Ultrasonic Imaging Modalities Research Articles

Analysis of Using Multi-Angle Conventional Ultrasound Scanning for Efficient 3-D Object Imaging

The purpose of this work is to examine the possibility of using multi-angle conventional ultrasound B-mode scanning in efficient 3-D imaging. In the paper, the volume of an object is reconstructed from vertical projections registered at fixed angular positions of the multi-element linear ultrasonic probe rotated in relation to the object submerged in water. The possible configurations are: vertical lateral, vertical top or vertical bottom. In the vertical lateral configuration, the ultrasonic probe acquires 2-D images of object’s vertical cross-sections, turning around its lateral surface. In the vertical top or bottom configuration, the ultrasonic probe acquires 2-D images of the object’s vertical cross-sections, turning on the horizontal plane over the top or under the bottom surface of the object. The method of recording 3-D volume of an object’s structure and reconstruction algorithm have been designed. Studies show the method in the vertical top or bottom configuration could be successfully applied to the effective 3-D visualisation of the structure of the female breast in vivo as the new complement ultrasonic imaging modality in the prototype of the developed ultrasound tomography scanner.

Acoustic Attenuation and Dispersion in Fatty Tissues and Tissue Phantoms Influencing Ultrasound Biomedical Imaging.

The development of ultrasonic imaging techniques is optimized using artificial tissue phantoms before the practical applications. However, due to the strong attenuation and dispersion, accumulated fatty tissues can significantly impact the resolution and even feasibility of certain ultrasonic imaging modalities. An appropriate characterization of the acoustic properties on fatty phantoms can help the community to overcome the limitations. Some of the existing methods heavily overestimate attenuation coefficients by including the reflection loss and dispersion effects. Hence, in this study, we use numerical simulation-based comparison between two major attenuation measurement configurations. We further pointed out the pulse dispersion in viscoelastic tissue phantoms by simulations, which barely attracted attention in the existing studies. Using the selected attenuation and dispersion testing methods that were selected from the numerical simulation, we experimentally characterized the acoustic properties of common fatty tissue phantoms and compared the acoustic properties with the natural porcine fatty tissue samples. Furthermore, we selected one of the tissue phantoms to construct ultrasound imaging samples with some biomasses. With the known attenuation and dispersion of the tissue phantom, we showed the clarity enhancement of ultrasound imaging by signal post-processing to weaken the attenuation and dispersion effects.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes.

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: “always‐on” and “turn‐on,” based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

Dilated Semantic Segmentation for Breast Ultrasonic Lesion Detection Using Parallel Feature Fusion.

Breast cancer is becoming more dangerous by the day. The death rate in developing countries is rapidly increasing. As a result, early detection of breast cancer is critical, leading to a lower death rate. Several researchers have worked on breast cancer segmentation and classification using various imaging modalities. The ultrasonic imaging modality is one of the most cost-effective imaging techniques, with a higher sensitivity for diagnosis. The proposed study segments ultrasonic breast lesion images using a Dilated Semantic Segmentation Network (Di-CNN) combined with a morphological erosion operation. For feature extraction, we used the deep neural network DenseNet201 with transfer learning. We propose a 24-layer CNN that uses transfer learning-based feature extraction to further validate and ensure the enriched features with target intensity. To classify the nodules, the feature vectors obtained from DenseNet201 and the 24-layer CNN were fused using parallel fusion. The proposed methods were evaluated using a 10-fold cross-validation on various vector combinations. The accuracy of CNN-activated feature vectors and DenseNet201-activated feature vectors combined with the Support Vector Machine (SVM) classifier was 90.11 percent and 98.45 percent, respectively. With 98.9 percent accuracy, the fused version of the feature vector with SVM outperformed other algorithms. When compared to recent algorithms, the proposed algorithm achieves a better breast cancer diagnosis rate.

Speckle Tracking Accuracy Enhancement by Temporal Super-Resolution of Three-Dimensional Echocardiography Images.

Background:Speckle tracking has always been a challenging issue in echocardiography images due to the lowcontrast and noisy nature of ultrasonic imaging modality. While in ultrasound imaging, framerate is limited by image size and sound speed in tissue, speckle tracking results get worse inthree-dimensional imaging due to its lower frame rate. Therefore, numerous techniques have beenreported to overcome this limitation and enhance tracking accuracy.Methods:In this work, we have proposedto increase the frame rate temporally for a sequence of three-dimensional (3D) echocardiographyframes to make tracking more accurate. To increase the number of frames, cubic B-spline is usedto interpolate between intensity variation time curves extracted from every single voxel in theimage during the cardiac cycle. We have shown that the frame rate increase will result in trackingaccuracy improvement.Results:To prove the efficiency of the proposed method, numerical evaluation metricsfor tracking are reported to make a comparison between high temporal resolution sequences andlow temporal resolution sequences. Anatomical affine optical flow is selected as the state-of-the-artspeckle tracking method, and a 3D echocardiography dataset is used to evaluate the proposedmethod.Conclusion:Results show that it is beneficial for speckle tracking to perform on temporally condensedframes rather than ordinary clinical 3D echocardiography images. Normalized mean enhancementvalues for mean absolute error, Hausdorff distance, and Dice index for all cases and all frames are0.44 ± 0.09, 0.42± 0.09, and 0.36 ± 0.06, respectively.

Dispersion characterization of magnetic actuated needleless injections with particle image velocimetry.

Conventional needle-based approaches in intravitreal drug delivery carry needle-stick-injury risk and could scare patients (belonephobia). Alternatively, our group has explored the application of an electromagnetic needleless injector in this paper. This work aims to improve intravitreal drug delivery, which in the future could assist physicians with automation and benefit patients by providing a needleless approach. Electromagnetic needleless intravitreal injections lack quantification studies. We investigate the delivery properties of the needleless injector where the characterization can be used to refine the design parameters of the prototype in subsequent iterations. Experiments were performed to characterize the injectant delivered from the electromagnetic needleless injector. Penetration tests were conducted to observe the influences of various injection barriers and tissues. Ultrasonic imaging modality was explored for future applications of the prototype. The dispersion of the injectant was controllable where injection depth and distribution is dependent on the input voltage. The synthetic barriers highlighted significant energy losses for penetration (maximum velocity falls from 4.46 to 1.57mm/s with a 0.1-mm barrier). The biological barriers were difficult to penetrate with the current prototype. Our results indicate that the current electromagnetic injector offers controllable dispersion (depth and distribution) correlated with input voltages, which should have increased injection power for use with biological tissue. Ultrasonic imaging modality produced velocity profiles comparable to the optical approach which is promising for future in vivo studies. The influences of injection barriers should be further investigated in in vivo experiments with ultrasonic imaging modalities. Graphical abstract .

Meshfree simulations of ultrasound vector flow imaging using smoothed particle hydrodynamics

Before embarking on a series of in vivo tests, design of ultrasound-flow-imaging modalities are generally more efficient through computational models as multiple configurations can be tested methodically. To that end, simulation models must generate realistic blood flow dynamics and Doppler signals. The current in silico ultrasound simulation techniques suffer mainly from uncertainty in providing accurate trajectories of moving ultrasound scatterers. In mesh-based Eulerian methods, numerical truncation errors from the interpolated velocities, both in the time and space dimensions, can accumulate significantly and make the pathlines unreliable. These errors can distort beam-to-beam inter-correlation present in ultrasound flow imaging. It is thus a technical issue to model a correct motion of the scatterers by considering their interaction with boundaries and neighboring scatterers. We hypothesized that in silico analysis of emerging ultrasonic imaging modalities can be implemented more accurately with meshfree approaches. We developed an original fluid-ultrasound simulation environment based on a meshfree Lagrangian CFD (computational fluid dynamics) formulation, which allows analysis of ultrasound flow imaging. This simulator combines smoothed particle hydrodynamics (SPH) and Fourier-domain linear acoustics (SIMUS = simulator for ultrasound imaging). With such a particle-based computation, the fluid particles also acted as individual ultrasound scatterers, resulting in a direct and physically sound fluid-ultrasonic coupling. We used the in-house algorithms for fluid and ultrasound simulations to simulate high-frame-rate vector flow imaging. The potential of the particle-based method was tested in 2D simulations of vector Doppler for the intracarotid flow. The Doppler-based velocity fields were compared with those issued from SPH. The numerical evaluations showed that the vector flow fields obtained by vector Doppler components were in good agreement with the original SPH velocities, with relative errors less than 10% and 2% in the cross-beam and axial directions, respectively. Our results showed that SPH-SIMUS coupling enables direct and realistic simulations of ultrasound flow imaging. The proposed coupled algorithm has also the advantage to be 3D compatible and parallelizable.

Automatic initialization for active contour model in breast cancer detection utilizing conventional ultrasound and Color Doppler.

Regular examination of breasts may prevent and help to cure because breast cancer is treatable when it is detected early. Therefore, a breast cancer screening modality being sensitivity and cost-effective like ultrasonic imaging modality (US), is strongly required. In addition, the combination of a conventional US and its adjunct, Color Doppler has been proved for decreasing the rate of false-positive in breast cancer diagnosis. Thus, combination of these imaging modalities in a breast cancer segmentation would provide some benefits as well. An effective method for feature segmentation, active contour model has been widely utilized for decades. A crucial stage that affects the performance of active contour model is the initialization. This paper proposes a novel method for an automatic initialization of active contour model designed specifically for US-based imaging modalities. The method estimates an initial contour by utilizing the fusion of conventional US and Color Doppler. Examples and comparisons with three state-of-the-art automatic initialization methods are demonstrated to present the advantages of the proposed method. The evaluation results show high accuracy of initialization as well as fast convergence to features of interest.

Histology-based simulation of ultrasonic scattering in cells and tissues

Previously developed computer programs for simulating ultrasonic scattering in cells and tissues at the microscopic level [T. E. Doyle and K. H. Warnick, J. Acoust. Soc. Am. 120, 3283 (2006)] have been further refined and tested. The programs model the cells and nuclei in tissues as spherical particles with the use of vector multipole expansions and boundary condition solutions for the scattered fields. In addition, theorems, iteration, and matrix methods are used to solve for multiple scattering both inside and outside the cells. The latest refinements include the development of algorithms for simulating ultrasonic scattering from cells with nuclei arbitrarily located within the cell, and not centered as in previous models. Backscatter spectra have also been acquired for simulated cell clusters of up to several thousand cells. The effects of tissue structure, nucleus size, extracellular elastic properties, and intracellular elastic properties were investigated. The models provide a mechanistic link between measurable parameters in medical ultrasound and histological changes associated with various tissue pathologies. The application of these results to the improvement of ultrasonic tissue characterization and the specificity of various ultrasonic imaging modalities are discussed.

Blood Contrast Enhancement with a Novel, Non-Gaseous Nanoparticle Contrast Agent

Modern ultrasound contrast agents primarily comprise microbubble formulations that circulate in the intravascular compartment and are designed to enhance acoustic signals reflected from the blood pool. A variety of shell materials have been utilized to stabilize gas bubbles of the order of 1–10 microns in diameter. Reflectivity from microbubbles is enhanced by resonance and non-linear physical effects. However, the overall efficacy of bubbles as contrast agents must be considered in light of their marked instability to insonification pressures, marked attenuation artifacts, “blooming” effects, and their short circulatory half-life. Low molecular weight gaseous perfluorocarbon formulations have been utilized in vivo because they may offer advantages in formulation and reflectivity. In contrast, higher molecular weight perfluorocarbon emulsions that are liquid at body temperature have been formulated as nongaseous nanoparticle preparations (diameters 100– 300 nanometers), originally for use as blood substitutes. Unfortunately they exhibit low inherent echogenicity and are poor blood pool contrast agents under conditions of conventional 2-D echocardiography or harmonic imaging, or when imaged with color flow or spectral Doppler. Nevertheless, these nanoparticle formulations are chemically inert, manifest long circulatory half-lives, are not destroyed by ultrasonic imaging, and they possess low acoustic attenuation. Such features might still render them of interest as blood pool contrast agents if properly formulated and imaged. Recently, a new ultrasonic imaging modality, Power Doppler Harmonic Imaging (PDHI), has been introduced (4). This technique color-encodes changes in acoustic signal amplitude and motion of ultrasonic scatterers between insonifying pulses. PDHI has been used in a number of clinical studies to assess coronary artery bypass graft patency, tumor blood flow, and myocardial perfusion. In view of the exquisite sensitivity of Doppler for detecting the presence of small scatterers with limited scattering cross-sections as compared to microbubbles (e.g., red blood cells), and the enhanced ability of PDHI to register backscatter power, we hypothesized that certain liquid perfluorocarbon nanoparticle emulsions (5) might be more efficiently detected with this new imaging modality. Furthermore, although we have demonstrated previously that the liquid nanoparticle emulsions do not manifest any appreciable resonance behavior at clinically relevant imaging frequencies, they have performed well as targeted imaging agents in vitro and in vivo over a very broad range of frequencies (5–50 MHz)(6–8). Thus we anticipated that the PDHI method might permit imaging of these nanoparticles in the blood pool without reliance on any intrinsic resonance behavior.

Impact of endovascular treatment on relationships between vascular surgeons and interventional radiologists

Currently available endovascular techniques include PTA and the use of lytic agents, caval filters, and intravascular occluding devices, such as coils. To date, these endovascular treatments can be applied to some, but not all, patients who have a valid rial thromboembolism, iliofemoral venous thrombosis, arteriovenous malformations, and some visceral artery aneurysms. Some of these lesions can now be treated effectively with percutaneous transluminal angioplasty (PTA), catheter-directed lytic drugs and aspiration, intracaval filters, or coil embolization. All these techniques have in common the use of endovascular pathways accessed from remote sites to treat the offending vascular lesion, usually under fluoroscopic guidance. Because these endovascular techniques have proven to be a simpler, safer way to treat some vascular disease patients, they have been embraced and used increasingly by vascular surgeons and others. In some cases, these catheterbased treatments have been used directly by the vascular surgeon; in other circumstances management has been by referral to a collaborating interventional radiologist or other interventional specialist. Because these endovascular techniques are increasingly gaining acceptance and because their less invasive nature renders them attractive to referring physicians and patients alike, it is reasonable to ask how they have affected and will affect the practices of vascular surgery and interventional radiology. The purposes of the present article are to examine some of the effects endovascular technology has already had on vascular disease management, to speculate on its future impact, and to Endovascular treatments are those administered through and within blood vessels. These treatments are catheter guidewire-based and use fluoroscopic or ultrasonic imaging modalities for localization and control within the vascular system. These endovascular treatments include local drug delivery systems and, more importantly, a variety of new technologies that permit mechanical correction of mural and intraluminal pathological lesions within the vascular system. Access to the vascular tree for these endovascular manipulative treatments can be gained via percutaneous puncture utilizing Seldinger wire-cathetersheath technology or, less commonly, by open exposure and arteriotomy or venotomy. Because of innovations in endovascular technology, the treatment of arterial and venous disease has changed over the last 20 years and will change even more dramatically in the years to come. Catheter guidewire-based techniques have already made significant contributions to the manipulative and surgical management of aortoiliac, femoropopliteal, tibial, and renal artery lesions, arteGefasschirurgie (1998) 3:199–204 © Springer-Verlag 1998 EDITORIAL

Sonographic abdominal circumference: Dynamic versus static imaging

The ultrasonic abdominal circumference (AC) measurement is one of the essential parameters used for assessment of fetal status. Whereas the AC was traditionally derived by static equipment, dynamic scanners are presently used for that purpose. In this study, the AC values obtained by two gray-scale ultrasonic imaging modalities (static and dynamic) were compared; the differences between the mean AC measurements were not statistically significant. Additionally, when the outline of the AC in a fetus near term was larger than the sonic field displayed by dynamic equipment, the partially incomplete boundary could be “filled in” without affecting the accuracy of the result.

Ultrasonic Imaging Modalities for Medical Applications

The ability to see with sound has long been an intriguing concept. Certain animals, such as bats and dolphins can do it readily but the human species is not so endowed by nature. However, this lack of natural ability has been overcome by developing an appropriate technology. For example, in various laboratories recently, workers were able to obtain true-focused orthographic images in real time of objects irradiated with sound rather than with light. Cross-sectional images have been available for a much longer period of time stemming from the development of pulse-echo techniques first used in the sonar systems of World War I. By now a wide variety of system concepts for acoustic imaging exist and have been or are being applied for medical diagnosis. The newer systems range from tomographic types using computers to holographic ones using lasers. These are dealt with briefly here.