In our previous studies, near-infrared (NIR) diffuse optical tomography (DOT) had been successfully applied to imaging
osteoarthritis (OA) in the finger joints where significant difference in optical properties of the joint tissues was evident
between healthy and OA finger joints. Here we report for the first time that large joints such as the knee can also be
optically imaged especially when DOT is combined with x-ray tomosynthesis where the 3D image of the bones from x-ray
is incorporated into the DOT reconstruction as spatial a priori structural information. This study demonstrates that
NIR light can image large joints such as the knee in addition to finger joints, which will drastically broaden the clinical
utility of our x-ray guided DOT technique for OA diagnosis.
In this study, a simplified spherical harmonics approximated higher order diffusion model is employed for 3-D diffuse optical tomography of osteoarthritis in the finger joints. We find that the use of a higher-order diffusion model in a stand-alone framework provides significant improvement in reconstruction accuracy over the diffusion approximation model. However, we also find that this is not the case in the image-guided setting when spatial prior knowledge from x-rays is incorporated. The results show that the reconstruction error between these two models is about 15 and 4%, respectively, for stand-alone and image-guided frameworks.
Our previous work has shown that near-infrared diffuse optical tomography has the potential to be a clinical tool in
diagnosis of osteoarthritis. Here we report a study of 38 joints from 38 females, including 20 OA and 18 healthy joints.
The quantitative results obtained show that there exists clear difference between OA and healthy joints in terms of the
ratio of optical properties of the joint soft tissues to that of the associated bone. Statistic analysis of these clinical data is
also presented.
To investigate the typical optical findings that can be used to characterize osteoarthritis, the distal
interphalangeal finger joints from 40 subjects including 22 patients and 18 healthy controllers
were examined clinically and scanned by a novel hybrid imaging system. The hybrid imaging
platform integrated a C-arm based x-ray tomosynthetic system with a multi-channel optic-fiber
based diffuse optical imaging system. Optical images were recovered qualitatively and
quantitatively based on a regularization-based reconstruction algorithm that can incorporate the
fine structural maps obtained from x-ray as a priori spatial information into diffuse optical
tomography reconstruction procedures. Our findings suggest statistically significant differences
between healthy and osteoarthritis finger joints. X-ray guided diffuse optical imaging may not
only detect radiologic features supporting the development of an inflammatory disorder but may
also help discriminate specific optical features that differ between osteoarthritic and healthy joints.
These quantitative optical features are also potentially important for a better understanding of
inflammatory arthritis in humans.
Multispectral and phase-contrast diffuse optical tomography are used to track treatment progress in a patient with locally
advanced invasive carcinoma of the breast cancer during neoadjuvant chemotherapy. Two types of chemotherapy
treatment including four cycles of Adriamycin/Cytoxin (AC cycles) and twelve cycles of Taxol/Herceptin (TH cycles)
were applied to patient. A total of eight optical exams were performed before and within the chemotherapy. Images of
tissue refractive index, and absorption and scattering coefficients, as well as oxy-hemoglobin and deoxy-hemoglobin
concentrations along with scattering particle volume fraction and mean diameter of cellular components were all
obtained. The tumor was identified through absorption and scattering images. Tumor shrinkage was observed during the
course of chemotherapy from all the optical images. Our results show that oxy-hemoglobin, deoxy-hemoglobin and total
hemoglobin in tumor decreased after chemotherapy compared to that of before chemotherapy. Significant changes in
tumor refractive index along with tumor cellular morphology during the entire chemotherapy are also observed.
Thus far optical imaging of the finger joints is limited to only one joint at a time. We have developed a CCD-based
system that can image a whole finger, covering multiple joints. We show that the two joints of a volunteer's index finger
can be imaged clearly and concurrently. The comparison of the optical images with the x-ray image of the same finger
indicates that the recovered size of the whole finger, the bones and the two joint spaces are consistent with the findings
from the x-ray. This study demonstrates a practicable system for full finger imaging and indicates the possibility of full
hand imaging if a fast laser source scanning subsystem is integrated with the system.
We report our continued study of phase-contrast diffuse optical tomography (PCCDOT) for evaluating its
fidelity in distinguishing malignant breast lesions form benign ones. 144 breast masses were examined
from 134 patients, aging from 22~82 with the mean age of 56. Tissue optical parameters including
refractive index, and absorption and scattering coefficients, were obtained and compared with their
corresponding biopsy/pathology reports. In consistent with our previous study, malignant masses tended to
have a decreased refractive index relative to their surrounding normal tissue, which acts as the key
character to differentiate them from benign masses. The results show that the specificity is improved
significantly over the previous smaller scale study (85% vs. 70%) due to the addition of significantly more
benign cases, while the sensitivity stays about the same (81% vs. 82%) due to the similar number of
malignant cases used compared to the smaller scale study.
We describe a new spectral approach for inversion of photoacoustic data with multi-wavelength
pulsed laser illumination. Multi-spectral PAT provides a means of recovery of different
chromophore concentrations and ultrasound velocity simultaneously and directly by incorporating
prior spectral information into the image reconstruction process. It is demonstrated from
simulation tests and small animal experiments that the multi-parameter recovery based on multispectral
PAT is reliable and accurate. The reconstructed multiple parameter images may provide
us a key tool to quantify physiological function, disease progression, or response to intervention.
A multi-modality imaging approach and instrument that integrate optical imaging system and
near-infrared spectroscopy into an x-ray tomosynthesis setup have been employed to perform a
clinical study of image-guided spectroscopy on osteoarthritis (OA) in the finger joints. The multiwavelength
spectroscopy of the joints using x-ray-guided spatial constraints provides 3D images
of oxygen saturation and water content with high resolution and improved quantitative capability.
Based on the recovered quantitative results from 18 healthy volunteers and 22 patients, we
observed that oxygen saturation and water content were significant discriminators for
differentiation of healthy joints from diseased ones. The recovered images appear to show that the
OA joints have high water values and decreased oxygen saturation.
KEYWORDS: Reconstruction algorithms, Absorption, 3D modeling, Scattering, Bone, 3D image processing, Diffusion, Cartilage, Spherical lenses, In vivo imaging
In this study, we present a simplified spherical
approximated-radiative transport model-based
reconstruction algorithm for three-dimensional diffuse optical tomography of finger joints. The
reconstruction algorithm is tested and validated using a series of phantom experiments and in
vivo data from healthy and osteoarthritic joints. In all the phantom and in vivo experiments, the
absorption and scattering images are recovered using both the transport model and diffusion
approximation based reconstruction algorithms. We observe that while both the diffusion and
transport based algorithms can effectively image the finger joints, the transport model based can
provide quantitatively improved reconstruction quality over the diffusion approximated based.
An automated procedure for detecting breast cancer using near-infrared (NIR) tomographic images is presented. This classification procedure automatically extracts attributes from three imaging parameters obtained by an NIR imaging system. These parameters include tissue absorption and reduced scattering coefficients, as well as a tissue refractive index obtained by a phase-contrast-based reconstruction approach. A support vector machine (SVM) classifier is utilized to distinguish the malignant from the benign lesions using the automatically extracted attributes. The classification results of in vivo tomographic images from 35 breast masses using absorption, scattering, and refractive index attributes demonstrate high sensitivity, specificity, and overall accuracy of 81.8%, 91.7%, and 88.6% respectively, while the classification sensitivity, specificity, and overall accuracy are 63.6%, 83.3%, and 77.1%, respectively, when only the absorption and scattering attributes are used. Furthermore, the automated classification procedure provides significantly improved specificity and overall accuracy for breast cancer detection compared to those by an experienced technician through visual examination.
We describe a multimodality imaging approach that combines x-ray tomosynthesis with near-infrared diffuse optical tomography (DOT) for high-resolution imaging of osteoarthritis in the finger joints. In this approach, we take advantage of high resolution x-ray imaging particularly of the bones and incorporate the fine structural maps obtained from x ray as a priori information into DOT reconstructions. To realize this multi-modality approach, we constructed a hybrid imaging platform that integrated a C-arm–based x-ray tomosynthetic system with a multichannel optic-fiber–based DOT system. We also implemented improved hybrid regularization-based reconstruction algorithms that have shown to be especially effective for high-resolution modality-guided DOT. Initial evaluation of our x-ray–guided DOT reconstruction approach in the finger joints shows that spatial resolution of DOT can be enhanced dramatically when the three-dimensional geometry of bones is known a priori. In particular, the improved quantitative capability of imaging absorption and scattering coefficients of the joint tissues allows for more accurate diagnosis of osteoarthritis over x-ray radiography or DOT alone.
This work presents a pilot study to show the potential of an emerging imaging modality, near-infrared diffuse optical tomography (DOT), for the diagnosis of osteoarthritis (OA). We report quantitative absorption and scattering images of joint tissue that allow for differentiation between diseased and healthy joints. An automatic, multichannel optical imaging system is used to image finger joints from two OA patients and three healthy volunteers. 3-D optical images of the joint tissue are recovered using a finite-element-based reconstruction algorithm. The reconstructed images demonstrate differences in optical properties at the joint region (cartilage/synovial fluid) between the OA and healthy joints. Quantitative analysis from the patients and healthy volunteers also indicate that the recovered joint sizes are consistent with those from x-ray findings. The results of this pilot study show potential for quantitative imaging and diagnosis of early OA by DOT.
We present experimental evidence that the optical absorption coefficient images of heterogeneous media
can be obtained with quantitative photoacoustic tomography (PAT). Photoacoustic images are obtained
from a series of tissue-like phantom experiments using a finite element-based reconstruction algorithm
coupled with a scanning photoacoustic imaging system. The experimental results show that optical
absorption images can be quantitatively reconstructed when the photon diffusion model is coupled with the
Helmholtz photoacoustic wave equation.
The optical and acoustic properties of heterogeneous media are recovered simultaneously
using finite element-based reconstruction algorithm coupled with a scanning photoacoustic
imaging system. The results show that the images obtained are quantitative in terms of the
shape, size, location and optical and acoustic properties of the heterogeneities examined.
In this report, a phase-contrast diffuse optical tomography system, which can measure the refractive indices
of human breast masses in vivo, is described. To investigate the utility of phase-contrast diffuse optical
tomography (PCDOT) for differentiation of malignant and benign breast masses in humans, and to compare
PCDOT with conventional diffuse optical tomography (DOT) for analysis of breast masses in humans. 35
breast masses were imaged in 33 patients (mean age = 51 years; range 22-80 years) using PCDOT. Images
characterizing the tissue refractive index, absorption and scattering of breast masses were obtained with a
finite element-based reconstruction algorithm. The accuracies of absorption and scattering images were
compared with images of refractive index in light of the pathology results. Absorption and scattering images
were unable to accurately discriminate benign from malignant lesions. Malignant lesions tended to have
decreased refractive index allowing them to discriminate from benign lesions in most cases. The sensitivity,
specificity, false positive value, and overall accuracy for refractive index were 81.8%, 70.8%, 29.2%, and
74.3%, respectively. Overall we show that benign and malignant breast masses in humans demonstrate
different refractive index and differences in refractive index properties can be used to discriminate benign
from malignant masses in patients with high accuracy. This opens up a new avenue for improved breast
cancer detection using NIR diffusing light.
Osteoarthritis (OA), characterized by the damage of the articular cartilage, is the most common joint problem worldwide.
In the effort of developing new clinical tools with the potential to alter the natural history of OA, near-infrared diffuse
optical tomography (DOT) has received much attention due to its unique advantages. For optical imaging in highly
heterogeneous media such as the finger joints, prior information could improve the quality of optical imaging. We report
a hybrid imaging system for early detection of OA in the finger joints by imposing the geometry information obtained by
X-ray on three-dimensional near-infrared DOT. X-ray tomosynthesis was employed to recover the three-dimensional
structure of the two bones based on 16 X-ray projections generated with a mini C-arm system at different directions
within a range of 180 degrees. The interface was carefully designed to guarantee an accurate co-registration of the
optical and x-ray modalities. The prior structural information of bones was incorporated into our multi-modality imaging
reconstruction algorithm to enhance the recovery of the optical properties of joint tissues. Several healthy and OA finger
joints were examined. The initial clinical results showed that this hybrid imaging system had the ability to provide much
enhanced image resolution and contrast than DOT alone for OA detection.
This paper put forward the conception of Sub-wavelength Micro-structure Film (SMF) firstly. The light transmission in multi-step SMF is then treated using vector theory. Eigen functions are expressed conveniently by piece-wise elementary functions instead of infinite series, making it both fast and accurate in solving eigen equations. Matrixes of mode conversion, reflection coefficients and transmission coefficients are introduced to obtain the electromagnetic wave amplitude matrix in each layer. A fast and steady recurrent formula to calculate the amplitude coefficient matrix is obtained by matching the modes. Rates of transmission and reflection of all the diffraction orders are therefore obtained for incident light wave of arbitrary polarization. The amounts of computer calculation are drastically decreased by using the method based on this paper. The program is steady and reliable and is implementable on PC. And, the program can treat the light transmission in multi-step SMF fast. Therefore, a fast, accurate, steady and simple algorithm is provided to design SMF elements with various particular properties.
In this paper, the special property of polarization- splitting of groove phase gratings with subwavelength structures is investigated by mode-matching method. For suitable parameters such as period, groove depth and filling factor, the gratings are be high-reflective for TE polarization and antireflective (high-transmissive) for TM polarization. Two linear polarized normal incident lights of different wavelengths are split whether their polarization directions are perpendicular or parallel. For unpolarized monochromatic incident light, linear polarized lights are obtained in both reflection and transmission. Loss of energy is maximally avoided.
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