Comparison of contrast in brightness mode and strain ultrasonography of glial brain tumours

ABSTRACT: BACKGROUND: Image contrast between normal tissue and brain tumours may sometimes appear to be low in intraoperative ultrasound. Ultrasound imaging of strain is an image modality that has been recently explored for intraoperative imaging of the brain. This study aims to investigate differences in image contrast between ultrasound brightness mode (B-mode) images and ultrasound strain magnitude images of brain tumours. METHODS: Ultrasound radiofrequency (RF) data was acquired during surgery in 15 patients with glial tumours. The data were subsequently processed to provide strain magnitude images. The contrast in the B-mode images and the strain images was determined in assumed normal brain tissue and tumour tissue at selected regions of interest (ROI). Three measurements of contrast were done in the ultrasound data for each patient. The B-mode and strain contrasts measurements were compared using the paired samples t- test. RESULTS: The statistical analysis of a total of 45 measurements shows that the contrasts in the strain magnitude images are significantly higher than in the conventional ultrasound B-mode images (P < 0.0001). CONCLUSIONS: The results indicate that ultrasound strain imaging provides better discrimination between normal brain tissue and glial tumour tissue than conventional ultrasound B- mode imaging. Ultrasound imaging of tissue strain therefore holds the potential of becoming a valuable adjunct to conventional intraoperative ultrasound imaging in brain tumour surgery.     

肝炎和肝硬化患者胆囊B超改变的观察与分析

目的研究肝炎肝硬化患者胆囊彩色B超声像图变化，并探讨其临床意义。方法采用彩色超声诊断仪对139例肝炎和肝硬化患者及65例非肝炎体检者进行胆囊超声检查。结果慢性肝炎、重型肝炎、肝硬化患者组与非肝炎对照组彩色B超胆囊异常率比较均差异非常显著（P〈0．01）。慢性肝炎与重型肝炎、肝硬化组之间胆囊异常率也存在明显的差异（P〈0．05）。结论慢性肝病患者胆囊异常并不是胆囊本身炎症所致，胆囊声像图的改变对判断肝脏实质性病变的严重程度及指导临床治疗有一定的作用。     

血浆甲状腺球蛋白、颈部超声以及99TcmO4-甲状腺静态显像对甲状腺结节良恶性鉴别的临床意义

目的 探讨术前血浆甲状腺球蛋白（Tg）、颈部超声及99TcmO4-甲状腺静态显像三者联合检查对鉴别甲状腺结节良恶性的临床意义.方法 对手术并有病理诊断的103例甲状腺结节患者进行回顾性资料分析.根据患者术前检查项目分为三组：三项完整检查者31例为A组,检查颈部超声和99TcmO4-甲状腺静态显像者43例为B组,仅检查颈部超声者29例为C组.按照术后病理结果分别获得三组检查结果的灵敏度、特异性和准确率.结果 A、B、C三组的灵敏度分别为28.5％、83.3％、56.2％;特异性分别为58.3％、58.1％、46.2％,准确率分别为51.6％,65.1％,51.7％.结论 颈部超声和99TcmO4-甲状腺静态显像联合检查组（B组）的灵敏度、特异性及准确率明显高于单独颈部超声检查组（C组）,A组三项联合检查的灵敏度、特异性和准确率与B,C两组相比无优势.甲状腺结节术前完善颈部超声和99TcmO4-甲状腺静态显像检查对于甲状腺结节的鉴别诊断是有必要的.     

Nonlinear ultrasound propagation through layered liquid and tissue-equivalent media: computational and experimental results at high frequency

Nonlinear propagation has been demonstrated to have a significant impact on ultrasound imaging. An efficient computational algorithm is presented to simulate nonlinear ultrasound propagation through layered liquid and tissue-equivalent media. Results are compared with hydrophone measurements. This study was undertaken to investigate the role of nonlinear propagation in high frequency ultrasound micro-imaging. The acoustic field of a focused transducer (20 MHz centre frequency, f-number 2.5) was simulated for layered media consisting of water and tissue-mimicking phantom, for several wide-bandwidth source pulses. The simulation model accounted for the effects of diffraction, attenuation and nonlinearity, with transmission and refraction at layer boundaries. The parameter of nonlinearity, B/A, of the water and tissue-mimicking phantom were assumed to be 5.2 and 7.4, respectively. The experimentally measured phantom B/A value found using a finite-amplitude insert-substitution method was shown to be 7.4 +/- 0.6. Relative amounts of measured second and third harmonic pressures as a function of the fundamental pressures at the focus were in good agreement with simulations. Agreement within 3% was found between measurements and simulations of the beam widths of the fundamental and second harmonic signals following propagation through the tissue phantom. The results demonstrate significant nonlinear propagation effects for high frequency imaging beams.     

基于经验模态分解和减影法高强度聚焦超声离体牛肝组织损伤的监控成像

背景：聚焦超声照射后,聚焦区域组织会在B超图像对应的位置形成强回声现象,这可能会在软组织中形成声阻抗差,对损伤检测造成干扰。 目的：提出一种基于经验模态分解和减影法的损伤成像方法,用于检测高强度聚焦超声治疗过程中的组织损伤。 方法：结合经验模态分解和减影算法各自的优点,针对牛肝组织回波信号信噪比较低的特点,利用经验模态分解对治疗前后超声回波信号进行自适应分解以消除噪声信号,然后对治疗后的每帧去噪信号和治疗前的去噪信号进行减影,最后对数据经过希尔伯特变换和对数变换后成像。 结果与结论：利用结合经验模态分解的减影方法获得了离体牛肝组织的监控图像及相应的B超图像和直接减影图。实验结果表明,结合经验模态分解的减影成像方法能够较有效地对聚焦超声引起的软组织损伤进行成像,并能检测到B超成像不能检测到的较小组织损伤,且其对比度和分辨率均高于直接减影成像。     

B超在早期宫角妊娠诊治中的临床应用价值

目的 探讨B超在早期宫角妊娠诊治中的临床应用价值.方法 选择川北医学院附属医院2005年6月至2010年6月临床拟诊早孕经B超诊断的早期官角妊娠自愿终止妊娠256例患者,年龄21～42岁.做二维或三维超声诊断,并在B超监测引导下施行人工流产或清官术,全部病例术后10d左右返院复诊.结果 全部病例经腹或经阴道B超(包括二...     

基于Golay互补序列的20 MHz眼科超声成像方法

目的研究一种新型20 MHz眼科超声扫描成像方法,可在满足临床成像分辨力和声能安全性要求的前提下,显著提高图像的探测深度,拓展20 MHz超声频段的临床应用范围。方法通过8位Golay互补序列,激励超声换能器产生超声波。回波信息经高速采集与匹配滤波后,采用相邻正、反编码扫描线数据复用的方法交替相加,完成解码运算。在保证图像扫描线数和扫描帧频的前提下,实现实时显像。最后通过钨丝靶线和仿组织超声体模实验,验证了新的成像方法在保持原有分辨能力与扫描帧频不变的前提下,提高了图像的探测深度。结果与传统单脉冲模式相比,Golay互补编码模式成像中轴向分辨率与侧向分辨率分别达到80μm和150μm,小信号探测深度增加约0.5 cm,图像信噪比也得到显著改善。结论基于Golay互补序列实现20 MHz眼部组织超声成像,相对于传统成像方式可极大改善图像质量,具有很好的临床应用前景。     

基于S-G滤波的超声造影分析参数灌注成像

为弥补以往超声造影定量分析软件将感兴趣区(ROI)作为均质的整体区域进行分析的不足,提出一种基于S-G滤波器的在时域内直接处理数据平滑问题的定量分析方法,针对ROI区域内部像素点进行灌注成像参数分析,快速并可最大限度地保留原始有用信息。首先获得超声造影的原始DICOM动态医学数据,获取ROI内每个像素点的时间强度曲线,用S-G滤波器对时间强度曲线进行分析,得到反映灌注时相和灌注强度的多项定量分析参数,如到达时间(AT)、达峰时间(TTP)、达峰强度(PI)、平均通过时间(MTT)、曲线下面积(AUC)和上升斜率(RS)等;然后再对像素点参数分别进行彩色编码并以不同颜色显示,从而准确量化和直观显示超声造影的各项灌注参数。为评估该分析方法的稳定性,比较3位研究者分别对15个肝细胞癌病灶的分析结果。经统计,所有参数的组间相关系数(ICC)>0.80,验证了该方法的可行性和稳定性。     

Deformation-compensated averaging for clutter reduction in epiphotoacoustic imaging in vivo

Photoacoustic imaging, based on ultrasound detected after laser irradiation, is an extension to diagnostic ultrasound for imaging the vasculature, blood oxygenation and the uptake of optical contrast media with promise for cancer diagnosis. For versatile scanning, the irradiation optics is preferably combined with the acoustic probe in an epi-style arrangement avoiding acoustically dense tissue in the acoustic propagation path from tissue irradiation to acoustic detection. Unfortunately epiphotoacoustic imaging suffers from strong clutter, arising from optical absorption in tissue outside the image plane, and from acoustic backscattering. This limits the imaging depth for useful photoacoustic image contrast to typically less than one centimeter. Deformation-compensated averaging (DCA), which takes advantage of clutter decorrelation induced by palpating the tissue with the imaging probe, has previously been proposed for clutter reduction. We demonstrate for the first time that DCA results in reduced clutter in real-time freehand clinical epiphotoacoustic imaging. For this purpose, combined photoacoustic and pulse-echo imaging at 10-Hz frame rate was implemented on a commercial scanner, allowing for ultrasound-based motion tracking inherently coregistered with photoacoustic frames. Results from the forearm and the neck confirm that contrast is improved and imaging depth increased by DCA.     

Varying ultrasound power level to distinguish surgical instruments and tissue

We investigate a new framework of surgical instrument detection based on power-varying ultrasound images with simple and efficient pixel-wise intensity processing. Without using complicated feature extraction methods, we identified the instrument with an estimated optimal power level and by comparing pixel values of varying transducer power level images. The proposed framework exploits the physics of ultrasound imaging system by varying the transducer power level to effectively distinguish metallic surgical instruments from tissue. This power-varying image-guidance is motivated from our observations that ultrasound imaging at different power levels exhibit different contrast enhancement capabilities between tissue and instruments in ultrasound-guided robotic beating-heart surgery. Using lower transducer power levels (ranging from 40 to 75% of the rated lowest ultrasound power levels of the two tested ultrasound scanners) can effectively suppress the strong imaging artifacts from metallic instruments and thus, can be utilized together with the images from normal transducer power levels to enhance the separability between instrument and tissue, improving intraoperative instrument tracking accuracy from the acquired noisy ultrasound volumetric images. We performed experiments in phantoms and ex vivo hearts in water tank environments. The proposed multi-level power-varying ultrasound imaging approach can identify robotic instruments of high acoustic impedance from low-signal-to-noise-ratio ultrasound images by power adjustments.     

Speckle reduction in ultrasonic images through a maximum likelihood based adaptive filter

Speckle poses serious problems in the interpretation of ultrasound images. It reduces contrast and resolution, making it difficult to identify the presence of abnormalities in B mode images. Using a recently proposed compound probability density function (pdf) for the statistics of the backscattered ultrasonic signals, an adaptive filter for speckle reduction is implemented and tested on B mode images of a tissue mimicking phantom. Results suggest that the adaptive filter based on a maximum likelihood approach improves the ability to classify targets in images while retaining the details in the original unprocessed image.     

基于矢量场预估的二维超声弹性成像方法

传统的超声弹性成像方法中以一维弹性超声成像为主，忽略被测体横向位移导致成像效果较差。本研究提出一种基于矢量场预估的准静态二维超声弹性成像方法。首先获取包络线特征峰值指纹信息，采用光流跟踪法对特征指纹进行跟踪并进行矢量场预估；然后根据预估矢量场采用相位相关算法对位移场进行精确计算；通过最小二乘法滤波求取应变场实现准静态二维弹性超声成像。采用有限元分析法对该方法进行有效性验证，对比在泊松比在0．4～0．48范围时该成像方法与其他成像方法的成像效果。实验结果表明，该方法是一种清晰度更高，鲁棒性更好的超声弹性成像方法。     

Ultrasound-guided microwave imaging of breast cancer: tissue phantom and pilot clinical experiments

Microwave imaging promises high contrast between tumor and normal breast tissues, but its spatial resolution is limited. Here, we present a multimodality approach for high-resolution microwave imaging, where microwave image reconstruction is structurally guided by ultrasound imaging. The combined imaging concept is demonstrated using tissue phantom measurements obtained from a 16 x 15 transmitter/receiver microwave imaging system and a modified B-mode ultrasound system. With the geometry of the target and background known a priori from ultrasound, successful dielectric property images are recovered using a finite element-based reconstruction algorithm. We show that a target as small as 1.2 mm in diameter can be imaged with the multimodality approach, whereas it is impossible to detect such a small-size object using microwave imaging alone. The pilot clinical studies on two cases suggest that breast tumors can be much more accurately detected by the multimodality method.     

Tumor bracketing and safety margin estimation using multimodal marker seeds: a proof of concept

Accurate tumor excision is crucial in the locoregional treatment of cancer, and for this purpose, surgeons often rely on guide wires or radioactive markers for guidance toward the lesion. Further improvement may be obtained by adding optical guidance to currently used methods, in the form of intra-operative fluorescence imaging. To achieve such a multimodal approach, we have generated markers that can be used in a pre-, intra-, and post-operative setting, based on a cocktail of a dual-emissive inorganic dye, lipids, and pertechnetate. Phantom experiments demonstrate that these seeds can be placed accurately around a surrogate tumor using ultrasound. Three-dimensional bracketing provides delineation of the entire lesion. Combined with the multimodal nature, this provides the opportunity to predetermine the resection margins by validating the placement accuracy using multiple imaging modalities (namely, x ray, MRI, SPECT/CT, and ultrasound). The dual-emissive fluorescent properties of the dye provide the unique opportunity to intra-operatively estimate the depth of the seed in the tissue via multispectral imaging: emission green λmax=520 nm≤5 mm penetration versus emission red λmax=660 nm≤12 mm penetration. By using particles with different colors, the original geographic orientation of the excised tissue can be determined.     

Feasibility assessment of shear wave elastography to rotator cuff muscle

Pre‐surgical measurement of supraspinatus muscle extensibility is important for rotator cuff repair. The purpose of the present study was to explore the potential feasibility of a shear wave ultrasound elastography (SWE)‐based method, combined with B‐mode ultrasound, to measure the in vivo stiffness of the supraspinatus muscle non‐invasively and thus obtain key information about supraspinatus muscle extensibility. Our investigation comprised two steps. First, we determined the orientation of the supraspinatus muscle fibers in cadaveric shoulders without rotator cuff tear in order to optimize the ultrasound probe positions for SWE imaging. Second, we investigated the feasibility of quantifying the stiffness of the normal supraspinatus muscle by SWE in vivo. The supraspinatus muscle was divided into four anatomical regions: anterior superficial (AS), posterior superficial (PS), anterior deep (AD), and posterior deep (PD). Each region was examined by SWE. The SWE stiffnesses of AD, AS, PD, and PS were 40.0 ± 12.4, 34.0 ± 9.9, 32.7 ± 12.7, 39.1 ± 15.7 kPa, respectively. SWE combined with B‐Mode ultrasound imaging could be a feasible method for quantifying the local stiffness of the rotator cuff muscles. Clin. Anat. 28:213–218, 2015. © 2014 Wiley Periodicals, Inc.     

The natural history of popliteal cysts in children: an ultrasound study.

The natural history of juvenile popliteal cysts is poorly defined. No previous study has used imaging to prove these cysts spontaneously resolve. Over 4 years, 14 children presented with popliteal swellings consistent with a popliteal cyst. A single ultrasound scan confirmed the diagnosis and measured the cyst dimension. No treatment was instituted. At a mean follow up of 28.6 months, repeat examination and ultrasound confirmed resolution of the popliteal cyst in seven cases. In six cases ultrasound confirmed the popliteal cysts remained at a mean follow up of 16.5 months. No cyst increased in size. True juvenile popliteal cysts can resolve spontaneously. This is accurately demonstrated with ultrasound imaging.     

Flow-cytometric DNA analysis of hematopoietic and lymphoid proliferations: a comparison of fresh, formalin-fixed and B5-fixed tissues

Flow-cytometric DNA analysis of human tumors using paraffin-embedded tissue samples is becoming an increasingly popular method of determining ploidy and proliferative rate. Particularly with hematopoietic/lymphoid proliferations, little is known about how these data compare with data from fresh suspension studies, or how B5-fixed tissues compare with those fixed in formalin. For these reasons, flow-cytometric DNA ploidy and cell cycle analysis was performed on 16 hyperplastic tonsils and 28 lymphoid/hematopoietic neoplasms using fresh (or fresh-frozen) cell suspensions (FR), B5-fixed paraffin-embedded (B5), and formalin-fixed paraffin-embedded (FO) tissue. Ploidy analysis showed all tonsil specimens to be diploid regardless of preparative method; however, for the neoplastic cases the FO and B5 preparations agreed with the FR preparations in 50% and 61% of the cases, respectively. Complete agreement between all three tissue preparation methods was present in only 36% of the neoplastic cases. Percent S or S + G2M phase fractions showed relatively poor correlation between the three preparative methods, with the best correlations found between the FR and B5 samples (S phase, r = 0.44; S + G2M, r = 0.43). In conclusion, while potentially useful data can be obtained from flow-cytometric DNA analysis of fixed, paraffin-embedded lymphoid/hematopoietic tissues, the specific limitations of such analyses must be recognized. Ploidy and proliferative phase data from fixed tissue preparations are not equivalent to information obtained from fresh suspension studies. B5-fixed tissue provides an acceptable alternative to formalin-fixed tissue for such analyses.     

Analysis of recoverable current from one component of magnetic flux density in MREIT and MRCDI

Magnetic resonance current density imaging (MRCDI) provides a current density image by measuring the induced magnetic flux density within the subject with a magnetic resonance imaging (MRI) scanner. Magnetic resonance electrical impedance tomography (MREIT) has been focused on extracting some useful information of the current density and conductivity distribution in the subject Omega using measured B(z), one component of the magnetic flux density B. In this paper, we analyze the map Tau from current density vector field J to one component of magnetic flux density B(z) without any assumption on the conductivity. The map Tau provides an orthogonal decomposition J = J(P) + J(N) of the current J where J(N) belongs to the null space of the map Tau. We explicitly describe the projected current density J(P) from measured B(z). Based on the decomposition, we prove that B(z) data due to one injection current guarantee a unique determination of the isotropic conductivity under assumptions that the current is two-dimensional and the conductivity value on the surface is known. For a two-dimensional dominating current case, the projected current density J(P) provides a good approximation of the true current J without accumulating noise effects. Numerical simulations show that J(P) from measured B(z) is quite similar to the target J. Biological tissue phantom experiments compare J(P) with the reconstructed J via the reconstructed isotropic conductivity using the harmonic B(z) algorithm.     

MRI-compatible transurethral ultrasound system for the treatment of localized prostate cancer using rotational control

Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy is a potential minimally invasive treatment for localized prostate cancer offering precise targeting of tissue within the gland, short treatment times, and the capability to quantify the spatial heating pattern delivered during therapy. A significant challenge in MRI-guided ultrasound therapy is the design and construction of MRI-compatible equipment capable of operation in a closed-bore MR imager. We describe a prototype system developed for MRI-guided transurethral ultrasound therapy and characterize the performance of the different components including the heating applicator design, rotational motor, and radio frequency electronics. The ultrasound heating applicator described in this study incorporates a planar transducer and is capable of producing high intensity ultrasound energy in a localized region of tissue. Results demonstrated that the heating applicator exhibits excellent MRI-compatibility, enabling precise MR temperature measurements to be acquired as close as 6 mm from the device. Simultaneous imaging and rotational motion was also possible during treatment using a motor based on piezoelectric actuators. Heating experiments performed in both phantoms and in a canine model with the prototype system verified the capability to perform simultaneous MR imaging and therapy delivery with this system. Real-time control over therapy using MR temperature measurements acquired during heating can be implemented to achieve precise patterns of thermal damage within the prostate gland. The technical feasibility of using the system developed in this study for MRI-guided transurethral ultrasound therapy in a closed-bore MR imager has been demonstrated.     

Ultrasonography-based 2D motion-compensated HIFU sonication integrated with reference-free MR temperature monitoring: a feasibility study ex vivo

Magnetic resonance imaging (MRI) and ultrasonography have been used simultaneously in this ex vivo study for the image-guidance of high intensity focused ultrasound (HIFU) treatment in moving tissue. A ventilator-driven balloon produced periodic and non-rigid (i.e. breathing-like) motion patterns in phantoms. MR-compatible ultrasound (US) imaging enabled near real-time 2D motion tracking based on optical flow detection, while near-harmonic reference-free proton resonance frequency shift (PRFS) MR thermometry (MRT) was used to monitor the thermal buildup on line. Reference-free MRT was applied to gradient-echo echo-planar imaging phase maps acquired at the frame rate of 250 to 300 ms/slice with voxel size 1.25×1.25×5 mm(3). The MR-US simultaneous imaging was completely free of mutual interferences while minor RF interferences from the HIFU device were detected in the far field of the US images. The effective duty-cycle of the HIFU sonication was close to 100 % and no off-interval was required to temporally decouple it from the ultrasonography. The motion compensation of the HIFU sonication was achieved with an 8 Hz frame rate and sub-millimeter spatial accuracy, both for single-focus mode and for an iterated multi-foci line scan. Near harmonic reference-less PRFS MRT delivered motion-robust thermal maps perpendicular or parallel to the HIFU beam (0.7 °C precision, 0.5 °C absolute accuracy). Out-of-plane motion compensation was not addressed in this study.