Biomedical subjects

Hongzhi Zhao

Publications and source records attributed to Hongzhi Zhao.

4 recordsLinked to original sources

PubMed2006

Finite-element-based photoacoustic tomography: phantom and chicken bone experiments.

We describe a photoacoustic image reconstruction algorithm that is based on the finite-element solution to the photoacoustic wave equation in the frequency domain. Our reconstruction approach is an iterative Newton method coupled with combined Marquardt and Tikhonov regularizations that can extract the spatial distribution of optical-absorption property in heterogeneous media. We demonstrate this algorithm by using phantom and chicken bone measurements from a circular scanning photoacoustic tomography system. The results obtained show that millimeter-sized phantom objects and chicken bones and/or joints can be clearly detected using our finite-element-based photoacoustic tomography method.

Algorithms↗

PubMed2006

Multispectral breast imaging using a ten-wavelength, 64 x 64 source/detector channels silicon photodiode-based diffuse optical tomography system.

We describe a compact diffuse optical tomography system specifically designed for breast imaging. The system consists of 64 silicon photodiode detectors, 64 excitation points, and 10 diode lasers in the near-infrared region, allowing multispectral, three-dimensional optical imaging of breast tissue. We also detail the system performance and optimization through a calibration procedure. The system is evaluated using tissue-like phantom experiments and an in vivo clinic experiment. Quantitative two-dimensional (2D) and three-dimensional (3D) images of absorption and reduced scattering coefficients are obtained from these experiments. The ten-wavelength spectra of the extracted reduced scattering coefficient enable quantitative morphological images to be reconstructed with this system. From the in vivo clinic experiment, functional images including deoxyhemoglobin, oxyhemoglobin, and water concentration are recovered and tumors are detected with correct size and position compared with the mammography.

Algorithms↗

PubMed2005

Imaging of small nanoparticle-containing objects by finite-element-based photoacoustic tomography.

We present semiquantitative photoacoustic images of small nanoparticle-containing objects having a wide range of contrast levels relative to the background. The images are obtained by a finite-element reconstruction algorithm that is based on the Helmholtz-like photoacoustic wave equation in the frequency domain. Our reconstruction approach is an iterative Newton method coupled with combined Marquardt and Tikhonov regularizations that can extract the spatial distribution of relative optical absorption property in heterogeneous media. We demonstrate experimental images in single- and multiple-object configurations with a circular scanning photoacoustic tomographic system. The results obtained show that millimeter-size nanoparticle-containing objects can be clearly detected in terms of position, size, and relative optical properties.

Acoustics↗

PubMed2005

Model-based ultrasound tomography: tissue phantom experiments.

We present a detailed experimental study to evaluate our finite element based nonlinear reconstruction algorithm for recovery of acoustic properties in heterogeneous scattering media. Using a circularly scanning ultrasound system at 500 KHz, tissue phantom experiments were performed to study spatial resolution and contrast issues in model-based ultrasound tomography. Our results show that both acoustic attenuation and speed images can be quantitatively reconstructed in terms of the location, size, shape, and acoustic property value of the target when different contrast levels between the target and background were used. We also demonstrate that a high contrast target as small as 3 mm in diameter can be quantitatively resolved with our acoustic speed and attenuation images.

Algorithms↗