ADC图在诊断超急性脑梗死缺血半暗带中的价值

目的探讨表观弥散系数(ADC)图在诊断急性脑梗死缺血半暗带中的价值。方法对27例发病时间在1~6h的超急性脑梗死患者行常规MRI、磁共振弥散加权成像(DWI)和磁共振灌注加权成像(PWI)确定缺血半暗带的范围,计算梗死中心区、IP区及对侧镜像区的ADC比值和相对ADC值(rADC)值并加以比较。结果在27例超急性脑梗死患者中,25例患者病灶区ADC值明显下降;21例患者PWI>DWI,其病灶中心rADC值与IP区相比显著下降。结论ADC图可以反映脑组织的损伤程度,通过测量脑梗死病灶中心区和边缘区rADC值可以判断缺血半暗带的存在。     

磁共振多层并采扩散峰度成像与传统扩散加权成像识别急性缺血性卒中梗死核心的研究

目的与磁共振成像(magnetic resonance imaging,MRI)传统扩散加权成像(diffusion weighted imaging,DWI)对比,探讨MRI多层并采扩散峰度成像(multi-band EPI diffusion kurtosis imaging,m-DKI)界定急性缺血性卒中梗死核心的准确性。方法选择在发病3~8 h进行MRI检查的急性缺血性卒中患者,所有患者经灌注加权成像(perfusion weighted imaging,PWI)判定不存在缺血半暗带,没有接受静脉溶栓/动脉取栓治疗。基线扫描时加入传统DWI以及m-DKI序列,并在患者发病亚急性期([7±1)d]复查MRI扫描,利用Mricron软件分别对基线MRI检查表观扩散系数(apparent diffusion coefficient,ADC)图,平均扩散峰度(mean kurtosis,MK)图以及复查MRI T_1加权成像(T_1 weighted imaging,T_1WI)责任病灶体积进行测量,分别计算ADC图、MK图与T_1WI责任病灶体积的差值,并进行比较。结果入组的19例患者,1例患者DWI显示缺血病灶,但MK图及复查MRI均未见责任病灶;1例患者病灶位于基底节区附近,影响MK图责任病灶观察及测量。余17例患者MK图显示责任病灶的体积与亚急性期T_1WI责任病灶体积的差值为(0.25±0.37),而ADC图显示责任病灶的体积与亚急性期T_1WI体积的差值为(0.73±0.72)(t=3.968,P=0.001)。MK图责任病灶的体积更接近T_1WI的体积。结论与传统DWI相比,基线m-DKI显示责任病灶的体积更接近复查T_1WI的体积,对最终梗死核心的界定更为准确。     

表观弥散系数在急性缺血性卒中分期及判断脑组织灌注状态中的作用

目的探索表观弥散系数(apparent diffusion coefficient,ADC)在急性缺血性卒中患者分期及判断缺血半暗带中的价值。方法收集经临床和影像确诊为急性缺血性卒中的患者,根据行磁共振成像(magnetic resonance imaging,MRI)检查距起病时间的长短分为6 h组,6~24 h组,24~48 h组,48~72 h组,所有患者在治疗前行MRI弥散加权像(diffusionweighted imaging,DWI)检查,评估DWI图像及常规MRI图像显示病变的情况,测定各时间段病灶的ADC、健康对侧相应位置的ADC值、病灶中心及边缘的ADC值。结果共纳入62例患者,发病时间6 h的病例10例,常规MRI图像阳性检出率为0(0/10),DWI阳性检出率为100%(10/10);发病6~24 h的病例27例、24~48 h的病例13例、48~72 h的病例12例,总共52例,其中常规MRI阳性检出率为88.4%(46/52),DWI阳性检出率为100%(52/52)。不同时间段病灶侧ADC值与健侧ADC值分别为:6 h组(0.601±0.079,1.261±0.085)×10~(-3)mm~2/s,6~24 h组(0.623±0.097,1.152±0.083)×10~(-3)mm~2/s,24~48 h组(0.635±0.103,1.036±0.112)×10~(-3)mm~2/s,48~72 h组(0.631±0.082,1.225±0.097)×10~(-3)mm~2/s;不同时间段病灶侧ADC值与健侧ADC值之间均有显著性差异(P分别为0.006,0.007,0.008和0.017)。不同时间段组病灶侧ADC值之间无显著差异。不同时间段组病灶中心及边缘的ADC值分别为:6 h组(0.547±0.089,0.624±0.096)×10~(-3)mm~2/s,两者之间有显著性差异(P=0.027);6~24 h组(0.572±0.074,0.647±0.107)×10~(-3)mm~2/s,两者之间有显著性差异(P=0.032);24~48 h组(0.615±0.104,0.636±0.082)×10~(-3)mm~2/s,两者之间无显著差异;48~72 h组(0.631±0.081,0.625±0.102)×10~(-3)mm~2/s,两者之间无显著差异。结论 DWI的ADC值可以早期准确发现急性缺血性卒中的责任病灶,而且可以区分24 h梗死灶的中心和边缘,边缘区可能为缺血半暗带,但对于急性缺血性卒中(0~3 d)的细化分期意义不大。     

TIA患者不同b值磁共振弥散加权成像研究

目的观察短暂性脑缺血发作(TIA)患者磁共振弥散加权成像(DWI)提高b值后的影像学表现,探讨TIA患者DWI高b值的临床应用价值。方法收集2014年3月至2015年3月在河北医科大学第二医院临床诊断的TIA而结构影像学(CT,MRI)无责任病灶的TIA患者44例,所有患者均在发病3 d内行常规MRI和不同b值DWI(b=1000、b=2000和b=3000)检查。比较DWI不同b值对TIA责任病灶的敏感性、病灶范围及图像伪影的影响,定量分析TIA责任病灶的体积大小、ADC值变化。结果提高DWI b值,并没有提高发现TIA患者责任病灶的敏感性,但可以发现部分病例存在更多层面的责任病灶。定性分析发现全部患者的责任病灶随着b值的提高,病灶显示更明显,在25例DWI阳性病例中有12例,12/25例患者责任病灶的范围有所增加。当b值过度提高(b=3000),会降低图像的质量,导致伪影加重,而不易区分真正的责任病灶。定量分析发现随着b值的提高,责任病灶的平均体积也在增加(P<0.05),而ADC值却在下降(P<0.05)。结论提高DWI b值(b=2000,b=3000)更有助于反应TIA患者责任病灶的体积,有助于发现潜在的微小的不易发现的病灶,但b值过度提高(b=3000)会降低图像的质量,因此建议取DWI(b=2000)对诊断及评估TIA患者更有优势。     

常规磁共振与弥散性磁共振检查对多发性硬化的诊断价值

目的：比较常规磁共振（MRI）检查和弥散磁共振（MR－DWI）检查技术对判定脑内多发性硬化（MS）的价值。方法：经临床表现与实验室检查明确MS的病例有26例行MRI扫描,T1,T2加权及质子密度像,MRDWI用平面回波成像技术,将两者所见进行比较,同时使用软件进行MRI－DWI的弥散系数（apparent diffusion coefficient ADC)值及影像分析。结果：MRI扫描在T2W1像上可见明确T2高信号及高质子密度者占25／26,脑室旁白质为主占病灶总数的83％,T1W1表现为低信号者占16／26,可见急性期发作的病灶均有不同程度的强化,96．5％是多病灶的,MR－DWI示发病早期12例可见高信号,ADC值高于脑缺血但低于脑肿瘤,结论：使用多种MRI技术可以明确判定脑内白质区的MS病灶是急性期还是非急性期。同时应用MR－DWI,ADC图检查对判断病灶是脑缺血性病灶或肿瘤有较大帮助,是诊断MS等脱髓鞘疾病的有效影像学方法。     

磁共振弥散成像及表观弥散系数早期诊断脑脓肿1例报告

随着磁共振弥散加权成像(diffusion weight image,DWI)以及表观弥散系数ADC值(apparent diffusion coefficient)的普遍应用,为鉴别脑脓肿及其他囊性病变提供了重要依据.但在脓肿早期,特别是明显的脓腔形成前,影像检查常常缺乏典型表现,DWI与ADC能否提供更多线索,协助脓肿的早期诊断识别,目前尚未见报道.现结合1例临床病例,进行其临床应用价值的相关尝试及探讨.     

小儿外伤性急性脑梗死FLAIR与DWI对比分析

目的探讨小儿外伤性急性脑梗死在液体衰减反转恢复(fluid-attenuated inversion-recovery,FLAIR)序列与弥散加权成像(diffusion-weighted imaging,DWI)上的表现,并对比分析双序列加权像在小儿外伤性急性脑梗死诊断的敏感性。方法对17例小儿头颅外伤后,临床上主要表现为不同程度的偏瘫患者均行CT扫描后行FLAIR和MRDWI扫描,对其病变的显示情况进行对比分析,并计算病变区表观扩散系数(Apparent Diffusion Coefficient,ADC)和rADC。结果在小儿外伤性急性脑梗死发病6h内,FLAIR显示病灶5枚,DWI显示病灶13枚,发现病灶的敏感度分别为29.4%与76.5%,病变区的平均ADC为6.05×10-4mm2/s,rADC为55.60%。结论小儿外伤性急性脑梗死的诊断DWI较FLAIR序列敏感,DWI且能对小儿外伤性急性脑梗死作定量评价。     

多 b 值弥散加权成像术前预测垂体瘤质地的研究

目的探讨多b值磁共振弥散加权成像(diffusion weighted imaging,DWI)及表观扩散系数(apparent diffusion coefficient,ADC)术前预测垂体腺瘤质地的应用价值。方法选取57例术后病理证实为垂体腺瘤的患者纳入研究。所有患者均在术前进行3. 0 T MRI多b值DWI扫描(b=0,b=1 000 s/mm~2,b=2 000 s/mm~2),以及内分泌激素检查。选取两种b值(b=1 000、2 000 s/mm~2)重建ADC图,并获取肿瘤实质区域的ADC值。根据术中肿瘤质地将患者分为质软组及质韧组;比较两种b值下,质软组与质韧组ADC均值的差异性;并分析肿瘤质地与患者性别、年龄、激素分型及肿瘤胶原含量的相关性。结果 b1000中,质软组与质韧组ADC均值的差异无统计学意义(P 0. 05); b2000中,两组间ADC均值的差异有统计学意义(P 0. 05)。在b1000和b2000中,肿瘤质地与患者年龄、性别及激素分型均无明显相关性;而质软组的肿瘤胶原含量均明显低于质韧组(均P 0. 05)。结论垂体腺瘤的质地与ADC值及肿瘤胶原含量有密切关系,与患者的性别、年龄及激素分型无关。DWI和ADC可在术前预测肿瘤质地,为手术入路的选择提供影像学依据。     

急性脑梗死缺血半暗带演变的磁共振成像研究

目的：探讨应用磁共振弥散／灌注成像技术判断急性脑梗死后缺血半暗带IP存在的范围和时间规律。方法：对72例发病时间在1～24h的急性脑梗死患者行常规MRI、磁共振弥散加权成像（DWI）和磁共振灌注加权成像（PWI）确定IP的范围，计算梗死中心区、IP区及对侧镜像区的ADC值和rADC值并加以比较。结果：26例发病时间〈6h的患者PWI显示存在低灌注区者，其中PWI〉DWI者21例，30例发病时间在6～24h的患者PWI显示存在低灌注区者，其中PWI〉DWI者2例；PWI〉DWI者病灶中心ADC值与IP区及对侧镜像区ADC值差异有统计学意义，其IP区ADC值与其对侧镜像区差异无统计学意义。结论：DWI和PWI结合能灵敏的判断IP的存在，IP存在的时间窗有一定的个体差异。     

弥散加权成像在超急性期脑梗死诊断中的应用

目的 将磁共振弥散加权成像（DWI）与常规MR技术作对比。评价DWI对超急性期脑梗死诊断的准确性和敏感性。方法 对52例超急性期，急性期，亚急性期，慢性期的患者行DWI，快速自旋回波T2WI，FLAIR及3DTOF法磁共振血管成像检查。对所有病例的病变部位均按神经解剖进行准确定位并与患者的症状，体征相联系。结果 超急性期和急性期脑梗死在DWI图像上表现为高信号，在表观弥散系数（ADC）图上表现为低信号，ADC值低于对侧相应的区域。在超急性期和急性期，病灶的ADC值显著下降,rADC值也明显下降。平均下降约59.12%。而在慢性期ADC值明显升高，甚至较正常组织还高，平均升高达20.3%。结论 DWI对6h症状起病的急性卒中的诊断明显高于传统MRI，DWI可以在超急期发现缺血病灶，早于常规T2WI及FLAR序列图像。DWI对脑梗死的早期诊断及评价起重要的作用。     

Spatial distribution of perfusion abnormality in acute MCA occlusion is associated with likelihood of later recanalization

The aim of this study is to investigate whether different spatial perfusion-deficit patterns, which indicate differing compensatory mechanisms, can be recognized and used to predict recanalization success of intravenous fibrinolytic therapy in acute stroke patients. Twenty-seven acute stroke data sets acquired within 6 hours from symptom onset including diffusion- (DWI) and perfusion-weighted magnetic resonance (MR) imaging (PWI) were analyzed and dichotomized regarding recanalization outcome using time-of-flight follow-up data sets. The DWI data sets were used for calculation of apparent diffusion coefficient (ADC) maps and subsequent infarct core segmentation. A patient-individual three-dimensional (3D) shell model was generated based on the segmentation and used for spatial analysis of the ADC as well as cerebral blood volume (CBV), cerebral blood flow, time to peak (TTP), and mean transit time (MTT) parameters derived from PWI. Skewness, kurtosis, area under the curve, and slope were calculated for each parameter curve and used for classification (recanalized/nonrecanalized) using a LogitBoost Alternating Decision Tree (LAD Tree). The LAD tree optimization revealed that only ADC skewness, CBV kurtosis, and MTT kurtosis are required for best possible prediction of recanalization success with a precision of 85%. Our results suggest that the propensity for macrovascular recanalization after intravenous fibrinolytic therapy depends not only on clot properties but also on distal microvascular bed perfusion. The 3D approach for characterization of perfusion parameters seems promising for further research.     

磁共振弥散张量成像在诊断中枢神经系统疾病的初步应用

目的 探讨磁共振(MRI)弥散张量成像(DTI)对中枢神经系统疾病的脑白质改变的诊断价值。方法 对10名健康志愿者和64例神经系统疾病患者(脑血管病31例，脱髓鞘疾病7例，炎症7例，肿瘤10例，变性病和先天性发育不良各2例，脑萎缩3例，其他2例)进行MRI检查，包括常规T1WI,T2WI,T2Flair,EWI以及ETI序列。并分别测量FA值。结果 本组59例(92．1％)可见病变区脑白质纤维束消融，FA值减低；12例(20．3％)可见边界清楚的侵蚀状改变，肿瘤病例均可见病变区域旁的白质纤维束推压和移位。结论 DTI可早期发现白质内的病变。与传统MRI相比，DTI能更好地显示脑白质纤维束的受损和移位。     

Diffusion tensor and dynamic susceptibility contrast MRI in glioblastoma

Objective

We prospectively investigated the correlation between diffusion tensor (DTI), dynamic susceptibility contrast (DSC) perfusion MRI metrics and Ki-67 labelling index in glioblastomas.

Methods

We studied seventeen patients who were operated on for glioblastoma. DTI and DSC MRI were performed within a week prior to surgical excision. Lesion/normal ratios were calculated for the apparent diffusion coefficient (ADC), fractional anisotropy (FA), relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and relative mean transit time (rMTT) ratio. In the excised tumour specimens Ki-67 antigen expression was evaluated by the MIB-1 immunostaining method.

Results

A significant correlation was observed between Ki-67 index and ADC ratio (r = −0.528, p = 0.029) and FA ratio (r = 0.589, p = 0.012). rCBV and rMTT presented a trend towards significant correlation with Ki-67 index (r = 0.628, p = 0.07 and r = 0.644, p = 0.06 respectively). There was a trend towards better survival for patients with gross total tumour excision and FA values lower than 0.48 (p = 0.1 and p = 0.09 respectively). No significant correlation was found between ADC ratio, rCBV, rCBF, rMTT and overall survival.

Conclusion

ADC ratio, FA ratio, rCBV and rMTT tumour/normal tissue ratios may represent indicators of glioma proliferation. FA values may hold promise for predicting survival in patients with glioblastoma.     

Noninvasive high-speed photoacoustic tomography of cerebral hemodynamics in awake-moving rats

We present a noninvasive method of photoacoustic tomography (PAT) for imaging cerebral hemodynamics in awake-moving rats. The wearable PAT (wPAT) system has a size of 15 mm in height and 33 mm in diameter, and a weight of ~8 g (excluding cabling). The wPAT achieved an imaging rate of 3.33 frames/s with a lateral resolution of 243 μm. Animal experiments were designed to show wPAT feasibility for imaging cerebral hemodynamics on awake-moving animals. Results showed that the cerebral oxy-hemoglobin and deoxy-hemoglobin changed significantly in response to hyperoxia; and, after the injection of pentylenetetrazol (PTZ), cerebral blood volume changed faster over time and larger in amplitude for rats in awake-moving state compared with rats under anesthesia. By providing a light-weight, high-resolution technology for in vivo monitoring of cerebral hemodynamics in awake-behaving animals, it will be possible to develop a comprehensive understanding on how activity alters hemodynamics in normal and diseased states.     

低血糖脑病的影像学特征

目的探讨低血糖脑病的影像学特征。方法回顾性分析7例低血糖脑病患者的核磁共振资料。结果低血糖脑损害有高度的区域选择性,可不对称。主要累及大脑皮层、海马、基底节和胼胝体压部,甚至皮层下白质;MRI表现为等或稍长T1、长T2信号,DWI呈高信号,伴ADC值降低,部分病变可逆;MRS示病变区乳酸峰无明显变化。结论低血糖脑损害有很强的区域选择性、可不对称;DWI对病变更敏感;大脑皮层和基底节区受累者预后不佳,侵犯胼胝体压部者预后好。     

Evolution of the diffusion-weighted signal and the apparent diffusion coefficient in the late phase after minor stroke

Introduction Diffusion-weighted imaging (DWI) is mainly used in acute stroke, and signal evolution in the acute phase has been studied extensively. However, patients with a minor stroke frequently present late. Recent studies suggest that DWI may be helpful at this stage, but only very few published data exist on the evolution of the DW-signal in the weeks and months after a stroke. We performed a follow-up study of DWI in the late stages after a minor stroke. Methods 28 patients who presented 48 hours to 14 days after a minor stroke underwent serial MRI at baseline, 4 weeks, 8 weeks, 12 weeks, 6 months and ≥9 months after their event. Signal intensity within the lesion was determined on T2-weighted images, DW-images and the Apparent Diffusion Coefficient (ADC) map at each time-point, and ratios were calculated with contralateral normal values (T2_r, DWI_r, ADC_r). Results T2_r was increased in all patients from the beginning, and showed no clear temporal evolution. ADC_r normalized within 8 weeks in 83% of patients, but still continued to increase for up to 6 months after the event. The DW-signal decreased over time, but was still elevated in 6 patients after ≥6 months. The evolution of ADC_r and DWI_r showed statistically highly significant inter-individual variation (p < 0.0001), which was not accounted for by age, sex, infarct size or infarct location. Conclusion The ADC and the DW-signal may continue to evolve for several months after a minor ischaemic stroke. Signal evolution is highly variable between individuals. Further studies are required to determine which factors influence the evolution of the ADC and the DW-signal. Received in revised form: 14 April 2006