Ultrasound in Medicine and Biology

Masthead

2012-02-01

Editorial Advisory Board

2012-02-01

Shear Wave Dispersion Measures Liver Steatosis

2011-12-19

Abstract: Crawling waves, which are interfering shear wave patterns, can be generated in liver tissue over a range of frequencies. Some important biomechanical properties of the liver can be determined by imaging the crawling waves using Doppler techniques and analyzing the patterns. We report that the dispersion of shear wave velocity and attenuation, that is, the frequency dependence of these parameters, are strongly correlated with the degree of steatosis in a mouse liver model, ex vivo. The results demonstrate the possibility of assessing liver steatosis using noninvasive imaging methods that are compatible with color Doppler scanners and, furthermore, suggest that liver steatosis can be separated from fibrosis by assessing the dispersion or frequency dependence of shear wave propagations.

Evaluation of Color Doppler Ultrasonography in Diagnosing Hepatic Alveolar Echinococcosis

2012-02-01

Abstract: To assess the accuracy of color Doppler ultrasonography in diagnosing hepatic alveolar echinococcosis, 129 patients were examined at the First Affiliated Hospital of Xinjiang Medical University between July 2004 and June 2010. Those patients suspected of having hepatic alveolar echinococcosis were examined and diagnosed by color Doppler ultrasound. All the cases were compared with the gold standard. The findings of their sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio and 95% confidence interval were recorded. Sensitivity: 95% (95% confidence interval: 90.7%–99.3%); specificity: 20.7% (95% confidence interval: 6.0%–35.4%); positive predictive value: 80.5%; negative predictive value: 54.5%; positive likelihood ratio: 1.2: negative likelihood ratio: 0.2. Our study indicates that color Doppler ultrasonography, when used in diagnosing hepatic alveolar echinococcosis, has high sensitivity although specificity is low. Color Doppler ultrasound is, thus, considered to be an efficient means for diagnosing hepatic alveolar echinococcosis.

Mapping of Superficial Extremity Veins: Normal Diameters and Trends in a Vascular Patient-Population

Dan E. Spivack, Patrick Kelly, John P. Gaughan, Paul S. van Bemmelen — 2012-02-01

Abstract: Ultrasonic measurement of superficial extremity veins is a common procedure. To establish normal values for vein-size in a population of vascular patients and to assess if measurements remain unchanged over time, we analyzed a database with results of 28,130 measurements in 2420 separate saphenous and 3206 cephalic veins. Mean size of the great saphenous vein ranges from 2.3 mm to 4.4 mm but did not follow a tapering pattern as is often assumed. The distal calf segment is smaller than the ankle segment. The mean cephalic vein size in the upper arm (2.4 mm) was smaller than at the antecubital level (2.7 mm). A decrease in vein diameter over time was noted in many locations and this reached statistical significance (p < 0.005 for the thigh segment). The clinical significance of this is a need to repeat ultrasonic vein-mapping if more than a year elapses between ultrasound and surgical vein harvest.

Shear Wave Elasticity Imaging of Cervical Lymph Nodes

2011-12-19

Abstract: A pilot study of real-time shear wave ultrasound elastography (SWE) for cervical lymphadenopathy in routine clinical practice was conducted on 55 nodes undergoing conventional ultrasound (US) with US-guided needle aspiration for cytology. Elastic moduli of stiffest regions in nodes were measured on colour-coded elastograms, which were correlated with cytology. Malignant nodes (n = 31, 56.4%) were stiffer (median 25.0 kPa, range 6.9–278.9 kPa) than benign nodes (median 21.4 kPa, range 8.9–30.2 kPa) (p = 0.008, Mann Whitney U test). A cut-off of 30.2 kPa attained highest accuracy of 61.8%, corresponding to 41.9% sensitivity, 100% specificity and 0.77 area under the receiver operating characteristic curve. Qualitatively, elastograms of benign nodes were homogeneously soft; malignant nodes were homogeneously soft or markedly heterogeneous with some including regions lacking elasticity signal. SWE is feasible for neck nodes. It appears unsuitable for cancer screening but may detect a subset of malignant nodes. The cause of spatial heterogeneity of malignant nodes on SWE is yet to be established.

Color Doppler Ultrasonography Evaluation for Chemotherapy Treatment Response of Osteogenic Sarcoma

2012-02-01

Abstract: The aim of this study was to evaluate the vascular parameters of the proximal peripheral arteries of limbs by color Doppler ultrasonography (CDUS) in individuals with osteogenic sarcoma (OGS) after neoadjuvant chemotherapy and their relation to the tumor necrosis rate. We recruited 50 individuals with osteogenic sarcoma who were scheduled for neoadjuvant chemotherapy before elective surgery from 2003 to 2010. Once enrolled, we evaluated these 50 subjects using color Doppler sonography to identify vascular parameters of tumor vessels before and after neoadjuvant therapy. The vascular parameters of the proximal peripheral arteries of limbs (peak systolic velocity [PSV], end-diastolic velocity [EDV], resistive index [RI]) and tumor neovascularity were compared before and after neoadjuvant chemotherapy using CDUS. Before chemotherapy, the PSV, EDV and RI differed significantly between the diseased and contralateral normal limbs (p < 0.001). Among the factors relating to the tumor necrosis rate before chemotherapy, the EDV of the diseased limb (p = 0.047) and tumor neovascularity (p = 0.027) showed significant differences. After chemotherapy, the PSV of the diseased limb (p = 0.022) and the difference in PSV between the diseased and contralateral limbs (p = 0.003) showed significant differences. The vascular parameters of the proximal peripheral arteries of limbs owing to tumor burden differ significantly between the diseased and contralateral normal limbs. For individuals with osteogenic sarcoma who still have a higher difference in PSV between the diseased and contralateral limbs after chemotherapy, another course of chemotherapy after surgery and close follow-up should be considered.

Transvaginal Ultrasound-Guided Embryo Aspiration Plus Local Administration of Low-Dose Methotrexate for Caesarean Scar Pregnancy

Na Li, Fufan Zhu, Shuxin Fu, Xiaobo Shi — 2011-12-19

Abstract: This study evaluated the effect of transvaginal ultrasound-guided embryo aspiration plus local administration of low-dose methotrexate (MTX) on caesarean scar pregnancy (CSP). Sixty-eight cases of CSP were randomly grouped for (1) systemic administration of MTX plus curettage with hysteroscopy (control group); and (2) transvaginal ultrasound-guided embryo aspiration plus local administration of low-dose MTX (experimental group). Serum β-HCG and transaminase levels, length of hospital stay, occurrence of hypoleukocytosis, vaginal bleeding and genital infection were analyzed. No statistical differences in the duration needed for β-HCG normalization, genital infection and length of hospital stay were observed between the two groups. However, the occurrence of massive vaginal bleeding, hypoleukocytosis and elevated transaminase levels were significantly lower in patients who received transvaginal ultrasound-guided embryo aspiration plus local administration of low-dose MTX compared with patients in the control group. Our study suggested that transvaginal ultrasound-guided embryo aspiration plus local administration of low-dose MTX should be recommended as a safe and effective treatment of caesarean scar pregnancy.

In Vivo Time Harmonic Elastography of the Human Heart

2011-12-19

Abstract: Time harmonic elastography is introduced as a modality for assessing myocardial elasticity changes during the cardiac cycle. It is based on external stimulation and real-time analysis of 30-Hz harmonic shear waves in axial direction of a parasternal line of sight through the lateral heart wall. In 20 healthy volunteers, the externally induced waves showed smaller amplitudes during systole (76.0 ± 30.8 μm) and higher amplitudes during diastole (126.7 ± 52.1 μm). This periodic wave amplitude alteration preceded ventricular contraction and dilation by about 100 ms. The amplitude ratio of 1.75 ± 0.49 indicates a relative change in myocardial shear elasticity on the order of 14 ± 11. These results well agree with observations made by cardiac magnetic resonance elastography for a similar displacement component and region of the heart. The proposed method provides reproducible elastodynamic information on the heart in real-time and may help in diagnosing myocardial relaxation abnormalities in the future.

Assessment of Carotid Elasticity During Exercise: A Reproducibility Study

2011-12-19

Abstract: The study aimed to evaluate the reproducibility of carotid elasticity during exercise. Eighteen healthy volunteers (nine males, age 34 ± 3 years, BMI 22 ± 6 kg/m2) underwent maximal exercise testing on a graded semi-supine cycle ergometer in two different sessions 3 days apart. Ultrasound B-mode image sequences of the right common carotid were acquired at different steps and analyzed by an automatic system; pressures were estimated by tonometry. Compliance (CC) and distensibility (DC) were significantly decreased at exercise peak and in the first recovery minute (CC from 1.6 ± 0.8 to 1 ± 0.6 mm^2/KPa, DC from 56.2 ± 25.3 to 34.5 ± 20 10^−3/KPa, p < 0.05). For the whole examination, intraclass coefficient was 0.780 for CC and 0.694 for DC. Mean coefficient of variation was maximum at peak exercise (CC = 19 ± 6%, DC = 24 ± 15%), but at first minute of recovery it was comparable to resting values (CC = 12 ± 9%, DC = 12 ± 11%). When designing future studies, acquisitions during first recovery minute might be preferred to peak measures.

Changes in Carotid Plaque Echogenicity with Time Since the Stroke Onset: An Early Marker of Plaque Remodeling?

2011-12-19

Abstract: Carotid plaques undergo histologic changes early after an ischemic stroke. However, the evolution of carotid plaques echolucency after a recent brain ischemia is not well known. A prospective observational study that included consecutive stroke patients and asymptomatic individuals with plaques showing ≥50% stenosis on duplex ultrasound was conducted. Plaque echogenicity was measured with the standardized gray-scale median (GSM) and compared with respect to symptoms presence and time from stroke onset. One hundred twenty-six carotid plaques in 124 patients were studied and four groups of plaques were analyzed: (1) plaques seen within 24 h of stroke onset (32); (2) between 1–7 days (50); (3) more than 7 days after stroke onset (22) and; (4) plaques without associated symptoms (22). Plaques of group 1 had less echogenicity than those of groups 2–4: median GSM (interquartile range) 14 (16), 19.5 (19), 22.5 (21), 26.5 (16) respectively (p = 0.001). In conclusion, carotid plaque echogenicity is increased with time from stroke onset and could be an early marker of plaque remodeling.

Low-Intensity Pulsed Ultrasound (LIPUS) May Prevent Polyethylene Induced Periprosthetic Osteolysis In Vivo

2012-02-01

Abstract: We investigated the effect of local low-intensity pulsed ultrasound (LIPUS) on polyethylene debris induced periprosthetic osteolysis. The periprosthetic osteolysis model was made by injecting endotoxin-free pure polyethylene particles into the distal part of the femur canal and inserting a stainless steel plug into this femur. The effects of polyethylene and LIPUS were assessed histologically and by the shear strength test and periprosthetic bone mineral density (BMD) test. Sixteen rabbits received a stainless steel plug on one side and both polyethylene and a stainless steel plug on the other side. Three months later, the side that received polyethylene showed periprosthetic osteolysis. Subsequently, another 16 rabbits received polyethylene plus local LIPUS (200 mW/cm2 for 20 min daily) on one side and polyethylene alone on the other side. Three months later, LIPUS effectively prevented the periprosthetic osteolysis caused by polyethylene in this rabbit model.

Ultrasound Enhanced Prehospital Thrombolysis Using Microbubbles Infusion in Patients with Acute ST Elevation Myocardial Infarction: Pilot of the Sonolysis Study

2011-12-19

Abstract: In animal studies, transthoracic ultrasound and microbubbles have shown to dissolve thrombi in ST elevation myocardial infarction (STEMI). To examine this effect in patients, we have initiated the Sonolysis trial. In this pilot study of 10 patients with a first acute STEMI, we investigated the safety and feasibility of this trial. After pretreatment in the ambulance, five patients were randomized to receive microbubbles with three-dimensional (3-D) guided high mechanical index impulses (1.18) for 15 min, whereas the control group received placebo without ultrasound. Subsequently, primary percutaneous coronary intervention (PPCI) was performed, if indicated. All patients successfully underwent study treatment and PPCI. No significant difference between treatment and control group in safety (minor adverse events 2/5 vs. 2/5, p = NS) and outcome (TIMI III flow 3/5 vs. 1/5 respectively, p = 0.23) was recorded. These results demonstrate that the study protocol is feasible in the acute cardiac care setting and safe during treatment and follow-up.

Disruption of Tumor Neovasculature by Microbubble Enhanced Ultrasound: A Potential New Physical Therapy of Anti-Angiogenesis

2011-12-19

Abstract: Tumor angiogenesis is of vital importance to the growth and metastasis of solid tumors. The angiogenesis is featured with a defective, leaky and fragile vascular construction. Microbubble enhanced ultrasound (MEUS) cavitation is capable of mechanical disruption of small blood vessels depending on effective acoustic pressure amplitude. We hypothesized that acoustic cavitation combining high-pressure amplitude pulsed ultrasound (US) and circulating microbubble could potentially disrupt tumor vasculature. A high-pressure amplitude, pulsed ultrasound device was developed to induce inertial cavitation of circulating microbubbles. The tumor vasculature of rat Walker 256 was insonated percutaneously with two acoustic pressures, 2.6 MPa and 4.8 MPa, both with intravenous injection of a lipid microbubble. The controls were treated by the ultrasound only or sham ultrasound exposure. Contrast enhanced ultrasound (CEUS) and histology were performed to assess tumor circulation and pathological changes. The CEUS results showed that the circulation of Walker 256 tumors could be completely blocked off for 24 hours in 4.8 MPa treated tumors. The CEUS gray scale value (GSV) indicated that there was significant GSV drop-off in both of the two experimental groups but none in the controls. Histology showed that the tumor microvasculature was disrupted into diffuse hematomas accompanied by thrombosis, intercellular edema and multiple cysts formation. The 24 hours of tumor circulation blockage resulted in massive necrosis of the tumor. MEUS provides a new, simple physical method for anti-angiogenic therapy and may have great potential for clinical applications.

Completely Automated Segmentation Approach for Breast Ultrasound Images Using Multiple-Domain Features

Juan Shan, H.D. Cheng, Yuxuan Wang — 2012-02-01

Abstract: Lesion segmentation is a challenging task for computer aided diagnosis systems. In this article, we propose a novel and fully automated segmentation approach for breast ultrasound (BUS) images. The major contributions of this work are: an efficient region-of-interest (ROI) generation method is developed and new features to characterize lesion boundaries are proposed. After a ROI is located automatically, two newly proposed lesion features (phase in max-energy orientation and radial distance), combined with a traditional intensity-and-texture feature, are utilized to detect the lesion by a trained artificial neural network. The proposed features are tested on a database of 120 images and the experimental results prove their strong distinguishing ability. Compared with other breast ultrasound segmentation methods, the proposed method improves the TP rate from 84.9% to 92.8%, similarity rate from 79.0% to 83.1% and reduces the FP rate from 14.1% to 12.0%, using the same database. In addition, sensitivity analysis demonstrates the robustness of the proposed method.

Speckle Noise Reduction in Ultrasound Biomedical B-Scan Images Using Discrete Topological Derivative

2012-02-01

Abstract: Over three decades, several despeckling techniques have been developed by researchers to reduce the speckle noise inherently present in ultrasound B-scan images without losing the diagnostic information. The topological derivative (TD) is the recently adopted technique in the area of biomedical image processing. In this work, we computed the topological derivative for an appropriate function associated to the ultrasound B-scan image gradient by assigning a diffusion factor k, which indicates the cost endowed to that particular image. In this article, a novel image denoising approach, called discrete topological derivative (DTD) has been implemented. The algorithm has been developed in MATLAB7.1 and tested over 200 ultrasound B-scan images of several organs such as the liver, kidney, gall bladder and pancreas. Further, the performance of the DTD algorithm has been estimated by calculating important performance metrics. A comparative study was carried out between the DTD and the traditional despeckling techniques. The calculated peak signal-to-noise ratio (PSNR) (the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation) value of the DTD despeckled liver image is found to be 28 which is comparable with the outperformed speckle reducing anisotropic diffusion (SRAD) filter. SRAD filter is an edge-sensitive diffusion method for speckled images of ultrasonic and radar imaging applications. Canny edge detection and visual inspection of DTD filtered images by the trained radiologist found that the DTD algorithm preserves the hypoechoic and hyperechoic regions resulting in improved diagnosis as well as tissue characterization.

Measurement of Mechanical Properties with Respect to Gap Healing in a Rabbit Osteotomy Model Using Echo Tracking

2011-12-19

Abstract: The most important issue in the assessment of fracture healing is to acquire information about the restoration of the mechanical integrity of bone. Echo tracking (ET) can noninvasively measure the displacement of a certain point on the bone surface under a load. Echo tracking has been used to assess the bone deformation angle of the fracture healing site. Although this method can be used to evaluate bending stiffness, previous studies have not validated the accuracy of bending stiffness. The purpose of the present study is to ensure the accuracy of bending stiffness as measured by ET. A four-point bending test of the gap-healing model in rabbit tibiae was performed to measure bending stiffness. Echo tracking probes were used to measure stiffness, and the results were compared with results of stiffness measurements performed using laser displacement gauges. The relationship between the stiffness measured by these two devices was completely linear, indicating that the ET method could precisely measure bone stiffness.

Integration of Crawling Waves in an Ultrasound Imaging System. Part 1: System and Design Considerations

Christopher Hazard, Zaegyoo Hah, Deborah Rubens, Kevin Parker — 2011-12-19

Abstract: An ultrasound system (GE Logiq 9) was modified to produce a synthetic crawling wave using shear wave displacements generated by the radiation force of focused beams formed at the left and the right edge of the region of interest (ROI). Two types of focusing, normal and axicon, were implemented. Baseband (IQ) data was collected to determine the left and right displacements, which were then used to calculate an interference pattern. By imposing a variable delay between the two pushes, the interference pattern moves across the ROI to produce crawling waves. Also temperature and pressure measurements were made to assess the safety issues. The temperature profiles measured in a veal liver along the focal line showed the maximum temperature rise less than 0.8°C, and the pressure measurements obtained in degassed water and derated by 0.3 dB/cm/MHz demonstrate that the system can operate within FDA safety guidelines.

Integration of Crawling Waves in an Ultrasound Imaging System. Part 2: Signal Processing and Applications

2011-12-19

Abstract: This paper introduces methods to generate crawling wave interference patterns from the displacement fields generated from radiation force pushes on a GE Logiq 9 scanner. The same transducer and system provides both the pushing pulses to generate the shear waves and the tracking pulses to measure the displacements. Acoustic power and system limitations result in largely impulsive displacement fields. Measured displacements from pushes on either side of a region-of-interest (ROI) are used to calculate continuously varying interference patterns. This technique is explained along with a brief discussion of the conventional mechanical source-driven crawling waves for comparison. We demonstrate the method on three example cases: a gelatin-based phantom with a cylindrical inclusion, an oil-gelatin phantom and mouse livers. The oil-gelatin phantom and the mouse livers demonstrate not only shear speed estimation, but the frequency dependence of the shear wave speeds.

Evaluation of the Accuracy of Articular Cartilage Thickness Measurement by B-Mode Ultrasonography with Conventional Imaging and Real-Time Spatial Compound Ultrasonography Imaging

2012-02-01

Abstract: The present study aimed to quantify the thickness of articular cartilage (Tc) in vitro using both conventional and real-time spatial compound B-mode ultrasonography (US) with a clinically used transducer and to evaluate the accuracy of measurement by comparing the results with values obtained microscopically. Femoral condyle samples were obtained from a 6-month-old pig and a 3-year-old pig. B-mode US images with conventional imaging and real-time spatial compound imaging (RTSCI) of osteochondral blocks were acquired. Tc determined using US (Tc-US) was measured from line data parallel to US beam direction acquired from B-mode images with an objective method for determining cartilage surface and bone-cartilage interfaces at the peak brightness values. Tc was also determined under microscopy (Tc-optical) using the corresponding points from US measurement. Tc-US was compared with Tc-optical to assess accuracy. Tc-US correlated significantly with Tc in both conventional imaging and RTSCI (r = 0.961, 0.976, respectively). Bland-Altman plots showed mean differences between Tc-optical and Tc-US were −0.0073 mm and 0.0139 mm with standard deviations of 0.171 mm and 0.131 mm for conventional imaging and RTSCI, respectively. Our results show that Tc-US measurement using B-mode US allows accurate measurement of Tc. Considering correlation coefficients between Tc-US and Tc-optical, RTSCI US may offer higher accuracy for measuring Tc than conventional methods when an objective tissue border determination algorithm is used, even though both showed good accuracy in our study.

Left Ventricular Assist Devices: Physiologic Assessment using Echocardiography for Management and Optimization

2012-02-01

Abstract: Left ventricular assist devices (LVAD) are being deployed increasingly in patients with severe left ventricular dysfunction and medically refractory congestive heart failure of any etiology. The United States Food and Drug Administration (FDA) recently approved the use of the Thoratec Heartmate II (Thoratec Corporation, Pleasanton, CA, USA) for outpatient use. Echocardiography is fundamental during each stage of patient management, pre-LVAD placement, during LVAD placement, for postoperative LVAD optimization and long-term follow-up. We present a pragmatic and systematic echocardiographic approach that serves as a guide for the management of left ventricular assist devices.

Ultrasonography in Vascular Diagnosis. A Therapy-Oriented Textbook and Atlas

Colin Deane — 2011-12-19

This is the English version of the third edition of Wilhelm Schaberle’s book, first published in German. An excellent translation covers major areas of vascular ultrasound, peripheral arteries, peripheral veins, “shunts” - intentional and unintentional A-V communications, extracranial cerebral arteries, visceral and retroperitoneal arteries and penile and scrotal vessels.

Calendar

2012-02-01

Ultrasound in Medicine and Biology

Masthead

Editorial Advisory Board

Contents

Shear Wave Dispersion Measures Liver Steatosis

Evaluation of Color Doppler Ultrasonography in Diagnosing Hepatic Alveolar Echinococcosis

Mapping of Superficial Extremity Veins: Normal Diameters and Trends in a Vascular Patient-Population

Shear Wave Elasticity Imaging of Cervical Lymph Nodes

Color Doppler Ultrasonography Evaluation for Chemotherapy Treatment Response of Osteogenic Sarcoma

Transvaginal Ultrasound-Guided Embryo Aspiration Plus Local Administration of Low-Dose Methotrexate for Caesarean Scar Pregnancy

In Vivo Time Harmonic Elastography of the Human Heart

Assessment of Carotid Elasticity During Exercise: A Reproducibility Study

Changes in Carotid Plaque Echogenicity with Time Since the Stroke Onset: An Early Marker of Plaque Remodeling?

Low-Intensity Pulsed Ultrasound (LIPUS) May Prevent Polyethylene Induced Periprosthetic Osteolysis In Vivo

Ultrasound Enhanced Prehospital Thrombolysis Using Microbubbles Infusion in Patients with Acute ST Elevation Myocardial Infarction: Pilot of the Sonolysis Study

Disruption of Tumor Neovasculature by Microbubble Enhanced Ultrasound: A Potential New Physical Therapy of Anti-Angiogenesis

Completely Automated Segmentation Approach for Breast Ultrasound Images Using Multiple-Domain Features

Speckle Noise Reduction in Ultrasound Biomedical B-Scan Images Using Discrete Topological Derivative

Measurement of Mechanical Properties with Respect to Gap Healing in a Rabbit Osteotomy Model Using Echo Tracking

Integration of Crawling Waves in an Ultrasound Imaging System. Part 1: System and Design Considerations

Integration of Crawling Waves in an Ultrasound Imaging System. Part 2: Signal Processing and Applications

Evaluation of the Accuracy of Articular Cartilage Thickness Measurement by B-Mode Ultrasonography with Conventional Imaging and Real-Time Spatial Compound Ultrasonography Imaging

Left Ventricular Assist Devices: Physiologic Assessment using Echocardiography for Management and Optimization

Ultrasonography in Vascular Diagnosis. A Therapy-Oriented Textbook and Atlas

Calendar