B-mode Data Research Articles

ADAPTIVE VOLUME RENDERING FOR ULTRASOUND COLOR FLOW DIAGNOSTIC IMAGING

Adaptive volume rendering is provided for medical diagnostic ultrasound. The opacity of B-mode data is set relative to the opacity of Doppler data. The opacities for the different types of data are set as a function of ray depth. For example, the opacity of B-mode data near a tissue border is set to be more opaque than for tissue away from the border, and the opacity for flow data near a flow border is set to be less opaque than for flow away from the border. An image is rendered using a rendering parameter set as a function of ray depth, B-mode information and Doppler information. Other processes for enhancing and/or using rendering may be used.

Differentiation of benign from malignant solid breast masses: comparison of two-dimensional and three-dimensional shear-wave elastography

To prospectively compare the diagnostic performances of two-dimensional (2D) and three-dimensional (3D) shear-wave elastography (SWE) for differentiating benign from malignant breast masses. B-mode ultrasound and SWE were performed for 134 consecutive women with 144 breast masses before biopsy. Quantitative elasticity values (maximum and mean elasticity in the stiffest portion of mass, Emax and Emean; lesion-to-fat elasticity ratio, Erat) were measured with both 2D and 3D SWE. The area under the receiver operating characteristic curve (AUC), sensitivity and specificity of B-mode, 2D, 3D SWE and combined data of B-mode and SWE were compared. Sixty-seven of the 144 breast masses (47 %) were malignant. Overall, higher elasticity values of 3D SWE than 2D SWE were noted for both benign and malignant masses. The AUC for 2D and 3D SWE were not significantly different: Emean, 0.938 vs 0.928; Emax, 0.939 vs 0.930; Erat, 0.907 vs 0.871. Either 2D or 3D SWE significantly improved the specificity of B-mode ultrasound from 29.9 % (23 of 77) up to 71.4 % (55 of 77) and 63.6 % (49 of 77) without a significant change in sensitivity. Two-dimensional and 3D SWE performed equally in distinguishing benign from malignant masses and both techniques improved the specificity of B-mode ultrasound.

Characterization of aortic remodeling following Kawasaki disease: Toward a fully developed automatic biparametric model

Mechanical properties of the arteries are essential in assessing cardiovascular diseases. New imaging modalities that allow mapping strain, shear and elasticity distributions within the arterial wall are rapidly evolving. Very recently, our group introduced an iterative optical flow-based elastography method devoted to B-mode data. In this paper, the authors propose an adaptation of the optical flow method to investigate aortic remodeling following Kawasaki disease, an early childhood vasculitis. Namely, displacement and strain of the aortic wall are used to assess aortic stiffness in this human disease model. The authors also introduce a fully developed automatic method to support postprocessing data analysis. The sequalae of Kawasaki disease on the ascending aorta were examined in children. The pathologic population (n = 4) was 15.00 ± 2.45 years old, while the healthy control population (n = 5) was 13.13 ± 0.18 years old. B-mode data were digitally recorded with commercially available cardiac echocardiography machines. Kawasaki disease had a very significant impact on the aortic stiffness. Indeed, pathologic subjects' aortic wall strain estimate was significantly lower compared to healthy controls (2.75% ± 0.56% versus 4.24% ± 0.65%, respectively; p < 0.001). Similarly, displacement of the aortic wall was also significantly lower compared to controls (p < 0.001). The potential of the optical flow-based method to quantify aortic wall remodeling in a human disease model was demonstrated. The authors now intend to extend this investigation to a larger pathologic cohort with various degrees of vasculitis severity.

Three-Dimensional Reconstruction of the Vessel Lumen as an Adjunct to the Cerebrovascular Duplex Evaluation

Introduction Color-flow duplex ultrasound is effective in the detection and quantification of carotid artery disease; however, diameter reduction estimates are most commonly derived by Doppler velocity measurements. In addition, direct visualization of the vessel lumen is only possible through the use of more expensive potentially invasive imaging procedures, such as computed tomography angiography, magnetic resonance angiography, and conventional angiography. Described here is a method to determine vessel diameter of the internal carotid artery (ICA) by the use of three-dimensional (3D) reconstruction of b-mode data to generate luminal diameter estimates. Materials and Methods A prospective review of 40 consecutive cerebrovascular duplex studies was performed. Testing protocols required transverse sweeps of the common carotid artery (CCA) and ICA in b-mode. Motion files were analyzed using software, which segmented the vessel lumen as the area of interest. The software created a 3D rendering of the lumen of the CCA and ICA. Vessel diameter reduction estimated by Doppler-derived velocities was then compared with the 3D rendering of the vessel lumen diameters. Results There was a 99% (n = 79, ρ = &lt; 0.001) correlation between velocity estimates and 3D visualization for estimating diameter reduction. Correlation for cases with less than 50% diameter reduction by duplex was 100% (n = 66, ρ = &lt; 0.004), whereas correlation for cases with 50% or greater diameter reduction by duplex was 92% (n = 13, ρ = &lt; 0.03). Conclusion 3D reconstruction of the vessel lumen shows a statistically significant correlation with velocity-derived diameter reduction measurements. Although more investigation with a larger group of patients is necessary, 3D reconstruction may be a valuable adjunct and may enhance the diagnostic capabilities of color-flow duplex ultrasound.

Fusion of Ultrasound B-Mode and Vibro-Elastography Images for Automatic 3-D Segmentation of the Prostate

Prostate segmentation in B-mode images is a challenging task even when done manually by experts. In this paper we propose a 3D automatic prostate segmentation algorithm which makes use of information from both ultrasound B-mode and vibro-elastography data.We exploit the high contrast to noise ratio of vibro-elastography images of the prostate, in addition to the commonly used B-mode images, to implement a 2D Active Shape Model (ASM)-based segmentation algorithm on the midgland image. The prostate model is deformed by a combination of two measures: the gray level similarity and the continuity of the prostate edge in both image types. The automatically obtained mid-gland contour is then used to initialize a 3D segmentation algorithm which models the prostate as a tapered and warped ellipsoid. Vibro-elastography images are used in addition to ultrasound images to improve boundary detection.We report a Dice similarity coefficient of 0.87±0.07 and 0.87±0.08 comparing the 2D automatic contours with manual contours of two observers on 61 images. For 11 cases, a whole gland volume error of 10.2±2.2% and 13.5±4.1% and whole gland volume difference of -7.2±9.1% and -13.3±12.6% between 3D automatic and manual surfaces of two observers is obtained. This is the first validated work showing the fusion of B-mode and vibro-elastography data for automatic 3D segmentation of the prostate.

Shear-wave Elastography Improves the Specificity of Breast US: The BE1 Multinational Study of 939 Masses

To determine whether adding shear-wave (SW) elastographic features could improve accuracy of ultrasonographic (US) assessment of breast masses. From September 2008 to September 2010, 958 women consented to repeat standard breast US supplemented by quantitative SW elastographic examination in this prospective multicenter institutional review board-approved, HIPAA-compliant protocol. B-mode Breast Imaging Reporting and Data System (BI-RADS) features and assessments were recorded. SW elastographic evaluation (mean, maximum, and minimum elasticity of stiffest portion of mass and surrounding tissue; lesion-to-fat elasticity ratio; ratio of SW elastographic-to-B-mode lesion diameter or area; SW elastographic lesion shape and homogeneity) was performed. Qualitative color SW elastographic stiffness was assessed independently. Nine hundred thirty-nine masses were analyzable; 102 BI-RADS category 2 masses were assumed to be benign; reference standard was available for 837 category 3 or higher lesions. Considering BI-RADS category 4a or higher as test positive for malignancy, effect of SW elastographic features on area under the receiver operating characteristic curve (AUC), sensitivity, and specificity after reclassifying category 3 and 4a masses was determined. Median participant age was 50 years; 289 of 939 (30.8%) masses were malignant (median mass size, 12 mm). B-mode BI-RADS AUC was 0.950; eight of 303 (2.6%) BI-RADS category 3 masses, 18 of 193 (9.3%) category 4a lesions, 41 of 97 (42%) category 4b lesions, 42 of 57 (74%) category 4c lesions, and 180 of 187 (96.3%) category 5 lesions were malignant. By using visual color stiffness to selectively upgrade category 3 and lack of stiffness to downgrade category 4a masses, specificity improved from 61.1% (397 of 650) to 78.5% (510 of 650) (P<.001); AUC increased to 0.962 (P=.005). Oval shape on SW elastographic images and quantitative maximum elasticity of 80 kPa (5.2 m/sec) or less improved specificity (69.4% [451 of 650] and 77.4% [503 of 650], P<.001 for both), without significant improvement in sensitivity or AUC. Adding SW elastographic features to BI-RADS feature analysis improved specificity of breast US mass assessment without loss of sensitivity.

THREE-DIMENSIONAL FLY-THROUGH SYSTEMS AND METHODS USING ULTRASOUND DATA

A volume is represented using high spatial resolution ultrasound data. By modulating B-mode data with Doppler or flow information, the spatial resolution or contrast of the B-mode data may be enhanced. The same set of ultrasound data is used for identifying a boundary, for placing the perspective position within the volume and rendering from the perspective position. The identification of the boundary and rendering are automated or performed by a processor. Ultrasound data may be used for generating three-dimensional fly-through representations, allowing for virtual endoscopy or other diagnostically useful views of structure or fluid flow channel. Virtual processes are not invasive, allow for more patient comfort, have selectable or different depths of focus, may allow for fly-through of different types of anatomy and may be used as a training tool.

Slip Imaging: Reducing Ambiguity in Breast Lesion Assessment

Ultrasound elasticity imaging (elastography) is gaining popularity as an adjunct to B-mode ultrasound for breast cancer diagnosis. Cancerous masses are usually stiffer than normal tissue, hence, using elasticity imaging should lead to better differentiation between benign and malignant masses than using B-mode alone. Clinicians assess the mobility of masses on palpation; cancers usually being less mobile. We introduce a method to estimate mobility, called slip imaging and combine it with conventional B-mode and elasticity data. In the reported evaluation on 70 women recalled to a breast assessment clinic, images were scored by three breast radiologists independently. Diagnostic accuracy increased from 75.7% with B-mode alone, to 78.1% when including elasticity imaging, to 80.0% when further including slip imaging. Specificity increased (74.6%:75.4%:82.5% respectively), with an apparent trade-off in sensitivity (77.1%:81.3%:77.1%). We conclude that Slip imaging is potentially a useful adjunct to B-mode and elasticity imaging and should undergo further research and development. (E-mail: noble@robots.ox.ac.uk)

Optical-Flow-Based B-Mode Elastography: Application in the Hypertensive Rat Carotid

Background-Ultrasound elastography is now used worldwide in tissue characterization. The primary premises of elastography are that speckle kinematics reproduces underlying tissue kinematics and that tissue motion can be inferred from speckle tracking. This implicitly assumes that speckle pattern is a material property that can be tracked with respect to time and space. It is then convenient to express the motion of such a material property in terms of total derivative, also known as optical flow (OF) equations. Aims-The present paper introduces a new iterative OF-based elastography (OFBE) method devoted to B-mode data. The first OFBE iteration computes axial and lateral displacement fields. Such displacement fields are used for data rigid registration, prior to the second OFBE iteration which computes the 2-D strain tensor. Methods-The OFBE method was validated in the common carotid artery of rat hypertension models. The effect of aging on carotid stiffness was investigated in female recombinant inbred rats (RI-17, (n=2)) in the first experiment. The outcomes of low/high-salt diets were examined in young male Dahl salt-sensitive rats (SS, n=6; SM12, n=6; SM9, n=6) in the second experiment. Results-Good concordance was observed between left and right carotid axial strain measurements with 11.4% relative error, whereas 4.6% relative error occurred between diastolic and systolic axial strain measurements. Old (80 and 85 weeks) RI-17 carotids were determined to be twice as stiff with 5.70 +/- 0.97% (strain+/-std) as young carotids (30 and 34 weeks) with 13.26 +/- 2.73%, p < 0.001. Carotid axial strain measurement also indicated that salt diets had a significant impact on SS (p=0.008) and SM12 (p < 0.001) but not on SM9 (p=0.881) rats.

Single-pulse tissue doppler using synthetic transmit beams

Tissue Doppler imaging (TDI) is a common technique for investigating myocardial function. Typically, B-mode data and TDI data are recorded using separate acquisitions and combined into a single, color overlaid image. In this work, we present a novel method for TDI imaging, where both TDI and B-mode are created from the same acquisition. Velocities are calculated from the phase shift between neighboring transmit events in the B-mode scan; hence the name singlepulse tissue Doppler (SPTD). Using a novel transmit beam interleaving pattern, this method provides TDI and B-mode at the same high frame rate with an adjustable Nyquist velocity limit. Through simulations and measurements, this work investigates the bias and variance of the SPTD velocities and compares the estimates to those of the conventional TDI autocorrelation estimation method. The results showed that the method introduces an additional bias and variance in the velocity estimates compared with conventional TDI. However, by applying bias compensation, the SPTD velocity estimates were close to those of regular TDI. Using SPTD, the whole left ventricle was imaged within a 65-degree sector at a frame rate of 110 frames per second (43 transmissions per frame).

Diagnosis of liver cirrhosis by transit-time analysis at contrast-enhanced ultrasonography

The aims of this prospective study were to evaluate analysis of sulfur-hexafluoride-filled microbubble contrast agent (Sonovue) transit times as a tool for differentiating liver cirrhosis from the noncirrhotic stage of liver disease and to compare its performance with that of conventional B-mode and Doppler ultrasonography (US). Contrast-enhanced hepatic ultrasonography with the US contrast agent Sonovue was performed on 38 patients with diagnoses of hepatic cirrhosis based on unequivocal clinical signs or liver biopsy findings (Child-Pugh classes A in 19, B in 16 and C in three), 31 patients with noncirrhotic diffuse liver disease (biopsy confirmed) and 14 controls without diffuse liver disease. Time curves of hepatic-vein signal intensity were analysed using objective criteria to determine the time of enhancement onset (hepatic-vein arrival time) and peak enhancement (hepatic-vein peak enhancement). Accuracy in diagnosing cirrhosis was compared with that based on B-mode and Doppler data. Hepatic-vein arrival time in cirrhotic patients was significantly shorter (p < 0.01) than in noncirrhotic (chronic liver disease and controls) patients. Peak enhancement times in these three groups were not significantly different. An arrival-time cutoff of 17 s distinguished cirrhotic from noncirrhotic patients with high accuracy (100% sensitivity, 93.3% specificity, positive and negative predictive values 92.6% and 100%, respectively) and excellent reproducibility (kappa coefficients of 1.0 and 0.93 for intraand interobserver agreement). Contrast-enhanced US showed better sensitivity than the B-mode and Doppler data. Analysis of the time of onset of US contrast enhancement of the hepatic vein appears to be a potentially useful noninvasive supplement to conventional sonography and Doppler in the follow-up of patients with chronic diffuse liver disease.

Ultrasound frame rate requirements for cardiac elastography: Experimental and in vivo results

Cardiac elastography using radiofrequency echo signals can provide improved 2D strain information compared to B-mode image data, provided data are acquired at sufficient frame rates. In this paper, we evaluate ultrasound frame rate requirements for unbiased and robust estimation of tissue displacements and strain. Both tissue-mimicking phantoms under cyclic compressions at rates that mimic the contractions of the heart and in vivo results are presented. Sinusoidal compressions were applied to the phantom at frequencies ranging from 0.5 to 3.5 cycles/sec, with a maximum deformation of 5% of the phantom height. Local displacements and strains were estimated using both a two-step one-dimensional and hybrid two-dimensional cross-correlation method. Accuracy and repeatability of local strains were assessed as a function of the ultrasound frame rate based on signal-to-noise ratio values. The maximum signal-to-noise ratio obtained in a uniformly elastic phantom is 20 dB for both a 1.26 Hz and a 2 Hz compression frequency when the radiofrequency echo acquisition is at least 12 Hz and 20 Hz respectively. However, for compression frequencies of 2.8 Hz and 4 Hz the maximum signal-to-noise ratio obtained is around 16 dB even for a 40 Hz frame rate. Our results indicate that unbiased estimation of displacements and strain require ultrasound frame rates greater than ten times the compression frequency, although a frame rate of about two times the compression frequency is sufficient to estimate the compression frequency imparted to the tissue-mimicking phantom. In vivo results derived from short-axis views of the heart acquired from normal human volunteers also demonstrate this frame rate requirement for elastography.

Estimation of ultrasound attenuation from broadband echo-signals using bandpass filtering

A problem with video signal analysis for estimating frequency-dependent ultrasonic attenuation is that relative echogenicity versus depth curves are distorted when broadband pulses are used. In this correspondence, we present results that demonstrate improved accuracy of attenuation estimates computed from B-mode or envelope data derived after narrowband (1 MHz BW) filtering at different frequencies around the center frequency of the broadband echo signal. Based on the premise that transducer center frequencies are selected in part on penetration or imaging depth requirements, simulation and experimental results for a typical ultrasound imaging system show that narrowband video signal analysis for frequencies lower than or at the center frequency of the broadband pulse provide unbiased attenuation estimation over this depth. Filtered signals above the center frequency of the pulse yield accurate results only at shallow depths.

Ultrasonic transmission/reception apparatus for generating an image based on ultrasonic echoes and vibro-acoustic sounds

An ultrasonic transmission/reception apparatus which can image both a minute tissue around a bone part in an object and a minute tissue inside the bone, at a high resolution. The apparatus includes a system control unit which controls the synthesizers so that a first ultrasonic wave may be transmitted from one of the transmission elements while its frequency is being swept, and that a second ultrasonic wave may be transmitted from the other transmission element while its frequency is being swept with a predetermined difference frequency held relative to the frequency of the first ultrasonic wave, a signal processing unit which subjects the detection signal of the ultrasonic echo to predetermined signal processing, a signal processing unit which subjects the detection signal of the vibro-acoustic sound to predetermined signal processing, and a display-image arithmetic unit which generates B-mode image data based on the detection signals subjected to the signal processing. The detection signal may be subjected to pulse compression processing.

Reconstruction of Ultrasonic Sound Velocity and Attenuation Coefficient Using Linear Arrays: Clinical Assessment

The aim of this study was to determine the efficacy of using sound velocity and tissue attenuation to clinically discriminate breast cancer from healthy tissues. The methods for reconstructing the sound-velocity and attenuation-coefficient distributions were previously proposed and tested on tissue-mimicking phantoms. The methods require only raw channel data acquired by a linear transducer array and can therefore be implemented on existing clinical systems. In this paper, these methods are tested on clinical data. A total of 19 biopsy-proven cases, consisting of five carcinomas (CAs), seven fibroadenomas (FAs), six adipose tissue (fat) and one oil cyst, were evaluated. A single imaging setup consisting of a 5-MHz, 128-channel linear array was used to simultaneously obtain B-mode image data, time-of-flight data and attenuation data. The sound velocity and attenuation coefficient can be reconstructed inside and outside a region of interest manually selected in the B-mode image. To reduce distortion caused by tissue inhomogeneities, an optimal filter derived from pulse-echo data—with water replacing the breast tissue—is applied. We found that the sound velocities in CA, FA and fat tissues relative to those in the surrounding tissues were 49.8 ± 35.2, 2.6 ± 27.3 and −25.1 ± 44.9 m/s (mean ± SD), respectively, whereas the relative attenuation coefficients were 0.21 ± 0.58, 0.27 ± 0.62 and −0.02 ± 0.59 dB/cm/MHz. These results indicate that CA can be discriminated from FA and fat by choosing an appropriate threshold for the relative sound velocity ( i.e., 18.5 m/s). However, the large variations in the attenuation within the same type of tissue make simple thresholding ineffective. Nevertheless, the method described in this paper has the potential to reduce negative biopsies and to improve the accuracy of breast cancer detection in clinics. (E-mail: paichi@cc.ee.ntu.edu.tw)

Blood Flow in Its Context: Combining 3D B-Mode and Color Doppler Ultrasonic Data

Visualization of volumetric multicomponent data sets is a high-dimensional problem, especially for color data. Medical 3D ultrasound (US) technology has rapidly advanced during the last few decades and scanners can now generate joint 3D scans of tissues (B-mode) and blood flow (power or color Doppler) in real time. Renderings of such data sets have to comprehensively convey both the relevant structures of the tissues that form the context for blood flow, as well as the distribution of blood flow itself. The narrow field of view in US data, which is often used to make real-time imaging possible, complicates volume exploration since only parts of organs are usually visible; that is, clearly defined anatomical landmarks are scarce. In addition, the noisy nature and low signal-to-contrast ratio of US data make effective visualization a challenge, whereby there are currently no convincing solutions for combined US B-mode and color Doppler data rendering. Therefore, displaying 2D slices out of the 3D data is still often the preferred visualization method. We present new combinations of photorealistic and nonphotorealistic rendering strategies for combined visualization of B-mode and color Doppler data, which are straightforward to implement, flexible, and suited for a wide range of US applications.

Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Polarization Analysis

The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the entire sky in five frequency bands between 23 and 94 GHz with polarization-sensitive radiometers. We present 3 year full-sky maps of the polarization and analyze them for foreground emission and cosmological implications. These observations open up a new window for understanding how the universe began and help set a foundation for future observations. WMAP observes significant levels of polarized foreground emission due to both Galactic synchrotron radiation and thermal dust emission. Synchrotron radiation is the dominant signal at l < 50 and ν 40 GHz, while thermal dust emission is evident at 94 GHz. The least contaminated channel is at 61 GHz. We present a model of polarized foreground emission that captures the large angular scale characteristics of the microwave sky. After applying a Galactic mask that cuts 25.7% of the sky, we show that the high Galactic latitude rms polarized foreground emission, averaged over l = 4-6, ranges from ≈5 μK at 22 GHz to 0.6 μK at 61 GHz. By comparison, the levels of intrinsic CMB polarization for a ΛCDM model with an optical depth of τ = 0.09 and assumed tensor-to-scalar ratio r = 0.3 are ≈0.3 μK for E-mode polarization and ≈0.1 μK for B-mode polarization. To analyze the maps for CMB polarization at l < 16, we subtract a model of the foreground emission that is based primarily on a scaling WMAP's 23 GHz map. In the foreground-corrected maps, we detect l(l + 1)C/2π = 0.086 ± 0.029 (μK)2. This is interpreted as the result of rescattering of the CMB by free electrons released during reionization at zr = 10.9 for a model with instantaneous reionization. By computing the likelihood of just the EE data as a function of τ we find τ = 0.10 ± 0.03. When the same EE data are used in the full six-parameter fit to all WMAP data (TT, TE, EE), we find τ = 0.09 ± 0.03. Marginalization over the foreground subtraction affects this value by δτ < 0.01. We see no evidence for B modes, limiting them to l(l + 1)C/2π = -0.04 ± 0.03 (μK)2. We perform a template fit to the E-mode and B-mode data with an approximate model for the tensor scalar ratio. We find that the limit from the polarization signals alone is r < 2.2 (95% CL), where r is evaluated at k = 0.002 Mpc-1. This corresponds to a limit on the cosmic density of gravitational waves of ΩGWh2 < 5 × 10-12. From the full WMAP analysis, we find r < 0.55 (95% CL) corresponding to a limit of ΩGWh2 < 1 × 10-12 (95% CL). The limit on r is approaching the upper bound of predictions for some of the simplest models of inflation, r ~ 0.3.

Two-dimensional multi-level strain estimation for discontinuous tissue

A large number of the strain estimation methods presented in the literature are based on the assumption of tissue continuity that establishes a continuous displacement field. However, in certain locations in the body such as the arteries in vivo scanning may produce displacement fields that are discontinuous between the two walls of the artery. Many of the displacement or strain estimators fail when the displacement fields are discontinuous. In this paper, we present a new 2D multi-level motion or displacement tracking method for accurate estimation of the strain in these situations. The final high-resolution displacement estimate is obtained using two processing steps. The first step involves an estimation of a coarse displacement estimate utilizing B-mode or envelope signals. To reduce computational time, the coarse displacement estimates are obtained starting from down-sampled B-mode pre- and post-compression image pairs using a pyramidal processing approach. The coarse displacement estimate obtained from the B-mode data is used to guide the final 2D cross-correlation computations on radio-frequency (RF) data. Results from finite element simulations and in vivo experimental data demonstrate the feasibility of this approach for imaging tissue with discontinuous displacement fields.

Assessment of myocardial regional strain and strain rate by tissue tracking in B-mode echocardiograms

To date, established ultrasonic methods for myocardial regional deformation recovery are based on the Doppler effect, which has inherent limitations restricting its accuracy and use. The reported time domain methods show in vivo insufficient accuracy. A novel approach is elaborated mimicking the human observer who reaches robust diagnosis upon the B-mode data. In a region-of-interest (ROI), acoustic markers stable for tracking are selected. A weighting index presenting the quality of tracking of each marker is used for spatial polynomial fitting. For the feasibility study, a simple straight ROI was selected, which matches the septum. A thorough proof of concept is provided by comparing with a gold standard method and by applying the method to clinical datasets. The peak systolic longitudinal strains of 12 normals were –15% + –2.3% and, of 12 patients with a light-to-mild dysfunction of the apical-septal segment, they were –9% + –0.8% ( p < 0.05). Enhancements of the method using spline fitting are introduced. (E-mail: dan@biomed.technion.ac.il)

Duplex Ultrasound Follow-up of Carotid Stents

Endovascular treatment of carotid disease continues to evolve. There have been few published reports describing the ultrasound follow-up of stented carotid arteries. It is the purpose of this study to evaluate the duplex ultrasound characteristics of carotid stents including comparing hemodynamic to B-mode and color-flow imaging data. During the past 5 years, 40 carotid stents have been placed in the common or internal carotid arteries of 37 patients. There were 21 males and 16 females with an average age of 67 ± 9 years. Duplex ultrasound examinations included peak systolic velocity (PSV) and end diastolic velocity (EDV) taken proximal to the stent (pre-stent), at the proximal, mid, and distal regions of the stent, and distal to the stent (post-stent). The stents were evaluated at 1 day, 3, 6, and 12 months postprocedure and yearly thereafter. The average follow-up interval was 6 ± 1 months from stent placement. In 31 patent internal carotid artery stents, the PSV proximally within the stent was 92 ± 6 cm/sec with an EDV of 24 ± 2 cm/sec (all velocity data expressed as mean ± SEM). The mid stent PSV was 86 ± 5 cm/sec with an EDV of 24 ± 2 cm/sec. The distal stent PSV was 90 ± 4 with an EDV of 26 ± 2 cm/sec. Proximal to the stent, the PSV was 70 ± 3 cm/sec with an EDV of 17 ± 1 cm/sec. Distal to the stent, the PSV was 77 ± 4 cm/sec with an EDV of 25 ± 2 cm/sec. There were no defects observed on B-mode image and no areas of color turbulence. Three stents developed stenotic areas with PSVs of 251, 383, and 512 cm/sec. The EDV was 50, 131, and 365 cm/sec, respectively. Poststenotic turbulence was present in each of these stents. An elevated PSV of greater than 125 cm/sec was found in 32% of the stents (9 of 28) without evidence of stenosis on B-mode image or poststenotic turbulence. These data demonstrate that velocities within stented carotid arteries can be elevated above established ranges for normal. In conclusion, velocity criteria may need to be adjusted when applied to stented carotid arteries.