Properties of photon density waves in multiple-scattering media.

Applied Optics (Impact Factor: 1.69). 02/1993; 32(4):607-16. DOI: 10.1364/AO.32.000607
Source: PubMed

ABSTRACT Amplitude-modulated light launched into multiple-scattering media, e.g., tissue, results in the propagation of density waves of diffuse photons. Photon density wave characteristics in turn depend on modulation frequency (omega) and media optical properties. The damped spherical wave solutions to the homogeneous form of the diffusion equation suggest two distinct regimes of behavior: (1) a high-frequency dispersion regime where density wave phase velocity V(p) has a radicalomega dependence and (2) a low-frequency domain where V(p), is frequency independent. Optical properties are determined for various tissue phantoms by fitting the recorded phase (?) and modulation (m) response to simple relations for theappropriate regime. Our results indicate that reliable estimates of tissue like optical properties can be obtained, particularly when multiple modulation frequencies are employed.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Instrument equivalence and quality control are critical elements of multi-center clinical trials. We currently have five identical Diffuse Optical Spectroscopic Imaging (DOSI) instruments enrolled in the American College of Radiology Imaging Network (ACRIN, #6691) trial located at five academic clinical research sites in the US. The goal of the study is to predict the response of breast tumors to neoadjuvant chemotherapy in 60 patients. In order to reliably compare DOSI measurements across different instruments, operators and sites, we must be confident that the data quality is comparable. We require objective and reliable methods for identifying, correcting, and rejecting low quality data. To achieve this goal, we developed and tested an automated quality control algorithm that rejects data points below the instrument noise floor, improves tissue optical property recovery, and outputs a detailed data quality report. Using a new protocol for obtaining dark-noise data, we applied the algorithm to ACRIN patient data and successfully improved the quality of recovered physiological data in some cases.
    Conference on Optical Tomography and Spectroscopy of Tissue X; 03/2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Noninvasive measurement of hemodynamics at the microvascular level may have a great impact on oncology in clinics for diagnosis, therapy planning and monitoring, and, in preclinical studies. To this end, diffuse optics is a strong candidate for noninvasive, repeated, deep tissue monitoring. In this multi-disciplinary, translational work, I have constructed and deployed hybrid devices which are the combination of two qualitatively different methods, near infrared diffuse optical spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS), for simultaneous measurement of microvascular total hemoglobin concentration, blood oxygen saturation and blood flow. In a preclinical study, I applied the hybrid device to monitor the response of renal cell carcinoma in mice to antiangiogenic therapy. The results suggest that we can predict the output of therapy from early hemodynamic changes, which provide us with valuable information for better understanding of the tumor resistance mechanism to antiangiogenic therapies. In two in vivo studies in human volunteers, I have developed protocols and probes to demonstrate the feasibility of noninvasive diffuse optical spectroscopy to investigate the pathophysiology of bone. First study was study on the physiology of the patella microvasculature, the other introduced the manubrium as a site that is rich in red bone mar- row and accessible to diffuse optics as a potential window to monitor the progression of hematological malignancies. Overall, during my Ph.D., I have developed instrumentation, algorithms and protocols and, then, applied this technique for preclinical and clinical investigations. My research is a link between preclinical and clinical studies and it opens new areas of applications in oncology.
    01/2014, Degree: PhD, Supervisor: Turgut Durduran
  • [Show abstract] [Hide abstract]
    ABSTRACT: We review research on time-resolved optical imaging of objects hidden in strongly scattering media, with emphasis on the application to breast cancer detection. A method is presented to simulate the propagation of light in turbid media. Based on a numerical algorithm to solve the time-dependent diffusion equation, the method takes into account spatial variations of the reduced scattering and absorption factors of the medium due to the presence of objects as well as random fluctuations of these factors. It is shown that the simulation method reproduces, without fitting, experimental results on tissue-like phantoms. Using experimental and simulation results, an assessment is made of the reliability for extracting the reduced scattering and absorption coefficients of the medium from time-resolved reflection and transillumination data. The simulation technique is employed to study the conditions for locating mm-sized objects immersed in a turbid medium, by direct, time-resolved imaging. We discuss a simple method to enhance the imaging power of the time-resolved technique. The mathematical justification of the method, as well as some applications to simple problems, is given. The simulation technique is employed to demonstrate the effectiveness of the data processing technique. Results of time-resolved reflection experiments and simulations are presented, showing that the use of the latter allow us to locate 1 mm diameter objects under conditions which would prevent detection otherwise. Our results demonstrate that the combination of simulation and the appropriate processing of the diffusive part of the time-resolved reflected or transmitted light intensity may substantially increase the potential of the time-resolved near-infrared diffusive light imaging technique as a diagnostic tool for breast cancer detection.
    Physics Reports 01/1998; 304(3). DOI:10.1016/S0370-1573(98)00023-4 · 22.91 Impact Factor

Full-text (2 Sources)

Available from
Apr 1, 2015