Browsing by Subject "ultrasound"
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Item A CPU-GPU Hybrid Approach for Accelerating Cross-correlation Based Strain Elastography(2011-10-21) Deka, SthitiElastography is a non-invasive imaging modality that uses ultrasound to estimate the elasticity of soft tissues. The resulting images are called 'elastograms'. Elastography techniques are promising as cost-effective tools in the early detection of pathological changes in soft tissues. The quality of elastographic images depends on the accuracy of the local displacement estimates. Cross-correlation based displacement estimators are precise and sensitive. However cross-correlation based techniques are computationally intense and may limit the use of elastography as a real-time diagnostic tool. This study investigates the use of parallel general purpose graphics processing unit (GPGPU) engines for speeding up generation of elastograms at real-time frame rates while preserving elastographic image quality. To achieve this goal, a cross-correlation based time-delay estimation algorithm was developed in C programming language and was profiled to locate performance blocks. The hotspots were addressed by employing software pipelining, read-ahead and eliminating redundant computations. The algorithm was then analyzed for parallelization on GPGPU and the stages that would map well to the GPGPU hardware were identified. By employing optimization principles for efficient memory access and efficient execution, a net improvement of 67x with respect to the original optimized C version of the estimator was achieved. For typical diagnostic depths of 3-4cm and elastographic processing parameters, this implementation can yield elastographic frame rates in the order of 50fps. It was also observed that all of the stages in elastography cannot be offloaded to the GPGPU for computation because some stages have sub-optimal memory access patterns. Additionally, data transfer from graphics card memory to system memory can be efficiently overlapped with concurrent CPU execution. Therefore a hybrid model of computation where computational load is optimally distributed between CPU and GPGPU was identified as an optimal approach to adequately tackle the speed-quality problem in real-time imaging. The results of this research suggest that use of GPGPU as a co-processor to CPU may allow generation of elastograms at real time frame rates without significant compromise in image quality, a scenario that could be very favorable in real-time clinical elastography.Item Applications of TAP-NDE technique to non-contact ultrasonic inspection in tubulars(Texas A&M University, 2005-02-17) Baltazar-Lopez, Martin EduardoThe possibility and feasibility of experimental detection of localized defects in tubes using laser-induced ultrasonic wave approach through Thermo Acousto Photonic Non Destructive Evaluation (TAP-NDE) and Signal processing through wavelet transform is examined in this research. Guided waves in cylindrical surfaces provide solutions for detection of different defects in the material. Several experiments were conducted to this respect. Wave propagation in both axial and circumferential directions was studied. The dispersive wave propagation of ultrasonic waves in hollow cylinders has been investigated experimentally, primarily for use in non-contact and nondestructive inspections of pipes and tubes. The laser ultrasonic waves propagated in cylindrical waveguides are particularly attractive because of their unique characteristics in the applications of nondestructive evaluation (NDE). Contrary to studies making use of only axially symmetric guided waves in hollow cylinders, here are analyzed also nonaxisymmetric waves. The analysis of data is made by using the Gabor wavelet transform. The capability of modeling the guided wave dispersion in hollow cylinders is used in developing guided wave experimental techniques for flaw detection. Good agreement was obtained when comparing the dispersion spectra between theory and experimentation. Measurement of group velocities of guided waves, which are obtained directly from the wavelet transform coefficients, can be used to determine allocation and sizing of flaws.Item Early pregnancy diagnosis and embryo/fetus mortality in cattle(Texas A&M University, 2006-04-12) Romano, Juan EduardoPregnancy diagnosis by transrectal ultrasonography (using a 5 MHZ linear probe) presented the maximum sensitivity and negative predictive values at day 26 and day 29 after estrus in heifers and cows, respectively. Palpation per rectum using the fetal membrane slip for pregnancy diagnosis did not increase embryo/fetus mortality when compared with a positive control group of non-palpated females. The use of a controlled randomized block design was a useful approach to study this problem. Blocking for category and number of embryos allowed us to remove these confounding factors. Factors that affected pregnancy loss during the first four months of pregnancy were: period of pregnancy, age of the animal, number of previous lactations and number of embryos. Pregnancy loss was higher during the embryonic than fetal periods. Spontaneous embryo/fetal mortality increased with the age of the animal and lactation number. The risk of spontaneous embryo/fetus mortality was higher in twin than in single pregnancies. Two types of embryo/fetus mortality were noted: Type I and Type II. Type I was characterized by presence of positive fetal membrane slip by palpation per rectum, signs of degeneration by transrectal ultrasonography and persistence of a functional corpus luteum. The uterus took approximately 3 weeks to be noted clean by transrectal ultrasonography and the animals showed estrus one month after the conceptus was diagnosed dead. Type II was characterized by absence of positive signs of pregnancy by palpation per rectum, absence of signs of degeneration by transrectal ultrasonography and absence of a functional corpus luteum. Pregnancy loss in nuclear transfer derived embryos was higher compared to in vivo derived embryos produced by artificial insemination. Pregnancy loss occurred mainly during the transition from the embryonic to the fetal period. Embryo/fetus mortality detected was Type I. Progesterone produced by the corpus luteum was noted at pregnancy levels for approximately two weeks after embryo/fetus death. Protein B, a hormonal placental marker, was maintained at pregnancy levels for approximately 3 weeks after embryo/fetus death. No differences in the levels of the two hormones were noted when comparing females with dead or live conceptuses.Item Effect of Boundary Conditions on Performance of Poroelastographic Imaging Techniques in Non Homogenous Poroelastic Media(2012-02-14) Chaudhry, AnujIn the study of the mechanical behavior of biological tissues, many complex tissues are often modeled as poroelastic systems due to their high fluid content and mobility. Fluid content and fluid transport mechanisms in tissues are known to be highly correlated with several pathologies. Thus, imaging techniques capable of providing accurate information about these mechanisms can potentially be of great diagnostic value. Ultrasound elastography is an imaging modality that is currently used as a complement to sonographic methods to detect a variety of tissue pathologies. Poroelastography is a new elastographic technique that has been recently proposed to image the mechanical behavior of tissues that can be modeled as poroelastic media. The few poroelastographic studies retrievable focus primarily on homogeneous poroelastic media. In this study, a statistical analysis of the performance of poroelastographic techniques in a non-homogeneous poroelastic simulation model under different loading conditions was carried out. The two loading conditions simulated were stress relaxation (application of constant strain) and creep compression (application of constant stress), both of which have been commonly used in the field of poroelastography. Simulations were performed using a FE poroelastic simulation software combined with ultrasound simulation software techniques and poroelastography processing algorithms developed in our laboratory. The non-homogeneous poroelastic medium was modeled as a cube (background) containing a cylindrical inclusion (target). Different permeability, Young?s modulus and Poisson?s ratio contrasts between the underlying matrix of the background and the target were considered. Both stress relaxation and creep compression loading conditions were simulated. The performance of poroelastography techniques was quantified in terms of accuracy, elastographic contrast?to?noise ratio and contrast transfer efficiency. The results of this study show that, in general, image quality of both axial strain and effective Poisson?s ratio poroelastograms is a complex function of time, which depends on the contrast between the poroelastic material properties of the background and the poroelastic material properties of the target and the boundary conditions. The results of this study could have important implications in defining the clinical range of applications of poroelastographic techniques and in the methodologies currently deployed.Item Performance Analysis of a New Ultrasound Axial Strain Time Constant Estimation(2011-08-08) Nair, Sanjay P.New elastographic techniques such as poroelastography and viscoelasticity imaging aim at imaging the temporal mechanical behavior of tissues. These techniques usually involve the use of curve fitting methods as applied to noisy data to estimate new elastographic parameters. As of today, however, image quality performance of these new elastographic imaging techniques is still largely unknown due to a paucity of data and the lack of systematic studies that analyze performance limitations of estimators suitable for these novel applications. Furthermore, current elastographic implementations of poroelasticity and viscoelasticity imaging methods are in general too slow and not optimized for clinical applications. In this paper, we propose a new elastographic time constant (TC) estimator, which is based on the use of the Least Square Error (LSE) curve-fitting method and the Levenberg-Marquardt (LM) optimization rule as applied to noisy elastographic data obtained from a tissue under creep compression. The estimator's performance is analyzed using simulations and quantified in terms of accuracy, precision, sensitivity, signal-to-noise ratio (SNR) and speed. Experiments are performed as a proof of principle of the technical applicability of the new estimator on real experimental data. The results of this study demonstrate that the new elastographic estimator described in this thesis can produce highly accurate, sensitive and precise time constant estimates in real-time and at high SNR. In the future, the use of this estimator could allow real-time imaging of the temporal behavior of complex tissues and provide advances in lymphedema and cancer imaging.Item Studies on Waterborne Pathogen Reactivation after Disinfection(2013-12-09) Kaur, JasjeetReactivation of different Escherichia coli strains and Aeromonas hydrophila after ultraviolet (UV), ultrasound, and photocatalytic disinfection treatments was addressed in this study. Photocatalytic disinfection was carried out under low pressure ultraviolet (LP UV) irradiation at five titanium dioxide (TiO_(2)) concentrations (1 g/L, 0.5 g/L, 0.75 g/L, and 0.1 g/L) to achieve 5 log_(10) reduction of a laboratory E. coli K-12 strain (ATCC? 10798). Regrowth and reactivation of E. coli in dark and light was studied up to 4 h after disinfection period. During the repair period, flow cytometry had shown 4-5 log_(10) higher cell counts than culture based method. Photocatalysis at 0.1 g/L TiO_(2) had resulted in 50% cells with intact cell membrane during the repair period and has lowered the repair rate of the E. coli (ATCC? 10798) after disinfection. Then ultrasound (24 kHz) and UV-C irradiation were applied to inactivate four E. coli isolates (ATCC?10798, E. coli isolate from feces of feral hog and deer, and treated wastewater effluent) to nearly 8 log_(10) reduction. Photoreactivation and dark repair of E. coli isolates were studied over a 24 h period after disinfection. In general, ultrasound disinfection had resulted in higher inactivation rate of 0.52 log min^(-1) than UV-C (0.39 log min^(-1)) for E. coli isolates. The extent of percent log repair of ultrasound inactivated E. coli isolates after 24 h of dark repair and photoreactivation were 30% lower than after UV-C. The metabolic activity of E. coli cells was greatly reduced after ultrasound as shown by AlamarBlue? assay. Transmission electron micrographs of ultrasound disinfected E. coli revealed shearing and size reduction of bacterial cells. Aeromonas hydrophila (ATCC? 35654), an emerging pathogen, was inactivated using a 24 kHz continuous ultrasound and UV-C in combination with three TiO_(2) concentrations (1g/L, 0.1 g/L and 0 g/L). High inactivation rate of 1.52 log min^(-1) was observed for ultrasound disinfection in absence of TiO_(2). Aeromonas hydrophila had showed a net log reduction of 6 log_(10) after ultrasound exposure in comparison to a net 2 log_(10) reduction after UV-C over a 24 h repair period. Metabolic activity of Aeromonas hydrophila was adversely affected by ultrasonication as well. Ultrasound appears to be effective in inactivating environmental E. coli isolates and Aeromonas hydrophila in water through shearing and breaking effects, which decreased the metabolic activity as well as photoreactivation and dark repair.Item The Adoption of Ultrasound Technology for Pregnancy Determination by New Mexico Cow-Calf Producers(2015-01-23) Lucas, Jessica JaneThe purpose of this study was to identify and describe the diffusion process and the rate of adoption of bovine ultrasound pregnancy determination by New Mexico cattle producers. The researcher from Texas A&M University and Caren Cowan from the New Mexico Cattle Producers Association collaborated on this work. Conclusions were drawn to provide suggestions on increasing the diffusion of ultrasound technology in New Mexico. Data were collected from a sample of 99 producers in the state. Descriptive statistics such as frequencies and percentages of nominal data and means and standard deviations of intervally-scaled variables were employed to describe the sample of producers and their levels of familiarity and use of ultrasound technology. The following were among the findings. Of the producers surveyed, most are using rectal palpation as their primary means of pregnancy determination. A small percentage of producers have adopted ultrasound and are using ultrasound alone, while another small percentage are using ultrasound in combination with other technologies to determine pregnancy in their herd. The diffusion process for ultrasound has begun and for some, it has been adopted. A plurality of producers are aware of the technology and know that it exists, with only a small percentage stating that they did not have any knowledge of the technology?s existence. Most producers were not aware of other producers who use ultrasound but would consider using ultrasound themselves. Producers learned about ultrasound from a veterinarian or their friends with only a very small percentage learning about the technology from an extension agent/extension specialist. Producers stated that they are not in contact with an extension agent/extension specialist about their cattle operation. The producers identified that their primary barrier to the adoption of ultrasound is the cost of the veterinarian/technician to perform the procedure. Recommendations were made based on these findings for use by the New Mexico Cooperative Extension Service and the New Mexico Cattle Growers Association seeking to effect change by the diffusion of new innovations.Item Ultrasound-modulated optical tomography for biomedical applications(Texas A&M University, 2004-11-15) Li, JunI experimentally studied ultrasound-modulated optical tomography, which holds the promise for biomedical diagnosis. I measured the degree of polarization of laser speckles generated by scattered light transmitted through turbid media, investigated three signal-detection schemes for extracting the intensity of the ultrasound-modulated light, carried out experiments to image thick biological-tissue samples, and studied two techniques providing resolution in the cross-sections containing the ultrasonic axis. The study of degree of polarization presented results important for the understanding of polarization phenomena in turbid media. I explored an optical-filtering based signal detection scheme, improved the parallel-lock-in speckle detection scheme and proposed a speckle-contrast detection scheme. With the speckle-contrast detection scheme, I successfully obtained images of biological-tissue samples up to 50 mm thick. Further I studied frequency-swept ultrasound-modulated optical tomography for sub-millimeter resolution imaging, and developed ultrasound-modulated optical computed tomography that was based on a back-projection image reconstruction method and obtained clear images of biological-tissue samples.