胞肿瘤病理证实结果为毛细胞星形细胞瘤7例，星形细胞瘤13例，间变性星形细胞瘤9例、多形性胶质母细胞瘤10例。正常组与病变组ADC值相比有显著性差异（F=253.643，P<0.001）；在病变组，肿瘤组织区ADC值与肿瘤坏死、囊变区ADC值相比有显著性差异（P<0.01）；肿瘤水肿区与肿瘤坏死、囊变区ADC值有显著性差异（P<0.05）；恶性肿瘤组织区与水肿区ADC值有显著性差异；良性肿瘤与恶性肿瘤ADC值有显著性差异（P<0.05）。良性肿瘤肿瘤组织间ADC值的变异度与恶性肿瘤肿瘤组织间ADC值的变异度有显著性差异（P<0.05）；正常脑白质三方向ADC值之间存在显著性差异；而脑皮质、基底节及星形细胞肿瘤三方向ADC值之间无显著性差异。肿瘤细胞构成密度与ADC值之间呈逆相关，相关系数为-0.848。
结论: ADC值的测定能鉴别肿瘤的不同成分(如星形细胞肿瘤的肿瘤组织、瘤周水肿、瘤内坏死、囊变)及正常组织。良性肿瘤与恶性肿瘤ADC值及良性肿瘤
组织之间与恶性肿瘤组织之间ADC值的变异度是鉴别良恶性病变的一个非常有价值的指标。正常脑白质弥散呈各向异性，而脑皮质及基底节弥散呈各向同性，星形细胞肿瘤肿瘤组织弥散呈各向同性的特点。肿瘤细胞构成密度越高，ADC值越小，肿瘤细胞构成密度越低，ADC值越大，良性肿瘤细胞密度低，平均ADC值大，恶性肿瘤生长活跃，细胞密度高，ADC值小。DWI能用于肿瘤生长方式的评估。另外，脑弥散成像在星形细胞肿瘤与脑梗塞、脑脓肿、脑转移瘤和星形细胞肿瘤的复发鉴别诊断中具有重要的作用。
objective:To evaluate the usefulness of diffusion-weighted imaging (DWI)and apparent diffusion coefficients（ADC） in the diagnosis of cerebral astrocytic tumors.
Materials and Methods: Using a 1.5-T superconducting MR unit(Magnetom Symphony;Siemens,Germany),Forty pathologically confirmed cerebral astrocytic tumors underwent conventional T1-weighted imaging, T2-weighted imaging, contrast-enhanced MR imaging and diffusion-weighted imaging,we used two different b values(b=0s/mm2 and b=1000s/mm2).In the normal group,We calculated ADC values and ADC maps values of normal ganglion basilare,cerebral cortex,brain white matter and CSF,In the abnormal group,we calculated ADC values and ADC maps values of tumorous areas,necrotic or cystic areas of tumors and surrounding edematous areas,The coefficient of variation (CV) of benign tumors and malignant tumors were measured and computed with toolbar(Freehand) of MR unit, ADC values of every direction(read、phase、slice、3trace) were calculated in brain ganglion basilare,cerebral cortex,brain white matter and astrocytic tumors,statistical significance was determined using one-way ANOVA or t test to compare them.In 40 cases,tumor cellularity of tumorous areas was computed with imaging anlaysis software, At the same time, ADC values of tumorous areas were measured in corresponding areas, statistical comparisons of the ADC values with tumor cellularity were made linear regresion analysis and Pearson`s correlation coefficient.
Results: 40 astrocytic tumors with pathologically-proved brain tumor included pilocytic astrocytomas (n=7),astrocytomas(n=13) ,anaplastic astrocytomas (n=9), glioblastoma multiformes (n=11).In our study, the apparent diffusion coefficient
values of the normal group had significantly different from that of the abnormal group (F=253.643，P<0.001),In abnormal group,A significant difference was found between the ADC values of tumorous areas and tumorous necrotic or cystic areas (P<0.01),between the ADC values of edematous areas and tumorous necrotic or cystic areas (P<0.05),between the ADC values of malignant tumorous areas and surrounding edematous areas (P<0.05),but not between benign tumorous areas and surrounding edematous areas(P>0.05). The CV of benign tumorous ADC values was statistically different from that of malignant tumorous ADC values, significant difference existed among the ADC values of read ,slice,phase directions in brain white matter(P<0.05),but not among in cerebral cortex,in ganglion basilare and in astrocytic tumors(P>0.05).The ADC values were inversely correlated with tumor cellularity,pearson`s correlation coefficient was –0.848.
Conclusion： Measuring ADC values enabled us to differentiate various components of the tumor (e.g. tumorous portion,cystic or necrotic portion,surrounding edematous portion )and normal tissue;ADC values and CV of ADC values had great clinical value in distinguishing benign tumor from malignant tumor；In brain white matter,diffusion is anisotropic,in cerebral cortex and ganglion basilare,diffusion is isotropic,in astrocytic tumors, diffusion had the characterization of isotropic；Tumor cellularity was higher,ADC value was lower, vice verse.Benign tumor cellularity was low,mean ADC values were high, malignant tumorous cells reproducted rapidly and tumor cellularity was high,ADC values were low.Diffusion-weighted imaging can be used to evaluate the ways of tumorous reproduction. In addition,cerebral diffusion- weighted imaging played a important role in differentiating astrocytic tumors from acute ischemic stroke,brain abscesses, brain matastasis and recurrent astrocytomas.
引文
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韩鸿宾,谢敬霞.MR扩散与灌注成像在脑缺血诊断中的应用[J].中华放射学杂志，1998,32(6):364-369.
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Eis M,Els T,Hoehn-Berlage M,High resolution quantitative and diffusion MRI of three different experimental brain tumors in rat,MRM.1995,34:835-844.
Sugahara T,Korogi Y,Kochi M,et al.Usefulness of diffusion-weighted MRI with echo-planar technique in the evaluation of cellularity in gliomas,J Magn Reson imaging,1999,Jan,9:53-60.
Holtas S,Geijer B,Stromblad LG,et al.A ring-enhancing metastasis with central high signal on diffusion-weighted imaging and low apparent diffusion coefficients. Neuroradiology, 2000,42:824-827.
Desprechins B,Stadnik T,Koerts G,et al.Use of diffusion-weighted MR
imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses. AJNR, 1999,20:1252-1257.
Barzo p,Marmarou A,Fatourous P,et al.Contribution of vasogenic and cellular edema to traumatic brain swelling measured by diffusion-weighted imaging.J Neurosurgery 1997,87:900-907.
Miller DH,Grossman RI,Reingold SC,et al.The role of magnetic resonance techniques in understanding and managing multiple sclerosis, Brain, 1998, 121:3-24.
洪讯宁,沈天真,陈星荣.ADC值在星形细胞肿瘤诊断中的应用价值初探[J].中国医学计算机成像杂志,2002,8(3):145-148.
Stejskal E,Tanner JE.Spin diffusion measurements:spin echoes in the presence of a time dependent field gradient.J chemical physics,1965,43:288-292.
Kleihues P,Burger PC,Scheithauer BW,WHO histiologic typing of tumors of the central nervous system.Second Edi 1995.
Le Bigan D，Turner R，Douek P, et al.Cytotoic brain edema: assessment with diffusion weighed MR imaging.Radiology,1992,185:687.
谢敬霞主编，核磁共振新技术研究与临床应用，北京：北京医科大学出版社，2001,6:89.
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耿道颖,沈天真,陈星荣,等.星形胶质细胞瘤MRI与病理对照研究[J].中华 放射学杂志,1999,33(2):79.
Edelman RR,Wielopolski P,Schmitt F,Echo-planar MR imaging[J]. radiology, 1994, 192:600-612.
韩鸿宾,谢敬霞.MR扩散与灌注成像在脑缺血诊断中的应用[J].中华放射学杂志，1998,32(6):364-369.
肖学宏，孔祥泉，刘定西，等.人脑弥散加权平面回波磁共振成像[J].临床放射学杂志，1999,18(3): 133-136.
Warach S,Gaa J,Siewert B,et al.Acute human stroke studied by whole brain echo planar diffusion-weighed magnetic resonance imaging [J].Ann Neurol 1995,37(2): 231-241.
Tien RD,Felsberg GJ,Friedman H,et al.MR imaging of high-grade cerebral gliomas: values of diffusion-weighted echo-planar pulse sequences.AJR,1994, 162:671-677.
Kono K,Inoue Y,Nakayama K,et al.The role of diffusion-weighted imaging in patients with brain tumors.AJNR,2001,22:1081-1088.
Eis M,Els T,Hoehn-Berlage M,High resolution quantitative and diffusion MRI of three different experimental brain tumors in rat,MRM.1995,34:835-844.
Sugahara T,Korogi Y,Kochi M,et al.Usefulness of diffusion-weighted MRI with echo-planar technique in the evaluation of cellularity in gliomas,J Magn Reson imaging,1999,Jan,9:53-60.
Holtas S,Geijer B,Stromblad LG,et al.A ring-enhancing metastasis with central high signal on diffusion-weighted imaging and low apparent diffusion coefficients. Neuroradiology, 2000,42:824-827.
Desprechins B,Stadnik T,Koerts G,et al.Use of diffusion-weighted MR
imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses. AJNR, 1999,20:1252-1257.
Barzo p,Marmarou A,Fatourous P,et al.Contribution of vasogenic and cellular edema to traumatic brain swelling measured by diffusion-weighted imaging.J Neurosurgery 1997,87:900-907.
Miller DH,Grossman RI,Reingold SC,et al.The role of magnetic resonance techniques in understanding and managing multiple sclerosis, Brain, 1998, 121:3-24.
洪讯宁,沈天真,陈星荣.ADC值在星形细胞肿瘤诊断中的应用价值初探[J].中国医学计算机成像杂志,2002,8(3):145-148.
Stejskal E,Tanner JE.Spin diffusion measurements:spin echoes in the presence of a time dependent field gradient.J chemical physics,1965,43:288-292.
Kleihues P,Burger PC,Scheithauer BW,WHO histiologic typing of tumors of the central nervous system.Second Edi 1995.
Le Bigan D，Turner R，Douek P, et al.Cytotoic brain edema: assessment with diffusion weighed MR imaging.Radiology,1992,185:687.
谢敬霞主编，核磁共振新技术研究与临床应用，北京：北京医科大学出版社，2001,6:89.
Barest GD,Sorensen AG,Gonzalez RG,Magnetic resonance imaging of cerebral infraction,Top Magn Reson Imaging,1998,9:199-207.
Lovblad KO,Laubach HJ,Band AE,et al.Clinical experience with diffusion- weightd MR in patients with acute stroke.AJNR,1998,19:1061-1066.
Le Bihan D,Breton E,Lallemand D,et al.Separation of diffusion and perfusion in intravoxel incoherrent motion MR imaing.Radiology,1988,168:497.
Warach S,Gaa J,Siewert B,et al.Acute human stroke studied by whole brain echo-planar diffusion-weighed magnetic resonance imaging.Ann Neruol, 1995, 37:231.
Marks MP,de Crespigny A,Lentz D,et al.Acute and chronic stroke:navigated
spin-echo diffusion-weighed MR imaging Radiology,1996,199:403.
Gonzales RG,Schaefer PW,Buonanno PS,et al.Diffusion-weighted MR imaging:diagnostic accurary in patients imaging within 6 hours of stroke symptom onset.Radiology,1999,210:155-162.
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