DWI、MRS和CASL-PWI联合应用在MELAS型线粒体脑肌病诊断中的价值

目的 明确扩散加权成像(DWI)、磁共振波谱成像(MRS)和连续动脉自旋标记(CASL)灌注成像(CASL PWI)等无创性检查的联合应用在线粒体脑肌病伴乳酸血症和卒中样发作(MELAS)诊断中的应用价值.资料与方法 2例MELAS患者,除了常规MRI检查序列,补充了DWI、MRS和CASL-PWI.结果 在MELAS急性期,DWI显示病灶呈略低信号,MRS显示乳酸峰升高,在看似正常的脑组织中乳酸峰亦轻度升高.CASL-PWI显示病灶为高灌注.结论 通过DWI、MRS和CASL-PWI等无创性检查联合应用对于MELAS有极大诊断价值,并且可以鉴别MELAS急性期与脑梗死急性期.     

磁共振常规及其功能成像在原发性颅内淋巴瘤的应用价值

目的：探讨磁共振成像(MRI)、扩散加权成像(DWI)、磁共振灌注成像(PWI)、磁共振波谱成像(MRS)在原发性颅内淋巴瘤诊断及鉴别诊断中的应用价值。方法回顾性分析27例原发性颅内淋巴瘤患者的 MRI、DWI、PWI、MRS 影像资料。结果所有病灶 T1 WI 呈低-等信号,T2 WI 呈等、稍高、高信号,DWI 呈稍高、高信号。增强扫描22例病灶呈明显均匀强化,5例病灶呈不均匀强化。19例病灶可见“蝶翼征”“握拳征”“缺口征”“尖角征”。18例病灶均为低灌注表现。MRS 表现为病灶实质区 NAA 峰明显降低或消失,Cho 峰增高,23例出现高大 Lip 峰,12例出现 Lac 峰。结论磁共振常规及其功能成像在原发性颅内淋巴瘤的诊断及鉴别诊断中具有很高的应用价值,低灌注、肿瘤实质区出现高耸的 Lip 峰是原发性颅内淋巴瘤的特征性表现。     

1H-MRS在细菌性脑脓肿中的应用研究

目的 回顾性分析细菌性脑脓肿氢质子磁共振波谱（^1H-MRS）特征,评价^1H-MRS在细菌性脑脓肿诊断和疗效监测中的应用价值。资料与方法 经病理组织学证实的细菌性脑脓肿20例,17例^1H-MRS有能分辨的信噪比（SNR）,点分辨波谱（PRESS）序列采集病灶中心,比较分析代谢物出现概率。结果 （1）17例细菌性脑脓肿：耳源性2例,肺源性3例,心源性2例,隐源性5例,其他5例。（2）15例细菌性脑脓肿有氨基酸（AA）峰,敏感性88．23％,特异性100％。另2例仅有乳酸（Lac）或脂质（Lip）峰。9例乙酸盐（Ace）峰,敏感性52．3％;7例琥珀酸盐（Sue）峰,敏感性41．2％;6例丙氨酸（Ah）峰,敏感性35．3％;Lip峰和胆碱（Cho）、氮-乙酰天门冬氨酸（NAA）、肌酸（Cr）／磷酸肌酸（PCr）峰各3例。（3）8例平均治疗38d后^1H-MRS复查,从峰和Ace峰降低或消失,仅剩Lae峰。（4）细菌性脑脓肿有两种波谱模式：一种是除了从峰、Lac峰,还有Ace峰、Sue峰或Ah峰（12例）;另一种是仅有从、Lac峰,而没有Ace峰、Sue峰或Ala峰（3例）。结论 从峰是细菌性脑脓肿特征性的峰;^1H-MRS能反映细菌性脑脓肿的疗效;脓肿不同波谱模式可能提示不同的细菌感染。     

鞍旁海绵状血管瘤的CT和MRI诊断

目的总结7例鞍旁海绵状血管瘤CT、MRI和磁共振波谱（MRS）表现,探讨其诊断和鉴别诊断。资料与方法7例均经手术病理证实,均行CT和MR平扫,2例行CT增强扫描,7例行MR增强扫描,5例行MR扩散加权成像（DWI）,6例行^1H MRS检查。结果鞍旁海绵状血管瘤体积大,并同时伸入到鞍内。CT平扫病变呈等或稍高密度,密度均匀,MR T1WI呈等或稍低于脑灰质信号,T2WI呈类似脑脊液高信号。增强扫描病变呈非常显著强化。DWI呈等或稍低信号,但表观扩散系数（ADC）值明显高于正常脑实质。。HMRS表现为NAA峰、Cr峰和Cho峰消失。可出现Lip峰。结论CT检查时鞍旁海绵状血管瘤与脑膜瘤和垂体瘤鉴别困难,MRI表现很有特点,T2WI呈极高信号,增强扫描非常显著强化,ADC值明显升高而DWI接近等信号,MRS检查无NAA峰、Cr峰和Cho峰,MRI可以对海绵窦海绵状血管瘤作出定性诊断。     

常规MRI联合MR脑血管成像在围产期脑后部可逆性脑病综合征中的应用研究

目的：探讨常规磁共振成像（MRI）联合MR脑血管成像在围产期脑后部可逆性脑病综合征（PRES）诊断和鉴别诊断中的应用价值。方法：5例围产期PRES患者,平均年龄为26.5岁,且均于起病后2 d内行常规MRI和MR脑血管成像,MR脑血管成像包括MR脑动脉成像（MRA）和MR脑静脉成像（MRV）。结果：病变均累及双侧顶枕叶,另累及额叶2例,基底节区2例,桥脑1例,病变占位效应不明显。病变主要位于皮层下白质,其中1例累及皮质。病变T1WI呈低、等信号,T2WI及液体衰减反转恢复序列（FLAIR）呈高信号。3例磁共振扩散加权成像（DWI）呈等信号,表观扩散系数（ADC）图为高信号,另2例部分病变DWI为高或稍高信号。增强扫描以上病变未见明确强化,MRA、MRV未见明确异常。结论：围产期RPES的MRI表现较具特征性,常规MRI联合MR脑血管成像有助于本病的早期诊断和鉴别诊断。     

1H-MRS联合DCE-MRI在乳腺癌中的应用价值

目的：探讨MR氢质子波谱（^1H-MRS）联合动态增强磁共振成像检查（DCE-MRI）在乳腺癌中的临床应用价值。材料和方法：38例临床疑似乳腺肿瘤患者行DCE-MRI和^1H-MRS检查,分析病灶时间-信号强度曲线及MRS表现,并与病理结果比较,判断DCE-MRI和MRS诊断乳腺癌的敏感性、特异性和准确性。结果：手术病理证实乳腺癌20例,良性肿瘤18例。20例乳腺癌中,2例时间-信号强度曲线呈缓慢上升型（Ⅰ型）,6例呈上升平台型（Ⅱ型）,12例呈快进快出型（Ⅲ型）;MRS检查11例出现胆碱峰。18例良性肿瘤中,12例时间-信号强度曲线呈Ⅰ型,6例呈Ⅱ型;MRS检查3例出现胆碱峰。时间-信号强度曲线诊断的敏感性为90.0%,特异性66.7%,准确性78.9%;胆碱峰诊断乳腺癌的敏感性55.0%,特异性83.3%,准确性68.4%;两者相结合诊断的敏感性为100%,特异性66.7%,准确性84.2%。结论：由于病灶本身和技术等因素,胆碱峰单独诊断乳腺癌的敏感性较低,联合时间-信号强度曲线表现可提高乳腺癌诊断的敏感性和准确性。     

大脑胶质瘤病磁共振成像结合磁共振波谱成像的诊断价值

目的：探讨磁共振成像（MRI）结合磁共振波谱成像（MRS）对大脑胶质瘤病的诊断价值。方法对15例经活体组织检查或手术病理证实的大脑胶质瘤病患者的临床表现及MRI平扫、增强,MRS影像学资料进行回顾性分析。MRI常规行T1WI、T2WI及FLAIR序列,采用时间飞跃法（TOF）的磁共振血管成像（MRA）,T1WI增强扫描。氢质子MRS采用单体素STEAM序列,并分析N-乙酰天门冬氨酸（NAA）、肌酸（Cr）、胆碱复合物（Cho）等物质峰值改变。结果所有病例均侵犯2个或2个以上脑叶,以颞叶、枕叶、胼胝体、基底节和丘脑等部位侵犯受累常见。病变区T1WI呈低或等低信号、T2WI呈高或混杂高信号、FLAIR上为高信号,未见明显坏死、钙化,受累区域脑组织肿胀,占位效应轻。注射钆喷酸葡胺增强扫描示10例无明显强化、3例斑片状强化、1例结节状强化、1例线状轻度强化。病变区域MRS表现为不同程度NAA降低,NAA/Cr比值降低;Cho上升,Cho/Cr和Cho/NAA的比值上升。结论 MRI结合MRS对大脑胶质瘤病的诊断及鉴别诊断具有临床价值,是目前诊断大脑胶质瘤病的首选影像学方法。     

颅内囊性病变1 H MR波谱分析

目的分析颅内囊性病变^1H磁共振波谱（^1HMRS）成像特征，评价。HMRS在颅内囊性病变中的应用价值。方法52例颅内囊性病变，单体素^1HMRS采集52个病灶，其中Ⅰ-Ⅱ级星形细胞瘤8例、胶质母细胞瘤9例、转移瘤13例、脑脓肿10例、表皮样囊肿4例、蛛网膜囊肿5例、脑囊虫病3例。点分辨波谱（PRESS，TE135ms或270ms）定域序列采集病灶中心。结果（1）8例Ⅰ-Ⅱ级星形细胞瘤仅显示乳酸（Lae）峰。9例胶质母细胞瘤除了显示Lac峰外，有4例显示了低的胆碱类复合物（Cho）和氮-乙酰天冬氨酸（NAA）峰，2例显示脂质（Lip）峰。（2）转移瘤13例，7例仅显示Lae峰，6例显示Cho峰，3例显示低的NAA峰，6例显示Lip峰。（3）10例脑脓肿除了显示Lac峰，9例显示氨基酸（AA）峰，6例显示乙酸盐（Ace）峰，5例显示琥珀酸盐（Sue）峰，5例显示丙氨酸（ma）峰，2例显示Lip峰；没有显示Cho和NAA峰。（4）4例表皮样囊肿显示Lae峰，1例显示Lip峰。5例蛛网膜囊肿中2例显示低的Lae峰，1例显示Lip峰。脑囊虫病3例，显示Lac、Ace、Sue、ma峰；没有显示AA、Cho和NAA峰。结论颅内囊性病变共有Lae峰，没有特异性。AA峰结合Ace、Sue、ma峰的显示对脑脓肿诊断特异性高。Ace、Sue、AJa峰的显示提示脑寄生虫囊肿存在的可能性。MRI结合MRS有助于对颅内囊性病变的定性诊断。     

^1H-MRS联合DCE-MRI扫描在乳腺癌诊断中的临床价值

磁共振氢质子波谱（^1H-MRS）中胆碱峰的升高有助于判断肿瘤的良恶性，而动态增强磁共振成像（DCE-MRI）技术可动态观察乳腺疾病的血流动力学变化，两者的联合应用有望提高乳腺癌诊断的敏感性和特异性。就^1H-MRS联合DCE-MRI扫描在乳腺癌诊断中的临床价值予以综述。     

磁共振DWI和ADC值在包膜期脑脓肿与坏死囊变性脑肿瘤鉴别诊断中的应用

目的探讨磁共振扩散加权成像(DWI)及表观扩散系数(ADC)值在包膜期脑脓肿与坏死囊变脑肿瘤鉴别中的临床应用价值。方法经手术病理证实的包膜期脑脓肿15例和坏死囊变脑肿瘤20例患者均经常规MRI扫描和DWI扫描,对比分析包膜期脑脓肿及坏死囊变脑肿瘤的DWI和ADC图表现,并测量脑脓肿脓腔及脑肿瘤坏死囊变区内的平均ADC值,进行统计学分析。结果包膜期脑脓肿脓腔在DWI上表现为高信号,ADC图呈低信号;脑肿瘤坏死囊变区在DWI上表现为低信号,ADC图呈高信号。所有脑脓肿的平均ADC值为(0.69±0.18)×10-3mm2/s,坏死囊变脑肿瘤的平均ADC值为(2.43±0.16)×10-3mm2/s,两者比较有显著性差异(P<0.01)。结论 DWI与ADC值测量能准确反映包膜期脑脓肿与坏死囊变脑肿瘤的不同液态性质,对其鉴别诊断有重要价值。     

Role of diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of ring-enhancing intracranial cystic mass lesions

OBJECTIVES: Proton magnetic resonance spectroscopy (PMRS) and diffusion-weighted imaging (DWI) were compared to determine which technique is more effective in the differential diagnosis of cystic intraparenchymal ring-enhancing lesions with variable perifocal edema. METHODS: Fifty-two patients (abscesses [n = 29], tumor cysts [n = 20], and benign cysts [n = 3]) formed the basis for comparative evaluation in this study. The criteria for abscess diagnosis were apparent diffusion coefficient (ADC) values less than 0.9 +/- 1.3 x 10 mm/s and presence of lactate cytosolic amino acids (AAs) with/without succinate, acetate, alanine, and glycine on PMRS. Criteria for nonabscess cyst identification were ADC values of 1.7-3.8 x 10 mm/s and presence of lactate and choline on PMRS. On the basis of these criteria, patients were categorized into abscess (n = 29) and nonabscess (n = 23) groups. Sensitivity and specificity of PMRS and DWI with respect to the final diagnosis were calculated based on the efficacy of these techniques. RESULTS:: Apparent diffusion coefficient values in 21 patients with abscesses were observed within the range of defined criteria, whereas in 8 patients, ADC values were beyond the range of defined criteria. Lactate and AAs with or without other metabolites were observed in 25 of 29 cases of abscesses on PMRS. In the nonabscess group, ADC values of cystic lesions in all patients were consistent with respect to the defined criteria. Only lactate was seen in 14 of 23 patients, whereas both lactate and choline were visible in 6 patients. In 3 patients with neurocysticercosis, AAs (n = 2), lactate (n = 3), acetate (n = 1), succinate (n = 3), choline (n = 2), and alanine (n = 3) were seen. The sensitivity of DWI and PMRS for differentiation of brain abscess from nonbrain abscess was 0.72 and 0.96, respectively, whereas the specificity was 1 for both techniques. CONCLUSION: Demonstration of restricted diffusion on DWI with reduced ADC is highly suggestive of brain abscess; however, in the absence of restriction, PMRS is mandatory to distinguish brain abscesses from cystic tumors.     

Role of diffusion-weighted MR in differential diagnosis of intracranial cystic lesions

AIM: The purpose of this study was to evaluate the role of diffusion-weighted imaging (DWI) in characterizing cerebral cystic lesions. The usefulness of the apparent diffusion coefficient (ADC) map in lesion characterization was also evaluated. METHODS: We compared the findings of conventional MR images with those of DWI: 63 cystic masses in 48 patients were examined with routine MR imaging and echo-planar DWI. The routine MR imaging included at least the axial T2- and T1-weighted sequences, and post-contrast T1 axial sequences. The DWI included an echo-planar spin-echo sequence with three values (0, 500 and 1000s/mm(2)) sensitizing gradient in the x, y, z direction, and it obtained an ADC map. RESULTS: The sensitivity of DWI for differentiating abscesses from primary brain tumours was 100%; for differentiating abscesses from metastatic tumours was 73%; for differentiating benign from malignant lesions was 90%. CONCLUSION: Although some metastatic lesions may appear hyperintense on DWI thus imitating an abscess, evaluation of the lesions with both DWI and conventional MRI may have an important contribution to the differentiation of tumours from abscesses.     

Diffusion-weighted imaging of fungal cerebral infection

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) is useful in diagnosing bacterial brain abscesses, but DWI features of fungal brain abscesses have not been characterized. Because fungal abscesses are not purulent, we hypothesized that their DWI characteristics are distinct from those of bacterial abscesses. METHODS: We reviewed clinical, neuropathologic and neuroimaging findings of patients with fungal brain infections due to Aspergillus (n = 6), Rhizopus (n = 1), or Scedosporium (n = 1) species. DWI and apparent diffusion coefficient (ADC) maps were obtained before definitive diagnosis and antifungal therapy. ADC ratios (lesion/contralateral white matter) were calculated. RESULTS: Two patients had a rapidly progressive, fatal course, with cerebritis and acute inflammation; fungal organisms were largely restricted to vessels. Lesions were predominantly nonenhancing and had heterogeneous foci of restricted diffusion. Six patients with subacute neurologic presentations had acute or chronic inflammation, capsule formation, focal necrosis, and fungal organisms disseminated throughout the lesion. Their abscesses were ring enhancing. In five, lesions had restricted diffusion in the central nonenhancing portions. The sixth patient had a lesion with a peripheral rim of restricted diffusion but elevated central diffusion; histopathology showed early abscess formation. Mean ADC for all lesions was 0.33 +/- 0.06 x 10(-3) mm(2)/s, with an average ADC ratio of 0.43. CONCLUSION: Fungal cerebral abscesses may have central restricted diffusion similar to that of bacterial abscesses but with histologic features of acute or chronic inflammation and necrosis rather than suppuration. Altered water diffusion in these lesions likely reflects highly proteinaceous fluid and cellular infiltration.     

脑结节性硬化的MR DWI分析

目的:使用磁共振扩散加权成像(DWI)研究结节性硬化(TS)患者脑灰质和白质内病灶的扩散特点,并观察表观扩散系数(ADC)的变化。方法:对18例临床影像学诊断的TS患儿使用1.5TMR系统行DWI检查,测量大脑皮质和皮质下61个结节的ADC值和对照组15例正常儿童的正常白质的ADC值。结果:TS患儿大脑皮质和白质病灶的ADC值明显高于健康儿童正常脑白质的ADC值,两者存在统计学差异(P<0.001)。其中4例TS伴发的室管膜下巨细胞星形细胞瘤ADC值与正常脑实质的相似,两者无统计学差异(P>0.05)。结论:DWI可提供TS患儿脑皮质和白质病灶的病理信息,TS脑白质内结节灶的高ADC值可区别常规MRI检查T1WI和T2WI信号与TS相似的其他疾病结节状病灶。     

Marchiafava-Bignami病的磁共振DWI、DTI初步研究

目的：探讨磁共振弥散加权成像（DwI）、弥散张量成像（DTI）对Marchiafava_Bignami（MBD）的诊断及预后评价的价值。方法：对10例MBD患者行DWI检查,其中4例再行DTI检查。结果：本组急性型8例,DWI显示病灶区信号明显增高,并有4例出现弥散受限改变;胼胝体膝部、压部的各向异性分数（FA）值与正常值比较差异有统计学意义（P〈O．05）,额叶白质、半卵圆中心白质与正常值比较差异也有统计学意义（P〈O．05）。结论：MBD的DWI、DTI改变可能反映其临床及预后。     

DWI和~1H-MRS在肝纤维化中的诊断价值

目的:探讨扩散加权成像(DWI)与氢质子波谱分析(1 H-MRS)在肝纤维化中的诊断价值。方法:使用腹腔注射CCl4溶液法诱导建立兔肝纤维化模型并进行DWI和1 H-MRS检查。DWI使用SE-EPI序列(b1=0s/mm2,b2=600s/mm2),1 H-MRS使用单体素点分辨波谱分析(PRESS)序列(TR 1500ms,TE 35ms),测量表观扩散系数(ADC)值及胆碱(Cho)和脂质(lipid)波峰下面积的比值(Cho/lipid)。以病理学肝纤维化分期为基础,将兔划分为无肝纤维化组(S0)、轻度-中度纤维化组(S1-S2)和重度纤维化及肝硬化组(S3-S4),比较不同组间ADC值和Cho/lipid变化规律。结果:随肝纤维化程度加重,ADC值依次降低(P<0.01),Cho/lipid依次升高(P<0.05);重度纤维化及肝硬化组与另两组ADC值及Cho/lipid差异均具有统计学意义(P均<0.05)。结论:DWI和1 H-MRS具备一定的定量肝纤维化及检测重度纤维化及肝硬化的能力。     

双b值扩散加权成像在脑梗死诊断中的应用

目的:比较双b值DWI对脑梗死体积及ADC值测量的影响,探讨较高b值DWI在脑梗死诊断中的应用价值。方法:回顾性研究30例脑梗死患者,年龄44～84岁,平均67岁,发病时间3～6d,DWI取b值1000和2000s/mm2,分析脑梗死DWI及ADC图,测量兴趣区与对侧正常部位的扩散系数(ADC)并计算相对扩散系数(rADC),测量并计算梗死灶体积。结果:急性和亚急性脑梗死灶均扩散受限,DWI呈高信号、ADC图呈低信号。与b值1000s/mm2相比,b值2000s/mm2DWI示脑灰白质对比度增加,病灶显示更清晰,还能发现新病灶。不同b值下rADC比较没有统计学意义(P=0.884,P>0.05),同侧ADC有统计学意义(P=0.005,P<0.05);对侧ADC有显著统计学意义(P<0.001)。较高b值下梗死体积较低b值增加,且有统计学意义(P=0.04,P<0.05)。结论:DWI是检测脑梗死的重要技术手段,rADC不受b值影响,rADC降低可指导脑梗死诊断;较高b值DWI上脑梗死灶体积测量更准确,有利于观察病灶演变和指导临床治疗。     

Diffusion-weighted MRI features of brain abscess and cystic or necrotic brain tumors: comparison with conventional MRI

BACKGROUND AND PURPOSE: The purpose of this study was to determine whether diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) can be used to distinguish brain abscesses from cystic or necrotic brain tumors, which are difficult to distinguish by conventional magnetic resonance imaging (MRI) techniques. METHODS: Eleven consecutive patients with brain abscesses [10 pyogenic and 1 toxoplasmosis (in an AIDS patient)] and 15 with cystic or necrotic brain gliomas or metastases were enrolled in this study. None of these lesions had apparent hemorrhage based on T1-weighted image (T1WI). The DWI was performed using a 1.5-T system, single-shot spin-echo echo-planar pulse sequence with b=1000 s/mm(2). The ADC was calculated using a two-point linear regression method at b=0 and b=1000 s/mm(2). The ratio (ADCR) of the lesion ADC to control region ADC was also measured. RESULTS: Increased signal was seen in all of the pyogenic abscess cavities to variable degrees on DWI. In vivo ADC maps showed restricted diffusion in the abscess cavity in all pyogenic abscesses [0.65+/-0.16 x 10(-3) (mean+/-S.D.) mm(2)/s, mean ADCR=0.63]. The case with multiple toxoplasmosis abscesses showed low signal intensity on DWI and high ADC values (mean 1.9 x 10(-3) mm(2)/s, ADCR=2.24). All cystic or necrotic tumors but one showed low signal intensity on DWI and their cystic or necrotic areas had high ADC values (2.70+/-0.31 x 10(-3) mm(2)/s, mean ADCR=3.42). One fibrillary low-grade astrocytoma had a high DWI signal intensity and a low ADC value in its central cystic area (0.44 x 10(-3) mm(2)/s, ADCR=0.49). Postcontrast T1WIs yielded a sensitivity of 60%, a specificity of 27.27%, a positive predictive value (PPV) of 52.94%, and a negative predictive value (NPV) of 33.33% in the diagnosis of necrotic tumors. DWI yielded a sensitivity of 93.33%, a specificity of 90.91%, a PPV of 93.33%, and a NPV of 90.91%. The area under receiver operating characteristic (ROC) curves for postcontrast T1WI was 0.44 and DWI was 0.92. Analysis of these areas under the ROC curves indicates significant difference between postcontrast T1WI and DWI (P<.001). CONCLUSION: With some exceptions, DWI is useful in providing a greater degree of confidence in distinguishing brain abscesses from cystic or necrotic brain tumors than conventional MRI and seems to be a valuable diagnostic tool.     

Role of diffusion-weighted echo-planar MRI in distinguishing between brain abscess and tumour: a preliminary report

Our purpose was to evaluate diffusion-weighted (DW) echo-planar MRI in differentiating between brain abscess and tumour. We examined two patients with surgically confirmed pyogenic brain abscess and 18 with metastatic brain tumours or high-grade glioma, using a 1.5 T system. The apparent diffusion coefficient (ADC) of each necrotic or solid contrast-enhancing lesion was measured with two different b values (20 and 1200 s/mm²). All capsule-stage brain abscesses (4 lesions) and zones of cerebritis (2 lesions) were identified on high-b-value DWI as markedly high-signal areas of decreased ADC (range, 0.58–0.70 [(10–3 mm²/s; mean, 0.63)]). All cystic or necrotic portions of brain tumours (14 lesions) were identified on high-b-value DWI as low-signal areas of increased ADC (range, 2.20–3.20 [(10–3 mm²/s; mean, 2.70)]). Solid, contrast-enhancing portions of brain tumours (19 lesions) were identified on high-b-value DWI as high-signal areas of sightly decreased or increased ADC (range, 0.77–1.29 [(10–3 mm²/s; mean, 0.94)]). Our preliminary results indicate that DW echo-planar MRI be used for distinguishing between brain abscess and tumour. Received: 23 January 1998 Accepted: 5 June 1998     

Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging

BACKGROUND AND PURPOSE: Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or MR imaging. We compared findings of proton MR spectroscopy ((1)H-MRS) with those of diffusion-weighted imaging to determine which technique was more effective for this differential diagnosis. METHODS: Fourteen patients (necrotic or cystic tumor [n = 7]; pyogenic abscess [n = 7]) who underwent 1.5-T (1)H-MRS and diffusion-weighted imaging and had findings of ring-shaped enhancement after contrast agent administration were enrolled in this study. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 1000 s/mm(2)). The apparent diffusion coefficient and ratio were also measured. RESULTS: Spectra for two patients were unacceptable because of either poor shimming conditions or contamination from neighboring fat. Spectra in three of five patients with abscess had lactate, amino acids (including valine, alanine, and leucine), and acetate peaks; one of the three spectra had an additional peak of succinate. In one patient with abscess treated by antibiotics, only lactate and lipid peaks were detected. Spectra for four of seven patients with cystic or necrotic tumors showed only lactate peaks. Lactate and lipids were found in three patients with tumors. Hyperintensity was seen in all the pyogenic abscess cavities and hypointensity in all the cystic and necrotic tumors on diffusion-weighted images. CONCLUSION: (1)H-MRS and diffusion-weighted imaging are useful for differentiating brain abscess from brain tumor, but the latter requires less time and is more accurate than is (1)H-MRS. (1)H-MRS is probably more limited in cases of smaller peripheral lesions, skull base lesions, and treated abscesses.