Showing papers by "Jie Yuan published in 2015"

Characterization of bone microstructure using photoacoustic spectrum analysis

Abstract: Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and the deterioration in bone microarchitecture. This study investigates the feasibility of characterizing bone microstructure by analyzing the frequency spectrum of the photoacoustic (PA) signal from the bone. Modeling and numerical simulation of PA signal were performed on trabecular bone simulations and CT scans with different trabecular thicknesses. The resulting quasi-linear photoacoustic spectra were fittted by linear regression, from which the spectral parameter slope was quantified. The simulation based on two different models both demonstrate that bone specimens with thinner trabecular thicknesses have higher slope. Experiment on osteoporotic rat femoral heads with different mineral content was conducted. The finding from the experiment was in good agreement with the simulation, demonstrating that the frequency-domain analysis of PA signals can provide an objective assessment of bone microstructure and deterioration. Considering that PA measurement is non-ionizing, non-invasive, and has sufficient penetration in both calcified and non-calcified tissues, this new bone evaluation method based on photoacoustic spectral analysis holds potential for clinical management of osteoporosis and other bone diseases.

Multi-step-ahead host load prediction using autoencoder and echo state networks in cloud computing

Abstract: Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released with minimal management effort or service provider interaction. There are many proposals for resource management approaches for cloud infrastructures, but effective resource management is still a major challenge for the leading cloud infrastructure operators (e.g., Amazon, Microsoft, Google), because the details of the underlying workloads and the real-world operational demands are too complex. Among those proposals, accurate host load prediction is one of the most effective measures to address this challenge. In this paper, we proposed a new method for host load prediction, which uses an autoencoder as the pre-recurrent feature layer of the echo state networks. The aim of our proposed method is to predict the host load in the future interval based on Google cluster usage dataset. Experiments performed on Google load traces show that our proposed method achieves higher accuracy than the state-of-the-art methods.

Bone assessment via thermal photo-acoustic measurements

Abstract: The feasibility of an innovative biomedical diagnostic technique, thermal photo-acoustic (TPA) measurement, for non-ionizing and non-invasive assessment of bone health is investigated. Unlike conventional photo-acoustic PA methods that are mostly focused on the measurement of absolute signal intensity, TPA targets the change in PA signal intensity as a function of the sample temperature, i.e., the temperature-dependent Grueneisen parameter that is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique are less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non-organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well-established rat models of bone loss and preservation, PA measurements of rat tibia bones were conducted over a temperature range from 37°C to 44°C. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis.

Bone assessment via thermal photoacoustic measurements

Abstract: The feasibility of an innovative biomedical diagnostic technique, thermal photoacoustic (TPA ) measurement, for non -ionizing and non -invasive assessment of bone health is investigated. Unlike conventional photoacoustic PA methods which are mostly focused on the measurement of absolute signal intensity, TPA targ ets the change in PA signal intensity as a function of the sample temperature, i.e. the temperature dependent Grueneisen parameter which is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, t he results from TPA technique is less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non -organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well -established rat models of bone loss and pr eservation, PA measurements of rat tibia bones were conducted over a temperature ra nge from 37 oC to 44 oC. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis. Keywords: thermal photoacoustic, bone assessment , temperature, organic tissue, non -organic mine ral

Photoacoustic imaging: a potential new platform for assessment of bone health

Abstract: The ultimate goal of this work is to develop a novel photoacoustic (QPA) platform for highly-sensitive and quantitative assessment of bone health. First, the feasibility to perform 3D photoacoustic imaging (PAI) of bone was investigated. Then another two techniques, including thermal photoacoustic measurement (TPAM) and photoacoustic spectral analysis (PASA), both being able to achieve quantitative results were investigated for bone characterization. TPAM, by evaluating the dependence of photoacoustic signal amplitude on the sample temperature, is sensitive to the chemical constituents in tissue and holds promise for assessment of bone mineral density (BMD). PASA characterizes micron size physical features in tissue, and has shown feasibility for objective assessment of bone microarchitecture (BMA). This integrated QPA platform can assess both bone mass and microstructure simultaneously without involving invasive biopsy or ionizing radiation. Since QPA is non-ionizing, non-invasive, and has sufficient penetration in both soft tissue and bone, it has unique advantages for clinical translation.

Temperature imaging with speed of ultrasonic transmission tomography for medical treatment control：A physical model-based method

Abstract: Hyperthermia is a promising method to enhance chemo and radiation therapy of breast cancer. In the process of hyperthermia, temperature monitoring is of great importance to assure the effectiveness of treatment. The transmission speed of ultrasound in biomedical tissue changes with temperature. However, when mapping the speed of sound directly to temperature in each pixel as desired for using all speeds of ultrasound data, temperature bipolar edge enhancement artifacts occur near the boundary of two tissues with different speeds of ultrasound. After the analysis of the reasons for causing these artifacts, an optimized method is introduced to rebuild the temperature field image by using the continuity constraint as the judgment criterion. The significant smoothness of the rebuilding image in the transitional area shows that our proposed method can build a more precise temperature image for controlling the medical thermal treatment.

Adaptive multi-sample-based photoacoustic tomography with imaging quality optimization

Abstract: The energy of light exposed on human skin is compulsively limited for safety reasons which affects the power of photoacoustic (PA) signal and its signal-to-noise ratio (SNR) level. Thus, the final reconstructed PA image quality is degraded. This Letter proposes an adaptive multi-sample-based approach to enhance the SNR of PA signals and in addition, detailed information in rebuilt PA images that used to be buried in the noise can be distinguished. Both ex vivo and in vivo experiments are conducted to validate the effectiveness of our proposed method which provides its potential value in clinical trials. OCIS codes: 100.2980, 170.1065, 170.5120. doi: 10.3788/COL201513.061001. Research on photoacoustic tomography (PAT) got prosperous development for its being promisingly characterized with noninvasive and nonionizing diagnose of breast cancer, arthritis, and relevant disease. PAT combines the metrics of both ultrasound imaging and pure optical imaging technique, providing high ultrasonic resolution and high optical contrast images [1–5] . Due to the peculiarity that the optical absorption characteristic of blood has a strong relationship with the hemoglobin content, functional imaging as well as structural imaging can also be realized by PAT, making this imaging modality extremely potential in clinical application [6] . The basic principle of PAT is that a tissue is irradiated with short nanosecond laser pulses, and then the absorbed energy may result in a thermo-elastic expansion and subsequent contraction of irradiated volume that generates time-trace photoacoustic (PA) waves, which can be acquired by scanning small-aperture ultrasound detectors over a surface that encloses the source under study. The recorded PA wave can then be reconstructed to spatially resolve the initial absorber distribution and concentration via PA reconstruction algorithms [7–9]. However, biomedical tissue is a highly scattering medium for electromagnetic waves in the optical spectral range, and the propagation ultrasound waves are extremely attenuated before received by ultrasound sensors. Furthermore, the dose of laser beam exposed on the biomedical tissue has to be limited under 20 mJ∕cm 2 for safety operation. Thus, in clinical trials, ultrasound transducer can only receive weak PA signals with low signal-to-noise ratio (SNR) which degraded the final reconstructed PA images [10–14] . This Letter proposes an adaptive multi-sample-based approach to enhance the SNR of PA signals and in addition, detailed information of PAT that used to be buried in the noise and artifacts can be distinguished. The PA reconstruction is an inverse problem of the source pressure. We assume that a tissue with inhomogeneous microwave absorption but a relatively homogeneous acoustic property and the heat diffusion’s effect on the thermoacoustic wave can be ignored. For cases where the scanning radius in a circular scan configuration is much greater than the PA wavelengths, the optical absorption p0ðrÞ within the sample at a given position r is given as [1]

Characterization of bone microstructure using photoacoustic spectrum analysis

Abstract: Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and deterioration in microarchitecture. This study investigates the feasibility of characterizing bone microstructure by analyzing the frequency spectrum of the photoacoustic signals from the bone. Modeling and numerical simulation of photoacoustic signals and their frequency-domain analysis were performed on trabecular bones with different mineral densities. The resulting quasilinear photoacoustic spectra were fit by linear regression, from which spectral parameter slope can be quantified. The modeling demonstrates that, at an optical wavelength of 685 nm, bone specimens with lower mineral densities have higher slope. Preliminary experiment on osteoporosis rat tibia bones with different mineral contents has also been conducted. The finding from the experiment has a good agreement with the modeling, both demonstrating that the frequency-domain analysis of photoacoustic signals can provide objective assessment of bone microstructure and deterioration. Considering that photoacoustic measurement is non-ionizing, non-invasive, and has sufficient penetration in both calcified and noncalcified tissues, this new technology holds unique potential for clinical translation.

Technique development for photoacoustic imaging guided interventions

Abstract: Laser-induced thermotherapy (LITT), i.e. tissue destruction induced by a local increase of temperature by means of laser light energy transmission, has been frequently used for minimally invasive treatments of various diseases such as benign thyroid nodules and liver cancer. The emerging photoacoustic (PA) imaging, when integrated with ultrasound (US), could contribute to LITT procedure. PA can enable a good visualization of percutaneous apparatus deep inside tissue and, therefore, can offer accurate guidance of the optical fibers to the target tissue. Our initial experiment demonstrated that, by picking the strong photoacoustic signals generated at the tips of optical fibers as a needle, the trajectory and position of the fibers could be visualized clearly using a commercial available US unit. When working the conventional US Bscan mode, the fibers disappeared when the angle between the fibers and the probe surface was larger than 60 degree; while working on the new PA mode, the fibers could be visualized without any problem even when the angle between the fibers and the probe surface was larger than 75 degree. Moreover, with PA imaging function integrated, the optical fibers positioned into the target tissue, besides delivering optical energy for thermotherapy, can also be used to generate PA signals for on-line evaluation of LITT. Powered by our recently developed PA physio-chemical analysis, PA measurements from the tissue can provide a direct and accurate feedback of the tissue responses to laser ablation, including the changes in not only chemical compositions but also histological microstructures. The initial experiment on the rat liver model has demonstrated the excellent sensitivity of PA imaging to the changes in tissue temperature rise and tissue status (from native to coagulated) when the tissue is treated in vivo with LITT.

Optimizing the optical wavelength for the photoacoustic imaging of inflammatory arthritis

Abstract: With the capability of assessing high resolution optical information in soft tissues at imaging depth up to several centimeters, innovative biomedical photoacoustic imaging (PAI) offers benefits to diagnosis and treatment monitoring of inflammatory arthritis, particularly in combination with more established ultrasonography (US). In this work, a PAI and US dual-modality system facilitating both imaging functions in a real-time fashion was developed and initially tested for its clinical performance on patients with active inflammatory arthritis. Photoacoustic (PA) images of metacarpophalangeal (MCP) joints were acquired at 580-nm wavelength that provides a desired balance between optical absorption of blood and attenuation in background tissue. The results from six patients and six normal volunteers used as a control demonstrated the satisfactory sensitivity of PAI in assessing the physiological changes in the joints, specifically enhanced blood flow as a result of active synovitis. This preliminary study suggests that PAI, by revealing vascular features suggestive of joint inflammation, could be a valuable supplement to musculoskeletal US for rheumatology clinic.

Photoacoustic imaging of human inflammatory arthritis

Abstract: To explore the value of photoacoustic imaging in future rheumatology clinic, in this work a newly developed photoacoustic and ultrasound dual-modality system facilitating real-time B-scan imaging was examined for its performance in mapping the enhanced synovial flow in human peripheral joints affected by inflammatory arthritis. The patients involved in this study were men and women over 18 years old, with clinically diagnosed inflammatory arthritis. Photoacoustic images of metacarpophalangeal joints were acquired at 580-nm wavelength that provides a desired balance between optical absorption of blood and attenuation in background tissue. The increased flow in the affected joints can be displayed successfully in photoacoustic images, and the difference between the arthritis group and the control group can be recognized. The results from arthritis patients and normal volunteers demonstrated the satisfactory sensitivity of photoacoustic imaging in assessing the physiological changes in the joints, specifically enhanced blood flow as a result of active synovitis. This study suggests that photoacoustic imaging, by revealing vascular features suggestive of joint inflammation, could be a valuable supplement to musculoskeletal ultrasound for rheumatology clinic.

An information hiding system based on high frame rate video

Abstract: There are two drawbacks in conventional steganography technology. First, hidden messages cannot be observed by human eyes. Second, decryption process is so complex that it is hard to reach real-time requirements. In this article, it is expected to find a new method, which is simple, fast and secure. Taking these principles into account, we establish a confidential display system based on high refresh rate display. The system consists of a FPGA, a high refresh rate screen and shutter glasses. Under the control of FPGA, useful frames are submerged in a large number of other redundant frames. Useful frames, together with redundant frames, display on the high refresh rate screen. Because of the redundant in-formation's interference, it is difficult for the human eyes to find out the useful information while it's easy to pick up useful information through the high-speed shutter glasses, which can exclude the redundant information.