迟发性放射性脑损伤DTI临床研究

目的:观察鼻咽癌迟发性放射性脑病(radiation encephalopathy,REP)的磁共振扩散张量成像(magnetic resonancediffusion tensor i maging,MR DTI)表现,并探讨MR DTI对REP的诊断应用价值。方法:对29例共40个颞叶病灶和健康正常人28例56个颞叶的MR DTI资料进行回顾性分析。在鼻咽癌放射治疗30月~9年行MRI检查,成像序列包括T1WI、T2WI、MR DTI和T1WI Gd-DTPA增强,分析REP磁共振及DTI表现特点。结果:29例REP中累及单侧颞叶18例,双侧颞叶11例,共40个病灶。40个病灶均有颞叶脑白质指状水肿。28个(70%)颞叶REP病灶Gd-DTPA增强扫描双侧颞极下部见不规则点片状强化影,23个(57.5%)病灶同时伴有明显的脑灰质受累。6个(15%)颞叶病灶伴有脑白质坏死囊性变。病变区各向同性值(ADCiso)升高,而各向异性值(RA、FA及1-VR)均有降低,与正常对照组比较统计学上有显著性差异。结论:鼻咽癌放射性脑病表现具有多样性,病灶内脑组织内水分子扩散异常,MR结合MR DTI可提高鼻咽癌放疗后迟发性放射性脑损伤的诊断准确性,同时鼻咽癌放疗后放射性脑病DTI异常表现也有助于脑肿瘤放疗后疗效的评估。     

鼻咽癌放射治疗后放射性脑损伤的影像学表现

目的 探讨鼻咽癌放射治疗(简称放疗)后放射性脑损伤的CT、MRI、正电子发射计算机体层摄影术(PET)的影像学以及组织病理学特征。方法 回顾分析鼻咽癌(NPC)放疗后放射性脑损伤71例患者的临床、CT、MRI、PET以及手术病理学资料。结果 病变位于颞叶、脑干或小脑，其CT表现为均匀或不均匀的低密度，位于颞叶者，呈“指状”低密度。23例患者(29个病灶)行CT增强扫描，86．2％(25／29)的病灶无强化。MRI示损伤脑组织的T1、T2弛豫时间延长，可呈不均匀信号改变。20例患者(29个病灶)行MR增强扫描，65．5％(19／29)的病灶呈“花环状”强化。2例病人行PET扫描，1例与CT及MRI所示病变相符合。3例患者颞叶手术切除术及组织病理学检查均为放射性脑坏死。结论 (1)MR平扫或增强扫描发现病变的敏感度均高于CT和PET。(2)T1WI和T2WI显示的不均匀信号提示为坏死，且均位于照射野内。(3)增强MRI所示的“花环状”强化，是放射性脑坏死的特征。(4)PET在放射性脑损伤诊断中可作为CT或MRI的补充。     

鼻咽癌放疗后早期放射性脑损伤的磁共振扩散加权成像研究

目的：探讨磁共振扩散加权成像（DWI）在观察鼻咽癌患者放疗后早期放射性脑损伤方面的价值。方法选取健康志愿者20名,男性10名,女性10名。年龄24-65岁,平均年龄为（43±4）岁。20例鼻咽癌患者,男性11例,女性9例。年龄27-78岁,平均年龄为（50±5）岁。所有健康志愿者均行磁共振成像（MRI）常规平扫及DWI成像,DWI成像时b值分别采用0和1000 s/mm2。结果健康志愿者双侧颞叶的表观弥散系数（ADC）值与鼻咽癌患者放疗前的双侧颞叶的ADC值比较差异无统计学意义。鼻咽癌患者放疗前的双侧颞叶的ADC值与首次放疗后3 d及放疗后3个月双侧颞叶白质的ADC值之间差异有统计学意义,放疗后6个月、12个月及18个月时的双侧颞叶的ADC值与放疗前比较差异无统计学意义。结论磁共振DWI能够反映鼻咽癌放疗后放射性脑损伤的病理变化,是一种能够发现早期放射性脑损伤的影像学诊断方法。     

超急性期放射性脑损伤的MRS和DTI研究

目的:探讨MRS和扩散张量成像(DTI)对超急性期放射性脑损伤的诊断价值.方法:18例经病理证实的鼻咽癌初诊患者,在放疗前及放疗后接受总放射剂量分别为20Gy、40Gy和60Gy时,进行颅脑MRI常规扫描、双侧颞叶1H-MRS多体素成像和DTI,将不同时期MRS检查所获得的颞叶Cho/Cr、NAA/Cr和NAA/Cho及DTI检查所测量的表观扩散系数(ADC)和部分各向异性(FA)值进行对比分析.结果:接受放射总剂量60Gy后,所有患者常规MRI扫描均未发现异常信号.MRS检查显示双侧颞叶前部的各代谢物比值在接受放射治疗后降低,并且所测各值的变化与放疗剂量呈负相关改变;DTI结果显示ADC值升高,FA值降低.结论:MRS和DTI能从组织细胞功能代谢水平对放射性脑损伤超急性反应进行评价,为临床对该疾病的病理发展过程进行研究提供客观可行的检测方法.     

鼻咽癌放射治疗后颞叶放射性脑病低场MR诊断

目的分析鼻咽癌(NPC)放疗后颞叶放射性脑病(REP)的低场强MRI表现,探讨其影像学特征性改变。方法分析25例鼻咽癌放疗后诊断为颞叶放射性脑病(REP)患者MRI表现和临床资料及随诊观察。结果 25例REP中累及单侧颞叶9例,累及双侧颞叶16例。表现为局限性脑水肿并局灶性坏死:病灶为斑片状或不规则形,T1WI呈低信号或等信号;T2WI呈高信号或等高混杂信号。T1WI+Gd-DTPA增强扫描可见脑回状或不规则环形强化。12例经治疗后行MRI复查,2例症状改善,MRI异常信号明显减少,9例病灶无变化,其中3例症状有改善,6例症状体征无变化,1例病灶增大。结论鼻咽癌放射治疗后REP的MRI表现有一定的特征性,可作为REP诊断的主要方法。     

鼻咽癌放疗后放射性脑病MRI评价

本文分析12例鼻咽癌放疗所致放射性脑病的CT和MRI表现。MRI检查采用SE序列(TR=1800ms,TE=99、132ms)和RARE序列,T_2加权成像。结果表明:MRI显示病变较CT敏感,以表现侧脑室旁白质内爪样高强度信号病灶为特征,颞叶病变最重,向上逐渐减轻,严重者累及颞叶灰质。作者认为MRI是放射性脑病的有效诊断手段。     

放射性脑损伤的MRI分析

目的：分析放射性脑损伤的MRI表现及MRI诊断的意义。方法：回顾性分析25例放射性脑损伤患者的MRI资料,观察并比较病变的部位、范围及增强表现。结果：急性放射性脑损伤1例,深部脑白质及胼胝体压部对称性长T2信号,脑白质和胼胝体压部肿胀,增强扫描无强化;早期迟发性放射性脑损伤18例,深部脑白质对称性长T2信号,增强扫描无强化;晚期迟发性放射性脑损伤6例,双侧颞叶不均匀长T1长T2信号,增强扫描呈明显花环样强化。结论：放射性脑损伤具有特征性MRI表现,MRI对诊断放射性脑损伤具有重要价值。     

常规MRI结合DWI、MRS诊断胚胎发育不良性神经上皮肿瘤的价值

目的探讨常规MRI结合DWI、MRS诊断胚胎发育不良性神经上皮肿瘤(DNET)的价值。方法回顾性分析6例经手术病理证实的DNET的MRI平扫、增强、DWI以及MRS的影像学特征。结果 6例DNET中病变位于颞叶3例,额叶3例,均位于大脑皮层,病灶边界清楚,瘤周无水肿或轻度水肿。MRI平扫病灶表现为长T_1长T_2信号,T_2 FLAIR呈稍高信号或中央低信号、周围环形高信号改变。3例病灶内见分隔样改变。4例病变形态为三角形,2例呈圆形。6例增强均未见强化。3例DWI表现为稍低信号,ADC值平均为2.05×10~(-3) mm~2/s。3例肿瘤区的NAA峰轻度下降,Cho峰和Cr峰改变不明显,NAA/Cho=0.84～1.15(平均值0.98),NAA/Cr=1.24～1.48(平均值1.36)。结论 DNET的发病部位、MRI平扫及增强表现具有一定的特征,结合DWI和MRS有助于术前正确诊断。     

MR增强扫描在鼻咽癌放疗后放射性脑损伤中的诊断价值

目的:探讨鼻咽癌放疗后颞叶放射性脑损伤的MR增强扫描表现特点及诊断价值。方法:回顾性分析36例鼻咽癌放疗后颞叶放射性脑损伤患者的临床及MR影像资料。按病变的主要发病部位及MR表现将其分为灰质型及白质型,其中白质型进一步分为白质型Ⅰ期和白质型Ⅱ期。结果:36例放射性脑损伤包括27例白质型及9例灰质型,其中27例白质型包括白质型Ⅰ期18例、白质型Ⅱ期9例。白质型Ⅰ期病例中增强扫描均表现为颞叶底部灰质内为主团块状或散在的斑点状、斑片状实质强化,强化区多位于颞叶底部内侧灰质及颞极区灰质;白质型Ⅱ期病例增强扫描主要表现为花环状强化,占强化病灶的56%,其它主要表现为坏死灶周边及颞叶底部灰质内不规则实质强化。灰质型病例中增强扫描表现为病变区斑点状或结节状强化。结论:鼻咽癌放疗后颞叶放射性脑损伤的强化部位、强化形状及强化范围均具有一定的特征性,增强扫描在放射性脑损伤的诊断及早期征象的发现中有重要价值,应作为常规扫描进行。     

肾上腺脑白质营养不良MRI诊断

目的 分析肾上腺脑白质营养不良(ALD)的影像图像特点,提高MRI对ALD诊断的准确性.方法 收集本院1993-2008年间经生化和临床证实的ALD共9例,所有病例均行MRI检查.结果 9例病人均表现为双侧对称性侧脑室三角区白质病变,呈T_1 WI低信号,T_2 WI高信号,经胼胝体压部相连,呈蝶翼状分布;其中1例仅累及枕叶, 6例累及顶枕叶,2例累及顶枕颞叶.8例累及胼胝体压部,5例累及丘脑后外部.2例增强扫描表现为病灶周边环状强化,脑干病灶亦强化.结论 MRI能准确反映ALD病变和病程.     

MRI FLAIR对脑挫裂伤的诊断价值

目的:探讨MRI FLAIR序列对脑挫裂伤的诊断价值。方法:回顾性分析22例脑挫裂伤的MR表现。结果:脑挫裂伤病变单发性3例,多发性19例。发生于颞叶2例,顶叶1例,双额叶3例,颞、顶叶3例,额、顶叶3例,额、颞、顶、枕复合伤10例。MRI表现为出血性改变8例,FLAIR序列表现为混杂高信号或低信号的病灶;非出血性病灶14例,FLAIR序列表现为高信号。常规T2WI发现病灶共58处,FLAIR上共发现病灶77处。结论:FLAIR序列对脑挫裂伤病变显示优于FSE序列T2WI,有很高的临床使用价值。     

鼻咽癌放射治疗后放射性脑损伤急性反应早期的1H-MR波谱研究

目的评价1H-MR波谱（1H-MRS）对鼻咽癌放射治疗（简称放疗）后放射性脑损伤急性反应早期的诊断价值.方法对18例已被病理证实且为首次行放疗的鼻咽癌患者进行前瞻性研究,于不同时间段对其双侧颞叶（共72个部位,颞叶前后部各为36处）进行常规MR和1H-MRS成像,成像时间为放疗前和放疗后接受放射剂量20Gy、40 Gy及60Gy时,成像序列为轴面SE T1WI、T2WI、T2液体衰减反转恢复序列（T2FLAIR）、三维扰相稳态梯度恢复采集T1序列（3D-SPGR T1＊）.以序列T2FLAIR或3D-SPGR T1＊为波谱成像的定位图,采用点分辨法进行多体素及单体素波谱成像,观察不同时间段颞叶各部位谱线的形态学改变及各代谢物间比值的变化.结果放疗后,双侧颞叶在常规MRI均未见明显信号改变,而在1H-MRS成像上,双侧颞叶前部谱线形态均有不同程度的改变,而颞叶后部无明显改变,表现为局部N-乙酰天门冬氨酸（NAA）峰和胆碱（Cho）峰降低,Cho/肌酸（Cr）、NAA/Cr及NAA/Cho比值在不同时间段均有下降;在接受放射剂量20Gy时,颞叶前叶有20处,占所有颞前叶的比例为56%（20/36）;40 Gy时有22处,占61%（22/36）;60Gy时有13处,占36%（13/36）.而谱线为NAA与Cho峰倒置在20Gy时,颞叶前叶有4处,占11%（4/36）;40 Gy时,有10处,占28%（10/36）;60 Gy时为23处,占64%（23/36）.与接受射线剂量呈明显正相关,不同剂量其同一比值差异有统计学意义（P＜0.05）.结论1H-MRS可在组织细胞代谢水平发现鼻咽癌放疗后急性反应早期的放射性脑损伤.     

鼻咽癌放疗后放射性脑病的MRI诊断

作者观察了８４例鼻咽癌放疗后放射性脑病（ＲＥＰ）。其ＭＲＩ表现：病变主要位于双侧颞叶、脑干及小脑，Ｔ１ＷＩ病灶以低信号为（８１．３％），Ｔ２ＷＩ均为高信号，占位征象占２７．４％，萎缩征象占９．５％。还讨论了ＲＥＰ与脑梗塞、脑干胶质瘤及脑转移瘤的鉴别诊断。并提出了ＲＥＰ的ＭＲＩ分型，可分为颞叶型、脑干型、小脑型和混合型。作者还强调了ＭＲＩ显示ＲＥＰ，特别是显示脑干、小脑和颞叶底部的病灶，为ＣＴ及其他     

Late temporal lobe necrosis in patients with nasopharyngeal carcinoma: evaluation with combined multi-section diffusion weighted and perfusion weighted MR imaging

Late temporal lobe necrosis is a well-known and serious complication in patients with nasopharyngeal carcinoma (NPC) following radiotherapy. Owing to the close proximity to the skull base, the medial temporal lobes are inevitably included in the target volume of irradiation. Patients with NPC provide a unique opportunity in study of delay radiation effect in normal human brain. The objective of this study was to evaluate late temporal lobe radiation injury by combined multi-section diffusion weighted and perfusion weighted MR imaging. We prospectively studied 16 patients with typical clinical symptoms of late temporal lobe necrosis or other abnormalities in the temporal lobes incidentally detected by conventional MR imaging. All patients had a previous history of radiotherapy for histologically proven NPC. Conventional T1- and T2-weighted images, fast gradient echo with echo-planar diffusion-weighted and perfusion-weighted MR imaging were performed. Apparent diffusion coefficient (ADC) map and relative cerebral blood volume (rCBV) map were computed via commercially available software. MR diffusion and perfusion images were then analyzed and graded by two independent observers with focusing on the diffusion and perfusion mismatch. The temporal lobe lesions displayed marked high diffusion on the ADC map. The rCBV map also revealed marked hypoperfusion in these temporal lobe lesions in all patients. The areas of abnormality on the rCBV map were significantly larger than the lesions on the ADC map in 14 patients (observer 1) and 13 patients (observer 2). Since late temporal lobe necrosis is probably caused by damage of the endothelium of vessels and ischemia, perfusion and diffusion mismatch might imply injured tissue but potentially salvageable brain tissue. A mismatch may be potentially used to predict the response to treatment in-patients with late temporal lobe necrosis.     

Proton magnetic resonance spectroscopy of late delayed radiation-induced injury of the brain.

We prospectively evaluated metabolite changes in late delayed radiation-induced injury to the temporal lobes on proton ((1)H) magnetic resonance spectroscopy (MRS) in 34 patients. Morphologically more severe injury on imaging tended to have lower N-acetyl aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) ratios. A significantly higher Cho/Cr ratio was found in the most severe grade of cerebral necrosis, in which lactate might be present. The progressive decrease in NAA with increasing severity reflected neuronal loss at different stages of late delayed radiation-induced brain injury. The absence of Cho elevation in mild and moderate lesions did not suggest demyelination or glial hyperplasia as an etiologic mechanism of late delayed radiation-induced brain injury. The association of severe morphologic lesions with elevated lactate suggests ischemia as the underlying mechanism for severe lesions. (1)H MRS may provide metabolite information conducive to the understanding of the pathophysiology of late radiation-induced brain injury. J. Magn. Reson. Imaging 1999;10:130-137.     

Diffusion-weighted magnetic resonance imaging in radiation-induced cerebral necrosis. Apparent diffusion coefficient in lesion components

OBJECTIVE: The objective of this retrospective study was to investigate the diffusivity of different components of radiation-induced cerebral necrosis with the hypothesis that the diffusivity of the various components is elevated to different degrees. METHODS: Twenty-two patients (18 men, 4 women, aged 34-72 years) with radiation injury to the temporal lobes after radiation therapy (RT) for nasopharyngeal carcinoma with diagnosis confirmed on serial magnetic resonance imaging (MRI) were studied with coronal T2-weighted, diffusion-weighted, and gadolinium-enhanced MRI. Using three diffusion directions for diffusion-weighted MRI, the apparent diffusion coefficients (ADCs) of the enhanced component, the cystic or liquefied component, and the edema component were measured. RESULTS: ADCs of all components of RT-induced cerebral necrosis (154 +/- 21.6 x 10(-5) mm2/s for contrast-enhanced component; 188 +/- 47.4 x 10(-5) mm2/s for cystic/liquefied component; 177 +/- 35.4 x 10(-5) mm2/s for edema component) were all significantly higher (P<0.00001) than ADC of the normal frontal lobe white matter (82 +/- 12.4 x 10(-5) mm2/s). The ADC of the enhanced component was significantly lower than that of the cystic/liquefied component (P=0.0096) and the edema component (P=0.003). A significantly lower ADC was shown in the enhanced component in temporal lobes showing both short-term morphologic deterioration (P=0.024) and occurrence of deterioration on long-term follow-up (P=0.04) compared with the temporal lobes that showed improvement or stable morphology. CONCLUSIONS: ADCs of the contrast-enhanced component, cystic/liquefied component, and edema in RT-induced cerebral necrosis was significantly higher than in normal brain parenchyma. There is association between a lower ADC in the contrast-enhanced component and morphologic deterioration.