Resolution Ultrasound Imaging Research Articles

A Comparative Evaluation of Rotator Cuff Injuries of the Shoulder Joint using High Resolution Ultrasound and Magnetic Resonance Imaging

Introduction: Pathology of the rotator cuff is the cause of most common problems at the shoulder joint and accurate diagnosis is essential for appropriate management. High-resolution real-time ultrasonography and MRI are successful imaging modalities for both rotator cuff and non–rotator cuff disorders and have important implications in the management of rotator cuff pathologies. This study was conducted to Compare the results obtained after the evaluation of rotator cuff injuries of shoulder joint by high resolution Ultrasonography and Magnetic Resonance Imaging. Methods: 50 patients with suspected rotator cuff injuries of the shoulder joint were included in this study over a period of 2years. Patients had presented with various complaints like prolonged pain in the shoulder joint with stiffness, restriction and difficulty in movement of the shoulder joint, traumatic injuries and recurrent dislocations of the shoulder joints. Results: Mean age was 41.6years ( range 15-80 ).Maximum patients were between 41-50 years (24%). 29 were males and 21 were females. In our study diagnostic accuracy of ultrasound in rotator cuff tears was 57. 14% for full thickness tears and 58.33 for partial thickness tears. The diagnostic accuracy of ultrasound in detection of complete tear of the supraspinatus muscle was 57.14% while that of MRI was 100%. Conclusion: High resolution Ultrasound being a dynamic study can be used as the first-line investigation for rotator cuff tear. Full-thickness rotator cuff tears can be identified using ultrasound and MRI with comparable accuracy. DOI: http://dx.doi.org/10.3126/mjsbh.v10i1.6443 Medical Journal of Shree Birendra Hospital Jan-June 2011 10(1) 9-14

A measurement-domain adaptive beamforming approach for ultrasound instrument based on distributed compressed sensing: Initial development

High efficient acquisition of the sensor array signals and accurate reconstruction of the backscattering medium are important issues in ultrasound imaging instrument. This paper presents a novel measurement-domain adaptive beamforming approach (MABF) based on distributed compressed sensing (DCS) which seeks to simultaneously measure signals that are each individually sparse in some domain(s) and also mutually correlated with much few measurements under the Nyquist rate. Instead of sampling conventional backscattering signals at the Nyquist rate, few linear projections of the returned signal with random vectors are taken as measurements, which can reduce the amount of samples per channel greatly and makes the real-time transmission of sensor array data possible. Then high resolution ultrasound image is reconstructed from the few measurements of DCS directly by the proposed MABF algorithm without recovering the raw sensor signals with complex convex optimization algorithm. The simulated results show the effectiveness of the proposed method.

레이저 유도방식의 실시간 광음향 단층영상 기술 개발과 팬텀이미지 평가

Photoacoustic Tomography (PAT) is a promising medical imaging modality by reason of its particularity. It combines optical imaging contrast of optical imaging with the spatial resolution of ultrasound imaging and can demonstrate change of biological feature in an image. For that reason, many studies are in progress to apply this technic for diagnosis. But, real-time PAT system is necessary to confirm a biological reaction induced by external stimulation immediately. Thus, we developed a real-time PAT system using linear array transducer and self-developed Data acquisition board (DAQ) resources, To evaluate the feasibility and performance of our proposed system, two type of phantom test were also performed. As a result of those experiments, the proposed system shows enough performance and confirm its usefulness.

Orthogonal quadratic chirp signals for simultaneous multi-zone focusing in medical ultrasound imaging

In medical ultrasound imaging, multi-zone focusing on transmission is used to enhance the lateral resolution at the expense of frame rate. As an alternative, this paper proposes a simultaneous multi-zone focusing method using orthogonal quadratic chirp signals to improve lateral resolution without sacrificing frame rate. In the proposed method, two weighted quadratic chirp signals with different spectra are simultaneously transmitted with different transmit time delays for multi-zone focusing. Because the two weighted quadratic chirps can be designed to have a desired level of cross-correlation after compression, the degradation of axial resolution resulting from the division of a spectrum is minimized. Through simulation, the performances of the proposed method were evaluated and compared with those of two-cycle pulsed excitation as a gold standard and two sub-band weighted linear chirps. In the simulation, the proposed method improved -6-dB and -20-dB lateral beam widths by factors of 1.67 and 1.84, respectively, compared with the pulsed excitation. The degradation of axial resolution in the proposed method was maximally 43% less than that in the linear chirp case. The results demonstrate that the proposed method is useful in the improvement of overall ultrasound image quality because the axial resolution of conventional ultrasound images is generally a few times higher than the lateral resolution.

Despeckling low SNR, low contrast ultrasound images via anisotropic level set diffusion

Speckle is a form of multiplicative and locally correlated noise which degrades the signal-to-noise ratio (SNR) and contrast resolution of ultrasound images. This paper presents a new anisotropic level set method for despeckling low SNR, low contrast ultrasound images. The coefficient of variation, a speckle-robust edge detector is embedded in the well known geodesic "snakes" model to smooth the image level sets, while preserving and sharpening edges of a speckled image. The method achieves much better speckle suppression and edge preservation compared to the traditional anisotropic diffusion based despeckling filters. In addition, the performance of the filter is less sensitive to the speckle scale of the image and edge contrast parameter, which makes it more suitable for the detection of low contrast features in an ultrasound image. We validate the method using both synthetic and real ultrasound images and quantify the performance improvement over other state-of-the-art algorithms in terms of speckle noise reduction and edge preservation indices.

Coded Transmission in Synthetic Transmit Aperture Ultrasound Imaging Method

The paper presents the study of synthetic transmit aperture method applying the Golay coded transmission for medical ultrasound imaging. Longer coded excitation allows to increase the total energy of the transmitted signal without incr easing the peak pressure. Signal-to-noise ratio and penetration dep th are improved maintaining high ultrasound image resolution. In the work the 128-element linear transducer array with 0.3 mm inter-element spacing excited by one cycle and the 8 and 16-bit Golay coded sequences at nominal frequencies 4 MHz was used. Single element transmission aperture was used to ge nerate a spherical wave covering the full image region and all the ele ments received the echo signals. The comparison of 2D ultrasound images of the wire phantom as well as of the tissue mimicking phantom is presented to demonstrate the benefits of the coded transmission. The results were obtained using the synthetic aperture algorithm w ith transmit and receive signals correction based on a single elemen t directivity function.

High Resolution Ultrasound Imaging Using Frequency Domain Interferometry

High Resolution Ultrasound Imaging Using Frequency Domain Interferometry

METHOD FOR PRODUCING HIGHLY CONSTRAINED ULTRASOUND IMAGES

A highly constrained image processing method is used to improve the quality, including spatial resolution and signal-to-noise ratio (SNR), of ultrasound image frames. Ultrasound image frames are accumulated to form a composite image that contains a priori information about the subject being imaged. This composite image is used in a HYPR processing method to improve the quality of the ultrasound image frame. For example, the SNR of the composite image is increased as a function of the number of ultrasound image frames used to produce it, and this increased SNR is passed on to each highly constrained image frame. Additionally, high spatial resolution ultrasound images are produced using an undersampled sampling density, and the quality of these images is restored to substantially the same level as a fully sampled image.

Non-invasive automated 3D thyroid lesion classification in ultrasound: A class of ThyroScan™ systems

Ultrasound-based thyroid nodule characterization into benign and malignant types is limited by subjective interpretations. This paper presents a Computer Aided Diagnostic (CAD) technique that would present more objective and accurate classification and further would offer the physician a valuable second opinion. In this paradigm, we first extracted the features that quantify the local changes in the texture characteristics of the ultrasound off-line training images from both benign and malignant nodules. These features include: Fractal Dimension (FD), Local Binary Pattern (LBP), Fourier Spectrum Descriptor (FS), and Laws Texture Energy (LTE). The resulting feature vectors were used to build seven different classifiers: Support Vector Machine (SVM), Decision Tree (DT), Sugeno Fuzzy, Gaussian Mixture Model (GMM), K-Nearest Neighbor (KNN), Radial Basis Probabilistic Neural Network (RBPNN), and Naive Bayes Classifier (NBC). Subsequently, the feature vector-classifier combination that results in the maximum classification accuracy was used to predict the class of a new on-line test thyroid ultrasound image. Two data sets with 3D Contrast-Enhanced Ultrasound (CEUS) and 3D High Resolution Ultrasound (HRUS) images of 20 nodules (10 benign and 10 malignant) were used. Fine needle aspiration biopsy and histology results were used to confirm malignancy. Our results show that a combination of texture features coupled with SVM or Fuzzy classifiers resulted in 100% accuracy for the HRUS dataset, while GMM classifier resulted in 98.1% accuracy for the CEUS dataset. Finally, for each dataset, we have proposed a novel integrated index called Thyroid Malignancy Index (TMI) using the combination of FD, LBP, LTE texture features, to diagnose benign or malignant nodules. This index can help clinicians to make a more objective differentiation of benign/malignant thyroid lesions. We have compared and benchmarked the system with existing methods.

ThyroScreen system: High resolution ultrasound thyroid image characterization into benign and malignant classes using novel combination of texture and discrete wavelet transform

Using right equipment and well trained personnel, ultrasound of the neck can detect a large number of non-palpable thyroid nodules. However, this technique often suffers from subjective interpretations and poor accuracy in the differential diagnosis of malignant and benign thyroid lesions. Therefore, we developed an automated identification system based on knowledge representation techniques for characterizing the intra-nodular vascularization of thyroid lesions. Twenty nodules (10 benign and 10 malignant), taken from 3-D high resolution ultrasound (HRUS) images were used for this work. Malignancy was confirmed using fine needle aspiration biopsy and subsequent histological studies. A combination of discrete wavelet transformation (DWT) and texture algorithms were used to extract relevant features from the thyroid images. These features were fed to different configurations of AdaBoost classifier. The performance of these configurations was compared using receiver operating characteristic (ROC) curves. Our results show that the combination of texture features and DWT features presented an accuracy value higher than that reported in the literature. Among the different classifier setups, the perceptron based AdaBoost yielded very good result and the area under the ROC curve was 1 and classification accuracy, sensitivity and specificity were 100%. Finally, we have composed an Integrated Index called thyroid malignancy index (TMI) made up of these DWT and texture features, to facilitate distinguishing and diagnosing benign or malignant nodules using just one index or number. This index would help the clinicians in more quantitative assessment of the thyroid nodules.

High resolution real-time medical imaging based on parallel beamforming technique

Improvement of frame-rate is very important for high quality ultrasound imaging of fast-moving structures. It is also one of the key technologies of Three-Dimension (3-D) real-time medical imaging. In this paper, we have demonstrated a beamforming method which gives imaging frame-rate increment without sacrificing the quality of medical images. By using wider and fewer transmit beams in combination with four narrower parallel receive beams, potentially increasing the imaging frame-rate by a factor four. Through employing full transmit aperture, controlling the mainlobe width, and suppressing sidelobes of angular responses, the inherent gain loss of normal parallel beamfomer can be compensated in the maximal degree. The noise and interference signals also can be suppressed effectively. Finally, we show comparable lateral resolution and contrast of ultrasound images to normal single widow weighting beamformer on simulated phantoms of point targets, cyst and fetus of 12th week. As the computational cost is linear with the number of array elements and the same with Delay And Sum (DAS) beamformers, this method has great advantages of possibility for high frame-rate real-time applications.

Automated regional analysis of B-mode ultrasound images of skeletal muscle movement

To understand the functional significance of skeletal muscle anatomy, a method of quantifying local shape changes in different tissue structures during dynamic tasks is required. Taking advantage of the good spatial and temporal resolution of B-mode ultrasound imaging, we describe a method of automatically segmenting images into fascicle and aponeurosis regions and tracking movement of features, independently, in localized portions of each tissue. Ultrasound images (25 Hz) of the medial gastrocnemius muscle were collected from eight participants during ankle joint rotation (2° and 20°), isometric contractions (1, 5, and 50 Nm), and deep knee bends. A Kanade-Lucas-Tomasi feature tracker was used to identify and track any distinctive and persistent features within the image sequences. A velocity field representation of local movement was then found and subdivided between fascicle and aponeurosis regions using segmentations from a multiresolution active shape model (ASM). Movement in each region was quantified by interpolating the effect of the fields on a set of probes. ASM segmentation results were compared with hand-labeled data, while aponeurosis and fascicle movement were compared with results from a previously documented cross-correlation approach. ASM provided good image segmentations (<1 mm average error), with fully automatic initialization possible in sequences from seven participants. Feature tracking provided similar length change results to the cross-correlation approach for small movements, while outperforming it in larger movements. The proposed method provides the potential to distinguish between active and passive changes in muscle shape and model strain distributions during different movements/conditions and quantify nonhomogeneous strain along aponeuroses.

Dynamic testing of regional viscoelastic behavior of canine sclera

Intraocular pressure (IOP) fluctuations have gained recent clinical interest and thus warrant an understanding of how the sclera responds to dynamic mechanical insults. The objective of this study was to characterize the regional dynamic viscoelastic properties of canine sclera under physiological cyclic loadings. Scleral strips were excised from the anterior, equatorial, and posterior sclera in ten canine eyes. The dimensions of each strip were measured using a high resolution ultrasound imaging system. The strips were tested in a humidity chamber at approximately 37 °C using a Rheometrics Systems Analyzer. A cyclic strain input (0.25%, 1 Hz) was applied to the strips, superimposed upon pre-stresses corresponding to an IOP of 15, 25, and 45 mmHg. The cyclic stress output was recorded and the dynamic properties were calculated based on linear viscoelasticity. Uni-axial tensile tests were also performed on the same samples and the results were compared to those reported for human eyes. The results showed that the sclera’s resistance to dynamic loading increased significantly while the damping capability decreased significantly with increasing pre-stresses for all regions of sclera (P < 0.001). Anterior sclera appeared to have a significantly higher damping capability than equatorial and posterior sclera (P = 0.003 and 0.018, respectively). The secant modulus from uni-axial tensile tests showed a decreasing trend from anterior to posterior sclera, displaying a similar pattern as in the human eye. In conclusion, all scleral regions in the canine eyes exhibited an increased ability to resist and a decreased ability to dampen cyclic stress insults at increasing pre-stress (i.e., increasing steady-state IOP). The regional variation of the dynamic properties differed from those of uni-axial tensile tests. Dynamic testing may provide useful information to better understand the mechanical behavior of the sclera in response to dynamic IOP.

Resolution in ultrasound imaging

Ultrasound scanning is now utilized in all aspects of anaesthesia, critical care, and pain management. Typical applications include determination of left ventricular function and cardiac output, assessment of haemodynamic instability, assistance with difficult venous access, and facilitation of accurate neural block. – 3 One aspect of competency in ultrasound imaging includes an understanding of how images can be displayed optimally. This article discusses three main aspects of the physics of diagnostic ultrasound, that is to say, spatial resolution, temporal resolution, and contrast resolution; it utilizes examples from perioperative echocardiography to illustrate these principles.

A rare case of hepatic cysticercosis

Human cysticercosis is an infection with the larval stage of Taenia solium and is commonly seen in developing countries. It usually involves the central nervous system but other organs like the heart, skeletal muscle and the orbit can also be involved. Rarely, the liver can also be the site of involvement. We report a case of a 25-year-old male with no premorbid illness but with a history of headache and vomiting. His physical and laboratory examinations suggested a diagnosis of tubercular meningitis. However, the high resolution ultrasound imaging of his abdomen showed that there were multiple cysticerci with scolices. IgG of cysticercosis detected by ELISA was also strongly positive, which supported the diagnosis of hepatic cysticercosis. He was managed with albendazole. This kind of cases has only been reported twice before in medical literature. It highlights the need to use high resolution ultrasonography in patients with a high index of suspicion of hepatic cysticercosis because of its occult presentation.

Biomedical photoacoustic imaging.

Photoacoustic (PA) imaging, also called optoacoustic imaging, is a new biomedical imaging modality based on the use of laser-generated ultrasound that has emerged over the last decade. It is a hybrid modality, combining the high-contrast and spectroscopic-based specificity of optical imaging with the high spatial resolution of ultrasound imaging. In essence, a PA image can be regarded as an ultrasound image in which the contrast depends not on the mechanical and elastic properties of the tissue, but its optical properties, specifically optical absorption. As a consequence, it offers greater specificity than conventional ultrasound imaging with the ability to detect haemoglobin, lipids, water and other light-absorbing chomophores, but with greater penetration depth than purely optical imaging modalities that rely on ballistic photons. As well as visualizing anatomical structures such as the microvasculature, it can also provide functional information in the form of blood oxygenation, blood flow and temperature. All of this can be achieved over a wide range of length scales from micrometres to centimetres with scalable spatial resolution. These attributes lend PA imaging to a wide variety of applications in clinical medicine, preclinical research and basic biology for studying cancer, cardiovascular disease, abnormalities of the microcirculation and other conditions. With the emergence of a variety of truly compelling in vivo images obtained by a number of groups around the world in the last 2-3 years, the technique has come of age and the promise of PA imaging is now beginning to be realized. Recent highlights include the demonstration of whole-body small-animal imaging, the first demonstrations of molecular imaging, the introduction of new microscopy modes and the first steps towards clinical breast imaging being taken as well as a myriad of in vivo preclinical imaging studies. In this article, the underlying physical principles of the technique, its practical implementation, and a range of clinical and preclinical applications are reviewed.

Pseudo-Spectrum Time Domain and Time Reversal Mirror technique using in Microwave-induced Thermo-Acoustic Tomography System

Microwave-Induced Thermo-Acoustic Tomograpphy (MITAT) has attracted more concerns in recent years in biomedical imaging field. It has both the high contrast of the microwave imaging and the high resolution of ultrasound imaging. As compared to optoacoustics, which uses instead a pulsed light for evoking optoacoustic response, thermo-acoustic imaging has the advantage of deeper tissue penetration, attaining the potential for wider clinical dissemination, especially for malignant tumors. In this paper, the induced thermo-acoustic wave propagating in a mimic biologic tissue is simulated by numeric method Pseudo-Spectrum Time Domain (PSTD). Due to the excellent performance in noisedepress and the stability for the fluctuation of the model parameters, Time Reversal Mirror (TRM) imaging technique is studied computationally for the simulative received thermo-acoustic signals. Some thermo-acoustic objects with different initial pressure distribution are designed and imaged by TRM technique to represent the complex biologic tissue case in a random media. The quality of images generated by TRM technique based on PSTD method hints the potential of the MITAT technique.

Ultrasound-mediated optical tomography: a review of current methods.

Ultrasound-mediated optical tomography (UOT) is a hybrid technique that is able to combine the high penetration depth and high spatial resolution of ultrasound imaging to overcome the limits imposed by optical scattering for deep tissue optical sensing and imaging. It has been proposed as a method to detect blood concentrations, oxygenation and metabolism at depth in tissue for the detection of vascularized tumours or the presence of absorbing or scattering contrast agents. In this paper, the basic principles of the method are outlined and methods for simulating the UOT signal are described. The main detection methods are then summarized with a discussion of the advantages and disadvantages of each. The recent focus on increasing the weak UOT signal through the use of the acoustic radiation force is explained, together with a summary of our results showing sensitivity to the mechanical shear stiffness and optical absorption properties of tissue-mimicking phantoms.

Synthetic aperture focusing for medical endoscopic ultrasonography

A new approach for synthetic aperture focusing (SAF) to enhance both signal to noise ratio (SNR) and resolution in endoscopic ultrasonography is presented in this paper. The technique uses the rotation feature of single element transducer probe, and transmits and receives the echoes at different time and locations during the rotary scanning. Based on theoretical simulation, axial and lateral matched-filters are developed according to the coded and linear frequency modulated characteristics of the echoes to implement axial and lateral compression. The effects of SNR and resolution enhancements by the new SAF approach are demonstrated by both Field II simulation and sample experiment. Data for 6 point targets are simulated and the performance of SAF is compared with those from conventional imaging method and Delay-and-Sum (DS) method. Pigskin samples are examined by a single element transducer at 8 MHz. The effects of sound speed errors and rotary scanning speed errors on both SNR and resolution are calculated to show the robustness of SAF algorithm. Both simulation and experimental results indicated that new SAF can improve SNR and resolution of ultrasound images by 9.38 dB and 51% respectively as compared with the conventional method. It therefore has potential for future clinical and research applications.

Carbon nanotube composite optoacoustic transmitters for strong and high frequency ultrasound generation

We demonstrate carbon nanotube (CNT) composite-based optoacoustic transmitters that generate strong and high frequency ultrasound. The composite consists of CNTs grown on a substrate, which are embedded in elastomeric polymer used as an acoustic transfer medium. Under pulsed laser excitation, the composite generates very strong optoacoustic pressure: 18 times stronger than a Cr film reference and five times stronger than a gold nanoparticle composite with the same polymer. This enhancement persists over a broadband frequency range of up to 120 MHz and is confirmed by calculation. We suggest the CNT-polymer composites as highly efficient optoacoustic transmitters for high resolution ultrasound imaging.