磁共振弥散成像对急性脑梗死的诊断价值

目的探讨磁共振弥散成像对超急性、急性脑梗死的诊断价值。方法对80例疑似急性期脑梗死患者,行磁共振常规T1WI、T2WI、水抑制序列(FLAIR)、弥散加权扫描(DWI)。结果80例中,超急性期脑梗死10例,急性期32例,超急性期、急性期脑梗死在DWI上表现为高信号,T2WI上为等信号或部分稍高信号,ADC图上表现为低信号。MRI扫描未见异常2例。结论磁共振弥散成像对超急性期、急性期脑梗死病变较常规MRI敏感,在多发梗死灶中可以发现责任病灶、为临床选择治疗方案提供依据。     

MRI急诊快速评价在超急性期缺血性脑卒中静脉溶栓治疗中的应用

目的:探讨MRI急诊快速评价在超急性期缺血性脑卒中静脉溶栓治疗中的应用.方法:对313例发病＜12h的急性脑梗死患者先行CT平扫,排除有明显低密度梗死灶后行MR快速成像序列检查[包括弥散加权成像(DWI),时飞法三维血管成像(3D TOF-MRA)及T2加权成像(T2WI)],约5min完成;筛选超急性期脑梗死(DWI略高信号,而T2 WI未见明显高信号)158例(52.1％),并对其行重组组织型纤溶酶原激活剂(rt-PA)静脉溶栓治疗及预后评估.结果:发病＜4.5 h组、4.5～≤9h组及＞9～12h组的患者中分别75.4％(43/57例)、54.1％ (73/135)及34.7％ (31/121例)患者符合超急性期脑梗死;其中136例患者行静脉溶栓治疗;溶栓后发生非症状性颅内出血12例(8.8％),症状性颅内出血4例(2.9％),1例(0.74％)死亡;90 d评估预后良好125例(91.9％).结论:急诊MRI快速评价界定超急性期脑梗死指导的静脉溶栓治疗是一种安全有效方法,能排除发病＜4.5 h但梗死灶已非超急性期脑梗死患者及界定发病＞4.5h或不明确时间窗的超急性期脑梗死患者.     

DWI结合ADC图诊断急性脑梗死的价值

目的:评价扩散加权成像(DWI)和表观扩散系数(ADC)图对急性期脑梗死诊断的准确性。方法:对临床上拟诊为急性脑梗死患者进行常规MR扫描及DWI检查。回顾性分析109例在T2WI、T1WI、DWI、ADC图上信号强度的变化。结果:发病3 h内(9例)在T2WI上呈稍高信号1例,等信号8例,T1WI上均为等信号,DWI上均为高信号,ADC图上均为明显低信号。发病4~15 h(56例)在T2WI、DWI上均为高到高信号,在T1WI、ADC图上均为低信号。发病16~21 h(22例)在T2WI、DWI上均为高信号;在T1WI上20例为低信号,2例为等低信号;ADC图上19例为低信号,3例为等低信号。发病22 h上(22例)在T2WI上均为稍高信号;DWI上19例为稍高信号,3例为等信号;T1WI上20例为稍低信号,2例为等低信号;ADC图上12例为稍低信号,7例为等信号,3例为等低信号。结论:DWI结合ADC图对急性期脑梗死的诊断具有高度准确性,但单独DWI图像不能完全鉴别急性或亚急性病灶,应与T2WI、ADC图结合才能判断不同时期脑梗死。     

大鼠超急性期脑缺血的磁共振扩散加权成像研究

目的：利用磁共振扩散加权成像（DWI）评价大鼠超急性期脑缺血的诊断价值。方法：12只Wistar雄性大鼠,采用线栓法制作右侧大脑中动脉闭塞（MCAO）脑缺血模型,分别于栓塞后1h和6h行大鼠冠状位磁共振DWI、T2WI和T1WI检查,并测量缺血区DWI异常高信号的体积、表观扩散系数（ADC）值,将所测值进行比较。磁共振检查结束后处死大鼠,断头取脑行TTC染色,并与DWI结果进行比较。结果：大鼠MCAO后1h进行MRI扫描右侧大脑中动脉供血区DWI可见异常稍高信号,ADC为低信号,T2WI和T1WI均未见异常信号;MCAO后6hDWI可见明显高信号,较1hADC值显著减低（P〈0.01）,DWI上梗死灶体积显著扩大（P〈0.01）,T2WI显示缺血区异常高信号,T1WI可见稍低信号。TTC染色者均显示脑梗死灶,与MCAO后6h的DWI显示脑缺血范围一致。结论：DWI对超急性期脑梗死较常规MRI敏感,是超急性期脑缺血重要的检查方法。     

弥散加强成像对静脉性脑梗死诊断价值

目的观察静脉性脑梗死的扩散加权成像(DWI)影像表现,比较DWI与T2WI的敏感性。方法回顾性分析32例经MR或DSA确诊的脑静脉窦血栓(CVST)患者的影像资料,所有患者全部伴有静脉性脑梗死。所有患者均在症状后1~48h行首次T1WI、T2WI、DWI、MRV序列检查。其中,25例进行了DSA检查。观察DWI和T2WI发现高信号梗死区的数量。并测量梗死区的表观扩散系数(ADC值)。结果静脉性脑梗死的急性期,DWI敏感性为90%,高于T2WI(32%)(P0.05)。静脉性脑梗死的亚急性期DWI的敏感性为24%低于T2WI(100%)(P0.05)。急性期静脉性梗死区的ADC值为5.32±1.03×10~(-4)mm~2/s低于亚急性期的ADC值(11.48±3.13×10~(-4)mm~2/s)(P0.05)。结论 DWI对诊断静脉性脑梗死有补充价值。在静脉性脑梗死的急性期,DWI序列的作用突出,此时T2WI敏感性较低。通过测量梗死区的ADC值,我们能判断静脉性脑梗死中脑水肿的性质。     

MRI快速FLAIR技术在脑梗死诊断中的应用

目的:评价快速液体衰减反转恢复(FLAIR)技术在脑梗死诊断中的临床应用价值。方法:150例脑梗死患者,均行常规TSE序列T2WI及快速FLAIR序列检查,对比、分析两种序列成像对梗死灶的显示能力。结果:磁共振多序列检查共发现梗死灶1103个,FLAIR序列显示1056个,达95.74%;T2WI序列显示937个,达84.95%,二者有显著性差异(P<0.005)。FLAIR序列较T2WI序列多显示的135个梗死灶多分布在大脑皮层、灰白质交界区及侧脑室周围;全部病灶中31个超急性期梗死灶和16个位于脑干区的其他期梗死灶FLAIR序列未能显示;FLAIR序列显示急性及亚急性期梗死灶呈高信号,慢性期梗死灶呈低、高混杂信号及中心区低信号、周边高信号,T2WI序列则全部显示为高信号;同时47例患者于两侧基底节区的VR腔隙,FLAIR序列显示为边界清晰的低信号,周围正常脑组织信号。结论:FLAIR序列对于显示靠近脑表面及侧脑室周围的梗死灶,以及鉴别新、旧梗死灶及鉴别腔隙性梗死灶与VR腔隙明显优于常规T2WI序列。     

低场磁共振扩散加权成像在超急性期脑梗死的应用

目的：评价低场磁共振的扩散加权成像（DWI）在超急性期脑梗死诊断上的应用价值。方法：用低场磁共振扩散加权成像诊断超急性期脑梗死36例,分析不同时间的影像学特点,并与常规 MRI 平扫进行比较。结果：低场磁共振DWI 能显示所有患者超急性脑梗死病灶,而有11例患者在常规 MRI 平扫上未发现异常,其中7例为发病2 h 内,4例为2～4 h。此外,DWI 还可发现发病1 h 内的脑梗死高信号灶,而且 DWI 显示的病灶范围较常规 T2 WI 显示的范围更大、信号更高。结论：颅脑低场强磁共振扩散成像可以诊断超急性期脑梗死,比 T2 WI、T2 FLAIR 平扫能更早显示病变,在发现病变、确定病变部位、病变范围具有较高的价值,可为临床早期治疗提供可靠的诊断依据。     

比较低场磁共振DWI、T_2WI、FLAIR序列在脑梗死分期诊断中的优势

目的比较低场磁共振弥散加权成像（DWI）、常规T2加权像（T2WI）及液体衰减反转恢复（FLAIR）序列对各期脑梗死的诊断优势。方法 465例脑梗死患者包括超急性期（发病后6h内）13例,急性期（发病后6～24h）175例,亚急性早期（发病后1～3d）106例,亚急性晚期（发病后4～14d）93例以及慢性期（发病后15d以上）78例,均经DWI、T2WI及FLAIR序列扫描。对上述不同成像序列诊断各期脑梗死的优势进行了对比性分析。结果 DWI对超急性期、急性期及亚急性早期脑梗死的诊断高度敏感,检出率达100%,但对亚急性晚期的检出率低于T2WI和FLAIR序列。然而,T2WI和FLAIR序列对慢性脑梗死的诊断高度敏感,检出率达100%,且能检出DWI扫描未发现的梗死灶。结论合理应用DWI、T2WI及FLAIR序列,有助于鉴别新旧脑梗死灶和进行术前分期,尤其能为选择治疗方案提供可靠依据。     

MR表观扩散系数图在脑梗死演变诊断中的价值

目的　探讨三向同性扩散加权成像 (DWI)表观扩散系数图 (ADCmapping)在各期脑梗死的诊断以及在判断脑梗死的转归和分期中的应用价值。方法　应用单次激发平面回波三向同性DWI和常规MRI对 70例脑梗死患者共进行 86次检查。其中超急性期 8次 ,急性期 13次 ,亚急性期32次 ,稳定期 11次 ,慢性期 2 2次。测定各期病灶平均ADC值、相对ADC(rADC)值及中心 边缘ADC值。结果　超急性、急性期脑梗死在DWI上表现为高信号 ,其ADC值较对侧相应区域明显下降 ,平均ADC值为 (0 6 98± 0 10 4 )× 10 -3 mm2 /s ,对侧为 (0 990± 0 16 1)× 10 -3 mm2 /s(t=- 14 372 ,P <0 0 0 1) ;超急性、急性期病灶中心rADC最低 ,从中心往外逐渐升高呈梯度征 ;超急性、急性期rADC最低 ,随时间延长rADC由低到高 ,于 8～ 14d出现假性正常化 ,于慢性期高于正常水平 ,rADC与时间具有显著相关性 (r =0 92 8,P <0 0 0 1)。结论　梗死灶ADC值具有特征性演变规律 ,结合DWI及T2 WI可以对脑梗死进行分期诊断 ,对临床个体化治疗有帮助。DWI、ADC图与T2 WI相结合对判断脑梗死缺血半暗带有价值 ,动态观察可以对疗效进行评价。     

不同期相脑梗死在扩散加权成像中的信号特征及临床应用

目的:探讨在不同期相脑梗死中DWI(核磁共振扩散加权成像)及ADC图(表观弥散系数图像)的信号特点及其成像技术对脑梗死的应用价值。方法:对54例脑梗死患者,应用SE-T1WI、FSE-T2WI、T2-FLAIR、DWI序列进行横断位扫描,及ADC图像重建,并按发病时间分为超急性期、急性期、亚急性期和慢性期,观察并测量DWI图像及ADC图在不同期相脑梗死中的信号强度和ADC值的大小。结果:对于超急性期和急性期的脑梗死病灶,其DWI信号明显高于正常脑组织(P<0.05),其ADC值则低于正常脑组织(P<0.05),二图对其均有很高的显示度;对于亚急性期病灶,其DWI信号高于正常脑组织(P<0.05),其ADC值与正常脑组织信号差别不大(P>0.05),DWI可以显示病灶;对于慢性期病灶,DWI信号等或稍低于正常脑组织,对病灶显示意义不大(P>0.05),而ADC值高于正常脑组织(P<0.05),可以显示病灶区域。结论:DWI和ADC图对超急性期、急性期脑梗死都有很大的诊断意义,DWI对亚急性期病灶有一定显示度,ADC图对慢性期梗死灶也有一定诊断意义。     

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.     

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.     

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.     

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.     

MR imaging of the heart: functional imaging

To date, most applications of cardiovascular MRI relate to the evaluation of major vessels rather than the heart itself. However, MRI plays a major role in the evaluation of specific types of cardiovascular pathology, namely intracardiac and paracardiac masses, pericardial disease, and congenital heart disease. In addition, because the visualization of cardiovascular anatomy with MR is non-invasive and permits three-dimensional analysis but also allows functional assessment of the cardiac pump, it is clear that MRI will have a growing and significant impact over the next years. We review some of the technical aspect of cardiac MRI and describe the current and potential clinical and investigative applications of this new methodology.