Digital high frame rate stress echocardiography for detection of coronary artery stenosis by high dose dipyridamole stress testing

Diagnostic accuracy of high dose dipyridamole stress echocardiography (0.84 mg i.v./kg) for detecting coronary artery stenosis was assessed in 94 patients undergoing coronary angiography, and adverse effects were registered in the total study population of 120 patients. Echocardiographic analysis was performed with digital systolic cineloops with high frame-rate (47 frames/sec) for optimal left ventricular wall motion display. Results showed sensitivity of 73% for detection of arterial luminal stenosis ≥ 75% or retrograde collateral flow to an occluded coronary artery. Sensitivity for detection of 1-vessel stenosis was 43% (6 of 14 patients), and for 2- and 3-vessel disease 79% (19 of 24) and 88% (16 of 18), respectively. Specificity was 92% (35 of 38), diagnostic accuracy 81%. The stenosed coronary artery was correctly localized in 85% of positive tests. Dipyridamole-induced increase in wall motion score index differed significantly between patients with 1-, 2-, and 3-vessel disease (0.02 ± 0.17, 0.15 ± 0.17, and 0.27 ± 0.24, respectively), and early positive tests (dipyridamole dose of 0.56 mg/kg) were almost exclusively seen in patients with multivessel disease. Six patients (5%) developed symptomatic bradycardia and hypotension during the test. In conclusion, dipyridamole stress echocardiography is useful for detection and localization of coronary artery stenosis, particularly in patients with multivessel disease.     

Effects of phase aberration on high frame rate imaging

A high frame-rate (HFR) imaging method (about 3750 frames/s for imaging of biological soft tissues at a depth of 200 mm) has been developed recently with limited diffraction beams. This method uses the fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) to construct images, and can be implemented with simple and inexpensive hardware, compared to the conventional delay-and-sum method where a digital beam former is usually used. In this paper, phase aberration effects are studied for both the high frame rate and the conventional methods by adding random phase shifts to echo signals obtained from an experiment. In the study, two broadband linear arrays were used to construct images of an ATS 539 tissue-equivalent phantom that has a frequency-dependent attenuation of about 0.5 dB/MHz/cm. The first array has 48 elements, a central frequency of 2.25 MHz, an aperture of 18.288 mm, and a width of 12.192 mm in elevation. The second has 64 elements, a central frequency of 2.5 MHz, and a dimension of 38.4 mm x 10 mm. The-6dB pulse-echo bandwidth of both arrays is about 40% of their center frequencies. Radiofrequency (RF) signals were digitized at 20 mega samples/s at a 12-bit resolution to construct images. Results show that phase aberration has about the same effect on both methods in terms of image resolution and contrast, although the high frame-rate method can be implemented with a simpler system.     

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.     

应变率成像预测冠状动脉多支病变

目的 探讨应变率成像技术预测非心肌梗死冠状动脉多支病变的价值。方法 选取接受CAG的非心肌梗死患者118例,其中多支病变43例(多支病变组),单支病变32例(单支病变组),43例造影正常(对照组),分析3组研究对象收缩期峰值应变(S_PI)及应变率(SR_SI)有无差异。结果 多支病变组SR_S和S_P绝对值均低于单支病变组及对照组(P＜0.05)。分别以S_P＞－15.0%、SR_S＞－1.01 s^-1作为截断值,诊断多支病变的敏感度分别为65.12%(28/43)和72.09%(31/43),特异度为90.67%(68/75)和74.67%(56/75)。结论 应变率成像能够预测冠状动脉多支病变。     

Measurement of regional pulse wave velocity using very high frame rate ultrasound

Purpose

Pulse wave velocity (PWV) is the propagation velocity of the pressure wave along the artery due to the heartbeat. The PWV becomes faster with progression of arteriosclerosis and, thus, can be used as a diagnostic index of arteriosclerosis. Measurement of PWV is known as a noninvasive approach for diagnosis of arteriosclerosis and is widely used in clinical situations. In the traditional PWV method, the average PWV is calculated between two points, the carotid and femoral arteries, at an interval of several tens of centimeters. However, PWV depends on part of the arterial tree, i.e., PWVs in the distal arteries are faster than those in the proximal arteries. Therefore, measurement of regional PWV is preferable.

Methods

To evaluate regional PWV in the present study, the minute vibration velocity of the human carotid arterial wall was measured at intervals of 0.2 mm at 72 points in the arterial longitudinal direction by the phased-tracking method at a high temporal resolution of 3472 Hz, and PWV was estimated by applying the Hilbert transform to those waveforms.

Results

In the present study, carotid arteries of three healthy subjects were measured in vivo. The PWVs in short segments of 14.4 mm in the arterial longitudinal direction were estimated to be 5.6, 6.4, and 6.7 m/s, which were in good agreement with those reported in the literature. Furthermore, for one of the subjects, a component was clearly found propagating from the periphery to the direction of the heart, i.e., a well known component reflected by the peripheral arteries. By using the proposed method, the propagation speed of the reflection component was also separately estimated to be ?8.4 m/s. The higher magnitude of PWV for the reflection component was considered to be the difference in blood pressure at the arrivals of the forward and reflection components.

Conclusion

Such a method would be useful for more sensitive evaluation of the change in elasticity due to progression of arteriosclerosis by measuring the regional PWV in a specific artery of interest (not the average PWV including other arteries).     

Effects of phase aberration and noise on extended high frame rate imaging

Based on the high frame rate (HFR) imaging theories, an extended HFR imaging method has been developed recently in our lab where multiple limited-diffraction array beams or steered plane waves are used in transmissions to reconstruct a high quality image of an equivalent dynamic focusing in both transmissions and receptions. The method has the potential to simplify imaging systems because the fast Fourier transform and square-wave aperture weightings can be used. The method is also flexible in using different numbers of transmissions for a continuous trade-off between image quality and frame rate. In this paper, we study the effects of phase aberration and noise on the extended HFR imaging method with in vitro experiments and compare the results with those obtained with a conventional delay-and-sum (D&S) method of a fixed-transmission focus and a dynamically-focused reception. In the experiments, an ATS539 tissue-mimicking phantom and an Acuson V2 phase array transducer (128 elements, 2.5 MHz, and 0.15-mm pitch) were used. The transducer was driven by a homemade general-purpose HFR imaging system that was capable of producing both the limited-diffraction array beams and steeredplane waves and echo data were acquired with the same system and then transferred to a personal computer via a universal serial bus (USB) 2.0 link for image reconstructions. The phase aberration was introduced by adding random phase shifts to both transmission and reception beams. The random noise was added to the received radiofrequency echo data. Results show that the phase aberration and noise degrade both the extended HFR and the conventional delay-and-sum (D&S) imaging method. However, images reconstructed with the extended HFR imaging method have an overall higher quality than those with the D&S method given the phase aberration and noise models studied.     

Acoustic shadowing on B-mode ultrasound of the carotid artery predicts CHD

The relationship between carotid artery lesions (CALs), with and without acoustic shadowing (AS) as an index of arterial mineralization, and incident coronary heart disease (CHD) was examined in the Atherosclerosis Risk in Communities study cohort. Among 12,375 individuals, ages 45-64 years, free of CHD at baseline, 399 CHD events occurred between 1987-1995. In a 3-cm segment centered at the carotid bifurcation, CALs with and without AS were identified by B-mode ultrasound (US). After adjustment for the major CHD risk factors, the CHD hazard ratio (HR) for women with CAL without AS compared to women without CAL was 1.78 (95% CI: 1.22, 2.60) and the HR comparing women with CAL with AS to women with CAL without AS was 1.73 (95% CI: 1.07, 2.80). Corresponding HRs for men were 1.59 (95% CI: 1.22, 2.07) and 1.04 (95% CI: 0.72, 1.51). CALs predicted CHD events; this association was stronger for mineralized CALs in women, but not men.     

应变率显像评价左冠状动脉异常起源于肺动脉患者的左心室功能

目的：探讨应变率成像（SRI）技术估测左冠状动脉异常起源于肺动脉（ALCAPA）患儿手术前、后左心室功能变化的准确性。方法：研究对象为39例正常儿童和16例ALCAPA患儿。应用SRI技术估测左心室不同心肌节段的应变及应变率值，并将16例ALCAPA患者手术前、后的应变值与正常儿童对比。结果：ALCAPA患者手术前收缩期及舒张期应变率及应变均低于正常儿童（P<0.01），手术后左心室收缩期及舒张期应变率及应变明显好转（P<0.01），但仍低于正常儿童（P<0.05）。结论：ALCAPA患者的左心功能较正常儿童差，早期行冠状动脉移植术可以改善患者的心功能；应用SRI技术可以比较准确地估测ALCAPA患者手术前后的心功能变化。     

Automatic recognition of the common carotid artery in longitudinal ultrasound B-mode scans

Many morphological and dynamic properties of the common carotid artery (CCA), e.g. lumen diameter, distension and wall thickness, can be measured non-invasively with ultrasound (US) techniques. As common to other medical image segmentation processes, this requires as a preliminary step the manual recognition of the artery of interest within the ultrasound image. In real-time US imaging, such manual initialization procedure interferes with the difficult task of the sonographer to select and maintain a proper image scan plane. Even for off-line US segmentation the requirement for human supervision and interaction precludes full automation. To eliminate user interference and to speed up processing for both real-time and off-line applications, we developed an algorithm for the automatic artery recognition in longitudinal US scans of the CCA. It acts directly on the envelopes of received radio frequency echo signals, eventually composing the ultrasound image. In order to properly exploit the information content of the arterial structure the envelopes are decimated, according to the two-dimensional resolution characteristics of the echo system, thereby substantially decreasing computational load. Subsequently, based upon the expected diameter range and a priori knowledge of the typical pattern in the echo envelope of the arterial wall-lumen complex, parametrical template matching is performed, resulting in the location of the lumen position along each echo line considered. Finally, in order to reject incorrect estimates, a spatial and temporal clustering method is applied. Adequate values for the parameters involved in the processing are obtained via off-line testing of the proposed algorithm on 128 echo data recordings from 45 subjects. Using those robust parameter values, correct and fast recognition of the artery is achieved in more than 98% of the 6185 processed frames. Since these results are obtained via rigorous data decimation and using a cascade of rather simple steps, the proposed automatic algorithm is suitable for real-time recognition of the CCA.     

3-D measurement of body tissues based on ultrasound images with 3-D spatial information

In this study, we developed a new method to perform 3-D measurements between the recorded B-scans using the corresponding spatial location and orientation of each B-scan, without the need to create a 3-D volume. A portable ultrasound (US) scanner and an electromagnetic spatial locator attached to the US probe were used. During data collection, the US probe was moved over the region-of-interest. A small number of B-scans containing interesting anatomical information were captured from different body parts and displayed in a 3-D space with their corresponding locations recorded by the spatial locator. In the B-scan planes, the distance between any two points, as well as the angle between any two lines, could be calculated. In validation experiments, three distances and three angles of a custom-designed phantom were measured using this method. In comparison with the results measured by a micrometer, the mean error of distance measurement was −0.8 ± 1.7 mm (−2.3 ± 3.6%) and that of angle measurement was −0.3 ± 2.9° (−0.1 ± 4.1%). The lengths of the first metatarsals and the angles between the first metatarsals and the middle part of the tibias of three subjects were measured in vivo using magnetic resonance imaging (MRI) and the US method by two operators before and after MRI scanning. The overall percentage differences of the length and angle measurements were 0.8 ± 2.2% and 2.5 ± 3.6%, respectively. The results showed that this US method had good repeatability and reproducibility (interclass correlation coefficient values > 0.75). We expect that this new method could potentially provide a quick and effective approach for the 3-D measurement of soft tissues and bones in the musculoskeletal system.     

Quantification of the wall inhomogeneity in B-mode sonographic images of the carotid artery.

OBJECTIVE: The process of atherosclerosis has been assessed increasingly by sonography in B-mode images of the carotid arteries. Carotid artery atherosclerosis is thought to be associated with major atherosclerotic diseases in other regions of the arterial bed, especially the coronary arteries. In addition to the intima-media thickening as an established surrogate parameter of the atherosclerotic wall process, changes of the sonographic morphologic pattern of the intima-media layer might reflect this process. METHODS: After automatic identification of the intimal and adventitial boundaries of the distal common carotid artery wall, the gray level inhomogeneity of the circumscribed intima-media area was quantified. Older subjects without cardiovascular disease (mean +/- SD, 66.2 +/- 3.8 years; n = 43) were compared with young subjects without cardiovascular disease (24.4 +/- 5.3 years; n = 34) and patients with manifest coronary artery disease (65.0 +/- 9.2 years; n = 69). RESULTS: Patients with coronary artery disease had a significantly higher intima-media thickness (0.92 +/- 0.21 mm; P < .05) and wall inhomogeneity (4.56 +/- 0.97; P < .001) than the old group (0.86 +/- 0.15 mm and 3.83 +/- 0.62). Both parameters were lowest in the young group (0.56 +/- 0.05 mm and 2.53 +/- 0.76; P < .05 for both parameters and groups). CONCLUSIONS: Measurement of gray level wall inhomogeneity of the intima-media layer of the common carotid artery may help discriminate between subjects with high and low atherosclerotic burden and may show age-related changes of the intima-media layer. This new quantitative parameter is thought to reflect the atherosclerotic wall process in addition to the intima-media thickness measurement.     

Taylor空间外固定架联合胫骨高位截骨术对膝骨性关节炎并膝内翻患者膝关节功能的影响

目的 探讨分析Taylor空间外固定架联合胫骨高位截骨术(HTO)在膝骨性关节炎并膝内翻患者中的应用.方法 回顾性选取2018年3月至2020年12月唐山市开滦总医院接受治疗的40例膝骨性关节炎并膝内翻患者,按照治疗方法不同分为2组,各20例.观察组患者采用Taylor外固定,对照组患者采用钢板内固定,2组均行HTO....     

超声弹性成像评价2型糖尿病患者桡动脉血管壁弹性

目的 应用超声弹性成像技术评价2型糖尿病(T2DM)患者桡动脉血管壁的弹性变化.方法 对T2DM组包括患者37例,正常对照组42名,以常规二维超声测量桡动脉收缩期内径(Ds)和舒张期内径(Dd);应用超声弹性成像技术计算受试者桡动脉内血液与血管壁的应变比值(B/A),并将上述两组受试者各指标进行比较.结果 T2DM组桡动脉的应变比值明显高于正常对照组,差异有统计学意义(P＜0.05);T2DM组桡动脉舒张期内径及收缩期内径与正常对照组相比差异无统计学意义(P＞0.05).结论 超声弹性成像技术可以评价T2DM患者桡动脉血管壁弹性的早期变化.     

Estimation of Doppler shift frequency using selected phase information for high frame rate color flow mapping

Purpose We describe a new approach to processing signals used to estimate the Doppler shift frequency in high frame-rate color flow mapping with fewer pulse transmissions. When an ultrasound pulse is transmitted to a large number of scatterers, the echoes from the scatterers overlap and interfere with one another. This interference causes the phase of the received echo signal to fluctuate, thus disturbing the estimated shift in Doppler frequency. The technique proposed here eliminates this disturbed phase information, leaving the remaining information for use in estimating the shift in Doppler frequency. The instantaneous frequency of the echo signal can serve as an index of the influence of interference.Methods To test this technique in vivo we used radio-frequency echo signals from the carotid artery for simulation and evaluated the error of the estimated Doppler shift frequency in several cases.Conclusion Performance was enhanced when the number of pulses transmitted was limited and this technique was used.This article is a translation of the original that was published in Jpn J Med Ultrasonics 2001;28:J15–23     

超声斑点追踪应变率成像技术结合多巴酚丁胺负荷试验评价冠状动脉粥样硬化性心脏病患者存活心肌的价值

目的探讨超声斑点追踪应变率成像技术(SRI)结合多巴酚丁胺负荷试验(DSE)评价冠状动脉粥样硬化性心脏病患者存活心肌的临床价值。方法 27例经超声心动图检查存在左心室室壁节段性运动异常和左心室收缩功能障碍(左心室射血分数<50%)的冠状动脉粥样硬化性心脏病患者,经皮冠状动脉介入治疗(PCI)之前进行联合DSE的斑点追踪SRI成像及双核素单光子发射型断层显像(DISA-SPECT)检查。PhilipsiE33彩色超声诊断仪分别录入静息及DSE状态下斑点追踪SRI图像并存储,Qlab7.0定量分析软件计算各节段的纵向收缩期峰值应变率(LSR)。所有患者在完成联合DSE的SRI及DISA-SPECT检查后1周内进行PCI术。术后1、3、6个月时分别复查超声心动图,PCI术后室壁运动改善作为判定存活心肌的金标准。绘制受试者操作特性曲线(ROC)评价LSR检测存活心肌的敏感度及特异度。结果超声心动图检出165个室壁运动异常节段(RWMA),PCI术后超声心动图(金标准)检出存活心肌106(64.2%,106/165)个节段,非存活心肌59(35.8%,59/165)个节段。DISA-SPECT检测出存活心肌104个节段,非存活心肌61个节段,与PCI术后超声心动图比较,其敏感度、特异度和准确性分别为87.7%(93/106)、81.4%(48/59)和85.5%(141/165)。静息状态下SRI参数LSR预测存活心肌ROC下面积为0.694(P<0.001),截断点为-1.08,敏感度为66.7%,特异度为62.7%;联合DSE后ROC下面积为0.859(P<0.001),截断点为-1.30,敏感度和特异度分别为84.4%和85.3%,较静息时均有显著提高(χ2=9.082、7.394,P<0.05)。静息状态下存活心肌和非存活心肌LSR分别为(-1.12±0.17)s-1、(-1.05±0.14)s-1,差异有统计学意义(t=16.84,P<0.01);DSE后存活心肌和非存活心肌LSR分别为(-1.64±0.31)s-1、(-1.09±0.42)s-1,差异亦有统计学意义(t=11.87,P<0.01)。SRI联合DSE检测冠状动脉粥样硬化性心脏病患者存活心肌与DISA-SPECT相比,敏感度略低(84.4%vs87.7%)、特异度略高(85.3%vs81.4%),但差异无统计学意义(χ2=0.621、0.241,P>0.05)。联合DSE的SRI检测存活心肌与DISA-SPECT有良好的相关性(rn=0.819,P<0.001)。结论联合DSE的SRI参数LSR检测存活心肌的敏感度及特异度较静息时均有显著提高,联合DSE的SRI检测冠状动脉粥样硬化性心脏病患者存活心肌的敏感度和特异度与DISA-SPECT基本相同,并具有良好的相关性。     

High frame rate strain rate imaging of the interventricular septum in healthy subjects.

OBJECTIVE: In the present study the feasibility was assessed of a new strain rate imaging method with a very high frame rate of around 300 frames per second. METHODS: Digital radio-frequency (RF) data were obtained in nine healthy subjects using a sector of 20-30 degrees in an apical four chamber view. The RF data were analysed using a dedicated software package that displays strain rate images and profiles and calculates strain rate values. With the new method, it is possible to study events and spatial-temporal differences in the heart cycle with duration down to 3.5-3 ms, including the pre-ejection period and the isovolumic relaxation period. Since the interventricular septum (IVS) is of crucial importance for the left and right ventricular function, we assessed changes through the heart cycle of the strain rate in the IVS. RESULTS: Mean peak systolic strain rate in the healthy subjects was -1.65+/-0.13 s(-1). Mean peak diastolic strain rate during early filling was 3.14+/-0.50 s(-1) and during atrial systole 0.99+/-0.09 s(-1). We found individual differences in the strain rate patterns, but in all subjects, the ventricular contraction started simultaneously in all parts of the septum. After the ejection period, the elongation started before aortic valve closure, in the midinferior septum and propagated towards the apex. CONCLUSION: High frame rate strain rate imaging makes it possible to study rapid deformation patterns in the heart walls.     

Texture of B-mode echograms: 3-D simulations and experiments of the effects of diffraction and scatterer density

B-mode echograms were simulated by employing the impulse response method in transmission and reception using a discrete scatterer tissue model, with and without attenuation. The analytic signal approach was used for demodulation of the RF A-mode lines. The simulations were performed in 3-D space and compared to B-mode echograms obtained from experiments with scattering tissue phantoms. The average echo amplitude appeared to increase towards the focus and to decrease beyond it. In the focal zone, the average amplitude increased proportionally to the square root of the scatterer density. The signal to noise ratio (SNR) was found to be independent of depth, i.e., 1.91 as predicted for a Rayleigh distribution of gray levels, although a minimum was found in the focal zone at relatively low scatterer densities. The SNR continuously increased with increasing scatterer density and reached the limit of 1.91 at relatively high densities (greater than 10(4) cm-3). The lateral full width at half maximum (FWHM) of the two dimensional autocovariance function of the speckle increased continuously from the transducer face to far beyond the focus and decreased thereafter due to the diffraction effect. The lateral FWHM decreased proportionally to the logarithm of the scatterer density at low densities and reached a limit at high densities. Introduction of attenuation in the simulated tissue resulted in a much more pronounced depth dependence of the texture. The axial FWHM was independent of the distance to the transducer to a first approximation and decreased slightly with increasing scatterer density until a limit was reached at densities larger than 10(3) cm-3. This limit was in agreement with theory. The experiments confirmed the simulations and it can be concluded that the presented results are of great importance to the understanding of B-mode echograms and to the potential use of the analysis of B-mode texture for tissue characterization.     

Evaluation of the accuracy of articular cartilage thickness measurement by B-mode ultrasonography with conventional imaging and real-time spatial compound ultrasonography imaging

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.