小儿流行性乙型脑炎的MRI特征分析

目的 探讨小儿流行性乙型脑炎的MRI特征.方法 回顾性分析40例乙型脑炎患儿的MRI表现,分析病灶的好发部位及其信号特征,数据采用构成比表示.40例(男24例,女16例)均在发病3～30 d期间行头颅常规T1WI、T2WI扫描,其中32例行轴位FLAIR扫描,31例行DWI扫描,7例行钆喷酸葡胺(Gd-DTPA)增强检查.结果 颅内病变主要在T1WI呈稍低信号,在T2WI呈稍高或高信号,在FLAIR序列以稍高信号多见,在DWI上多数呈高信号,部分呈稍高信号.40例中,37例病灶累及丘脑(92.5%),15例累及基底节(37.5%),12例累及大脑脚(30%),8例累及大脑皮层(20%),5例累及脑干(12.5%),2例累及胼胝体(5%).病灶常呈双侧对称性分布,增强扫描病灶均未见明显强化.结论小儿乙型脑炎的MRI的特征以双侧丘脑受累最多见,其次是基底节及大脑脚受累,而大脑皮层、脑干及胼胝体受累较少见.     

扩散加权成像诊断超急性和急性脑梗塞的应用价值

目的:探讨DWI和ADC图诊断超急性和急性脑梗塞的价值.材料和方法:14例脑梗塞患者(超急性期6例,急性期8例)采用1.5T MR机进行扫描,对DWI、ADC图及常规T1WI、T2WI进行对比研究分析.结果:超急性和急性脑梗塞DWI均表现为高信号,ADC图均表现为低信号,DWI对病变显示达100%.6例超急性期脑梗塞患者仅DWI可显示病变而常规T1WI、T2WI无任何相应的异常发现.全部病灶ADC值均低于其相对应的正常脑组织.结论:DWI对急性脑梗塞诊断敏感、准确,且能对脑梗塞作定量分析.     

山豆根中毒的脑MRI表现

目的 探讨山豆根中毒的脑MRI表现。方法 对临床诊断为山豆根中毒的4例患者采用1．5TMR仪行常规MR（T2WI和T2WI）和扩散加权成像（DWI）检查。结果 4例小脑齿状核均呈对称性小片状长T1、T2信号改变，DWI呈等信号，表观扩散系数（ADC）图信号升高，其中1例同时累及双侧脑干背侧和丘脑，1例症状较重患儿伴有双侧基底节区对称性片状长T1、T2信号改变，DWI呈高信号，ADC图信号减低。2例复查显示齿状核异常信号消失，1例基底节受累病灶趋向囊性变（长TnT2信号），DWI显示为低信号。结论 山豆根中毒可以特异性累及齿状核和豆状核，MRI和DWI有利于早期诊断、鉴别诊断和评估预后。     

桥本脑病的MRI特点

目的 探讨桥本脑病(HE)的MRI特点及其机制,以提高诊断及鉴别诊断能力.方法 回顾性分析5例临床诊断为HE患者的临床和MRI资料.5例患者均行头颅常规MR扫描,并对其中常规MRI表现异常的3例患者行DWI、MRA和增强扫描.观察病变的分布和信号特点,测量病变处和对侧无病变区组织的ADC值.并通过分析2例有连续临床和MRI资料的患者,推测其机制.结果 5例患者中有3例发现脑内异常改变,3例均表现为深部白质内斑点样异常信号,T1WI、DWI呈等信号,T2WI、液体衰减反转恢复(FLAIR)序列呈高信号,同时伴脑内其他部位多发斑片状病变,灰、白质均受累,主要累及基底节核团、海马和扣带回,发病初期T1WI呈等、低信号,T2WI、FLAIR、DWI呈高信号,病变区ADC值[(0.449±0.092)×10-3 mm2/s]较对侧无病灶区[(0.838±0.062)×10 -3 mm2/s]均明显降低.所有患者均无MRA异常改变和强化表现.对2例经糖皮质激素治疗症状缓解的患者连续追踪,1例MRI表现为病灶明显缩小,T1WI呈高信号,T2WI、FLAIR呈等、高信号,DWI呈低信号,ADC值明显升高;另1例病灶完全消失.结论 桥本脑病的MRI表现具有一定特点,可以作为HE诊断、鉴别诊断和疗效判断的手段之一,并可能成为活体研究HE病理机制的有效方法.     

肝移植术后渗透性髓鞘溶解症的MR特征

目的 探讨肝移植术后并发脑桥中央髓鞘溶解症(CPM)和脑桥外髓鞘溶解症(EPM)的MRI表现及MR扩散加权成像(DWI)的诊断价值.方法 搜集并分析肝移植术后5例CPM和3例CPM伴EPM患者的临床和影像资料.8例患者原发病3例为乙肝肝硬化,1例为乙肝肝硬化、肝癌,1例为丙肝合并血吸虫性肝硬化,2例为丙肝肝硬化,1例为胆汁性肝硬化,男女各4例.所有患者检查均于Philips 1.5 T MR机上进行.MR序列包括:T1WI,T2WI,横断面SE-回波平面成像(SE-EPI)DWI序列.结果 MRI显示脑桥中央呈蝴蝶形、圆形、四边形长T1长T2信号影,周围脑桥组织和皮质脊髓束信号正常.病变于DWI上呈高信号,表观弥散系数(ADC)图上呈等或稍低信号,提示病变内水分子扩散受限.2例患者2个月复查MRI显示病变范围较前缩小,DWI呈等信号,ADC呈高信号,提示病变内水分子扩散增加;3例患者除脑桥中央病灶外,尾状核、苍白球、丘脑、外侧膝状体及大脑皮层于DWI及T2WI上亦可见高信号.结论 MR扩散成像能够早期并敏感地显示脑桥中央及脑桥外髓鞘溶解症病变.     

磁共振扩散加权成像在病毒性脑炎中的临床价值分析

目的 探讨磁共振扩散加权成像（diffusion weighted imaging,DWI）在病毒性脑炎临床诊断中的应用价值.方法 收集2010年8月～2012年8月对收治的病毒性脑炎患者行MRI平扫加DWI检查,并对病灶部位及其对侧的正常脑组织进行ADC值测量,比较病灶部位与对侧的正常部位ADC值大小.结果 42例病毒性脑炎患者在经过MRI检查后,呈大片或斑片状稍长T1、稍长T2信号,信号较均匀,其中累及颞叶26例,额叶6例,侧脑室旁6例,基底节丘脑区3例,胼胝体1例.42例患者中DWI呈低信号35例,呈等或稍低信号6例,呈稍高信号1例;ADC图呈稍高信号.病毒性脑炎患者病灶部位的ADC值较对侧正常脑组织明显升高,且差异具有统计学意义（t=45.73,P＜0.05）.结论 DWI及ADC值可以反映病毒性脑炎病变组织的微观结构变化信息,可早期发现病毒性脑炎病灶,对定位、定量判断病情严重性及预后评价具有重要价值.     

高血压脑病的MRI表现

目的 分析高血压脑病的MRI表现。资料与方法 搜集8例经临床诊断高血压脑病患者,行MR T1WI和T2WI检查,其中4例加行扩散加权成像（DWI）,分析血压变化、MRI表现及ADC值变化。结果 发病时平均血压199．63／123．5mmHg（1mmHg=0．133kPa）,平均升高25．73％／28．71％。MRI上病变主要呈TI稍低、T2稍高信号,以顶枕叶、小脑半球多见。DWI病变呈等及稍高信号,ADC值较正常平均升高58％。仅1个病灶DWI出现明显高信号,ADC值减低。结论 MRI有助于高血压脑病的诊断及鉴别诊断、预后及疗效观察,DWI是将其与急性脑梗死区分开的最佳影像学检查方法。     

低场强磁共振弥散成像在脑梗死诊断中的应用价值

目的 评价低场磁共振弥散序列对各期脑梗死的诊断作用。方法 应用磁共振T1W1，T2WI和水抑制反转恢复成像(T2 FLAIR)和DWI对70例各期脑梗死病人进行86人次MRI检查，并作ADC图，测定ADC值。结果在超急性脑梗死病例中，DWI和ADC图均表现缺血，但T2及T2FLAIR成像表现正常，病灶的ADC值随梗死时间延长，呈由低向高变化的趋势。结论低场磁共振DWI对急性期及超急性期脑缺血病变高度敏感，显示率及敏感性是100％．常规T2WI敏感性37％；ADC图可进一步量化缺血程度，二者结合应用对脑梗死的早期诊断和病灶的转归评估有重要意义。     

流行性乙型脑炎的MRI诊断及临床意义

目的 探讨流行性乙型脑炎(乙脑)的MRI影像表现和临床应用价值.资料与方法 经临床血清学检测确诊的14例乙脑患者.全部行MRI扫描,扫描序列包括:T1-液体衰减反转恢复序列(FLAIR)、T2WI、T2-FLAIR和扩散加权成像(DWI).分析病灶累及部位和各序列的MRI信号特征.结果 病灶单独累及丘脑者3例,累及双侧丘脑同时伴有单个或多个其他部位受累10例,其中大脑脚、基底节、大脑皮层及小脑齿状核受累分别为6、4、2、1例.1例为右侧额叶广泛受累.病灶在T1-FLAIR多数呈低信号,在T2WI呈高信号.DWI上高信号7例,等信号4例,低信号3例.14例在T2-FLAIR上全部呈高信号.2例病灶中合并有出血灶.结论 乙脑可以累及多个部位,但以双侧丘脑损害为特征性表现.T2-FLAIR和DWI对乙脑诊断及治疗中随访观察有很高的诊断价值,MRI可作为乙脑的首选影像诊断手段.     

多发性硬化脑内病灶的扩散张量成像

目的研究多发性硬化(MS)的脑内病灶在磁共振扩散张量成像(DTI)上的主要特征,量化分析不同时期病灶的ADC值的差异,探讨DTI在反映MS病理变化中的价值。方法应用3.0 T磁共振设备对34例MS病人行常规头颅MRI和DTI检查,根据病灶有无强化和在T1WI上的信号强度,进行急慢性期病灶的分组。分析不同时期MS病灶在DTI后处理所获得的DWI、ADC、FA图上的特征,并测量各组病灶的ADC值。结果35个急性期病灶中的33个病灶(94.3%)于DWI上呈高信号,5个环形强化病灶在DWI上亦呈环形高信号。急、慢性期病灶的ADC值均升高。慢性期病灶的ADC值明显高于急性期病灶[(12.43±3.78)×10-4 mm2/s∶(10.10±2.28)×10-4 mm2/s,P=0.001]。急性期环形强化病灶的ADC值较非环形强化病灶的高,慢性期T1WI低信号病灶的ADC值较T1WI等信号病灶的高,T1WI明显低信号病灶的ADC值最高。急、慢性期病灶的FA值均降低。FA图能够清晰显示纤维通路上的病灶和纤维束的中断,定位上明显优于常规MRI。病灶于FA图上显示的范围较常规MRI T2WI上显示的大。结论DTI可以反映MS不同时期病灶的病理变化,为观测疾病演变和评价临床疗效提供有效的指标。     

Molecular imaging techniques in body imaging

Molecular imaging of the body involves new techniques to image cellular biochemical processes, which results in studies with high sensitivity, specificity, and signal-to-background. The most prevalently used molecular imaging technique in body imaging is currently fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET). FDG PET has become the method of choice for the staging and restaging of many of the most common cancers, including lymphoma, lung cancer, breast cancer, and colorectal cancer. FDG PET has also become extremely valuable in monitoring the response to therapeutic drugs in many cancers. New PET agents, such as fluorothymidine and acetate, have also shown promise in the evaluation of response to therapy and in the staging of prostate cancer. Magnetic resonance (MR) spectroscopy has shown promise in the evaluation of prostate cancer. Breast cancer evaluation benefits from advances in spectroscopic imaging and contrast-enhanced kinetic evaluation of vascular permeability, which is altered in neoplastic processes because of release of angiogenic factors. Superparamagnetic iron oxide (SPIO) particles represent the first of an expanding line of MR contrast agents that target specific cellular processes. SPIO particles have also been used in the evaluation of the cirrhotic liver and at MR lymphangiography.     

Molecular imaging: integration of molecular imaging into the musculoskeletal imaging practice

Chronic musculoskeletal diseases such as arthritis, malignancy, and chronic injury and/or inflammation, all of which may produce chronic musculoskeletal pain, often pose challenges for current clinical imaging methods. The ability to distinguish an acute flare from chronic changes in rheumatoid arthritis, to survey early articular cartilage breakdown, to distinguish sarcomatous recurrence from posttherapeutic inflammation, and to directly identify generators of chronic pain are a few examples of current diagnostic limitations. There is hope that a growing field known as molecular imaging will provide solutions to these diagnostic puzzles. These techniques aim to depict, noninvasively, specific abnormal cellular, molecular, and physiologic events associated with these and other diseases. For example, the presence and mobilization of specific cell populations can be monitored with molecular imaging. Cellular metabolism, stress, and apoptosis can also be followed. Furthermore, disease-specific molecules can be targeted, and particular gene-related events can be assayed in living subjects. Relatively recent molecular and cellular imaging protocols confirm important advances in imaging technology, engineering, chemistry, molecular biology, and genetics that have coalesced into a multidisciplinary and multimodality effort. Molecular probes are currently being developed not only for radionuclide-based techniques but also for magnetic resonance (MR) imaging, MR spectroscopy, ultrasonography, and the emerging field of optical imaging. Furthermore, molecular imaging is facilitating the development of molecular therapies and gene therapy, because molecular imaging makes it possible to noninvasively track and monitor targeted molecular therapies. Implementation of molecular imaging procedures will be essential to a clinical imaging practice. With this in mind, the goal of the following discussion is to promote a better understanding of how such procedures may help address specific musculoskeletal issues, both now and in the years ahead.     

Molecular imaging will replace myocardial perfusion imaging

Conclusion   “The order is rapidly fadin’. And the first one now will later be last ...” In 2008 myocardial perfusion imaging is the main-stay of nuclear cardiology. However, the lyrics of Dylan from the 1960s are applicable today, as we are in rapidly changing times in medicine. We are seeing a paradigm shift in disease detection and treatment from a focus on cardiovascular morphology, function, and pathophysiology to genetic and molecular events. Cardiovascular molecular imaging will be the vanguard of noninvasive imaging in this era. Nuclear cardiology is uniquely positioned to play a central role in both the clinical and research applications of cardiovascular molecular imaging. The question should not be whether myocardial perfusion imaging will remain the dominant clinical application but how does nuclear cardiology transition to embrace and foster cardiovascular molecular imaging. If we do not do this, there are several other imaging specialties that will be more than willing to fill this void.     

用于肿瘤显像的三种显像剂

肿瘤阳性显像具有较高的敏感性和特异性,易于对肿瘤的原发、复发以及转移做出定性、定位诊断。201Tl、99mTc-甲氧基异丁基异腈已经用于鉴别诊断良恶性病灶、寻找转移灶、评价治疗效果和判断预后,99mTc-氮-二(N-乙基-N-乙氧基二硫代氨基甲酸盐)在肿瘤中的应用则尚在探讨中。     

Optimizing joint imaging: MR imaging techniques

For optimizing MR of the joints, a sophisticated knowledge of MR system hard-and software condition, and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surfacecoilsas well as the different conventional and fast imagingsequences, including three-dimensional (3D)MR imaging. In addition, the applications of contrast agents as well as the most important contrast prepaation techniques are reviewed.     

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented.     

Comparison of contrast-enhanced fundamental imaging, second-harmonic imaging, and pulse-inversion harmonic imaging

RATIONALE AND OBJECTIVES: To investigate the feasibility of recent contrast-specific ultrasound techniques in depicting vascular flow and the effects of changing the output power of the transducer and insonation mode on contrast enhancement, the authors performed an experimental study with a flow phantom. METHODS: While changing the mechanical index and the sound insonation mode (continuous and intermittent), images were obtained with three contrast-enhanced ultrasound techniques: fundamental, second-harmonic, and pulse-inversion harmonic imaging (PIHI) after a bolus injection of microbubble contrast agent. The images were compared on a time-intensity curve. RESULTS: In assessing fixed flow (10 cm/s), PIHI showed the best depiction of flow signal. In intermittent scanning, increases in the mechanical index caused stronger flow signals and longer enhancement duration in all techniques. However, continuous scanning revealed poor depiction of flow signal regardless of the technique or changes in the mechanical index because of significant bubble destruction. CONCLUSIONS: Microbubble-enhanced PIHI with intermittent scanning at a high mechanical index can depict vascular flow highly effectively without shortening the duration of enhancement.     

Undersampled projection-reconstruction imaging for time-resolved contrast-enhanced imaging.

In time-resolved contrast-enhanced 3D MR angiography, spatial resolution is traded for high temporal resolution. A hybrid method is presented that attempts to reduce this tradeoff in two of the spatial dimensions. It combines an undersampled projection acquisition in two dimensions with variable rate k-space sampling in the third. Spatial resolution in the projection plane is determined by readout resolution and is limited primarily by signal-to-noise ratio. Oversampling the center of k-space combined with temporal k-space interpolation provides time frames with minimal venous contamination. Results demonstrating improved resolution in phantoms and volunteers are presented using angular undersampling factors up to eight with acceptable projection reconstruction artifacts.