Ultrasound in Medicine and Biology - Articles in Press

Quantitative Ultrasound for the Monitoring of Novel Microbubble and Ultrasound Radiosensitization - Corrected Proof

2012-05-14

Abstract: There is a need for cancer imaging to provide “real-time” information about the metabolic and cellular responses of tumours. Quantitative ultrasound techniques have recently been demonstrated to be a potential method of assessing tumour response at the cellular level. Anti-cancer treatments administered to xenograft-bearing mice consisted of radiotherapy and a novel antivascular therapy utilizing encapsulated microbubble agents in the presence of ultrasound. Radiation dose and microbubble concentrations were varied and the treatment modalities were given in combination to assess the possible enhancement of tumour cell death. Quantitative methods were used to non-invasively assess responses. Results demonstrated statistically significant changes in backscatter parameters (midband fit, spectral intercept) in tumours treated with high doses of radiotherapy or a high concentration of microbubbles. Combined treatments demonstrated further increases in ultrasound parameters. Histopathologic assessment was used and tumour cell death was found to correlate with increases in ultrasound parameters.

The Relationship of Carotid Three-Dimensional Ultrasound Vessel Wall Volume with Age and Sex: Comparison to Carotid Intima-Media Thickness - Corrected Proof

2012-05-14

Abstract: The relationship of three-dimensional ultrasound (3DUS)-derived carotid vessel wall volume (VWV) was evaluated with respect to age and sex. B-mode and 3DUS images were acquired for 316 subjects from diverse groups including obese primary prevention, diabetic nephropathy, renal transplant and rheumatoid arthritis populations. The relationship for intima-media thickness (IMT) and VWV with age and sex were determined using Pearson-product-moment correlations. Mean IMT (r = 0.18, p = 0.001) and VWV (r = 0.24, p < 0.01) correlated modestly with age. There were modest correlations in males (IMT, r = 0.19, p = 0.003; VWV, r = 0.34, p < 0.001) and in females for IMT and age (r = 0.30, p = 0.007) but not between 3DUS VWV and age in females (r = 0.10, p = 0.4). Significant associations between plaque and VWV (r = 0.36, p = 0.001) but not IMT suggest different correlations in females that may be attributed to plaque.

Intracardiac Echocardiography Measurement of Dynamic Myocardial Stiffness with Shear Wave Velocimetry - Corrected Proof

Peter J. Hollender, Patrick D. Wolf, Robi Goswami, Gregg E. Trahey — 2012-05-14

Abstract: Acoustic radiation force (ARF)–based methods have been demonstrated to be a viable tool for noninvasively estimating tissue elastic properties, and shear wave velocimetry has been used to measure quantitatively the stiffening and relaxation of myocardial tissue in open-chest experiments. Dynamic stiffness metrics may prove to be indicators for certain cardiac diseases, but a clinically viable means of remotely generating and tracking transverse wave propagation in myocardium is needed. Intracardiac echocardiography (ICE) catheter-tip transducers are demonstrated here as a viable tool for making this measurement. ICE probes achieve favorable proximity to the myocardium, enabling the use of shear wave velocimetry from within the right ventricle throughout the cardiac cycle. This article describes the techniques used to overcome the challenges of using a small probe to perform ARF-driven shear-wave velocimetry and presents in vivo porcine data showing the effectiveness of this method in the interventricular septum.

Computer-Aided Diagnosis Based on Speckle Patterns In Ultrasound Images - Corrected Proof

Woo Kyung Moon, Chung-Ming Lo, Chiun-Sheng Huang, Jeon-Hor Chen, Ruey-Feng Chang — 2012-05-14

Abstract: For breast ultrasound, the scatterer number density from backscattered echo was demonstrated in previous research to be a useful feature for tumor characterization. To take advantage of the scatterer number density in B-mode images, spatial compound imaging was obtained, and the statistical properties of speckle patterns were analyzed in this study for use in distinguishing between benign and malignant lesions. A total of 137 breast masses (95 benign cases and 42 malignant cases) were used in the proposed computer-aided diagnosis (CAD) system. For each mass, the average number of speckle pixels in a region of interest (ROI) was calculated to use the concept of scatterer number density. In addition, the first-order and second-order statistics of the speckle pixels were quantified to obtain the distributions of the pixel values and the spatial relations among the pixels. The performance of the speckle features extracted from each ROI was compared with the performance of the segmentation features extracted from each segmented tumor. As a result, the proposed CAD system using the speckle features achieved an accuracy of 89.1% (122/137); a sensitivity of 81.0% (34/42); and a specificity of 92.6% (88/95). All of the differences between the speckle features and the segmentation features are not statistically significant (p > 0.05). In a receiver operating characteristic (ROC) curve analysis, the Az value, area under ROC curve, of the speckle features was significantly better than the Az value of the segmentation features (0.93 vs. 0.86, p = 0.0359). The performance of this approach supports the notion that the speckle patterns induced by the scatterers in tissues can provide information for classifying tumors. The proposed speckle features, which were extracted readily from drawing an ROI without any preprocessing, also provide a more efficient classification approach than tumor segmentation.

Intra- and Interoperator Reproducibility of Acoustic Radiation Force Impulse (ARFI) Elastography–Preliminary Results - Corrected Proof

2012-05-14

Abstract: Our study assessed acoustic radiation force impulse (ARFI) reproducibility and the factors influencing it. The intra- and interoperator reproducibility were studied in 33 and 58 patients, respectively. Intraclass correlation coefficient (ICC) was used to assess ARFI reproducibility. The overall intraoperator agreement was better than the interoperator one: ICC 0.90 vs. ICC 0.81. The correlation of repeated ARFI measurements was higher, but not significantly so, in cases in which intraoperator reproducibility was assessed compared with the ones in which interoperator reproducibility was studied: r = 0.848 vs. r = 0.694 (p = 0.08). For both intra- and interoperator reproducibility, the ICCs were smaller in women vs. men (0.88 vs. 0.91 and 0.67 vs. 0.86, respectively), in patients with high body mass index (BMI) ≥25 kg/m² vs. <25 kg/m² (0.88 vs. 0.91 and 0.79 vs. 0.82, respectively), in patients with ascites vs. no ascites (0.80 vs. 0.93 and 0.78 vs. 0.84, respectively) and in noncirrhotic vs. cirrhotic patients (0.77 vs. 0.82 and 0.70 vs. 0.83, respectively).

Does Probe Frequency Influence Diagnostic Accuracy in Newborn Hip Ultrasound? - Corrected Proof

2012-05-14

Abstract: Ultrasonography of the hip has gained wide acceptance as reliable method for diagnosing developmental hip dysplasia in infants. This blinded study was conducted to investigate the influence of two linear probes with different frequency on diagnostic accuracy and reproducibility. In 206 consecutive newborns, the bony roof angle (α-angle) and cartilage roof angle (β-angle) were assessed by three investigators according to Graf. The hips were measured twice both with a 7.5 MHz and a 12 MHz linear transducer (Sonoline G60S® ultrasound system; Siemens, Erlangen, Germany). Each investigator evaluated his sonograms 6 weeks later. Depending on the mean values for α-angle and β-angle, the hips were classified. Reproducibility of the Graf classification was not found to be influenced. In two of three investigators, we observed significant improvement concerning variation of the β-angle with the 12 MHz probe. The use of high-resolution transmitters may improve diagnostic accuracy in ultrasonography of the newborn’s hip.

Ex Vivo Lung Sonography: Morphologic-Ultrasound Relationship - Corrected Proof

2012-05-14

Abstract: Ultrasound (US) interstitial syndrome is a sonographic lung pattern characterized by the presence of acoustic artifacts (B-lines and white lung). The purpose of this study was to demonstrate how interstitial syndrome is determined by acoustic interactions in lungs of variable density and in healthy organs deflated to a nonphysiologic level of density. Normal rabbit lungs were studied ex vivo by US at varying known degrees of inflation, and their histologic appearances were described. In this experimental setting, US interstitial syndrome recognizes a mechanism related to tissue density or porosity. Artifacts (B-lines and white lung) appear in the normal rabbit lung through air-dependent increases in density. As in pathologic conditions, US interstitial syndrome can be reproduced in histologically normal lungs that are deflated to a critical level (>0.45 g/mL) of density, which is not achievable under physiologic conditions.

Color Doppler Twinkling Artifacts from Gallbladder Adenomyomatosis With 1.8 Mhz and 4.0 Mhz Color Doppler Frequencies - Corrected Proof

2012-05-14

Abstract: The purpose of this study was to investigate the diagnostic value of color Doppler twinkling artifacts (CDTAs) in the evaluation of gallbladder adenomyomatosis with differently colored Doppler frequencies. An ultrasound was performed by an experienced radiologist in 17 patients with typical gallbladder adenomyomatosis. Two abdominal radiologists retrospectively evaluated the anatomic locations, the intensity of 69 CDTAs on 1.8 MHz and 4.0 MHz Doppler frequencies, and the intensity of the corresponding comet-tail artifacts. Statistical analysis was performed using the Friedman and Kruskal-Wallis test. The intensity of the CDTAs was significantly greater than that of the comet-tail artifacts, regardless of the color Doppler frequency and anatomic location (p < 0.001). The intensity of the CDTAs on 1.8 MHz was significantly higher than that on 4.0 MHz color Doppler frequency (p < 0.05). In conclusion, CDTAs may be useful in recognizing gallbladder adenomyomatosis, and 1.8 MHz color Doppler frequency is more highly recommended than 4.0 MHz for the visualization of CDTAs.

Intra- and Interobserver Agreement Among Bronchial Endosonographers for the Description of Intrathoracic Lymph Nodes - Corrected Proof

2012-05-14

Abstract: Several sonographic features observed by endobronchial ultrasonography have been suggested to be useful to predict malignancy in mediastinal lymph nodes. To evaluate agreement to describe sonographic features, 28 video images were evaluated twice by eight expert bronchoscopists. The observers reviewed each case for the presence of coagulation necrosis sign (CNS), central hilar structure (CHS), heterogeneity, distinct margin, round shape, size >1 cm and malignancy. Intraobserver agreement was almost perfect for size (κ = 0.826), substantial for CNS (κ = 0.721) and shape (κ = 0.615), and moderate for CHS (κ = 0.565), heterogeneity (κ = 0.441) and margin (κ = 0.407). Interobserver agreement was substantial for size (κ = 0.641), moderate for shape (κ = 0.445), and fair for CNS (κ = 0.340) and margin (κ = 0.274). In conclusion, inter- and intraobserver agreement of the endosonographic features for mediastinal or hilar lymph nodes is good for shape or size but not good enough for the other ultrasonographic features.

Detection of Intracerebral Hemorrhage and Transient Blood-Supply Shortage in Focused-Ultrasound-Induced Blood–Brain Barrier Disruption by Ultrasound Imaging - Corrected Proof

2012-05-14

Abstract: Focused ultrasound (FUS) in the presence of microbubbles can selectively open the blood–brain barrier (BBB). However, since overexcitation by FUS probably induces intracerebral hemorrhage, it is essential to develop an imaging approach for real-time detection of hemorrhage and blood-flow changes during FUS-induced BBB disruption. Here we investigated the feasibility of using ultrasound imaging to monitor the transient responses of FUS-induced BBB disruption. The BBB was disrupted with in-house-manufactured microbubbles in rats by 1-MHz FUS with a pressure of 1.1 MPa (pulse repetition frequency: 1 Hz, pulse duration: 10 ms, exposure time: 60 s) and imaged for the next 2 h. Ultrasound B-mode imaging was used to detect hyperechoic changes induced by hemorrhage and contrast-enhanced ultrasound (US) imaging was performed to analyze changes in blood flow. Hyperechoic spots appeared in B-mode images at 5 s after FUS sonication and contrast-enhanced US images simultaneously showed a region of transient blood-supply shortage in the sonicated area. Thus, the location of hyperechoic spots correlated with hemorrhagic patterns and the blood-supply-shortage region was consistent with the BBB-disrupted areas. Furthermore, we detected a transient hyperemic response in the unsonicated contralateral hemisphere brain. Our approach has potential as an immediate-feedback control tool for preventing the induction of intracerebral hemorrhage during FUS treatment.

Improved Parameterization of the Transcranial Doppler Signal - Corrected Proof

Arjen Schaafsma — 2012-05-14

Abstract: The great potential of transcranial Doppler (TCD) as a tool for neuromonitoring is limited by the current parameterization of the signal. This article proposes a set of new parameters that more accurately represents the shape of the waveform and eliminates a number of confounding factors. This set of parameters was tested in 227 patients with ipsilateral carotid artery stenosis and compared with 31 normal subjects recruited at our laboratory. From the TCD waveform, we calculated on a beat-to-beat basis the maximal change in flow velocity at stroke onset (acceleration or acc), the maximal flow velocity during the first 100 ms of systole (sys1) and the maximal flow velocity in the remaining part of systole (sys2). All data were normalized relative to the mean diastolic flow velocity over an interval ranging from 520 till 600 ms after stroke onset (dias@560). For the group with carotid stenosis compared with the normal controls the average ± SD for acc (20.2 ± 9.5 vs. 20.2 ± 6.7; p = 0.98) and sys1 (1.82 ± 0.38 vs. 1.77 ± 0.56; p = 0.35) did not differ significantly. The average ±SD for sys2 (1.94 ± 0.33 vs. 1.50 ± 0.12; p < 0.001), however, was significantly higher in the group with carotid stenosis than in the group of normal subjects. The difference between sys1 and sys2 (“sys1–sys2”) was lower in the patient group than in controls (−0.12 ± 0.16 vs. 0.27 ± 0.22; p < 0.001). For the acc, there was a significantly higher variance in the group with stenosis than without (p < 0.001). Of the old parameters, the beat-to-beat mean (37.0 ± 13.1 vs. 41.3 ± 15.9; p = 0.17) and the pulsatility index (PI; 1.00 ± 0.26 vs. 0.91 ± 0.23; p = 0.06)) were not significantly different between groups. Graphed together the acc and “sys1–sys2” parameters allowed a clear demarcation of both groups whereas in a graph of the old parameters mean and PI both groups overlapped considerably. In conclusion, the proposed set of new parameters not only has theoretical and practical benefits but also has excellent discriminative power in a group of carotid patients compared with normal controls.

Improved Objective Selection of Power Doppler Wall-Filter Cut-Off Velocity for Accurate Vascular Quantification - Corrected Proof

Mai Elfarnawany, Stephen Z. Pinter, James C. Lacefield — 2012-05-14

Abstract: The wall-filter selection curve method is proposed to objectively identify a cut-off velocity that minimizes artifacts in power Doppler images. A selection curve, which is constructed by plotting the color pixel density (CPD) as a function of the cut-off velocity, exhibits characteristic intervals hypothesized to include the optimum cut-off velocity. This article presents an improved implementation of the method that automatically detects characteristic intervals in a selection curve and selects an operating point cut-off velocity along a characteristic interval. The method is applied to subregions within the Doppler image to adapt the cut-off velocity to local variations in vascularity. The method's performance is evaluated in 30-MHz power Doppler images of a four-vessel flow phantom. At high (>5 mm/s) flow velocities, qualitative improvements in vessel delineation are achieved and the CPD in the resulting images is accurate to within 3% of the vascular volume fraction of the phantom.

EFFECTS OF ACOUSTIC RADIATION FORCE ON THE BINDING EFFICIENCY OF BR55, A VEGFR2-SPECIFIC ULTRASOUND CONTRAST AGENT - Corrected Proof

2012-05-14

Abstract: This work describes an in vivo study analyzing the effect of acoustic radiation force (ARF) on the binding of BR55 VEGFR2-specific contrast-agent microbubbles in a model of prostatic adenocarcinoma in rat. A commercial ultrasound system was modified by implementing high duty-cycle 3.5-MHz center frequency ARF bursts in a scanning configuration. This enabled comparing the effects of ARF on binding in tumor and healthy tissue effectively in the same field of view. Bubble binding was established by measuring late-phase enhancement in amplitude modulation (AM) contrast-specific imaging mode (4 MHz, 150 kPa) 10 min after agent injection when the unbound bubbles were cleared from the circulation. Optimal experimental conditions, such as agent concentration (0.4 × 108–1.6 × 108 bubbles/kg), acoustic pressure amplitude (26–51 kPa) and duty-cycle (20%–95%) of the ARF bursts, were evaluated in their ability to enhance binding in tumor without significantly increasing binding in healthy tissue. Using the optimal conditions (38 kPa peak-negative pressure, 95% duty cycle), ARF-assisted binding of BR55 improved significantly in tumor (by a factor of 7) at a lower agent dose compared with binding without ARF, and it had an insignificant effect on binding in healthy tissue. Thus, the high binding specificity of BR55 microbubbles for targeting VEGFR2 present at sites of active angiogenesis was confirmed by this study. Therefore, it is believed that based on the results obtained in this work, ultrasound molecular imaging using target-specific contrast-agent microbubbles should preferably be performed in combination with ARF.

Quantitative Ultrasound Bone Measurements in Pre-Pubertal Children with Type 1 Diabetes - Corrected Proof

2012-04-30

Abstract: This case-control study aimed to assess bone status in children with type 1 diabetes mellitus (T1DM). Fifty-seven pre-pubertal patients (37 boys, aged 7.9 ± 2.5 years, T1DM duration 3.1 ± 1.6 years) and 171 age-matched healthy controls (111 boys) were studied. Quantitative ultrasound (QUS) was used to measure amplitude dependent speed of sound (Ad-SoS) at hand phalanges (expressed as standard deviation score [SDS]). Anthropometric and disease-related data (including mean HbA1c from whole T1DM duration [T], last year [Y], examination day [D]) were collected. Mean Ad-SoS SDS in patients (−0.13 ± 1.32 (95% confidence interval [CI] −0.48, 0.22) was similar to that of controls. Subgroups discriminated according to HbA1c D, Y and T (cut-off 7.0%) did not differ regarding analyzed parameters. In patients, Ad-SoS SDS was comparable for both genders. Multivariable stepwise regression analysis showed significant negative influence of diabetes duration on Ad-SoS SDS. QUS findings in pre-pubertal children with T1DM do not differ from those in healthy children. Disease duration seems to affect negatively Ad-SoS SDS. However, independent prospective studies are needed to elucidate the true associations.

Quantitative Ultrasound Criteria for Risk Stratification in Clinical Practice: A Comparative Assessment - Corrected Proof

2012-04-30

Abstract: This study aimed to compare two different classifications of the risk of fracture/osteoporosis (OP) based on quantitative ultrasound (QUS). Analyses were based on data from the Epidemiological Study on the Prevalence of Osteoporosis, a cross-sectional study conducted in 2000 aimed at assessing the risk of OP in a representative sample of the Italian population. Subjects were classified into 5 groups considering the cross-classification found in previous studies; logistic regression models were defined separately for women and men to study the fracture risk attributable to groups defined by the cross-classification, adjusting for traditional risk factors. Eight-thousand six-hundred eighty-one subjects were considered in the analyses. Logistic regression models revealed that the two classifications seem to be able to identify a common core of individuals at low and at high risk of fractures, and the importance of a multidimensional assessment in older patients to evaluate clinical risk factors together with a simple, inexpensive, radiation-free device such as QUS.

In vitro sonothrombolysis of human blood clots with BR38 microbubbles - Corrected Proof

2012-04-30

Abstract: Microbubble-mediated sonothrombolysis is a promising approach for ischemic stroke treatment. The aim of this in vitro study was to evaluate a new microbubble (MB) formulation (BR38) for sonothrombolysis and to investigate the involved mechanisms. Human whole-blood clots were exposed to different combinations of recombinant tissue plasminogen activator (rtPA), ultrasound (US) and MB. Ultrasound at 1.6 MHz was used at 150, 300, 600 and 1000 kPa (peak-negative pressure). Thrombolysis efficacy was assessed by measuring clot diameter changes during 60-min US exposure. The rate of clot diameter loss (RDL) in μm/min was determined and clot lysis profiles were analyzed. The most efficient clot lysis (5.9 μm/min) was obtained at acoustic pressures of 600 and 1000 kPa in combination with MB and a low concentration of rtPA (0.3 μg/mL). This is comparable with the rate obtained with rtPA at 3 μg/mL alone (6.6 μm/min, p > 0.05). Clot lysis profiles were shown to be related to US beam profiles and microbubble cavitation.

High Diagnostic Accuracy and Interobserver Reliability of Real-Time Elastography in the Evaluation of Thyroid Nodules - Corrected Proof

2012-04-30

Abstract: Elastography is a new diagnostic tool in the evaluation of thyroid nodules. Aim of the study was to evaluate the accuracy and reliability of elastography in discriminating thyroid lesions and the interobserver variability. One hundred thirty-two nodules in 115 patients selected for thyroid surgery underwent conventional ultrasound and elastographic evaluation. Elastography score was divided in four categories (totally elastic nodule, mainly elastic, mainly rigid and totally rigid) according to signal distribution. Three independent operators conducted the study. Final histology showed 92 benign nodules and 40 malignant. On elastography, 77/92 benign nodules were classified as score 1 or 2 and 34/40 malignant nodules as score 3 or 4 (sensitivity 85%, specificity 83.7%, positive predictive value [PPV] 69.3%, negative predictive value [NPV] 92.7%). Rate of concordance between operators was good (K test: 0.64, p < 0.0001). Simple to use, with good interobserver agreement, elastography has all the requisites to become an important complement of conventional US examination in the near future.

Ultrasonography for Diagnosing Carpal Tunnel Syndrome: A Meta-analysis of Diagnostic Test Accuracy - Corrected Proof

Ta-Wei Tai, Cheng-Yi Wu, Fong-Chin Su, Tai-Chang Chern, I-Ming Jou — 2012-04-30

Abstract: Ultrasonography is widely used to diagnose carpal tunnel syndrome (CTS), a common peripheral neuropathy, but the reported diagnostic accuracy varies. This meta-analysis focused on the diagnostic test accuracy of ultrasonography for diagnosing CTS. Structured searches of PubMed for 1990–2010 were done and the data were extracted and meta-analyzed by pooling estimates of sensitivity, specificity, likelihood ratios and diagnostic odds ratios. Diagnostic performance was also judged by using a summary receiver operating characteristic curve. Twenty-eight trials involving 3995 wrists were included. A greater cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet (CSA-I) and a greater flattening ratio at the level of the hamate were seen in CTS wrists than in control wrists. A CSA-I ≥9 mm2 is the best single diagnostic criterion, with a diagnostic odds ratio of 40.4 (sensitivity 87.3%, specificity 83.3%).

Tumor and Non-Tumor Liver Angiogenesis is Traced and Evaluated by Hepatic Arterial Ultrasound in Murine Models - Corrected Proof

2012-04-30

Abstract: We studied the relationships between hepatic and mesenteric mean blood-flow velocities (mBFVs) measured by ultrasound imaging and (1) downstream tumor angiogenesis during liver metastasis induced by spleen injection of LS174 human colon cells overexpressing the antiangiogenic Netrin4 (LS174-NT4) or not (LS174-WT) and (2) downstream normal angiogenesis during hepatic regeneration after 50% hepatectomy. Liver volume and mBFVs were measured before and after surgery, at day 30 in the first model and at days 2, 7 and 16 in the second model. LS174-NT-4 vs. LS174-WT mice presented fewer metastases (25% vs. 90%, p < 0.001) and decreased hepatic mBFVs (16.5 ± 0.8 vs. 21.8 ± 1.4 cm s−1, p < 0.01), without difference in mesenteric mBFVs. After partial hepatectomy, hepatic and mesenteric mBFVs increased at day 7, from 12.4 ± 1.7 and 11.8 ± 2.6 to 19.1 ± 1.8 and 17.5 ± 2.4 cm s−1, respectively, (p < 0.01) then returned to baseline as liver volume. Duplex Doppler ultrasonography reliably assesses normal or tumor angiogenesis and may provide follow-up functional evaluation.

Ultrasound and Cisplatin Combined Treatment of Human Melanoma Cells A375–the Study of Sonodynamic Therapy - Corrected Proof

Vladan Bernard, Vojtěch Mornstein, Jiřina Škorpíková, Josef Jaroš — 2012-04-16

Abstract: Sonodynamic therapy, an effect of low-power ultrasound field and the anticancer drug cisplatin, was studied in vitro on human melanoma cells A375. The viability of cells has been studied by standard 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide viability assay according to different modes of treatment: application of cisplatin alone, exposure of ultrasound field alone, exposure to ultrasound followed by cisplatin and application of cisplatin followed by exposure to ultrasound. Ultrasound was used at a therapeutic intensity of 1 W∙cm−2 for 10 min. Concentration of cisplatin in the cell suspension was always 2.3 μM. The results show that sonodynamic therapy is one of the possibilities of how to intensify standard cytostatic therapy. This conclusion is supported by reducing the viability of studied cells, especially 72 h after the treatment. The time sequence of application of ultrasonic field and cytostatics appears to be a significant factor affecting the changes in cell viability. Maximum suppression of viability has been found when applying the experimental design involving application of cisplatin followed by exposure to ultrasound; the final value of viability of combined affected cells was more than 10% lower than for cisplatin treatment alone.

The Speed of Sound and Attenuation of an IEC Agar-Based Tissue-Mimicking Material for High Frequency Ultrasound Applications - Corrected Proof

2012-04-16

Abstract: This study characterized the acoustic properties of an International Electromechanical Commission (IEC) agar-based tissue mimicking material (TMM) at ultrasound frequencies in the range 10–47 MHz. A broadband reflection substitution technique was employed using two independent systems at 21°C ± 1°C. Using a commercially available preclinical ultrasound scanner and a scanning acoustic macroscope, the measured speeds of sound were 1547.4 ± 1.4 m∙s−1 and 1548.0 ± 6.1 m∙s−1, respectively, and were approximately constant over the frequency range. The measured attenuation (dB∙cm−1) was found to vary with frequency f (MHz) as 0.40f + 0.0076f2. Using this polynomial equation and extrapolating to lower frequencies give values comparable to those published at lower frequencies and can estimate the attenuation of this TMM in the frequency range up to 47 MHz. This characterisation enhances understanding in the use of this TMM as a tissue equivalent material for high frequency ultrasound applications.

The Usefulness of Ultrasound Colour-Doppler Twinkling Artefact for Detecting Urolithiasis Compared with Low Dose Nonenhanced Computerized Tomography - Corrected Proof

Rikke Rass Winkel, Anna Kalhauge, Knud-Erik Fredfeldt — 2012-04-16

Abstract: This prospective study evaluates the usefulness of the twinkling artefact (TA) seen on colour-Doppler ultrasound (US) in diagnosing urolithiasis. US and standard computed tomography (CT) were performed blinded on 105 patients. B-mode US and colour-Doppler used separately and in combination showed 55% sensitivity and 99% specificity (positive predictive value [PPV] 67% and negative predictive value [NPV] 98%). Of CT verified stones, 61% were ≤3 mm. TAs were present in 74% of the B-mode stones (43% of all CT verified stones). Patients with CT verified stone disease had significantly more TAs in other foci than the stone(s) found on CT, suggestive of microlithiasis. In conclusion, colour-Doppler TA is a helpful supplement for detecting urolithiasis when CT is contraindicated. In addition, US can be valuable in monitoring stones left to pass without intervention if they have presented a TA. CT, US and US with colour-Doppler TA can be useful as complementary techniques for detecting stones.

The Effect of Preactivation Vial Temperature on the Acoustic Properties of DefinityTM - Corrected Proof

Brandon L. Helfield, Xuan Huo, Ross Williams, David E. Goertz — 2012-04-16

Abstract: DefinityTM is a widely available clinically approved ultrasound contrast agent. The manufacturer’s instructions indicate that the refrigerated vial should be allowed to reach room temperature prior to its 45 s mechanical agitation activation process. Activation results in vial heating and it has been previously observed that “smaller” bubbles are formed later in this process (>10 s) when the vial temperature is elevated. The objective of this work was to examine the effects of preactivation vial temperature on the size distribution, frequency dependent attenuation (1.5–27 MHz) and nonlinear imaging performance of DefinityTM. Experiments were conducted with vials at refrigerator temperature (2°C), room temperature (22°C) or 37°C at the outset of the activation procedure. The size distributions were found to be strongly dependent on preactivation vial temperature and the attenuation results indicated considerable differences in the frequency response of the agent, most notably the appearance of a peak at 4 MHz for the 2°C case. Nonlinear imaging results performed using a 1–5 MHz transducer probe with a wall-less vessel phantom indicated that 2°C vials produced a signal enhancement 5.1 dB greater than for 22°C DefinityTM (p < 0.05). These results, therefore, indicate that not permitting the vial to reach room temperature has a considerable impact on the imaging performance of DefinityTM. Conversely, activating a cooled vial can provide a means by which to improve contrast enhancement when using low frequency clinical transducers.

A New Method of Evaluating the Lower Limit of Cerebral Autoregulation and its Correlation with Blood Pressure by Transcranial Doppler in Rats - Corrected Proof

Qing Chun Gao, Xian Fu, Xiang Yan Chen, Jin Sheng Zeng, Ru Xun Huang — 2012-04-16

Abstract: The aim of present study was to validate the assessment of lower limit of cerebral autoregulation (LLCA) as derived from mean artery blood pressure (MABP) and cerebral zero flow pressure (ZFP) by means of transcranial Doppler (TCD) and to determine the accurate relationship between LLCA and MABP in stroke-prone renovascular hypertensive rats (RHRSP). We studied two groups of rats: RHRSP and normal controls. Blood flow velocity of middle cerebral artery was monitored by TCD and arterial blood pressure was recorded in right femoral artery to compute the ZFP. The value of LLCA was determined as the difference between MABP and ZFP and validated by the value determined by blood withdrawal-induced cerebral autoregulation. In normal rats, the LLCA derived from the new method was 69.8 ± 8.7 mm Hg, from the change of blood velocity was 69.4 ± 9.8 mmHg and from blood volume flow after blood withdrawal was 68.8 ± 9.7 mmHg. In the RHRSP group, the corresponding values of LLCA were 109.1 ± 17.2 mm Hg, 110.0 ± 18.0 mm Hg and 109.0 ± 19.3 mm Hg, respectively. In each group, there was no statistically significant difference among the three values. LLCA in RHRSP began to increase 6 weeks after hypertension-induced operation, significantly higher than controls (p < 0.05), and stabilized at 110 mm Hg, 10 weeks after operation. The increase of LLCA was positively correlated with MABP, following an “S” curve, demonstrating that the change of LLCA was more obvious in the middle range of MABP in RHRSP (R2 = 0.8848, p < 0.05). In conclusion, TCD is a valid and noninvasive method for determination of LLCA compared with the classic method in rats. Our data demonstrated that the change of LLCA may be correlated with MABP, following an “S” curve relationship.