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Curren t imaging devices such as computed tomography ( C T ) , u l t rasound (US) and magnetic resonance imaging ( M R I ) are not d i rect ly capable of measuring the mechanical properties of soft tissue even though such measurement wou... more
Curren t imaging devices such as computed tomography ( C T ) , u l t rasound (US) and magnetic resonance imaging ( M R I ) are not d i rect ly capable of measuring the mechanical properties of soft tissue even though such measurement wou ld have a h igh c l in ica l demand. Elas tography w i t h the a id of ul t rasound has been wel l established i n the l i terature as a s t ra in imag ing technique. Unde r cer ta in condit ions, these s t ra in images can give a clear i l lus t ra t ion of the under ly ing tissue stiffness dis t r ibut ions which has been shown to provide useful c l in ica l informat ion. V i b r o Elas tography is another new imaging system that performs a transfer function analysis of the tissue mot ion . T h e shape of the transfer function can be analyzed further and the stiffness of tissue can be est imated from the magnitude of the transfer functions at low-frequencies. T h i s thesis introduces a fast and accurate mot ion t rack ing a lgor i thm wh ich is a...
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Research Interests: Computer Science, Algorithms, Signal Processing, Finite element method, Medicine, and 15 moreElasticity, Motion estimation, Cross Correlation, Computer Simulation, Radio Frequency, Conference Proceedings, Motion, Reproducibility of Results, Radio Waves, Estimator, Simulation Software, Simulation Framework, Compression test, Simulation Technique, and Interpolation Method
This paper describes a new ultrasound-based system for high frame rate measurement of periodic motion in 2D for tissue elasticity imaging. The system acquires the RF signals from the region of interest from multiple steering angles in... more
This paper describes a new ultrasound-based system for high frame rate measurement of periodic motion in 2D for tissue elasticity imaging. The system acquires the RF signals from the region of interest from multiple steering angles in order to reconstruct the 2D motion from 1D estimation along each angle. To increase the temporal resolution, the acquisition area is divided into
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ABSTRACT Tissue elasticity can be deduced from the study of the propagation of shear waves. Transient elastography by means of mechanical vibration has been well established in the literature as a means of assessing the elasticity of the... more
ABSTRACT Tissue elasticity can be deduced from the study of the propagation of shear waves. Transient elastography by means of mechanical vibration has been well established in the literature as a means of assessing the elasticity of the soft tissue and shown to be useful in different clinical applications. Previous studies have focused mainly on custom single element ultrasound transducers and ultrafast ultrasound scanners. In this work, we report the design and implementation of a transient elastography system on a standard ultrasound scanner that enables quantitative assessment of tissue elasticity in real-time. We presents the actuator design as well as the proposed data acquisition schemes that enable imaging of transient shear waves both in 1D and 2D in addition to the reconstruction algorithms for estimating the Young's modulus from these 1D and 2D wave images. The performance of the system is validated experimentally using a commercial elasticity phantom. In both 1D and 2D imaging modes, a good agreement was observed between the Young's modulus reported by the phantom manufacturer and the Young's modulus estimated by our system.
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ABSTRACT Breast cancer causes the most cancer deaths in women all over the world. Given the unknown cause and invasive nature of the disease, early detection and treatment is crucial to the survival of the cancer patients. X-rays... more
ABSTRACT Breast cancer causes the most cancer deaths in women all over the world. Given the unknown cause and invasive nature of the disease, early detection and treatment is crucial to the survival of the cancer patients. X-rays mammography is an effective screening tool for breast cancer but misses nearly half of them in women with dense breasts, in which case supplemental ultrasound (US) screening must be used. Recent development in 3D automated breast ultrasound (ABUS) provides a faster and potentially more accurate alternative to the conventional 2D hand-held US in detecting the tumors. Typically in these systems, a custom-built linear or curvilinear transducer is automatically swept over or rotated around the tissue to acquire a set of 2D images, from which a 3D high-resolution volume of the breast can be reconstructed. In this work, we study the importance of transducer position tracking in the ABUS volume reconstruction process. Our experiments show that an accurate localization of the images results in a more accurate volume reconstruction.
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ABSTRACT An automated breast ultrasound system (ABUS) has recently been introduced for breast screening and monitoring of cancer treatment. ABUS enables clinicians to acquire ultrasound images from the entire breast tissue in a few... more
ABSTRACT An automated breast ultrasound system (ABUS) has recently been introduced for breast screening and monitoring of cancer treatment. ABUS enables clinicians to acquire ultrasound images from the entire breast tissue in a few minutes. In this work we report the addition of tissue elasticity imaging to the ABUS system that enables the clinician to automatically acquire 3D strain volume of the breast tissue. The performance of the system is validated experimentally using a commercial breast elasticity phantom. The results show that the proposed automated system can reliably generate elasticity images of the breast tissue that can be reviewed by clinicians along side ultrasound images.
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Research Interests: Physics, Brachytherapy, Finite element method, Finite Element, Medicine, and 15 moreCross Correlation, Humans, Computer Simulation, Male, Parameter Identification, Radio Frequency, Prostate, Conference Proceedings, Interaction model, Materials Testing, Experimental Data, Needles, Amplitude, Biomechanical Phenomena, and Elastography
The past two decades have witnessed the development of a new medical imaging modality: tissue elastography. The contrast in the images produced by an elastography system is based on the tissue elasticity, hence these images are called... more
The past two decades have witnessed the development of a new medical imaging modality: tissue elastography. The contrast in the images produced by an elastography system is based on the tissue elasticity, hence these images are called elastograms. Tissue elasticity is of clinical interest, because it is often correlated with pathology [1]. Different approaches to tissue elastography have emerged [2, 3]. In this article we report a tissue elastography system and its implementation on an ultrasound machine which provides consistent elastograms of a commercial quality assurance elastography phantom. The system uses our previously developed high frame rate sequencing and phase compensation techniques to measure axial and lateral motions at a typical frame rate of 1.25 kHz [4]. The system uses the curl of the displacements in a direct inversion algorithm to reconstruct elasticity. The most important benefit of this method is that the obtained elastograms are not dependent on the boundary...
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Research Interests: Engineering, Computer Science, Open Access, Ultrasound Imaging, Temporal Resolution, and 15 moreUltrasound, Computer Hardware, Medicine, Beamforming, Data acquisition, Physical sciences, Ultrasonics, Minimum variance, Research Purpose, Data transfer, Cross Section, Adaptive Beamforming, Data Acquisition System, Proof of Concept, and plane waves
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This paper describes a new ultrasound-based system for high-frame-rate measurement of periodic motion in 2-D for tissue elasticity imaging. Similarly to conventional 2-D flow vector imaging, the system acquires the RF signals from the... more
This paper describes a new ultrasound-based system for high-frame-rate measurement of periodic motion in 2-D for tissue elasticity imaging. Similarly to conventional 2-D flow vector imaging, the system acquires the RF signals from the region of interest at multiple steering angles. A custom sector subdivision technique is used to increase the temporal resolution while keeping the total acquisition time within the range suitable for real-time applications. Within each sector, 1-D motion is estimated along the beam direction. The intra- and inter-sector delays are compensated using our recently introduced delay compensation algorithm. In-plane 2-D motion vectors are then reconstructed from these delay-compensated 1-D motions. We show that Young's modulus images can be reconstructed from these 2-D motion vectors using local inversion algorithms. The performance of the system is validated quantitatively using a commercial flow phantom and a commercial elasticity phantom. At the frame rate of 1667 Hz, the estimated flow velocities with the system are in agreement with the velocity measured with a pulsed-wave Doppler imaging mode of a commercial ultrasound machine with manual angle correction. At the frame rate of 1250 Hz, phantom Young's moduli of 29, 6, and 54 kPa for the background, the soft inclusion, and the hard inclusion, are estimated to be 30, 11, and 53 kPa, respectively.
Research Interests: Engineering, Algorithms, Physics, Temporal Resolution, Ultrasound, and 12 moreMedicine, Movement, Physical sciences, Real Time Application, Reproducibility of Results, Elastic Modulus, Flow Velocity, Frequency Control, Region of Interest, Elastography, Delay Compensation, and Elasticity Imaging Techniques
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Recent research in the field of elastography has sought to expand displacement tracking to three dimensions. Once the 3-D volumes of displacement data have been obtained, they must be scan converted so that further processing, such as... more
Recent research in the field of elastography has sought to expand displacement tracking to three dimensions. Once the 3-D volumes of displacement data have been obtained, they must be scan converted so that further processing, such as inversion methods to obtain tissue elasticity, can take place in Cartesian coordinates. This paper details an efficient and geometrically accurate algorithm to scan convert 3-D volumes of displacement vectors obtained from a motorized sector transducer. The proposed algorithm utilizes the physical scan geometry to convert the 3-D volumes of displacement data to both Cartesian coordinates and Cartesian displacements. Spatially varying filters are also proposed to prevent aliasing while minimizing data loss. Validation of the system has shown the algorithm to be correct to floating point precision, and the 3-D scan conversion and filtering can be performed faster than the native rate of data acquisition for the motorized transducer.