Ultrasonic Tissue Characterization Research Articles

Simulation of elastic wave scattering in living tissue at the cellular level

Elastic wave scattering in biological tissue has been simulated at the cellular level by incorporating a first-order approximation of the cell structure and multiple scattering between cells. The cells were modeled with a concentric spherical shell-core structure embedded in a medium, with the core, shell, and medium representing the cell nucleus, the cell cytoplasm, and the extracellular matrix, respectively. Using vector multipole expansions and boundary conditions, scattering solutions were derived for a single cell with either solid or fluid properties for each of the cell components. Multiple scattering between cells was simulated using addition theorems to translate the multipole fields from cell to cell and using an iterative process to refine the scattering solutions. Backscattering simulations of single cells demonstrated that changes in the nuclear diameter had the greatest effect on the frequency spectra as compared to changes in cell size, density, and shear modulus. Wave field images and spectra from clusters of up to several hundred cells were also simulated, and they exhibited phenomena such as wave field enhancement at the cell membrane and nuclear envelope due to the scattering processes. Relevant applications for these models include ultrasonic tissue characterization and ultrasound-mediated gene transfection and drug delivery.

Integrated backscatter for the assessment of myocardial viability

Ultrasonic tissue characterization is a non-invasive diagnostic method that uses myocardial integrated backscatter analysis to determine contractile performance and myocardial viability independent of wall motion. This review discusses recent clinical findings regarding the application of ultrasonic tissue characterization for the assessment of myocardial viability. As this technique is non-invasive, ultrasonic tissue characterization can be used to predict the patency of infarct-related arteries in patients in the early stage of acute myocardial infarction. Several recent studies have shown that this technique is useful in identifying myocardial contractile reserve. The accuracy of ultrasonic tissue characterization for predicting functional recovery after coronary reperfusion is comparable to dobutamine echocardiography and radionuclide methods. Several studies have suggested that the cyclic variation of myocardial integrated backscatter reflects myocardial viability rather than contractile reserve. The cyclic variation of integrated backscatter is associated with myocardial viability confirmed by the integrity of the microvasculature identified by contrast echocardiography. In addition, the cyclic variation of integrated backscatter better reflects myocardial viability confirmed by the integrity of cellar metabolism than contractile reserve. Ultrasonic tissue characterization with integrated backscatter is a useful non-invasive method that can provide unique information for the assessment of myocardial viability.

OP10.05: Ultrasonic fetal and placental tissue characterisation and the role of 3D and Doppler ultrasound in lung maturity

OP10.05: Ultrasonic fetal and placental tissue characterisation and the role of 3D and Doppler ultrasound in lung maturity

Ultrasonic tissue characterization of vulnerable carotid plaque: correlation between videodensitometric method and histological examination

BackgroundTo establish the correlation between quantitative analysis based on B-mode ultrasound images of vulnerable carotid plaque and histological examination of the surgically removed plaque, on the basis of a videodensitometric digital texture characterization.MethodsTwenty-five patients (18 males, mean age 67 ± 6.9 years) admitted for carotid endarterectomy for extracranial high-grade internal carotid artery stenosis (≥ 70% luminal narrowing) underwent to quantitative ultrasonic tissue characterization of carotid plaque before surgery. A computer software (Carotid Plaque Analysis Software) was developed to perform the videodensitometric analysis. The patients were divided into 2 groups according to symptomatology (group I, 15 symptomatic patients; and group II, 10 patients asymptomatic). Tissue specimens were analysed for lipid, fibromuscular tissue and calcium.ResultsThe first order statistic parameter mean gray level was able to distinguish the groups I and II (p = 0.04). The second order parameter energy also was able to distinguish the groups (p = 0,02). A histological correlation showed a tendency of mean gray level to have progressively greater values from specimens with < 50% to >75% of fibrosis.ConclusionVideodensitometric computer analysis of scan images may be used to identify vulnerable and potentially unstable lipid-rich carotid plaques, which are less echogenic in density than stable or asymptomatic, more densely fibrotic plaques.

Experimental Study of Acute Organophosphorus Compound Poisoning in Rabbit Kidneys by Ultrasonic Tissue Characterization

The purpose of this study was to investigate the value of integrated backscatter (IBS) of kidneys in acute organophosphorus compound poisoning in rabbits. Eighteen rabbits were poisoned by dimethyl dichlorovinyl phosphate to establish animal models. Sonographic examinations were performed before (T0) and after (T1-T9) the rabbits were poisoned. The echo and size of kidneys were evaluated by 2-dimensional gray scale sonography. Changes of the renal cortex and medulla were analyzed quantitatively with IBS. No change of the cortex echo was found before and after poisoning. A significant change of the volume of kidneys on both sides began at T6 compared with that at T0 (P < .05). A significant change of renal length on both sides began at T7 compared with that at T0 (P < .05). The volume change was earlier than that of length. A significant change in IBS% of the renal cortex began at T5 compared with that at T0 (P < .05), whereas a significant change in IBS% of the renal medulla began at T6 compared with that at T(0) (P < .05). The change in IBS% of the renal cortex was earlier. More useful information provided by IBS% has been found in acute organophosphorus compound poisoning in rabbits.

Computer simulation model on ultrasonic myocardial backscatter

Myocardial ultrasonic tissue characterization with integrated backscatter (IB) has been studied in recent years. To evaluate the dynamic characters of the myocardium, dynamic tracing of each unit volume of myocardium is a key point. Thus, a 2D CVIB imaging algorithm based on an auto-tracing method was developed in our previous work. Where, an auto-tracking method was used in CVIB-weighted images so that the POI in each frame throughout the cardiac cycle is automatically traced to reflect the real myocardial tissue movement. It is necessary to validate the auto-tracing method. However, at present there are no appropriate models to support the process. In order to validate the auto-tracing method, two myocardium models have been established to simulate the short and long axis view of echocardiography. The motions of partially ischemic myocardium have been simulated. The models have been used to validate the 2D CVIB imaging methods in the detection of myocardial ischemia. The simulation results show that the auto-tracing algorithm is effective. The model developed in this work provides a tool for studying and developing technologies in myocardial behavior.

Correlation of Endoscopic Ultrasound and Texture Analysis of Endoscopic Images in Esophageal Cancer Staging

Introduction: EUS has been shown to be the most accurate technique to determine tumor depth of infiltration. However, understaging and overstaging can occur in EUS staging. Texture analysis has been applied in ultrasonic tissue characterization of liver. We tried to evaluate the feasibility of using texture analysis of endoscopic imaging in aiding cancer staging in addition to EUS.

1257: Impaired intrinsic contractility detected by echocardiographic techniques

Speckle images are emerging new techniques for detecting and measuring cardiac mechanical dysfunction. In the past decade, the most commonly used methods to study the interaction between the ultrasound beam and the tissue speckles were the Doppler shift or power reflected from the tissue or blood cells and the radiofrequency ultrasound signal backscattered from the tissue. Ultrasonic tissue characterization (UTC) with cardiac cycle-dependent variation of integrated backscatters (IBS) has been shown as the intrinsic myocardial contractility and a potential indicator for early systolic dysfunction. Normal myocardium exhibits a cycle-dependent variation of IBS that will be blunted in the amplitude and have a temporal shift in the nadir by experimental ischemia. Reperfusing the acutely infarcted myocardium will restore the cyclic variation before the wall motion recovery, suggesting the detection of stunned myocardium. In hibernating myocardium, recent investigations have shown that the intramural contractility is relatively independent of resting wall motion and parallels contractile reserve. Using this technique, it has been demonstrated that diastolic abnormalities of left ventricular (LV) function, in arterial hypertension, are related and progress with systolic intrinsic dysfunction. Doppler tissue imaging (DTI) is another new objective method that accurately quantifies myocardial tissue velocities, deformation, time intervals and LV filling pressure. It has also been widely used for evaluating intrinsic contractility during myocardial ischemia, the reverse remodeling and improved synchronicity by simultaneously delaying regional contraction after biventricular pacing therapy in heart failure, and the assessment of LV function in different stages of chronic renal disease. In conclusion, speckle image represents a relatively new diagnostic tool, which allows integration of the conventional echocardiographic evaluation, in order to obtain specific textural parameters that reflect the myocardial ultrastructural texture and intrinsic contractility.

Measurements of the anisotropy of ultrasonic attenuation in freshly excised myocardium

Echocardiography requires imaging of the heart with sound propagating at varying angles relative to the predominant direction of the myofibers. The degree of anisotropy of attenuation can significantly influence ultrasonic imaging and tissue characterization measurements in vivo. This study quantifies the anisotropy of attenuation of freshly excised myocardium at frequencies typical of echocardiographic imaging. Results show a significantly larger anisotropy than previously reported in specimens of locally unidirectional myofibers. Through-transmission radio frequency-based measurements were performed on specimens from 12 ovine and 12 bovine hearts. Although ovine hearts are closer in size to human, the larger size of bovine hearts offers the potential for specimens in which myofibers are more nearly unidirectionally aligned. The attenuation coefficient increased approximately linearly with frequency. The mean slope of attenuation with frequency was 3-4 times larger for propagation parallel than for perpendicular to the myofibers. At perpendicular insonification, slopes between ovine and bovine myocardium were approximately equal. However, attenuation in bovine specimens was larger for angles approaching parallel. The difference in results for parallel appears consistent with what might be expected from increased myofiber curvature associated with smaller lamb hearts. Quantitative knowledge of anisotropy of attenuation may be useful in understanding mechanisms underlying the interaction of ultrasound with myocardium.

Inverse scattering bioacoustics: Under the influence of Fred Lizzi

A long‐standing problem in bioacoustics is the assessment of soft tissue health from an analysis of backscattered echo signals—an inverse problem known as tissue characterization. Pathologists view magnified images of tissue morphology to assess tissue function and grade disease states. Ultrasonic tissue characterization methods are attempts to accomplish the same assessment noninvasively. The goal is not to image the microstructure directly, but rather to diagnose tissues from measurements of statistical moments of the echo spectrum properly normalized to isolate tissue features. Fred Lizzi pioneered this approach and provided an analytical framework used widely. It will be shown how his analysis evolved from classic studies in atmospheric physics to give a clear picture of what is becoming a material science approach to diagnosis using ultrasonics. Dr. Lizzi’s methods have been used by many to diagnosis and monitor treatment of cancer from a very small feature space. Others have expanded these methods t...

Ultrasonic backscattering in tissue: characterization through Nakagami-generalized inverse Gaussian distribution

Ultrasonic tissue characterization through composite probability distributions such as Nakagami-lognormal, Nakagami-gamma, Nakagami-inverse Gaussian has been found to be useful. Such a probabilistic description also depicts heavy tails which arise from multiple scattering in tissue besides local and global variations in scattering cross-sections. A new composite probability distribution, viz. Nakagami-generalized inverse Gaussian distribution (NGIGD) with four parameters is proposed which under different limiting conditions results in approximating the known distributions. A salient aspect of the new distribution is that the probability density function (pdf) of NGIGD variate is available in closed form and is analytically tractable.

Program and Abstracts: 31st International Symposium on Ultrasonic Imaging and Tissue Characterization

Program and Abstracts: 31st International Symposium on Ultrasonic Imaging and Tissue Characterization

862 Ultrasonic tissue characterization and myocardial performance in patients with acromegaly

862 Ultrasonic tissue characterization and myocardial performance in patients with acromegaly

865 Early myocardial alterations in subclinical hypothyroidism (SH): an ultrasonic tissue characterization backscatter analysis

865 Early myocardial alterations in subclinical hypothyroidism (SH): an ultrasonic tissue characterization backscatter analysis

Fetal lung development in pregnancies of diabetic women assessed by quantitative ultrasonic tissue characterization

This study was performed to compare quantitative ultrasonic tissue characterization of the fetal lung at different gestational ages in uncontrolled diabetic patients with that in normal uncomplicated pregnancies. A total of 44 women at 24-37 weeks' gestation with the diagnosis of diabetes in pregnancy were enrolled. Data were compared to those of the control group, which consisted of 140 women with uncomplicated pregnancies of the same gestational age. Longitudinal and transverse sections of the fetal thorax and upper abdomen were examined. A region of interest of constant size was defined and the tissue-specific gray scale was determined by using interactive software. Compared with normal pregnancies, fetal lungs of diabetic pregnancies have a higher echogenicity between 28 and 37 weeks of gestation. The lung mean gray values (MGV) only differed significantly between 30 and 31 weeks of gestation in the group with diabetes (P = 0.033) compared to the control group. The MGV of the liver in diabetic and normal pregnancies is similar during pregnancy, significant differences being found only at 30-31 weeks of gestation (P = 0.038). The lung-to-liver ratio in the control group showed a significant increase from 24 to 31 weeks and a slight non-significant decrease after 31 weeks. The ratio in the group with diabetes increased slightly up to week 33 and decreased slightly afterwards. Fetal lung MGV in uncontrolled diabetic pregnancies compared to that in uncomplicated pregnancies differs significantly only between 30 and 31 weeks of gestation.

Signal processing to enhance ultrasonic tissue characterization in diagnostic medical imaging

The goal of this presentation is to lay the background for identifying potential new contributions to medical diagnosis with ultrasonic imaging that might be provided by advanced signal-processing techniques. The focus of this talk is on ultrasonic tissue characterization, an approach that complements and extends presently available high-resolution imaging. Regional estimates of intrinsic material properties of normal and pathologically altered tissue are obtained from local measurements of attenuation and backscatter derived from the same signals that are used to form the ultrasonic images. Examples are drawn primarily from echocardiography, in part because imaging and characterizing the beating heart present significant challenges. Current echocardiographic images, frequently acquired with harmonic mode (nonlinear) imaging, exhibit substantial resolution of anatomical detail. Nevertheless, the estimates provided by tissue characterization of alterations in tissue properties arising from specific pathologies offer the promise of elevating echocardiographic imaging to a new plane. Among the challenges to be met in order to accomplish this goal are properly accounting for the intrinsic anisotropy of the heart and overcoming limitations that arise as a result of phase and amplitude aberrations associated with propagation through an intrinsically inhomogeneous medium. [Work supported by NIH R37HL40302 and R01 HL72761.]

A Tutorial on the Use of ROC Analysis for Computer-Aided Diagnostic Systems

The application of the receiver operating characteristic (ROC) curve for computer-aided diagnostic systems is reviewed. A statistical framework is presented and different methods of evaluating the classification performance of computer-aided diagnostic systems, and, in particular, systems for ultrasonic tissue characterization, are derived. Most classifiers that are used today are dependent on a separation threshold, which can be chosen freely in many cases. The separation threshold separates the range of output values of the classification system into different target groups, thus conducting the actual classification process. In the first part of this paper, threshold specific performance measures, e.g., sensitivity and specificity, are presented. In the second part, a threshold-independent performance measure, the area under the ROC curve, is reviewed. Only the use of separation threshold-independent performance measures provides classification results that are overall representative for computer-aided diagnostic systems. The following text was motivated by the lack of a complete and definite discussion of the underlying subject in available textbooks, references and publications. Most manuscripts published so far address the theme of performance evaluation using ROC analysis in a manner too general to be practical for everyday use in the development of computer-aided diagnostic systems. Nowadays, the user of computer-aided diagnostic systems typically handles huge amounts of numerical data, not always distributed normally. Many assumptions made in more or less theoretical works on ROC analysis are no longer valid for real-life data. The paper aims at closing the gap between theoretical works and real-life data. The review provides the interested scientist with information needed to conduct ROC analysis and to integrate algorithms performing ROC analysis into classification systems while understanding the basic principles of classification.

The effect of logarithmic compression on estimation of the Nakagami parameter for ultrasonic tissue characterization: a simulation study

Previous studies have demonstrated that the Nakagami parameter estimated using the envelopes of backscattered ultrasound is useful in detecting variations in the concentration of scatterers in tissues. The signal processing in those studies was linear, whereas nonlinear logarithmic compression is routinely employed in existing ultrasonic scanners. We therefore explored the effect of the logarithmic compression on the estimation of the Nakagami parameter in this study. Computer simulations were used to produce backscattered signals of various scatterer concentrations for the estimation of the Nakagami parameters before and after applying the logarithmic compression on the backscattered envelopes. The simulated results showed that the logarithmic compression would move the statistics of the backscattered envelopes towards post-Rayleigh distributions for most scatterer concentrations. Moreover, the Nakagami parameter calculated using compressed backscattered envelopes is more sensitive than that calculated using uncompressed envelopes in differentiating variations in the scatterer concentration, making the former better at quantifying the scatterer concentration in biological tissues.

Ultrasonic Tissue Characterization Predicts Left Ventricular Remodeling in Patients with Acute Anterior Myocardial Infarction after Primary Coronary Angioplasty

The aim of this study was to assess the role of cyclic variation (CV) of myocardial integrated backscatter (IBS) in the prediction of left ventricular (LV) remodeling in patients with anterior acute myocardial infarction (AMI) after primary coronary angioplasty. Some studies have shown that the CV of myocardial IBS predicts myocardial viability for patients with AMI. We recorded short-axis IBS images within 24 hours of angioplasty in 80 patients with anterior AMI. Two parameters were measured: the magnitude of CV and the normalized time delay (NTD). The increase in LV end-diastolic volume (LVEDV) at 4 weeks (DeltaLVEDV) was defined as LV remodeling (>20% increase from baseline). Patients were divided into two groups according to LV remodeling status: the remodeling group (n = 41) and the nonremodeling group (n = 39). There was a significant difference in the magnitude of CV between the two groups (5.11 +/- 1.47 vs 5.96 +/- 189 dB, P < .05), and the NTD was significantly different in the two groups (1.57 +/- 0.31 vs 1.23 +/- 0.32, P < .0001). The correlation between the magnitude of CV and DeltaLVEDV was significant but weak (r = -0.338, P < .01). There was significant correlation between NTD and DeltaLVEDV (r = 0.443, P < .0001). Using NTD greater than 1.35 as the optimal cutoff, the sensitivity, specificity, and positive and negative predictive values to predict LV remodeling were 82%, 86%, 87%, and 80%, respectively. Myocardial IBS, especially NTD, is useful for predicting LV remodeling in patients with AMI after primary coronary angioplasty.

Serum markers of angiogenesis and myocardial ultrasonic tissue characterization in patients with dilated cardiomyopathy

It has been proven that a disturbance in angiogenesis contributes to the progression of myocardial interstitial fibrosis in idiopathic dilated cardiomyopathy (DCM). This study was designed to evaluate the relationship between serum activity of angiogenic factors and myocardial ultrasonic tissue characterization in patients with DCM. We studied 30 patients with DCM and 15 healthy control subjects. Serum levels of vascular endothelial growth factor (VEGF), interleukin (IL)-4 and IL-13 were measured using enzyme-linked immunosorbent assay. We determined calibrated myocardial integrated backscatter (IB) as the value of myocardial interstitial fibrosis using ultrasonic tissue characterization and also quantified the magnitude of cyclic variations in IB (CV-IB). Serum levels of VEGF and IL-13 were significantly higher in patients with DCM than in control subjects (both P<0.05). Calibrated IB was significantly higher and CV-IB was markedly lower in patients with DCM than in control subjects (both P<0.01). In patients with DCM, the levels of IL-13 significantly correlated with calibrated IB (r=0.520, P=0.018). In addition, there was a significant negative correlation between levels of VEGF and CV-IB (r=-0.611, P=0.007). The increase in serum VEGF and IL-13 may be closely related to alterations in myocardial texture in DCM.