Diffuse optical tomography (DOT) images the distribution of the optical properties, such as the absorption and scattering coefficients, via the image reconstruction from the light intensities measured at the surface of the biological medium. The changes in the optical properties reflect the conditions of the tissues. Therefore, DOT image can provide the information which is not obtained from the other modalities and is useful for medical diagnoses. In this study, the application of the DOT to thyroid cancer diagnosis was investigated. The ultrasound technique is usually carried out for the thyroid cancer diagnosis. It is, however, difficult to distinguish follicular carcinoma from adenoma of thyroid. The optical properties may be helpful for the diagnosis. The image reconstruction algorithm employing the regularization minimizing lp-norm (0 < p < 2) of the reconstructed image was developed. The image was reconstructed from the timeresolved measurement data. The numerical simulations of the image reconstruction were tried. The numerical simulation demonstrated that the developed algorithm was able to image the changes in the optical properties in the medium. Additionally, the image reconstruction of the numerical neck phantom was simulated. The thyroid cancer region was reconstructed successfully. It was demonstrated that the developed algorithm had the possibility to image thyroid cancer.
An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product; then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis.
Development of a physically accurate and computationally efficient photon migration model for turbid media is
crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper
constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation.
In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive
regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency
of computation. The coupling model provides an accurate description of the photon migration in various turbid
media in a wide range of the optical properties, and reduces computational loads when compared with those of
full calculation of the RTE.
Accurate modeling and efficient calculation of photon migration in biological tissues is requested for determination of the optical properties of living tissues by invivo experiments. This study develops a calculation scheme of photon migration for determination of the optical properties of the rat cerebral cortex (ca 0.2 cm thick) based on the three-dimensional time-dependent radiative transport equation assuming a homogeneous object. It is shown that the time-resolved profiles calculated by the developed scheme agree with the profiles measured by invivo experiments using near infrared light. Also, an efficient calculation method is tested using the delta-Eddington approximation of the scattering phase function.
For improvement of diffuse optical tomography, one needs a numerical model to compute photon propagation accurately and efficiently. Thus, in the paper, we construct a hybrid model based on the radiative transfer equation (RTE) and diffusion equation (DE) in the time domain under the refractive-index-mismatching at boundary. At first, a fictive interface between the RTE and DE regions is determined, which is characterized by a length scale ρDA. By comparing the fluence rate calculated based on the RTE to that on the DE, we estimate ρDA at ~10/μt, where μt denotes the extinction coefficient. Next, we determine a coefficient representing the reflectivity in the Robin boundary condition of the DE by analyzing the fluence rates in the domain outside ρDA. Then, the hybrid model is constructed by using the determinations. The fluence rates based on this hybrid algorithm is consistent with those on the RTE in a whole range of the medium and computational costs are reduced efficiently.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.