局部心肌功能评价的新方法一斑点追踪技术和速度向量显像

局部心肌功能评价在各种类型的心脏病中都有重要的作用,过去常用的评价方法以组织多普勒技术为基础,该技术局限性主要为角度依赖性。二维图像斑点追踪技术和速度向量显像能够克服组织多普勒技术的局限性来检测局部心肌功能。本文对二维图像斑点追踪技术和速度向量显像的原理、临床应用、存在的问题及发展前景综述如下。     

斑点追踪技术对评价急性心梗患者 PCI术后左室功能恢复的临床应用价值

目的：应用二维斑点追踪显像技术（ STI）检测急性心肌梗死（ AMI）患者在经皮冠状动脉介入治疗术（PCI）前后不同时期左心室收缩及舒张功能的变化,探讨斑点追踪显像技术对定量评价再灌注后心肌功能恢复的临床应用价值。方法选择成功行PCI术治疗的急性心肌梗死患者35例,分别于PCI术前、术后7天及术后2个月行超声心动图检查及相关参数采集,并选择同期健康体检者32例作为对照组进行相同检查及图像采集分析。测量二尖瓣E峰和A峰,并计算出E／A值;用改良的Simpson′s公式测量左心室射血分数（ LVEF）;采用斑点追踪显像技术测量狭窄冠脉供血的缺血心肌和正常冠脉供血的非缺血心肌应变指标： LS、RSpeak、TP、SRe及SRa值。结果急性心肌梗死会导致心脏整体及局部的收缩及舒张功能改变,再灌注后,心肌舒张功能的恢复较收缩功能需更长时间;心脏整体功能恢复正常时,其局部心肌运动功能仍可存在异常。结论应用STI技术可以定量评价急性心肌梗死患者经PCI术治疗后左心室的整体及局部功能的恢复情况。     

三维斑点追踪显像评估左心功能的新进展

心肌纤维排列的多样性决定了左心室在三维空间运动的复杂性,二维斑点跟踪技术不能准确地评估心肌的三维运动。三维斑点追踪显像是一项在立体空间内而非平面上追踪心肌斑点运动的新技术,可以测量各个方向上的心肌应变,比二维斑点追踪更能真实反映心肌的变形和运动。本文对三维图像斑点追踪显像的原理、临床应用、存在的问题及发展前景综述如下。     

超声二维斑点迪踪显像技术在心脏疾病诊断中的临床应用进展

超声二维斑点追踪成像技术（speckle tracking imaging,STI）是新近发展起来的超声定量分析工具,是通过逐帧追踪灰阶图像中小于入射超声波长的细小结构产生的背向散射斑点信息,实时跟踪不同帧频间同一位置的心肌运动轨迹,可无创、准确地测量左心室旋转及扭转角度。斑点追踪技术克服了传统的组织多普勒技术（TDI）的角度依赖性,也可以用于检测局部心肌功能。     

彩色组织追踪显像在心力衰竭患者左心室心肌运动异常中的应用价值

 目的 探讨彩色组织追踪显像(CTTI)在评价心力衰竭患者左室壁心肌运动异常方面的临床价值.方法 应用彩色组织追踪显像对36例心力衰竭患者(异常组)及30例健康者(对照组)左心室壁各节段收缩期运动位移进行检测和分析,并将异常组与对照组进行显著性检验.结果 健康人左室壁各节段收缩期运动位移有一定的规律性,在同一室壁从基底段到心尖段逐渐减低,心力衰竭患者可检出运动异常节段,表现为位移值的减低及其彩色编码显像和曲线波形的改变.异常组的运动位移值均低于对照组的相应节段,两者比较差异有统计学意义(P<0.05).结论 彩色组织追踪显像通过定量检测心力衰竭患者左室壁异常心肌运动的位移值及观察彩色编码显像变化和曲线波形的改变,能够快速及无创的定量评价左心室节段性收缩功能和左室壁心肌运动异常.     

超声评估左室扭转运动研究进展

近年来,超声技术在左室扭转运动评估中的应用越来越广泛,其自身技术特性各有优势与缺陷。组织多普勒显像可准确评价左室扭转运动,但其可能对左室扭转运动低估。定量组织速度成像可简捷直观且准确地观察左室扭转运动,但局限于对扭转的定性研究。斑点追踪技术显像准确、重现性好,但对图像质量要求较高。本文拟对各种超声技术在左室扭转运动评估中的研究进展作一综述,以期有助于超声技术的合理选择和良好应用。     

静息门控~（99m）Tc－MIBI心肌断层显像定量分析在诊断心肌缺血中的临床价值

静息门控９９ｍＴｃ－甲氧基异丁基异腈心肌断层显像能同时评价局部心肌灌注与功能，对功能较好的心肌缺血节段的检测优于潘生丁负荷－静息心肌断层显像．此方法能预测９７％的无再分布、８１％的再分布和２９％的反向再分布灌注低下室壁节段．     

PET心肌灌注显像测定心肌血流量及冠状动脉血流储备的研究进展

PET心肌灌注显像可绝对定量测定局部心肌血流量（MBF）和冠状动脉血流储备（CFR）。由于显像剂半衰期短,允许在短时间内重复进行PET心肌灌注显像,获得静息态、冷加压试验和药物负荷试验等不同状态下的MBF,进而评价冠状动脉血管内皮依赖性和非依赖性的CFR功能。在早期诊断冠心病,准确诊断冠状动脉多支病变,评价微血管病变,早期检测冠状动脉内皮细胞功能异常及CFR功能的异常,估测预后,帮助临床治疗方案的制定以及检测疗效等方面,PET心肌灌注显像有重要的临床价值。该文将介绍PET心肌灌注显像相关知识及其在心血管领域的主要应用。     

多普勒组织成像在临床心脏电生理学中的应用

多普勒组织成像(Doppler Tissue Imaging, DTI)是一种观察心肌室壁运动的新技术,将心肌室壁运动产生的低频多普勒信号以色彩、频谱或曲线方式选择性地成像.1992年McDicken首次报道将彩色编码技术应用于模拟多普勒组织超声,以评价心肌组织运动速度的大小和方向,至今已在心脏功能、心脏激动研究中广泛应用.DTI主要有七种显示模式:(1)多普勒组织速度成像(DTV)的彩色二维组织速度图(C-TVI);(2)基于DTV的多普勒组织加速度图(DTA);(3)多普勒组织能量图(DTE);(4)应变率成像(SMR);(5)彩色多普勒组织M 型(DT-M);(6)多普勒组织频谱图(DT-PW);(7)曲线化解剖M型技术.在DTI中,DTA图可直观半定量地反映局部心肌运动的速度变化率;DT-M主要反映心肌运动的方向与速度,时间分辨力高;DT-PW可精确定量,反映不同室壁、不同节段心内、外膜的运动速度的变化.DTI技术反映心肌机械收缩情况 [1],而电激动与机械收缩是互相关联的,故DTI也可反映心肌激动传导顺序.本文简单介绍了DTI在心脏电生理学方面的应用.     

超声心动图新技术在心脏再同步化治疗中的应用

心脏再同步化(CRT)治疗顽固性心力衰竭可提高生活质量、降低再住院率及病死率。随着超声心动图技术的发展,目前推出了可以准确评价心脏不同步性,指导、评价CRT治疗的新技术。现综述如下。1 CRT不同步性评估超声心动图新技术1·1二维超声心动图可直观观察心室肌的不同步运动,但由于时间分辨率低,评价心肌的不同步运动敏感性较低。1·2 M型超声心动图通过间隔和后壁的延迟(SPWMD)来评价室内的不同步运动。SPWMD≥130 ms对于识别CRT的中长期疗效有很好的阴性预测值,能应用于识别患者能否受益于CRT[2],但当室壁运动障碍时无法准确评估,此外,其只能提供间隔与后壁2个壁段信息等,不能准确识别心室内的不同步。1·3脉冲多普勒用于评价心脏的房室间不同步及左右室间不同步,血流多普勒也可以通过测量主动脉速度时间积分(VTI)等优化房室间期和左、右心室起搏间期[3]。1·4组织多普勒技术包括组织多普勒成像(TDI)和组织追踪显像、应变率显像、组织同步化显像。TDI能精确地定量分析机械不同步、左心室整体和局部的功能,在CRT中得到了广泛的应用。Yu等[4]比较了TDI 3种显像模式,在CRT治疗心力衰竭55例3个月后预测...     

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.     

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.     

Computer-assisted imaging of the fetus with magnetic resonance imaging

The purpose of this paper is to review the use of magnetic resonance imaging (MRI) of the fetus and to propose future techniques and applications. Institutional review board approved MR images of the fetus were acquired in 66 patients with sonographically suspected fetal abnormalities. Axial, coronal, and sagittal short TR, short TE images were obtained. In addition, 12 studies were performed with rapid scans requiring 700–1200 ms using either GRASS or Spoiled GRASS techniques. Sequential studies demonstrating fetal motion were also performed. Three studies with 3D IR prepped GRASS were performed. These allowed for orthogonal and non-orthogonal reformatted views and 3D display. Normal fetal structures were shown with MRI, including brain, heart, liver, stomach, intestines, and bladder. Gross fetal anomalies could generally be demonstrated with MRI. MRI may give additional information to that of sonography in fetal anomalies, particularly those involving the central nervous system, and in the detection of fat, blood, and meconium. MRI of the fetus can demonstrate normal and abnormal structures. Newer techniques with faster imaging will allow for greater possibility of computer assisted manipulation of data.     

Invited. Ultrafast MR imaging of the abdomen: Echo planar imaging and diffusion-weighted imaging

Ultrafast MRI technique has become available with the introduction of new generation MR scanners for abdominal imaging. However, there is no consensus about the optimal imaging acquisition at the present time. Because single shot echo planar imaging (EPI) technique is based on high technology and had just applied in clinical imaging, further clinical investigation will be needed. Currently, the hypersensitivity to magnetic inhomogeneity and local magnetic susceptibility and the low spatial resolution may limit the widespread application of EPI technique. In addition to providing information for morphologic diagnosis, EPI will be more widely used for functional and qualitative diagnosis. Diffusion-weighted imaging can be used for differentiation of solid tumors according to their different cellular construction, evaluation of cystic lesions based on the different viscosity of their contents, and assessment of diffused pathologic changes in the parenchyma of solid organs. In addition to the previous parameters such as proton density and T1 and T2 values, diffusion factors may provide important information for the qualitative and dynamic evaluation of abdominal pathologic changes. Even though there are many difficulties that must be solved for diffusion-weighted imaging, a more wide application of this technique is expected through technologic improvement.     

Whole-body imaging of the musculoskeletal system: the value of MR imaging

In clinical practice various modalities are used for whole-body imaging of the musculoskeletal system, including radiography, bone scintigraphy, computed tomography, magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT). Multislice CT is far more sensitive than radiographs in the assessment of trabecular and cortical bone destruction and allows for evaluation of fracture risk. The introduction of combined PET-CT scanners has markedly increased diagnostic accuracy for the detection of skeletal metastases compared with PET alone. The unique soft-tissue contrast of MRI enables for precise assessment of bone marrow infiltration and adjacent soft tissue structures so that alterations within the bone marrow may be detected before osseous destruction becomes apparent in CT or metabolic changes occur on bone scintigraphy or PET scan. Improvements in hard- and software, including parallel image acquisition acceleration, have made high resolution whole-body MRI clinically feasible. Whole-body MRI has successfully been applied for bone marrow screening of metastasis and systemic primary bone malignancies, like multiple myeloma. Furthermore, it has recently been proposed for the assessment of systemic bone diseases predisposing for malignancy (e.g., multiple cartilaginous exostoses) and muscle disease (e.g., muscle dystrophy). The following article gives an overview on state-of-the-art whole-body imaging of the musculoskeletal system and highlights present and potential future applications, especially in the field of whole-body MRI.     

Osteoporosis imaging: state of the art and advanced imaging

Osteoporosis is becoming an increasingly important public health issue, and effective treatments to prevent fragility fractures are available. Osteoporosis imaging is of critical importance in identifying individuals at risk for fractures who would require pharmacotherapy to reduce fracture risk and also in monitoring response to treatment. Dual x-ray absorptiometry is currently the state-of-the-art technique to measure bone mineral density and to diagnose osteoporosis according to the World Health Organization guidelines. Motivated by a 2000 National Institutes of Health consensus conference, substantial research efforts have focused on assessing bone quality by using advanced imaging techniques. Among these techniques aimed at better characterizing fracture risk and treatment effects, high-resolution peripheral quantitative computed tomography (CT) currently plays a central role, and a large number of recent studies have used this technique to study trabecular and cortical bone architecture. Other techniques to analyze bone quality include multidetector CT, magnetic resonance imaging, and quantitative ultrasonography. In addition to quantitative imaging techniques measuring bone density and quality, imaging needs to be used to diagnose prevalent osteoporotic fractures, such as spine fractures on chest radiographs and sagittal multidetector CT reconstructions. Radiologists need to be sensitized to the fact that the presence of fragility fractures will alter patient care, and these fractures need to be described in the report. This review article covers state-of-the-art imaging techniques to measure bone mineral density, describes novel techniques to study bone quality, and focuses on how standard imaging techniques should be used to diagnose prevalent osteoporotic fractures.     

Thin-section diffusion-weighted magnetic resonance imaging of the brain with parallel imaging

BACKGROUND: Thin-section diffusion-weighted imaging (DWI) is known to improve lesion detectability, with long imaging time as a drawback. Parallel imaging (PI) is a technique that takes advantage of spatial sensitivity information inherent in an array of multiple-receiver surface coils to partially replace time-consuming spatial encoding and reduce imaging time. PURPOSE: To prospectively evaluate a 3-mm-thin-section DWI technique combined with PI by means of qualitative and quantitative measurements. MATERIAL AND METHODS: 30 patients underwent conventional echo-planar (EPI) DWI (5-mm section thickness, 1-mm intersection gap) without parallel imaging, and thin-section EPI-DWI with PI (3-mm section thickness, 0-mm intersection gap) for a b value of 1000 s/mm(2), with an imaging time of 40 and 80 s, respectively. Signal-to-noise ratio (SNR), relative signal intensity (rSI), and apparent diffusion coefficient (ADC) values were measured over a lesion-free cerebral region on both series by two radiologists. A quality score was assigned for each set of images to assess the image quality. When a brain lesion was present, contrast-to-noise ratio (CNR) and corresponding ADC were also measured. Student t-tests were used for statistical analysis. RESULTS: Mean SNR values of the normal brain were 33.61+/-4.35 and 32.98+/-7.19 for conventional and thin-slice DWI (P>0.05), respectively. Relative signal intensities were significantly higher on thin-section DWI (P<0.05). Mean ADCs of the brain obtained by both techniques were comparable (P>0.05). Quality scores and overall lesion CNR were found to be higher in thin-section DWI with parallel imaging. CONCLUSION: A thin-section technique combined with PI improves rSI, CNR, and image quality without compromising SNR and ADC measurements in an acceptable imaging time.