扩散系数值在脑星形细胞肿瘤病理学分级中的应用

目的探讨扩散系数值对脑星形细胞肿瘤病理学分级的应用价值。方法对56例脑星形细胞肿瘤进行扩散加权成像（DWI）检查，分别测量肿瘤实质部分、瘤周水肿区、瘤周T1WI正常表现白质区（瘤周白质区）、瘤体镜面对侧正常白质区及瘤周镜面对侧正常白质区的表观扩散系数（ADC）值和指数扩散系数（EDC）值，并计算肿瘤实质部分、瘤周水肿区、瘤周白质区的相对表观扩散系数（rADC）值和相对指数扩散系数（rEDC）值。分析各测量区的扩散系数值与肿瘤病理学分级的关系。结果56例脑星形细胞肿瘤经手术病理证实，低级星形细胞瘤35例（Ⅰ、Ⅱ级），间变性星形细胞瘤8例（Ⅲ级），胶质母细胞瘤13例（Ⅳ级）。低级星形细胞瘤、间变性星形细胞瘤和胶质母细胞瘤肿瘤实质部分的ADC值分别为（1．44±0．26）×10^-3、（0．98±0．22）×10^-3和（0．83±0．15）×10^-3mm^2／s，rADC值分别为（1．91±0．39）％、（1．34±0．33）％和（1．06±0．20）％，EDC值分别为0．26±0．11、0．39±0．09和0．44±0．07，rEDC值分别为（0．55±0．20）％、（0．81±0．19）％和（0．98±0．16）％，各指标间差异均有统计学意义（F值分别为36．189、31．756、19．623和24．760，P值均为0．000）。高级星形细胞瘤（间变性星形细胞瘤和胶质母细胞瘤）的肿瘤实质部分的ADC值和rADC值分别为（0．89±0．19）×10^-3mm^2／s和（1．17±0．28）％，明显低于低级星形细胞瘤（t值分别为8．332和7．620，P值均为0．000），EDC值和rEDC值分别为0．42±0．08和（0．91±0．18）％，明显高于低级星形细胞瘤（t值分别为-6．082和-6．776，P值均为0．000）。以低级星形细胞瘤实质部分的rADC值的下限（1．52％）作为判断低、高级别星形细胞瘤阈值的准确性为89．3％。结论肿瘤实质部分的扩散系数值对脑星形细胞肿瘤的病理学分级准确性较高，尤以rADC值为佳。     

Frequency and clinical context of decreased apparent diffusion coefficient reversal in the human brain

PURPOSE: To determine the probability that regions of decreased apparent diffusion coefficient (ADC) return to normal without persistent symptoms or T2 change and the settings in which these ADC reversals occur. MATERIALS AND METHODS: Three hundred magnetic resonance (MR) imaging studies were selected at random from a database of 7,147 examinations to determine the probability of a pathologically decreased ADC. In cases with decreased ADC, the clinical history was recorded and, if available, follow-up MR imaging findings were evaluated. Five cases of ADC reversal became known during the same period and were evaluated to determine the initial ADC decrease, clinical outcome, and findings at follow-up imaging. RESULTS: Findings in 116 of 300 MR imaging studies revealed regions of decreased ADC. In 49 of 116 studies, follow-up MR imaging examinations were performed at least 4 weeks after the onset of symptoms; ADC did not reverse. Five cases of ADC reversal were identified in the same period, giving an estimated 0.2%-0.4% probability of ADC reversal. Clinical settings were venous sinus thrombosis and seizure (n = 3), hemiplegic migraine (n = 1), and hyperacute arterial infarction (n = 1). Both white matter (n = 3) and gray matter (n = 3) regions were involved. CONCLUSION: Reversal of ADC lesions is rare, occurs in complicated clinical settings, and can involve white or gray matter.     

Malignant astrocytic tumors: clinical importance of apparent diffusion coefficient in prediction of grade and prognosis

PURPOSE: To retrospectively assess the apparent diffusion coefficient (ADC) for prediction of malignancy and prognosis of malignant astrocytic tumors. MATERIALS AND METHODS: The institutional review board approved this study and did not require patient informed consent. Findings from 37 consecutive patients (21 men, 16 women; mean age, 43 years) with pathologically proved malignant astrocytic tumors that included 22 glioblastomas (GBMs) and 15 anaplastic astrocytomas (AAs) were retrospectively evaluated. The minimum ADC value of each tumor was preoperatively determined from several regions of interest defined in the tumor, preferably with avoidance of cystic or necrotic components, on ADC maps derived from isotropic diffusion-weighted images. Surgical intervention, followed by radiation therapy, was undertaken in all cases according to hospital protocol. Immunohistologically, Ki-67 labeling index (LI), indicating cell proliferation, was also determined. The patients were classified into two groups, progressive and stable, according to the 2-year observation after the initial treatment. Correlation analysis (Pearson product moment correlation), Student t test, Welch test, receiver operating characteristic analysis, and Kaplan-Meier method with log-rank test were used for statistical evaluation. RESULTS: There was a significant negative correlation between minimum ADC and Ki-67 LI (r = -0.562, P < .001). The mean minimum ADC (0.834 x 10(-3) mm2 x sec(-1)) of GBM was significantly lower than that (1.06 x 10(-3) mm2 x sec(-1)) of AA (P < .001, Student t test). The mean minimum ADC (0.80 x 10(-3) mm2 x sec(-1)) of the progressive group was significantly lower than that (1.037 x 10(-3) mm2 x sec(-1)) of the stable group (P < .001). The cutoff value of 0.90 x 10(-3) mm2 x sec(-1) for minimum ADC for differentiation of patients with a favorable prognosis from those with a poor prognosis provided the best combination of sensitivity (79%) and specificity (81%) (receiver operating characteristic analysis). The significant difference in the prognosis between two groups classified by using this cutoff value of minimum ADC was noted (P = .002, log-rank test). Conclusion: The minimum ADC of malignant astrocytomas can provide additional information about their clinical malignancy related to posttreatment prognosis.     

A change in the apparent diffusion coefficient after treatment with bevacizumab is associated with decreased survival in patients with recurrent glioblastoma multiforme

Objectives

The aim of this study was to determine the prognostic significance of changes in parameters derived from diffusion tensor imaging (DTI) that occur in response to treatment with bevacizumab and irinotecan in patients with recurrent glioblastoma multiforme.

Methods

15 patients with recurrent glioblastoma multiforme underwent serial 1.5 T MRI. Axial single-shot echo planar DTI was obtained on scans performed 3 days and 1 day prior to and 6 weeks after initiation of therapy with bevacizumab and irinotecan. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps were registered to whole brain contrast-enhanced three-dimensional (3D) spoiled gradient recalled and 3D fluid attenuation inversion recovery (FLAIR) image volumes. Anatomic image volumes were segmented to isolate regions of interest defined by tumour-related enhancement (TRE) and FLAIR signal abnormality (FSA). Mean ADC and mean FA were calculated for each region. A Bland–Altman repeatability coefficient was also calculated for each parameter based on the two pre-treatment studies. A patient was considered to have a change in FA or ADC after therapy if the difference between the pre- and post-treatment values was greater than the repeatability coefficient for that parameter. Survival was compared using a Cox proportional hazard model.

Results

DTI detected a change in ADC within FSA after therapy in nine patients (five in whom ADC was increased; four in whom it was decreased). Patients with a change in ADC within FSA had significantly shorter overall survival (p=0.032) and progression free survival (p=0.046) than those with no change.

Conclusion

In patients with recurrent glioblastoma multiforme treated with bevacizumab and irinotecan, a change in ADC after therapy in FSA is associated with decreased survival.Genotypic heterogeneity within histologically indistinguishable tumours remains a major barrier to successful treatment of patients with high-grade primary brain tumours [1]. Because of this heterogeneity, only a minority of individual tumours are likely to respond to any given chemotherapeutic agent [2]. Early identification of non-responders would allow potentially more effective therapy to be instituted while minimising the morbidity and financial cost associated with prolonged, ineffective treatment. Current assessment of therapeutic efficacy relies on changes in cross-sectional area estimated weeks to months after the completion of a treatment protocol [3,4]. Unfortunately, patients with aggressive tumours may experience significant disease progression with related morbidity and mortality before therapy can be evaluated and altered using this approach. Biomarkers of treatment response that are independent of late changes in tumour volume will be crucial for optimal treatment of this patient group.Diffusion-weighted MRI (DWI) can be used to characterise early tissue microstructural changes associated with cell death [4,5]. Since parameters derived from DWI can provide a quantitative assessment of such effects, there is increasing interest in this technique as a biomarker of therapeutic efficacy. Although there is good evidence that DWI can be used to characterise treatment effects, the optimal parameter and region of interest are yet to be determined [4,6-12].The preponderance of studies on this subject has quantified the apparent diffusion coefficient (ADC) within regions of interest defined by abnormal tumour-related enhancement [6,9,11]. In vivo, the ADC is primarily determined by cell density [4,8,13,14]. As a result, changes in the ADC are sensitive to early alterations in tissue microstructure related to cell death; these changes include cell swelling and loss of membrane integrity associated with early necrosis as well as cell shrinkage due to apoptosis [11,15]. Indeed, it has been demonstrated that changes in the ADC within enhancing regions of interest can be used to identify the response to chemotherapy earlier than standard MRI [9]. Recent evidence, however, suggests the importance of non-enhancing, infiltrative tumour, as defined on fluid attenuation inversion recovery (FLAIR) images, with respect to tumour progression [16,17]. This non-enhancing component of tumour seems to be of particular relevance to patients treated with anti-angiogenesis agents [16,17]. Since the ADC is sensitive to variations in vasogenic oedema (increasing oedema tends to decrease cell density), in addition to the aforementioned direct effects on tumour cells, we hypothesise that the ADC would be an ideal parameter to characterise the effects of treatment within regions of interest defined by abnormal tumour-related FLAIR signals.Although there are few data in patients with brain tumours, there is some evidence that parameters of diffusion anisotropy derived from diffusion tensor imaging (DTI) may more accurately depict early changes in brain tissue microstructure than the ADC in central nervous system (CNS) diseases [18]. Fractional anisotropy (FA) is a measure of the degree of directional variation of the diffusion of water protons. Like the ADC, FA has been shown to correlate with cell density [7,18,19], but FA provides additional information regarding the integrity and alignment of parenchymal fibre tracts [20]. A recent study in patients with primary brain tumours demonstrated increasing FA across the study population within regions of interest defined by tumour-related contrast enhancement as early as 1 day after initiation of chemotherapy [12]. This same study failed to detect a significant change in the ADC at the same time point, raising the possibility that FA may be a more sensitive parameter to early treatment response.Although these preliminary results are promising, the significance of such changes with respect to patient survival has not been widely studied. In addition, there are very few data regarding the test–retest reproducibility of these parameters in patients with primary brain tumours, information which is crucial for understanding whether changes in these parameters can be used to guide therapy. In particular, an understanding of the magnitude of variability intrinsic to the method will be required to ascribe significance to changes in these parameters that occur after therapy in an individual patient.The goal of this study is to use the repeatability of ADC and FA derived from DTI to devise a method by which prognostic significance can be assigned to changes in these parameters that occur after therapy in patients with glioblastoma multiforme. In particular, we prospectively identified the following two null hypotheses:

• Patients with an increase in FA within regions of interest defined by tumour-related enhancement will not survive longer than those with no change or a decrease in FA.
• Patients with a change in ADC within regions of interest defined by an abnormal FLAIR signal will not survive longer than those with no change.

Although it may seem counterintuitive to evaluate the significance of any change in the ADC without respect for direction, there is evidence that both increasing and decreasing the ADC may reflect a clinically relevant treatment response [9,11].     

Correlation of early reduction in the apparent diffusion coefficient of water with blood flow reduction during middle cerebral artery occlusion in rats

To determine the relationship between reductions in the apparent diffusion coefficient of water (ADC) and in cerebral blood flow (CBF) during focal ischemia, we used diffusion-weighted magnetic resonance (D-MR) imaging and autoradiographic CBF analysis to examine rats subjected to 30 or 90 min of permanent middle cerebral artery (MCA) occlusion. In the 30-min occlusion group (n = 10), the area with substantially reduced ADC (15% or more below the contralateral level [ADC₁₅]) corresponded best to the area with CBF below 25 ml/100 g/min and was significantly smaller than the area with CBF below 50 ml/100 g/min (CBF₅₀), a level associated with reduced protein synthesis and delayed necrosis (40 ± 13% versus 74 ± 8% of the ischemic hemisphere; P < 0.0001). In the 90-min occlusion group (n = 6), the ADC₁₅ area corresponded best to the CBF₃₀ to CBF₃₅ area and was again significantly smaller than the CBF₅₀ area (54 ± 13% versus 73 ± 20%, P < 0.05). Thus, the area of substantially reduced ADC at 30 and 90 min represents only 53% and 74%, respectively, of the tissue at risk for infarction. These findings indicate a potential limitation in using early D-MR imaging to predict stroke outcome.     

Measurement of the apparent diffusion coefficient in paediatric mitochondrial encephalopathy cases and a comparison of parenchymal changes associated with the disease using follow-up diffusion coefficient measurements

Objectives

To reveal the contribution of MRI and diffusion-weighted imaging (DWI) to the diagnosis of mitochondrial encephalopathy (ME) and to evaluate the parenchymal changes associated with this disease in the involved parenchymal areas using the apparent diffusion coefficient (ADC) parameter.

Methods

Ten patients who had undergone MRI and DWI analysis with a pre-diagnosis of neurometabolic disease, and who were subsequently diagnosed with ME in laboratory and/or genetic studies, were included in our study. ADC values were compared with a control group composed of 20 patients of similar age with normal brains. Evaluations involved measurements made in 20 different areas determined on the ADC map. The dominance or contribution of ADC coefficient measurements to the conventional sequences was compared with the controls.

Results

In the first examination, an increase in both diffusion and ADC values was detected in six cases and diffusion restriction and a decrease in ADC values in three patients. While an increase in both diffusion and ADC values was demonstrated in four cases, there was diffusion restriction and a decrease in ADC values in three cases in the control examinations.

Conclusions

DWI provides information that complements conventional MRI sequences in the diagnosis of ME.     

Relationship between choline and apparent diffusion coefficient in patients with gliomas

PURPOSE: To examine the relationship between apparent diffusion coefficients (ADC) from diffusion weighted imaging (DWI) and choline levels from proton magnetic resonance spectroscopic imaging (MRSI) in newly diagnosed Grade II and IV gliomas within distinct anatomic regions. MATERIALS AND METHODS: A total of 37 patients with Grade II and 28 patients with Grade IV glioma were scanned on a 1.5T system with 3D MRSI and DWI. Region level analysis included Spearman rank correlation between median normalized ADC and choline for each patient per grade within each distinct abnormal anatomical region. Voxel level analysis calculated a Spearman rank correlation per region, per patient. RESULTS: Grade II lesions showed no evidence of a correlation between normalized ADC and choline using either the region or voxel level analysis. Region level analysis of Grade IV lesions did not appear to correlate in the contrast enhancement or necrotic core, but did suggest a significant negative correlation in the more heterogeneous nonenhancing and combined regions. CONCLUSION: There appears to be differences in the relationship between ADC and choline levels in Grade II and Grade IV gliomas. Correlation within these regions in Grade IV lesions was strongest when all regions were included, suggesting heterogeneity may be driving the relationship.     

Fat confounds the observed apparent diffusion coefficient in patients with hepatic steatosis

Purpose: Triglyceride signal contained in peaks near the water peak remains unsuppressed by conventional fat suppression techniques used in diffusion‐weighted imaging. In this work, we investigated the dependence of the apparent diffusion coefficient (ADC) on liver fat content and whether it is confounded by fat signal. Methods: 43 patients underwent liver diffusion‐weighted imaging (b = 0, 500 s/mm²) and single‐voxel MR‐spectroscopy. Proton density fat‐fraction (PDFF; range 0.23–34.5%) was measured from MR‐spectroscopy. A theoretical model was developed to account for the effects of fat on observed ADC, and used to correct the ADC. Linear correlation analysis was performed to assess the relationship between PDFF and ADC before and after correction. Results: Linear correlation analysis showed an inverse dependence between observed ADC and PDFF before correction (r² = 0.132; P = 0.017), and no dependence after correction (r² = 0.033; P = 0.24). Conclusion: The observed decrease in ADC in patients with fatty liver is, at least in part, artifactual due to residual fat signal near the water peak. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

不同类型正常乳腺表观扩散系数值差异的研究

目的 研究不同类型正常乳腺表观扩散系数（ADC）值的差异，探讨ADC值与组织学分型之间的关系。方法 采用单次激发平面回波（EPI）技术，扩散敏感因子（b）值分别为0、500、1000s／mm^2，对62个正常乳腺（包括42例乳腺病变患者的对侧正常乳腺及10名健康志愿者20个乳腺）进行MR扫描及MR扩散加权成像（DWI）检查，计算62个正常乳腺分别在不同b值时的ADC值。将62个正常乳腺分为3型，比较3型之间ADC值的差异及不同b值时ADC值的差异。结果 42例乳腺病变患者对侧正常乳腺的DWI及ADC图与组织切片对比，不同类型乳腺组织学结构不同，其DWI及ADC图表现亦有差异。62个正常乳腺分为致密型10个，分叶斑点型42个及退化型10个。致密型和分叶斑点型乳腺随b值降低ADC值升高，而退化型乳腺随b值降低ADC值变化不明显。b=1000—0s／mm^2时，致密型、分叶斑点型、退化型乳腺ADC值分别为（1．70±0．37）、（1．93±0．46）、（1．18±0．65）×10^-3mm^2／s，3组间比较差异有统计学意义（F=12．998，P=0．000）。不同b值时每2种类型间进行单因素方差分析，致密型和分叶斑点型之间差异无统计学意义（F=2．167，P=0．147）；致密型和退化型之间、分叶斑点型和退化型之间差异均有统计学意义（F值分别为5．593、19．128，P值分别为0．029、0．000）。结论 3型正常乳腺ADC值受乳腺组织学结构的影响，致密型和分叶斑点型乳腺ADC值受b值高低的影响。     

Longitudinal evaluation of apparent diffusion coefficient in children with neurofibromatosis type 1

OBJECTIVES: Foci of T2-prolongation in both supra- and infratentorial brain in neurofibromatosis type-1 (NF1) patients have been called hamartoma-like NF1 lesions (HLL); however, their behavior is not consistent with this definition. Diffusion-weighted imaging has been used to study structure and cellularity of intracranial lesions. We applied this technique to characterize HLL as they change with time in pediatric patients. METHODS: We retrospectively studied 12 children (ages 2-20 years) with proven NF1. Forty lesions were studied longitudinally on multiple exams for a total of 166 measurements. Apparent diffusion coefficients (ADCs) were also obtained from a comparison group comprising 14 normal children (ages 2-16 years). RESULTS: The ADC for the lesions was generally greater than normal brain. Both supra- and infratentorial lesions had increasing ADC with patient age. This is contrasted to our comparison group of normal subjects who showed decreasing ADC with age. Linear regression analysis of infratentorial lesions yielded a slope of 2.70 x 10(-6) mm2 x s(-1) x year(-1) versus a slope of 17.57 x 10(-6) mm2 x s(-1) x year(-1) for supratentorial lesions. CONCLUSIONS: Our observed increase in ADC of lesions in pediatric patients with NF1 suggests increasing water in the extracellular space and/or decreasing cellularity with patient age. This change may be due to increased number or size of myelin vacuoles in NF1 lesions. Supratentorial lesions had a statistically significant increase in the rate of change of ADC compared with infratentorial lesions which may reflect an intrinsic difference in the lesion or similar lesions expressed in different environments.     

Correlation of apparent diffusion coefficient with neuropsychological testing in temporal lobe epilepsy

BACKGROUND AND PURPOSE: Patients with nonlesional temporal lobe epilepsy have long been known to have abnormalities of memory. Recently, these patients have been shown to have increased diffusivity in the hippocampus. We hypothesized that in these patients, a negative correlation would exist between diffusivity measures of the mesial temporal lobe and performance on neuropsychological tests. METHODS: Twenty presurgical patients with temporal lobe epilepsy and 20 age- and sex-matched healthy controls underwent MR imaging of the brain. Apparent diffusion coefficient region of interest measures were taken in both hippocampi and parahippocampal gyri by 2 independent observers. Mean whole brain diffusivity was calculated. All patients completed neuropsychological testing. Electroencephalogram and pathology results were collected. Patients and controls were compared with respect to each apparent diffusion coefficient measure. In patients, apparent diffusion coefficients ipsilateral and contralateral to the seizure focus were compared. Associations were assessed between diffusivity measures and neuropsychological scores. RESULTS: Eleven patients had right-sided seizure foci and 9 had left-sided seizure foci. Patients demonstrated higher apparent diffusion coefficient values than controls over the whole brain, in the hippocampi, and in the parahippocampal gyri (P < .05). Patients demonstrated higher apparent diffusion coefficient within the ipsilateral hippocampus (1.19 +/- 0.22 x 10(-3) s/mm2) and parahippocampal gyrus (1.02 +/- 0.12 x 10(-3) s/mm2) compared with the contralateral side (1.02 +/- 0.16 x 10(-3) s/mm2 and 0.96 +/- 0.09 x 10(-3) s/mm2, respectively) (P < .05). Negative correlations were seen between hippocampal apparent diffusion coefficients and multiple memory tests (P < .05). CONCLUSION: Quantitative diffusion measurements in the hippocampus correlate with memory dysfunction in patients with temporal lobe epilepsy.     

弥散加权成像及表观弥散系数在前列腺病变诊断中的价值

目的：探讨弥散加权成像（DWI）及表观弥散系数（ADC）在前列腺病变诊断中的应用价值。方法对64例前列腺病病变患者采用磁共振常规扫描和磁共振弥散加权成像检查,选取感兴趣区记录DWI的信号强度和表观弥散系数（apparent diffusion coefficient ,ADC）值,并对得到的数据进行方差分析。结果64例经经手术或穿刺活检诊断结果显示前列腺癌35例,前列腺增生29例。当b取800s／mm2时,以前列腺癌组外周带癌灶的平均ADC值单值上界95％可信区间的上限为0．87×10‐3 mm2／s ,而前列腺增生结节的ADC值单值上界95％可信区间的上限为1．30×10‐3 mm2／s ,两组ADC之间无交叉,所以以ADC值≤0．87×10‐3 mm2／s作为诊断前列腺癌的阈值,其诊断敏感度为88．57％,特异性为89.66％,准确性为89．06％,Kappa＝0．67,P ＜0．01,说明其与病理结果具有较好的一致性。结论 DWI对于前列腺增生、前列腺癌可提供定量诊断信息,ADC值是鉴别前列腺增生与前列腺癌的一个很有价值的参数。     

实验性脑星形细胞水肿的CT灌注成像及其病理学研究

目的　评价星形细胞水肿对局部脑血流量的影响。方法　随机选取体重在 2 80g至36 0 g之间的雄性Wistar大鼠 16只 ,分为实验组和对照组 ,分别将反式 1 氨基环戊基 1,3 二羧酸(tACPD)溶液或生理盐水 (NS)通过微量注射器注入右侧尾状核。脑水含量通过干湿称重法测定 ;动态CT灌注成像通过微机辅助CT脑灌注成像软件完成 ;Evan蓝是否外渗入脑作为检测血脑屏障(BBB)和内皮细胞受损的指示剂 ;组织病理学检查包括光学显微镜和超微电子显微镜 ,均在尾状核注射操作完成后 6h进行。结果　注射tACPD 6h后的脑组织水含量与对照组及实验组对侧尾状核比较差异有显著性意义 (t值分别为 11 2 15和 10 4 37,P值均 <0 0 5 )。组织病理学检查可以显示星形细胞水肿状况及其与微循环的关系 ,组间差异亦存在显著性。Evan蓝外渗试验未见脑组织蓝染 ,提示tACPD的注入并未使血脑屏障的通透性增加。CT灌注成像中 ,实验组和对照组中局部脑血流量(rCBF)、平均通过时间 (MTT)和最大峰值时间 (TTP)测值组间差异有显著性意义 (t值分别为15 6 90、- 7 916和 - 5 2 34,P值均 <0 0 5 ) ,rCBV组间差异无显著性意义 (t=1 815 ,P >0 0 5 )。结论　星形细胞水肿可以诱发或加重局部脑血流量的减低。有效缓解初期星形细胞水肿 ,可以为脑缺血     

Cerebral spinal fluid contamination of the measurement of the apparent diffusion coefficient of water in acute stroke.

The measurement of the apparent diffusion coefficient (ADC) of water in brains of stroke patients is used in models developed to help distinguish reversible from irreversible ischemic injury. The ADC by conventional methods may be overestimated by the presence of cerebral spinal fluid (CSF) in sulci and perivascular spaces. In this study the hypothesis that DWI with CSF suppression (FLAIR-DWI) would result in different ADC values than those obtained with the conventional DWI technique was investigated. Thirty-one patients with stroke onset of less than 6 hr and an acute lesion on conventional DWI were studied. Both conventional isotropic DWI and FLAIR-DWI were performed using a single-shot echo-planar technique. In all 31 patients, CSF-suppressed ADC was lower than conventional ADC. The mean (SD) of the 31 patients' lesion ADC was 0.64 (0.08) x 10(-3) mm(2) s(-1) with FLAIR-DWI and 0.72 (0.09) x 10(-3) mm(2) s(-1) with conventional DWI (P < 0.001). The overestimation of ADC in conventional DWI corresponded to the percentage of the voxel that contained CSF. Suppression of CSF leads to lesion ADC values that are more homogeneous and more than 15% lower than those obtained with conventional DWI techniques. This suggests that FLAIR-DWI ADC measurements are more accurate than conventional ADC maps.