A new method for the acquisition of ultrasonic strain image volumes

This article presents a new method for acquiring three-dimensional (3-D) volumes of ultrasonic axial strain data. The method uses a mechanically-swept probe to sweep out a single volume while applying a continuously varying axial compression. Acquisition of a volume takes 15-20 s. A strain volume is then calculated by comparing frame pairs throughout the sequence. The method uses strain quality estimates to automatically pick out high quality frame pairs, and so does not require careful control of the axial compression. In a series of in vitro and in vivo experiments, we quantify the image quality of the new method and also assess its ease of use. Results are compared with those for the current best alternative, which calculates strain between two complete volumes. The volume pair approach can produce high quality data, but skillful scanning is required to acquire two volumes with appropriate relative strain. In the new method, the automatic quality-weighted selection of image pairs overcomes this difficulty and the method produces superior quality images with a relatively relaxed scanning technique. (E-mail: rjh80@eng.cam.ac.uk)     

Bone Remodeling and in Vivo Strain Analysis of Intact and Implanted Greyhound Proximal Femora

Pre- and poststudy motion and gait analyses of eight size-matched male greyhounds confirmed uniform loading of their femora. Subminiature strain gages implanted on the intact inferior and anterior aspects of the femoral neck in six greyhounds indicated in vivo strain variations among test animals. Motion and gait analyses confirmed uniform loading of femora following unilateral hemiarthroplasty with cobalt-chromium hip implants. In vivo strain measurements adjacent to the implants indicated large variations among test animals. A consistent direction of strain change relative to the intact femur was noted, even though strain changes varied in magnitude. Image analysis of microradiographs indicated insignificant differences in the cortical areas of implanted and intact femora. Extensive new trabecular bone formation was noted along the implant in the endosteal cavity and correlated with a combination of implant placement and exercise level. Most of the bone was formed with centrally placed implants in exercised dogs, and the least with stems on the medial neck surface in rested dogs. Iliac crest biopsies indicated that bone formation rates slowed in rested animals and remained constant throughout the study in exercised animals. All implanted femora had a thin (<1 mm thick) aligned fibrous tissue layer separating the implant from bone. It varied in thickness as a function of the aspect of the implant. Exercised dogs had a larger proportion of fibrous tissue on the anterior and posterior aspects, while rested dogs had a larger proportion of fibrous tissue on the medial and lateral aspects.     

Characterization of Responder Profiles for Cardiac Resynchronization Therapy through Unsupervised Clustering of Clinical and Strain Data

1. Download : Download high-res image (249KB)
2. Download : Download full-size image

     

Ultrasound-based elastography: a novel approach to assess radio frequency ablation of liver masses performed with expandable ablation probes: a feasibility study

OBJECTIVE: The purpose of this study was to evaluate the technical feasibility of ultrasound-based elastography as a tool for assessing the size and shape of the coagulation necrosis caused by radio frequency ablation (RFA) probes using expandable electrodes ex vivo as well as in a patient with a liver metastasis. METHODS: A commercially available expandable RFA probe was used to create a 3-cm ablation in a piece of bovine liver. The ablation probe was used in situ to induce tissue deformation for elastography before and after ablation. Ultrasonic radio frequency data were processed to generate elasticity strain images. The appearance of the ablation zone was compared with magnetic resonance imaging and a gross section specimen. One patient with malignant metastatic disease to the liver and a clinical indication for RFA was investigated for the feasibility of percutaneous elastography of RFA using the same technique. Sonographic strain images were compared with the appearance of the nonenhancing ablation zone on contrast-enhanced computed tomography. RESULTS: Ex vivo, the ablation zone on ultrasound-based elastography was represented by an area of increased stiffness and was well demarcated from the nonablated surrounding tissue. The size and shape of the ablated zone on the strain image correlated well with the gross specimen and the magnetic resonance imaging appearance. Strain images obtained from the patient showed results similar to those of the ex vivo experiment and correlated well with the nonenhancing area of ablation on contrast-enhanced computed tomography. CONCLUSIONS: Ultrasound-based elastography may be a promising tool for displaying the ablation zone created by expandable RFA probes.     

二维应变超声心动图评价移植心脏左心室收缩功能

目的应用二维应变超声心动图检测移植心脏左室壁峰值收缩应变,探讨二维应变超声心动图评价移植心脏左室收缩功能的价值。方法9例心脏移植受者共进行41次超声检查;23例正常人作为对照。记录心尖长轴观、心尖两腔观及心尖四腔观的高帧频二维图像,应用二维应变分析软件测量左室壁各节段的峰值收缩应变及心尖各切面观心肌总的峰值收缩应变、左室整体平均峰值收缩应变。结果无排异反应的心脏移植受者与正常人相比,除了4个心尖节段（后壁心尖段、前间隔心尖段、侧壁心尖段、前壁心尖段）外,左室壁各节段峰值收缩应变均显著降低（P〈0.05）;心尖各切面观心肌总的峰值收缩应变及左室整体平均峰值收缩应变均较正常显著降低（P〈0.05）。急性排异反应与无排异反应的心脏移植受者后室间隔及侧壁各节段相比,峰值收缩应变均有下降趋势,但仅后室间隔心尖段峰值收缩应变降低具有统计学意义（P〈0.05）。急性排异反应的心脏移植受者心尖四腔观心肌总的峰值收缩应变较无排异反应的心脏移植受者则显著降低（P〈0.05）。结论二维应变超声心动图可用于快速准确评价移植心脏左室收缩功能,在排异反应诊断方面具有潜在价值。     

Prevalence of β-lactamase-nonproducing ampicillin-resistant <Emphasis Type="Italic">Haemophilus influenzae</Emphasis> and <Emphasis Type="Italic">Haemophilus influenzae</Emphasis> type b strains obtained from children with lower respiratory tract infections

The prevalence of strains with ampicillin (ABPC) resistance among Haemophilus influenzae strains isolated from the nasopharynx of children with lower respiratory tract infections has increased significantly during the 6 years from 2000, when it was 41.9%, to 2005, when it reached 60.1%. From 2002, the prevalence exceeded 50%, and the prevalence of β-lactamase-nonproducing ABPC-resistant (BLNAR) strains with a minimum inhibitory concentration (MIC) of ABPC of over 4 μg/ml doubled, from 28.2% in 2002 to 54.7% in 2005. In H. influenzae strains obtained from the nasopharynx of children with lower respiratory tract infections between April 2004 and March 2006, identification of serotype b was defined, using the slide agglutination method. The frequency of isolation of H. influenzae type b (Hib) strains was then measured and the ABPC resistance conditions of the Hib strains were also evaluated. The frequency of the Hib strains was found to be 30 out of 479 strains, 6.3%. Of these 30 strains, BLNAR accounted for 53.3% (16 strains), approximately the same frequency of isolation as that of the BLNAR isolated from all H. influenzae strains during the same period. In Japan, the prevalence of BLNAR strains among clinically isolated H. influenzae strains has continued to increase, and the frequency of isolation of BLNAR strains among Hib strains has also continued to rise. As a countermeasure, attempts at improving resistance have been made through judicious antibiotic use, but concern that the choice of antibiotics for Hib meningitis may become complicated has sparked a keen interest in the introduction of Hib conjugate vaccine. Part of this report was presented at the fifty-fourth general meeting of the Japanese Society of Chemotherapy (Kyoto, May 2006).     

纵向应变在评估主动脉瓣狭窄置换术后患者心肌功能中的作用

利用斑点追踪技术得出的纵向应变可发现射血分数下降之前的心肌功能损伤,在预测主动脉瓣狭窄术后患者的死亡率及症状发展方面具有重要的临床应用价值。本文对目前应用纵向应变评估主动脉瓣狭窄置换术后患者心肌功能的现状作一综述。