Reza Zahiri - Profile on Academia.edu (original) (raw)

Papers by Reza Zahiri

MIPPR 2009: Multispectral Image Acquisition and Processing, 2009

The Sonix RP is an easy to use ultrasound imaging device that is capable of acquiring high qualit... more The Sonix RP is an easy to use ultrasound imaging device that is capable of acquiring high quality images. In addition to supporting the acquisition of multiple data types such as RF, elastography, and color doppler data, the machine is an open ended system providing users with full control over imaging parameters through an investigational research interface. Since the Sonix RP is PC based and it supports open-source software development toolkits, programs can be developed and executed directly onto the device, thus eliminating the need for extra hardware that is often required for data collection and analysis. Due to these advantages, many universities and research institutes have successfully used the Sonix RP to test and implement their customized solutions for different applications.

Lecture Notes in Computer Science, 2006

We present an ultrasound vibro-elastography system designed to acquire viscoelastic properties of... more We present an ultrasound vibro-elastography system designed to acquire viscoelastic properties of the prostate and peri-prostatic tissue. An excitation stage imparts low-frequency (<20 Hz), limited amplitude (< ± 2mm), broadband vibratory motion to an endorectal transducer, along a radial/transversal direction. The induced tissue motion is estimated from ultrasound radio-frequency data and is used to estimate the mechanical frequency response of tissue to the excitation at different spatial locations. This can be used to determine the spatial distribution of various mechanical parameters of tissue, such as stiffness and viscosity. Phantom and in-vivo images are presented. The results obtained demonstrate high phantom and tissue linearity and high signal-to-noise ratio.

The Techniques and Methods of Hair Transplantation

FUE Hair Transplantation, 2018

Curren t imaging devices such as computed tomography ( C T ) , u l t rasound (US) and magnetic re... 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...

2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2007

Motion estimation in sequences of ultrasound echo signals is essential for a wide range of applic... more Motion estimation in sequences of ultrasound echo signals is essential for a wide range of applications. In time domain cross correlation, which is a common motion estimation technique, the displacements are typically not integral multiples of the sampling period. Therefore, to estimate the motion with sub-sample accuracy, 1D and 2D interpolation methods such as parabolic, cosine, and ellipsoid fitting have been introduced in the literature. In this paper, a simulation framework is presented in order to compare the performance of currently available techniques. First, the tissue deformation is modeled using the finite element method (FEM) and then the corresponding pre-/post-deformation radio-frequency (RF) signals are generated using Field II ultrasound simulation software. Using these simulated RF data of deformation, both axial and lateral tissue motion are estimated with sub-sample accuracy. The estimated displacements are then evaluated by comparing them to the known displacements computed by the FEM. This simulation approach was used to evaluate three different lateral motion estimation techniques employing (i) two separate 1D sub-sampling, (ii) two consecutive 1D sub-sampling, and (iii) 2D joint sub-sampling estimators. The estimation errors during two different tissue compression tests are presented with and without spatial filtering. Results show that RF signal processing methods involving tissue deformation can be evaluated using the proposed simulation technique, which employs accurate models.

Dynamic elastography using delay compensated and angularly compounded high frame rate 2D motion vectors

2010 IEEE International Ultrasonics Symposium, 2010

This paper describes a new ultrasound-based system for high frame rate measurement of periodic mo... 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

Real-time transient elastography on standard ultrasound using mechanically induced vibration: System design and initial results

2011 IEEE International Ultrasonics Symposium, 2011

ABSTRACT Tissue elasticity can be deduced from the study of the propagation of shear waves. Trans... 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.

Importance of transducer position tracking for automated breast ultrasound: Initial assessments

2012 IEEE International Ultrasonics Symposium, 2012

ABSTRACT Breast cancer causes the most cancer deaths in women all over the world. Given the unkno... 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.

Computer Aided Surgery, 2008

Needle insertion simulators find use in a number of medical interventions, such as prostate brach... more Needle insertion simulators find use in a number of medical interventions, such as prostate brachytherapy. A needle insertion simulator has three main components: the needle model, the tissue model, and the model of interaction between the needle and the tissue. In this paper, a new methodology is introduced for the joint modeling of tissue and needle-tissue interactions. The approach consists of the measurement of tissue motion using ultrasound, and of the needle position and base force. Tissue motion is determined using a correlation-based algorithm that processes the ultrasound radiofrequency data. The tissue elastic parameters and the parameters of the tissue-needle interaction model are determined by using numerical optimization to match the response of the needle insertion model to the measured data. Phantom experiments were carried out in which a brachytherapy needle was inserted into a two-layer non-homogeneous phantom mimicking a prostate and its surrounding tissue. Experimental results show good agreement with the model obtained. In particular, the parameters of a three-parameter force model were identified for each layer of the phantom to fit the measured force to the simulated one. Also, the Young's modulus of each layer was identified to match the measured and simulated nodal axial displacements. This is the first report of the use of ultrasound radiofrequency data to characterize tissue motion during needle insertion. As the method is non-invasive and does not involve ionizing radiation, its application in patient studies is feasible.