超声定位中晚孕期胎儿脊髓圆锥位置

目的 评估超声成像定位胎儿脊髓圆锥的价值。方法 采用二维及三维超声检查438胎正常胎儿腰骶部及脊髓圆锥,中孕组(20⁺⁶~26⁺²周)261胎,晚孕组 (29⁺²~40⁺³周)177胎,记录脊髓圆锥位置,分析不同孕期胎儿脊髓位置的差异;跟踪检查其中的61胎作为对照观察组,观察胎儿中孕期及晚孕期脊髓圆锥位置。结果 中孕组胎儿脊髓圆锥下缘止于L2~3.5,晚孕组胎儿脊髓圆锥下缘止于L1~3,较中孕组平均上移0.66个椎体(P<0.001)。对照观察组61胎,晚孕期胎儿圆锥位置较中孕期平均上移0.89个椎体(P<0.001)。结论 胎儿脊髓圆锥随孕周增加而上移;三维超声能准确定位中孕期胎儿脊髓圆锥位置。     

产前超声于左无名静脉切面测量孕20~38周胎儿胸腺参数

目的 观察产前超声于左无名静脉切面测量孕20~38周胎儿胸腺参数的价值。方法 前瞻性纳入661名孕20~38周健康单胎妊娠孕妇,采用超声分别于三血管切面和左无名静脉切面测量胎儿胸腺参数,包括胸腺横径、前后径、周长及横断面积,分析各参数与孕周的相关性,观察并对比于两切面测量胸腺参数的价值。结果 超声于三血管切面所测孕35~38周胎儿胸腺横径及孕20~38周胎儿胸腺前后径、周长和横断面积均小于左无名静脉切面（P均<0.05）;且相同切面所测胎儿胸腺参数均随孕周增长而增高（P均<0.05）。三血管切面（r=0.873、0.793、0.839、0.858,P均<0.001）和左无名静脉切面（r=0.901、0.796、0.866、0.904,P均<0.001）胸腺横径、前后径、周长及横断面积测值均与孕周呈正相关。观察者间及观察者内测量胸腺参数的一致性均好（ICC均>0.75,P均<0.001）,于左无名静脉切面测量的ICC略高。结论 产前超声于左无名静脉切面测量孕20~38周胎儿胸腺各参数可减小测量误差,在一定程度上弥补三血管切面测量的不足。     

超声测距法定位中晚孕期胎儿脊髓圆锥位置

目的 通过二维和三维超声测量中晚孕期胎儿脊髓圆锥(CM)末端至骶尾部最后一个骨化中心(CS)的距离来定位CM,探索胎儿期CM位置变化的规律。方法 采用二维超声成像及三维超声表面成像检查孕19~34周566名孕妇,测量胎儿CS距离。采用3D容积存储系统存储图像、real-time 3D View软件离线分析,采用组内相关系数(ICC)评价二维与三维超声检测CS距离的一致性。分析胎儿期各孕周CS距离变化规律。结果 共253名二维与三维超声成像测量的CS距离一致性好(ICC=0.974)。CS距离与胎儿孕周呈正相关(r=0.956,P<0.001),线性回归方程为:Y=0.262X-2.508(Y:CS距离,X:孕周)。结论 三维超声表面成像测量CS距离的方法简单有效,适用于临床;CS距离与胎儿GA间的相关性可作为胎儿期CM是否低置的判断标准。     

快速平衡稳态采集与单次激发快速自旋回波序列

目的 比较MRI快速平衡稳态采集（FIESTA）与单次激发快速自旋回波（SSFSE）序列诊断正常胎儿胸腺的价值。方法 对366胎正常胎儿行MR检查,采用FIESTA与SSFSE序列分别观察胎儿胸腺的解剖和MR表现,结果行Kappa和χ²检验。于"三血管"层面测量胸腺面积（TA）、横径（TD）,于矢状位测量上下径（SID）,计算各孕周参数均值,拟合各参数与孕周的回归方程。结果 2名医师对FIESTA和SSFSE序列图像的评价结果一致性较好（Kappa=0.745、0.802,P均<0.01）,FIESTA和SSFSE序列图像显示清晰率分别为86.34%（632/732）和37.70%（276/732）,差异有统计学意义（χ²=367.520,P<0.001）。胎儿胸腺大小随孕周延长而增大,回归方程分别为：TA=－5.80+0.35×孕周（r=0.820,P<0.01）;TD=－14.59+1.63×孕周（r=0.817,P<0.01）;SID=－9.63+1.44×孕周（r=0.778,P<0.01）。结论 FIESTA较SSFSE序列可更清晰地显示胎儿胸腺的细微结构及其轮廓,MRI能清晰地显示孕22周后的胎儿胸腺。     

胎儿高位空肠闭锁超声表现

目的 观察胎儿高位空肠闭锁的超声表现。方法 回顾性分析经出生后手术确诊高位空肠闭锁的32胎胎儿资料，观察其特征性超声表现，评价产前超声所测增宽肠管的长度与生后术中测量空肠闭锁部位至屈氏（Treitz）韧带之间肠管长度的关系。结果 产前超声中，32胎多见增宽肠管呈"C"型分布，且末端均超过脊柱左缘，孕晚期增宽肠管长度均大于胃泡长度；21胎于孕28周前、11胎于孕28周及之后检出异常；31胎肠管增宽或呈"双泡征"，1胎于孕21⁺³周见腹腔钙化灶，无肠管增宽及腹腔积液；25胎增宽肠管与胃泡相通、7胎不相通；28胎增宽肠管长度及内径均随孕周而增加，2胎仅见增宽肠管内径增加，2胎内径减小。孕晚期产前超声所测增宽肠管的长度（Y）与术中测量的闭锁部位至屈氏韧带之间的肠管长度（X）呈线性正相关，回归方程为Y=0.33X+86.43（F=7.719，R²=0.36，P<0.05）。结论 高位空肠闭锁胎儿超声多见增宽肠管呈"C"型分布并与胃泡相通，其末端超过脊柱左缘；结合超声测量增宽肠管的长度有助于诊断。     

妊娠中晚期正常胎儿颅后窝生长发育规律

目的 观察妊娠中晚期正常胎儿颅后窝的生长发育规律。方法 回顾性纳入493胎妊娠25~36周正常胎儿,于图像存储与传输系统(PACS)工作站测量其MRI所示小脑横径及体积、颅后窝宽度及体积,并计算小脑体积/颅后窝体积,分析颅后窝随孕周变化的规律。结果 正常胎儿小脑横径与孕周呈直线相关,直线方程为y=－21.15+1.90x(R²=0.85,P＜0.01);小脑体积随孕周增加呈指数增长,曲线方程为y=150.52e^(0.13x)(R²=0.73,P＜0.01)。胎儿颅后窝宽度与孕周无明显相关(R²＜0.01,P=0.30),而颅后窝体积及小脑体积/颅后窝体积均随孕周增加而呈指数增长,曲线方程分别为y=1 098.50e^(0.10x)(R²=0.60,P＜0.01)及y=0.14e^(0.04x)(R²=0.30,P＜0.01)。结论 妊娠中晚期正常胎儿小脑及颅后窝体积均随孕周增加而呈指数增长,且小脑生长速度快于颅后窝。     

产前超声评价正常孕中晚期胎儿主动脉峡部血流动力学变化

目的 应用产前超声分析胎儿主动脉峡部血流动力学的变化规律及收缩末期切迹与胎儿大脑血管发育的关系。方法 收集发育正常的151胎孕23~36⁺⁶周胎儿,采用CDFI和脉冲多普勒技术采集胎儿主动脉峡部及大脑中动脉血流频谱,测量大脑中动脉收缩期峰值血流速度（MCA-S）、主动脉峡部收缩期峰值血流速度（PSV）和收缩末期最低点血流速度（NS）,计算收缩指数（ISI）,并分析PSV、NS、ISI、MCA-S与孕周及NS与MCA-S的相关关系。结果 孕23周胎儿主动脉峡部频谱可见收缩末期浅切迹,随孕周增加逐渐加深,至孕30周左右时到达基线,之后出现反向。随着孕周增加,胎儿主动脉峡部PSV和MCA-S逐渐增大,而NS及ISI逐渐减小;随着MCA-S增加,NS呈现降低趋势。以孕周为自变量X,分别以主动脉峡部PSV、NS、ISI和MCA-S为因变量Y行曲线拟合,获得曲线方程分别为NS：Y=-110.982+10.975X-0.242X²（R²=0.971,P<0.001）;PSV：Y=-20.077+5.840X-0.073X²（R²=0.794,P<0.001）;ISI：Y=-0.705+0.087X-0.002X²（R²=0.970,P<0.001）;MCA-S：Y=-67.291+4.841X-0.036X²（R²=0.911,P<0.001）。以MCA-S为自变量X,NS为因变量Y进行拟合,获得曲线方程为Y=12.757+0.580X-0.020X²（R²=0.854,P<0.001）。结论 随孕周增加,胎儿MCA-S和主动脉峡部PSV增大,NS和ISI均减小。NS与MCA-S呈负相关,推测胎儿主动脉峡部收缩末期减速切迹的变化与大脑血管网的发育有关。     

三维超声评估胎儿心室壁体积的可行性

目的 探讨三维超声时空相关成像（STIC）及虚拟器官计算机辅助分析（VOCAL）技术评估胎儿心室壁体积的可行性。方法 测量247胎22~32⁺⁶周正常胎儿心室壁体积,采用组内相关系数（ICC）分析观察者内及观察者间一致性。测量14胎心脏异常胎儿数据进行有效性验证。结果 胎儿心脏平均室壁体积与孕周具有良好相关性,左心室壁体积=－6.542+0.339×孕周（r²=0.98）,右心室壁体积=－7.509+0.384×孕周（r²=0.74）。右心室壁体积（ICC=0.994、0.888）及左心室壁体积（ICC=0.995、0.972）的观察者内及观察者间一致性良好。14胎心脏异常胎儿中,6胎心室壁体积发生改变（小于第5或大于第95百分位数）。结论 STIC及VOCAL技术可用于估测胎儿心室壁体积的参考范围,可重复性良好。     

弥散加权成像观察胼胝体发育异常胎儿脑发育

目的 采用弥散加权成像(DWI)观察胼胝体发育异常胎儿脑组织发育。方法 回顾性分析100名接受产前胎儿MR检查的单胎妊娠孕妇资料,根据胎儿胼胝体发育异常与否分为异常组(n=25)和正常组(n=75),测量双侧额叶、顶叶、颞叶、枕叶、小脑半球、半卵圆中心及脑桥表观弥散系数(ADC)并比较其组间差异,分析其随孕周变化规律。结果 100胎左、右侧脑区ADC差异均无统计学意义(P均＞0.05)。异常组与正常组胎儿颞叶ADC差异有统计学意义(P＜0.05),且顶叶ADC均最高(1.85×10^－3 mm²/s、1.87×10^－3mm²/s)而脑桥ADC均最低(1.32×10^－3 mm²/s、1.31×10^－3mm²/s)。异常组胎儿各脑区ADC与孕周均无明显相关性(P均＞0.05)。正常组胎儿额叶、顶叶、颞叶、枕叶及半卵圆中心ADC与孕周存在曲线相关(r=0.50、0.26、0.51、0.25、0.33,P均＜0.05),小脑半球及脑桥ADC与孕周呈线性负相关(r=－0.31、－0.23,P均＜0.05)。结论 胼胝体发育异常胎儿颞叶ADC高于正常胎儿, 且其各脑区ADC均与孕周无明显相关性。     

胎儿颅脑正中矢状位MRI脑桥生物学指标与孕周的相关性

目的 观察胎儿颅脑正中矢状位MRI脑桥生物学指标与孕周的相关性。方法 回顾性分析226胎孕23~38 周中枢神经系统未见明显异常胎儿（正常组）及17胎异常胎儿（异常组）头部MRI,基于正中矢状位图像获得脑桥生物学指标,包括脑桥前后径（PAD）、脑桥截面积（TPA）、脑桥基底部前后径（AP）、脑桥基底部上下径（CC）、脑桥基底部截面积（BPA）及中脑脑桥角（MAP）。根据孕周将正常组胎儿分为8个亚组,统计不同孕周胎儿脑桥生物学指标分布范围,分析正常组胎儿脑桥生物学指标与孕周的相关性,并据以判断异常组胎儿脑桥发育。结果 正常组胎儿PAD、TPA、AP、CC及BPA均与孕周均呈线性正相关（r=0.887、0.914、0.787、0.866、0.865,P均<0.001）,MAP与孕周无明显相关（P>0.05）。异常组17胎中,8胎PAD异常、8胎TPA异常、14胎AP异常、3胎CC异常、11胎BPA异常。结论 胎儿颅脑正中矢状位MRI脑桥生物学指标（PAD、TPA、AP、CC、BPA）与孕周呈正相关,可用于评估胎儿脑桥发育。     

Three-dimensional ultrasound imaging

The objective of this article is to provide scientists, engineers and clinicians with an up-to–date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment.     

Artifacts in ultrasound imaging

Ultrasound imaging artifacts of acoustic origin relating to resolution, propagation path, and attenuation are reviewed. Lateral and axial resolution limitations are artifactual in nature since a failure to resolve means a loss of detail and two adjacent structures may be visualized as one. Apparent resolution close to the transducer (speckle) is not directly related to tissue texture but is a result of interference effects from the distribution of scatterers in the tissue. Reverberation produces a set of equally spaced artifactual echoes distal to the real reflectors. The mirror image artifact is the presentation of objects that are present on one side of a strong reflector, appearing on the other side as well. Shadowing and enhancement are useful artifacts for determining the nature of masses. Enhancement results from low attenuation objects in the sound path while shadowing results from strongly reflecting or strongly attenuating objects. Additional artifacts include section thickness, refraction, multipath, side lobe, grating lobe, focal enhancement, comet tail, ring down, speed error, and range ambiguity.     

超声分子影像学研究进展

随着超声分子探针技术的兴起,超声分子成像成为当前医学影像学研究的热点之一.分子探针的设计是超声分子成像研究的重点和先决条件.靶向超声微泡(球)造影剂在分子影像中的研究、应用,愈来愈受到关注,而多学科的融合使其具有更大的发展空间.     

子宫的三维超声成像

目的：探讨子宫三维超声成像的应用价值。方法：对32例子宫作经阴道超声检查并进行三维图像重建。结果：图像满意率96．6％,畸有子宫诊断准确率及对子宫病变定位的准确率分别为100％和96．6％。结论：三维超声对诊断子宫畸形和对子宫病变的定位具有极大的价值。     

Calibrated parametric medical ultrasound imaging

The goal of this study was to develop a calibrated on-line technique to extract as much diagnostically-relevant information as possible from conventional video-format echograms. The final aim is to improve the diagnostic potentials of medical ultrasound. Video-output images were acquired by a frame grabber board incorporated in a multiprocessor workstation. Calibration images were obtained from a stable tissue-mimicking phantom with known acoustic characteristics. Using these images as reference, depth dependence of the gray level could fairly be corrected for the transducer performance characteristics, for the observer-dependent equipment settings and for attenuation in the examined tissues. Second-order statistical parameters still displayed some nonconsistent depth dependencies. The results obtained with two echoscanners for the same phantom were different; hence, an a posteriori normalization of clinical data with the phantom data is indicated. Prior to processing of clinical echograms,. the anatomical reflections and echoless voids were removed automatically. The final step in the preprocessing concerned the compensation of the overall attenuation in the tissue. A 'sliding window' processing was then applied to a region of interest (ROI) in the 'back-scan converted' images. A number of first and second order statistical texture parameters and acoustical parameters were estimated in each window and assigned to the central pixel. This procedure results in a set of new 'parametric' images of the ROI, which can be inserted in the original echogram (gray value, color) or presented as a color overlay. A clinical example is presented for illustrating the potentials of the developed technique. Depending on the choice of the parameters, four full resolution calibrated parametric images can be calculated and simultaneously displayed within 5 to 20 seconds. In conclusion, an on-line technique has been developed to estimate acoustic and texture parameters with a reduced equipment dependence and to display acoustical and textural information that is present in conventional echograms.     

Nonlinear intravascular ultrasound contrast imaging

Nonlinear contrast agent imaging with intravascular ultrasound (IVUS) is investigated using a prototype IVUS system and an experimental small bubble contrast agent. The IVUS system employed a mechanically scanned single element transducer and was operated at a 20 MHz transmit frequency (F20) for second harmonic imaging (H40), and at a 40 MHz transmit frequency (F40) for subharmonic imaging (SH20). Characterization experiments were performed with agent and tissue phantom signals acquired during transducer rotation. The suppression of transmit frequency tissue signals was achieved using a combination of pulse-inversion and bandpass filtering. H40 was found to improve the contrast-to-tissue signal ratio (CTR) by up to 22 dB relative to F20, but suffered from tissue propagation harmonics at higher pressures (>0.3 MPa). SH20 was also shown to be possible at a range of pressures (approximately 0.25 to 1.8 MPa), with tissue signals suppressed to near the noise floor. Coronary phantom experiments demonstrated the detection of agent in 1 mm diameter vessels outside a larger 4 mm diameter vessel in which the IVUS catheter was situated. These results suggest the feasibility of harmonic IVUS contrast imaging, which may have applications in coronary lumen boundary detection and vasa vasorum imaging.     

Real-time excitation-enhanced ultrasound contrast imaging

A new nonlinear contrast specific imaging modality, excitation-enhanced imaging (EEI) has been implemented on commercially-available scanners for real-time imaging. This novel technique employs two acoustic fields: a low-frequency, high-intensity ultrasound field (the excitation field) to actively condition contrast microbubbles, and a second lower-intensity regular imaging field applied shortly afterwards to detect enhanced contrast scattering. A Logiq 9 scanner (GE Healthcare, Milwaukee, WI) with a 3.5C curved linear array and an AN2300 digital ultrasound engine (Analogic Corporation, Peabody, MA) with a P4-2 phased array transducer (Philips Medical Systems, Bothell, WA) were modified to perform EEI on a vector-by-vector basis in fundamental and pulse inversion harmonic grayscale modes. Ultrasound contrast microbubbles within an 8 mm vessel embedded in a tissue-mimicking flow phantom (ATS Laboratories, Bridgeport, CT) were imaged in vitro. While video intensities of scattered signals from the surrounding tissue were unchanged, video intensities of echoes from contrast bubbles within the vessel were markedly enhanced. The maximum enhancement achieved was 10.4 dB in harmonic mode (mean enhancement: 6.3 dB; p = 0.0007). In conclusion, EEI may improve the sensitivity of ultrasound contrast imaging, but further work is required to assess the in vivo potential of this new technique.