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.     

Contrast-enhanced ultrasound in abdominal imaging

The administration of a contrast agent is considered an essential tool to evaluate abdominal diseases using Ultrasound. The most targeted organ is the liver, especially to characterize focal liver lesions and to assess the response to percutaneous treatment. However, the expanding abdominal indications of contrast-enhanced ultrasound make this technique an important tool in the assessment of organ perfusion including the evaluation of ischemic, traumatic, and inflammatory diseases.     

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。     

Artifacts and the visualization of fetal distal extremities using three-dimensional ultrasound.

OBJECTIVES: To demonstrate that acoustic shadowing in 3D US may give rise to artifacts simulating limb defects and provide a solution to eliminate its occurrence. METHODS: Twenty second trimester fetuses (gestational age 15-24 weeks) were scanned with three-dimensional ultrasound (3D US) using a sagittal acquisition plane. Fetal tibia/fibula and radius/ulna pairs were assessed for completeness of imaging. A further 20 fetuses (gestational age 20-26 weeks) were scanned in both axial and sagittal planes and the results compared to verify clear visualization of both bones. RESULTS: Shadowing from adjacent structures produced an apparent limb defect in 55% of the first 20 fetuses imaged only sagittally (18% of limb pairs). Acquiring data from more than one orientation avoided this artifact. CONCLUSIONS: The 3D US is subject to the same artifacts as two-dimensional (2D US) in terms of acoustic shadowing, although their presentation may be different. Awareness of this fact is essential for correct interpretation of 3D US studies. Three-dimensional scanning protocols should be modified to ensure that fetal structures are adequately visualized by acquiring volume data in more than one acquisition orientation.     

三维超声容积对比成像和断层超声成像技术观察胎儿脊髓栓系

目的 探讨三维超声容积对比成像（VCI）及断层超声成像（TUI）技术观察胎儿脊髓圆锥（CM）所对应的椎体位置、脊髓腰膨大的大小及形态,评估是否存在胎儿脊髓栓系（TC）的价值。方法 记录病例组17胎脊柱区病变或畸形伴TC胎儿的CM末端位置和腰膨大位置,测量脊髓腰膨大处的横径、前后径。并与300胎正常胎儿进行对比分析。结果 随着孕周的增长CM末端位置上升,300胎正常胎儿的CM末端均位于L3或L3以上椎体水平。正常胎儿脊髓腰膨大的横径和前后径均与孕周有较好的线性关系,线性回归方程为：腰膨大横径（mm）=0.677+0.147×孕周（R²=0.836,P<0.05）,腰膨大前后径（mm）=－0.994+0.152×孕周（R²=0.894,P<0.05）。与正常胎儿相应孕周正常值比较,病例组TC胎儿脊髓腰膨大的前后径减小（P=0.002）,横径差异无统计学意义（P=0.082）。结论 通过三维超声VCI及TUI技术对胎儿CM位置进行判定并分析脊髓腰膨大的形态变化,可为TC胎儿的产前诊断提供有价值的参考依据。     

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.     

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.     

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.     

Technical advances in breast ultrasound imaging.

Breast sonography plays an integral role in breast imaging. The technical advances in the field have made breast sonography an essential component of the breast imaging evaluation. In its clinical nascence, the role of breast sonography was primarily to differentiate cysts from solid masses. Technical advances such as compound imaging and harmonics have resulted in improved lesion characterization. Other technical advances such as Doppler imaging, extended field-of-view, fremitus imaging, intravenous contrast, computer-aided diagnosis, and elastography have also expanded the clinical applications of breast sonography. While some of these technical advances are still in the research phase, many are available today for clinical use. We will review these technical advances and examine their roles in clinical breast imaging today.     

基于PC平台的扩展视野超声成像

扩展视野超声成像技术可以利用常规超声成像系统获得观察视野更大的图像,使得医生能够全面了解被成像部位的解剖结构,从而得出更客观和准确的诊断结果.本文给出一种基于PC平台的扩展视野超声成像系统及图像配准和拼接的快速算法.实验证明此算法不仅有较好的成像精度,并且有望实现实时成像.     

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.     

Pipeline sampled-delay focusing in ultrasound imaging systems

A sampled-delay focusing technique was recently proposed by the authors which completely eliminates the use of analog L-C delay lines for beam focusing in completely eliminates the use of analog L-C delay lines for beam focusing in ultrasound B-mode imaging systems. With this approach, the product of sampling rate and maximum time delay is required to be less than unity. To remove this constraint, we propose in this paper a first-in-first-out pipelining technique. This allows one to perform beam steering and dynamic focusing simultaneously on a resolution-cell basis and in a completely digital fashion without the use of analog L-C delay lines.     

超声影像学技术在吞咽障碍中的应用

近年来,超声影像学技术在康复医学科中的应用越来越广,其在吞咽障碍评估和治疗方面的应用也逐渐受到关注。研究表明超声影像学检查不仅可评估吞咽障碍,还可使吞咽障碍的治疗精确化。另外超声影像学技术还有助于在其他颈部疾病的治疗中避免损伤吞咽相关结构,预防吞咽障碍的发生。该文总结了相关研究进展,以指导临床应用。     

Real-time spatial compound imaging in breast ultrasound

To determine the role of real-time spatial compound imaging in breast ultrasound (US), 38 patients with a total of 50 benign changes (fibroadenomas, cysts, lactiferous duct dilatation) underwent both conventional B-mode US and real-time spatial compound imaging under standardized examination settings. Subsequently, images were reviewed independently by three readers experienced in breast US and evaluated according to a multistage scoring system with regard to the presence of artefacts, delineation of boundaries and depiction of internal structures. With significant reader concordance, real-time spatial compound imaging was found to produce speckle reduction with improvement of tissue differentiation, increased conspicuity of low-contrast lesions, enhanced delineation of capsular margins and ducts, and improved depiction of internal architecture of solid lesions, as well as clearer visualization of cystic contents due to clutter reduction. Preservation of central acoustic enhancement and lateral edge shadowing in cysts and fibroadenomas, however, was recorded better in conventional imaging.