Ultrasound Imaging Applications Research Articles

Extrusion: A New Method for Rapid Formulation of High-Yield, Monodisperse Nanobubbles.

Shell-stabilized gas microbubbles (MB) and nanobubbles (NB) are frequently used for biomedical ultrasound imaging and therapeutic applications. While it is widely recognized that monodisperse bubbles can be more effective in these applications, the efficient formulation of uniform bubbles at high concentrations is difficult to achieve. Here, it is demonstrated that a standard mini-extruder setup, commonly used to make vesicles or liposomes, can be used to quickly and efficiently generate monodisperse NBs with high yield. In this highly reproducible technique, the NBs obtained have an average diameter of 0.16± 0.05µm and concentration of 6.2± 1.8 × 1010 NBs mL-1 compared to 0.32± 0.1µm and 3.2± 0.7 × 1011 mL-1 for NBs made using mechanical agitation. Parameters affecting the extrusion and NB generation process including the temperature, concentration of the lipid solution, and the number of passages through the extruder are also examined. Moreover, it is demonstrated that extruded NBs show a strong acoustic response in vitro and a strong and persistent US signal enhancement under nonlinear contrast enhanced ultrasound imaging in mice. The extrusion process is a new, efficient, and scalable technique that can be used to easily produce high yield smaller monodispersed nanobubbles.

Deep Learning-Based Classification of Reduced Lung Ultrasound Data From COVID-19 Patients.

The application of lung ultrasound (LUS) imaging for the diagnosis of lung diseases has recently captured significant interest within the research community. With the ongoing COVID-19 pandemic, many efforts have been made to evaluate LUS data. A four-level scoring system has been introduced to semiquantitatively assess the state of the lung, classifying the patients. Various deep learning (DL) algorithms supported with clinical validations have been proposed to automate the stratification process. However, no work has been done to evaluate the impact on the automated decision by varying pixel resolution and bit depth, leading to the reduction in size of overall data. This article evaluates the performance of DL algorithm over LUS data with varying pixel and gray-level resolution. The algorithm is evaluated over a dataset of 448 LUS videos captured from 34 examinations of 20 patients. All videos are resampled by a factor of 2, 3, and 4 of original resolution, and quantized to 128, 64, and 32 levels, followed by score prediction. The results indicate that the automated scoring shows negligible variation in accuracy when it comes to the quantization of intensity levels only. Combined effect of intensity quantization with spatial down-sampling resulted in a prognostic agreement ranging from 73.5% to 82.3%.These results also suggest that such level of prognostic agreement can be achieved over evaluation of data reduced to 32 times of its original size. Thus, laying foundation to efficient processing of data in resource constrained environments.

Nanobubbles are Non-Echogenic for Fundamental-Mode Contrast-Enhanced Ultrasound Imaging.

Microbubbles (1-10 μm diameter) have been used as conventional ultrasound contrast agents (UCAs) for applications in contrast-enhanced ultrasound (CEUS) imaging. Nanobubbles (<1 μm diameter) have recently been proposed as potential extravascular UCAs that can extravasate from the leaky vasculature of tumors or sites of inflammation. However, the echogenicity of nanobubbles for CEUS remains controversial owing to prior studies that have shown very low ultrasound backscatter. We hypothesize that microbubble contamination in nanobubble formulations may explain the discrepancy. To test our hypothesis, we examined the size distributions of lipid-coated nanobubble and microbubble suspensions using multiple sizing techniques, examined their echogenicity in an agar phantom with fundamental-mode CEUS at 7 MHz and 330 kPa peak negative pressure, and interpreted our results with simulations of the modified Rayleigh-Plesset model. We found that nanobubble formulations contained a small contamination of microbubbles. Once the contribution from these microbubbles is removed from the acoustic backscatter, the acoustic contrast of the nanobubbles was shown to be near noise levels. This result indicates that nanobubbles have limited utility as UCAs for CEUS.

Biomimetic lung surfactant nanodrops for ultrasound imaging

Nanodrops comprising a perfluorocarbon liquid core can be acoustically vaporized into echogenic microbubbles for ultrasound imaging. Packaging the microbubble in its condensed liquid state provides some advantages, including in situ activation of the acoustic signal, longer circulation persistence, and the advent of expanded diagnostic and therapeutic applications in pathologies, which exhibit compromised vasculature. One obstacle to clinical translation is the inability of the limited surfactant present on the nanodrop to encapsulate the greatly expanded microbubble interface, resulting in ephemeral microbubbles with limited utility. In this study, we examine a biomimetic approach to stabilizing an expanding gas surface by employing the lung surfactant replacement, Beractant. Lung surfactant contains a suite of lipids and surfactant proteins that provides efficient shuttling of material from bilayer folds to the monolayer surface. We hypothesized that Beractant would improve stability of acoustically vaporized microbubbles. To test this hypothesis, we characterized Beractant surface dilation mechanics and revealed a novel biophysical phenomenon of rapid interfacial melting, spreading, and re-solidification. We then harnessed this unique spreading capability to increase the stability and echogenicity of microbubbles produced after acoustic droplet vaporization for in vivo ultrasound imaging. Such biomimetic lung surfactant-stabilized nanodrops may be useful for applications in ultrasound imaging and therapy.

Scale-Invariant Feature Transform (SIFT) Algorithm-Based Detection of Cardiac Insufficiency in Sepsis Patients with Echocardiography

This research aimed to explore the application of cardiac ultrasound imaging (CUI) in the examination and diagnosis of sepsis patients with cardiac insufficiency under a speckle tracking algorithm (STA). Scale-invariant feature transform (SIFT) algorithm was introduced to process images of CUI through STA under feature points of cardiac ultrasonic images. 90 patients with sepsis who were admitted to the hospital were selected and randomly divided into a sound cardiac function group (n = 62) (group A) and a cardiac insufficient group (n = 28) (group B) under whether they had cardiac insufficiency, and 20 healthy people were selected as a control group. Sepsis patients were examined on the seventh day after diagnosis including laboratory-related indicators, echocardiography, and echocardiographic data. The results showed that there were differences in cardiac ultrasound, cardiac marker, and laboratory examinations of subjects in the three groups ( P &lt; 0.05). Creatine kinase isoenzyme-MB (CK-MB), glycogen phosphorylase isoenzyme BB (GPBB), and heart-type fatty acid-binding protein (H-FABP) of subjects in the three groups showed statistically marked differences ( P &lt; 0.05). The other results indicated tricuspid late diastolic blood flow velocity (A′) value was greater than stroke volume (SV) and isovolumetric relaxation time (IVRT) value, followed by left ventricular ejection fraction (EF) and cardiac output per minute output (CO), and EF and CO values were over peak velocity of right ventricular free wall tricuspid valve systolic movement (SM) and left ventricular fractional shortening (FS) value, and left ventricular end-diastolic volume (EDV) value came next. The analysis of CUI based on STA could help doctors to judge sepsis patients with cardiac function. In addition, sepsis patients with sound cardiac function and sepsis patients with cardiac insufficiency could be distinguished by CUI, which had certain guiding significance for clinical diagnosis.

Three-Dimensional Carpal Arch Morphology Using Robot-Assisted Ultrasonography.

The morphology of the carpal arch implicates the available space for the median nerve within the carpal tunnel. The purposes of this study were to 1) reconstruct the three-dimensional (3D) carpal arch by robot-assisted ultrasonography with a linear array transducer using cadaveric hands, and 2) investigate the 3D morphological properties of the carpal arch. An ultrasound probe with two-dimensional (2D) linear array was integrated on a robotic arm and maneuvered over the cadaveric carpal tunnels to scan the entire transverse carpal ligament and its osseous attachments to carpal bones. The acquired series of 2D ultrasound images together with robot positioning were utilized to reconstruct the 3D carpal arch for morphometric analyses. Total carpal arch volume was 1099.4 ± 163.2 mm3 with the distal, middle, and proximal regions contributing 18.2 ± 1.5%, 32.7 ± 1.2%, and 49.1 ± 2.3%, respectively. The ligament surface area was 420.1 ± 63.9 mm2. The carpal arch width, height, curvature, length, area, and palmar bowing index progressively increased from the distal to proximal locations within the tunnel (p < 0.01). The incorporation of the robot technology with the ultrasound system advanced the applications of traditional 2D ultrasound imaging for a 3D carpal arch reconstruction, allowing for comprehensive morphological assessment of the carpal arch. The developed workflow can be used for the reconstruction and analysis of other anatomical features in vivo.

Development of Cardiac Phased Array With Large-Size PZN-5.5 %PT Single Crystals.

In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn1/3Nb2/3)O3-PbTiO3, also called PZN-PT], has been enhanced with improvements in size, consistency, and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This article mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254-mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about -46 dB, while a crosstalk between the adjacent elements was less than -31 dB. The wire phantom can be distinctly imaged with the phased array, and the axial and lateral resolutions were measured to be 660 and [Formula: see text], respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.

Current Applications of Ultrasound Imaging in the Preoperative Planning of DIEP Flaps.

The deep inferior epigastric artery perforator (DIEP) flap has become the gold standard for autologous breast reconstruction at many institutions. Although the deep inferior epigastric artery displays significant anatomic variability in its intramuscular course, branching pattern and location of perforating vessels, the ability to preoperatively visualize and map relevant vascular anatomy has increased the efficiency, safety and reliability of the DIEP flap. While computed tomography angiography (CTA) is often cited as the preoperative imaging modality of choice for perforator flaps, more recent advances in ultrasound technology have made it an increasingly attractive alternative. An extensive literature review was performed to identify the most common applications of ultrasound technology in the preoperative planning of DIEP flaps. This review demonstrated that multiple potential uses for ultrasound technology in DIEP flap reconstruction including preoperative perforator mapping, evaluation of the superficial inferior epigastric system and as a potential adjunct in flap delay procedures. Available studies suggest that ultrasound compares favorably to other widely-used imaging modalities for these indications. This article presents an in-depth review of the current applications of ultrasound in the preoperative planning of DIEP flaps and explores some potential areas for future investigation.

Applications of Ultrasound in the Postoperative Period: A Review.

Recent advances in ultrasound technology have further increased its potential for routine use by plastic and reconstructive surgeons. An extensive literature review was performed to determine the most common applications of ultrasound in the postoperative care of plastic and reconstructive surgery patients. In contrast with other available imaging modalities, ultrasound is cost-effective, rapid to obtain, eliminates the need for ionizing radiation or intravenous contrast, and has virtually no contraindications. In addition to its diagnostic capabilities, ultrasound can also be used to facilitate treatment of common postoperative concerns conveniently at the bedside or in an office setting. This article presents a review of the current applications of ultrasound imaging in the postoperative care of plastic and reconstructive surgery patients, including free flap monitoring following microsurgery, diagnosis and treatment of hematoma and seroma, including those associated with BIA-ALCL, and breast implant surveillance.

E-Health Ultrasonic Diagnostic Monitoring for Analysis of Cardiac Insufficiency and Neuronal Regulation in Patients with Sepsis in Emergency Department under Image Reconstruction Algorithm.

An anisotropic diffusion filtering- (ADF-) ultrasound (ADF-U) for ultrasound reconstruction was constructed based on the ADF to explore the diagnostic application of ultrasound imaging based on electronic health (E-health) for cardiac insufficiency and neuronal regulation in patients with sepsis. The 144 patients with sepsis were divided into an experimental group (78 patients with cardiac insufficiency) and a control group (66 patients with normal cardiac function), and another 58 healthy people were included in a blank control. The ultrasound examination was performed on all patients. In addition, new ultrasound image reconstruction and diagnosis were performed based on ADF and E-health, and its reconstruction effects were compared with those of the Bilateral Filter-ultrasonic (BFU) algorithm and the Wavelet Threshold-ultrasonic (WTU) algorithm. The left and right ventricular parameters and neuropeptide levels were detected and recorded. The results show that the running time, average gradient (AG), and peak signal-to-noise ratio (SNR) (PSNR) of the ADF-U algorithm were greater than those of the Bilateral Filter-ultrasonic (BFU) and Wavelet Threshold-ultrasonic (WTU), but the mean square error (MSE) was opposite (P < 0.05); the left ventricular end-systolic volume (LVESV) and the vertical distance between the mitral valve E-point to septal separation (EPSS) in the experimental group were higher than those in the control and blank group, while the left ventricular ejection fraction (LVEF), stroke volume (SV), cardiac output (CO), and left ventricular fractional shortening (LVFS) were opposite (P < 0.05); the systolic peak velocity of right ventricular free wall tricuspid annulus (Sm) and pulmonary valve blood velocity (PVBV) in the experimental group were lower than those of the control group and blank group (P < 0.05); the messenger ribonucleic acid (mRNA) of Proopiomelanocortin (POMC) and Cocain and amphetamine-regulated transcript (CART) was higher than the mRNA IN control group and blank group (P < 0.05). In short, the ADF-U algorithm proposed in this study improved the resolution, SNR, and reconstruction efficiency of E-health ultrasound images and provided an effective reference value for the diagnosis of cardiac insufficiency and neuronal adjustment analysis in patients with sepsis in the emergency department.

A Review of Deep Learning Applications in Lung Ultrasound Imaging of COVID-19 Patients

The massive and continuous spread of COVID-19 has motivated researchers around the world to intensely explore, understand, and develop new techniques for diagnosis and treatment. Although lung ultrasound imaging is a less established approach when compared to other medical imaging modalities such as X-ray and CT, multiple studies have demonstrated its promise to diagnose COVID-19 patients. At the same time, many deep learning models have been built to improve the diagnostic efficiency of medical imaging. The integration of these initially parallel efforts has led multiple researchers to report deep learning applications in medical imaging of COVID-19 patients, most of which demonstrate the outstanding potential of deep learning to aid in the diagnosis of COVID-19. This invited review is focused on deep learning applications in lung ultrasound imaging of COVID-19 and provides a comprehensive overview of ultrasound systems utilized for data acquisition, associated datasets, deep learning models, and comparative performance.

Speckle Reduction in Medical Ultrasound Imaging based on Visual Perception Model

Ultrasound imaging technology is one of the most important clinical imaging modalities due to its safety, low cost, in addition to its versatile applications. The main technical problem in this technology is its noisy appearance due to the presence of speckle, which makes reading imaging more difficult. In this study, a new method of speckle reduction in medical ultrasound images is proposed based on adaptive shifting of the contrast sensitivity function of human vision using a bias field map estimated from the original image. The aim of this work is to have an effective image enhancement strategy that reduces speckle while preserving diagnostically useful image features and allowing practical implementation in real-time for medical ultrasound imaging applications. The new method is used to improve the visual perception of image quality of ultrasound images by adding a local brightness bias to the areas with speckle noise. This allows the variations in image pixels due to speckle noise to be better perceived by the human observer because of the visual perception model. The performance of the proposed method is objectively assessed using quantitative image quality metrics and compared to previous methods. Furthermore, given that image quality perception is subjective, the level of added bias is controlled by a single parameter that accommodates the different needs for different users and applications. This method has potential to offer better viewing conditions of ultrasound images, which translates to higher diagnostic accuracy.

Fabrication and Determination of Radiation Sensitive Features of Tissue Equivalent Gels in Radiation Dosimetry and Diagnostic Radiology

Various types of gel dosimeters have been developed so far with the names PVAL gel and MAGIC gel, have been abundantly applied in medical physics. This work is divided into two parts. First, this study aims to analyze an ultrasonic imaging device for accurate patient positioning and organ motion detection during prostate radiotherapy. The images of gel were taken before and after the irradiation, using CT, ultrasound and MRI and dose profiles were plotted. This gel will be used as a prostate phantom for the applications in trans-rectal ultrasound imaging. Secondly, this work aims to develop a realistic artificial breast Using PVAL Gel. The gel was X-rayed on a digital mammography machine which has 3 different programs which will select 3 different beam energies. Results for 2 sample thicknesses were compared against Perspex. PVAL gel was confirmed to be a close match to the Perspex for three beam energies.

Guided Waves in the Skull.

Skull bone is the main obstacle for transcranial ultrasound therapy and imaging applications. Most efforts in characterizing ultrasonic properties of the skull have been limited to a narrow frequency range and normal incidence. On the other hand, acoustic guided waves in plates have been used in non-destructive evaluation of materials and also to assess the strength of long bones. Recent work has likewise revealed the existence of skull-guided waves (SGWs) in mice and humans when performing measurements over a broad range of frequencies and incidence angles. Here we provide an overview on the recent progress in our understanding on the propagation of SGWs, describe the measurement techniques used to detect SGWs, the experimental observations, and the accompanying modeling efforts. Finally, the outstanding challenges to harness SGWs in applications such as transcranial therapy, imaging, and cranial bone assessment are discussed.

Correlation-based ultrasound imaging of strong reflectors with phase coherence filtering

Two main metrics are usually employed to assess the quality of medical ultrasound (US) images, namely the contrast and the spatial resolution. A number of imaging algorithms have been proposed to improve one of those metrics, often at the expense of the other one. This paper presents the application of a correlation-based ultrasound imaging method, called Excitelet, to medical US imaging applications and the inclusion of a new Phase Coherence (PC) metric within its formalism. The main idea behind this algorithm, originally developed and validated for Non-Destructive Testing (NDT) applications, is to correlate a reference signal database with the measured signals acquired from a transducer array. In this paper, it is shown that improved lateral resolutions and a reduction of imaging artifacts are obtained over the Synthetic Aperture Focusing Technique (SAFT) when using Excitelet in conjunction with a PC filter. This novel method shows potential for the imaging of specular reflectors, such as invasive surgical tools. Numerical and experimental results presented in this paper demonstrate the benefit, in terms of contrast and resolution, of using the Excitelet method combined with PC for the imaging of strong reflectors.

PFP@PLGA/Cu12Sb4S13-mediated PTT ablates hepatocellular carcinoma by inhibiting the RAS/MAPK/MT-CO1 signaling pathway

Hepatocellular carcinoma (HCC) is one of the most malignant tumors in the world, and patients with HCC face a poor prognosis. The conventional therapeutic strategies for HCC have undergone a challenge-riddled evolution owing to side effects and unsatisfactory efficacy. Here, aiming to provide a new method of HCC elimination, we formulated a novel multifunctional nanocapsule (PFP@PLGA/Cu12Sb4S13, PPCu) with applications in contrast-enhanced ultrasound imaging (CEUS) and photothermal therapy (PTT). These PPCu were successfully constructed with an average diameter of 346 nm (polydispersity index, PDI = 0.276). The reinforced contrast ratio of these PPCu was determined by CEUS, revealing their promising applications in image-guided monitoring of HCC treatment. Furthermore, the excellent photoabsorption and biocompatibility indicated by organ H&E staining indicated that PPCu meet quality expectations for use as photothermal transduction agent (PTA). PPCu treatment at 50 °C and higher temperatures efficiently repressed the proliferation, induced the apoptosis and decreased the motility of HCC cells. These effects might have been results of RAS/MAPK/MT-CO1 signaling pathway inhibition. In summary, PPCu were constructed to integrate CEUS and PTT successfully into therapy, which can lead to HCC elimination through RAS/MAPK/MT-CO1 signaling pathway repression.

Ultrasound Image Features under Deep Learning in Breast Conservation Surgery for Breast Cancer.

This study was to analyze the effect of the combined application of deep learning technology and ultrasound imaging on the effect of breast-conserving surgery for breast cancer. A deep label distribution learning (LDL) model was designed, and the semiautomatic segmentation algorithm based on the region growing and active contour technology (RA) and the segmentation model based on optimized nearest neighbors (ON) were introduced for comparison. The designed algorithm was applied to the breast-conserving surgery of breast cancer patients. According to the difference in intraoperative guidance methods, 102 female patients with early breast cancer were divided into three groups: 34 cases in W1 group (ultrasound guidance based on deep learning segmentation model), 34 cases in W2 group (ultrasound guidance), and 34 cases in W3 group (palpation guidance). The results revealed that the tumor area segmented by the LDL algorithm constructed in this study was closer to the real tumor area; the segmentation accuracy (AC), Jaccard, and true-positive (TP) values of the LDL algorithm were obviously greater than those of the RA and ON algorithms, while the false-positive (FP) value was significantly lower in contrast to the RA and ON algorithms, showing statistically observable differences (P < 0.05); the actual resection volume of the patients in the W1 group was the closest to the ideal resection volume, which was much smaller in contrast to that of the patients in the W2 and W3 groups, showing statistical differences (P < 0.05); the positive margins of the patients in the W1 group were statistically lower than those in the W2 and W3 groups (P < 0.05). In addition, 1 patient in the W1 group was not satisfied with the cosmetic effect, 3 patients in the W2 group were not satisfied with the cosmetic effect, and 9 patients in the W3 group were not satisfied with the cosmetic effect. Finally, it was found that the ultrasound image based on the deep LDL model effectively improved the AC of tumor resection and negative margins, reduced the probability of normal tissue being removed, and improved the postoperative cosmetic effect of breast.

New application of multimodal ultrasound imaging for identification of myofascial trigger points in the trapezius muscle.

The study aimed to quantify the characteristics of trapezius myofascial trigger points (MTrPs) using shear wave elastography (SWE) and contrast-enhanced ultrasound (CEUS) and explore the application value of the new ultrasound techniques in identifying MTrPs. Forty patients participated in this study. MTrPs in the trapezius muscle were determined by palpation, and SWE and CEUS were used to quantify the focal and adjacent areas. The elastic modulus values and CEUS parameters between the focal area of MTrPs and adjacent areas were evaluated and compared. Pathological biopsy was performed according to the above two methods, and the pathological tissues were observed by Masson staining, immunohistochemistry and electron microscope. The elastic modulus values were significantly higher for the focal area of MTrPs compared to those for adjacent areas (P<0.05). There were statistically significant differences in MTrP parameters, including peak intensity, mean transit time, and area between the focal and adjacent areas (P<0.05). Masson staining showed that there were inflammatory cell infiltration dominated by lymphocytes in the vascular wall. Electron microscopy showed a large number of fibroblast proliferation, lamellar collagen proliferation and lysosomal deposition; immunohistochemical results: the expression of CD3+, CD4+, CD8+, CD68+, mhc-1+, dys+, CD8 was more than that of CD20 (F=4.385, P=0.036). Combined use of SWE and CEUS provides a new detection approach for quantitative identification of MTrPs in the trapezius muscle, which has high application value and is a method worthy of wider use in clinical practice.

The role of the sonographer – An investigation into the scope of practice for the sonographer internationally

IntroductionThere is global variance in the role of a practicing sonographer. Literature examining global sonographic roles and scope of practice is limited, despite the international applicability of ultrasound imaging. This study aimed to examine the common and divergent features of a practicing sonographer internationally, and their impact upon the development of a global standard of practice. MethodsAn ethically approved mixed-methods online survey was conducted. The purposive sample included all 75 current elected council members of the ISRRT [International Society of Radiographers and Radiological Technologists], an international professional organisation. ResultsThirty-six individuals from at least 32 different countries responded, reflecting the sonography profession in all four ISRRT regions. The results suggest that sonographer education requirements differ widely, from on the job training (16%, 6/36) to undergraduate or postgraduate schooling (44%, 16/36). Registration and accreditation bodies were present in the jurisdiction of 41% (14/34) and 35% (12/33) of respondents respectively, though many were voluntary, physician-focused or non-specific to sonographers. Five of 11 (45%) respondents suggested that the sonographer–radiologist relationship is individual-dependent, and not primarily positive or negative. Ten of 28 (36%) suggested that other professionals do not know the role of the sonographer. ConclusionThe majority of ISRRT council member respondents believe that an international scope of practice could benefit and be implemented in their jurisdiction (26/28, 93% and 22/33, 67%). The key advantages noted were standardisation of education and improved professional mobility. However, lack of sonographer education and radiologist acceptance are important potential barriers. Implications for practiceAn international scope of practice could be beneficial and implementable in most ISRRT jurisdictions. Professional mobility and education standardization are the primary advantages. Insufficient sonographer education and physician acceptance are the key potential obstacles.

Dual-Frequency CMUT Arrays for Multiband Ultrasound Imaging Applications.

Dual-frequency capacitive micromachined ultrasonic transducers (CMUTs) are introduced for multiscale imaging applications, where a single array transducer can be used for both deep low-resolution imaging and shallow high-resolution imaging. These transducers consist of low- and high-frequency membranes interlaced within each subarray element. They are fabricated using a modified sacrificial release process. Successful performance is demonstrated using wafer-level vibrometer testing, as well as acoustic testing on wirebonded dies consisting of arrays of 2- and 9-MHz elements of up to 64 elements for each subarray. The arrays are demonstrated to provide multiscale, multiresolution imaging using wire phantoms and can span frequencies from 2 MHz up to as high as 17 MHz. Peak transmit sensitivities of 27 and 7.5 kPa/V are achieved with the low- and high-frequency subarrays, respectively. At 16-mm imaging depth, lateral spatial resolution achieved is 0.84 and 0.33 mm for low- and high-frequency subarrays, respectively. The signal-to-noise ratio of the low-frequency subarray is significantly higher for deep targets compared to the high-frequency subarray. The array achieves multiband imaging capabilities difficult to achieve with current transducer technologies and may have applications to multipurpose probes and novel contrast agent imaging schemes.