Investigation of tissue optics requires accurate values of the bulk optical parameters: the scattering coefficient μs, absorption coefficient μa, anisotropy factor g and the real refractive index nr. We employed a coherent reflectance curve method to determine the refractive index of fresh porcine skin dermis at 8 wavelengths between 325 and 1557nm. The surface profiles of fresh dermis samples were measured with a non-contact method of confocal imaging and the roughness parameters were extracted. To determine tissue optical parameters, a single integrating sphere was used to measure the diffused reflectance and transmittance with slab samples of fresh porcine skin dermis. Collimated transmittance was measured with the samples in situ using a spatial filtering setup. Based on these results, a Monte Carlo code capable of handling surface roughness of the tissue sample has been developed and used to inversely determine the bulk values of μs, μa and g at the 8 wavelengths which are significantly different from the reported values.
This paper presents an image analysis method based on a short-time-Fourier-transform (STFT) for extracting the size of polystyrene microspheres with different nominal diameters from diffraction images obtained with a newly developed diffraction imaging flow cytometer. The center frequency of STFT and its relation with the image row index are explored to extract the microspheres' diameter. We have shown that the STFT based method provides a new and rapid method for determination of microsphere sizes and their distribution using the diffraction imaging flow cytometer.
We constructed an automated reflectometry system for accurate measurement of coherent reflectance curves of turbid samples and analyzed the presence of coherent and diffuse reflection near the specular reflection angle. An existing method has been validated to determine the complex refractive indices of turbid samples on the basis of nonlinear regression of the coherent reflectance curves by Fresnel's equations. The complex refractive indices of fresh porcine skin epidermis and dermis tissues and Intralipid solutions were determined at eight wavelengths: 325, 442, 532, 633, 850, 1064, 1310, and 1557 nm.
An imaging based method has been investigated for the determination of spatial distribution of the optical parameters of a heterogeneous medium by comparing reflectance images with full-field illumination from Monte Carlo simulations and phantom measurements.
Direct flow measurement in native epicardial coronary arteries, bypass conduits, and anastomoses is severely limited by the invasiveness and inaccuracy of existing technologies. As a result, less than 25% of patients undergoing coronary artery bypass grafting (CABG) worldwide have any intraoperative evaluation performed. A simple, accurate, and noninvasive technology to directly quantify blood flow and rheology surrounding anastomotic sites is a critical unmet need in CABG.Existing technology limitations drove development of a different technology solution. With an optical physics approach, flow in conduits and tissue can be quantified in real time with nonionizing broad-spectrum imaging as well as temporal and spatial analyses. Cardiac motion, calibration, and combining anatomy + physiology in imaging were challenges requiring solutions.This patented imaging technology was developed and tested in an established porcine cardiac experimental model and in clinical proof-of-concept studies. Flow velocities and flows in epicardial coronary arteries vary physiologically with the cardiac cycle and with acute ischemia, as predicted by previous studies using traditional technologies. Imaging data are captured from a 30-cm viewing distance, analyzed and displayed in real time as a video. The field of view enables capture of flow in the proximal and distal epicardial coronary, the conduit, at the anastomosis and in the distal myocardium simultaneously.Rheologic flow interaction between conduit and native coronary at the anastomosis remains the most poorly understood technical aspect of CABG. A noninvasive, noncontact, no-risk imaging technology as simple as a snapshot can provide this critical physiologic information, validate and document intraoperative quality, and improve even further CABG outcomes.
Noninvasive detection of malignant melanoma in early stages is critical to improve patients’ prognosis. We acquired in vivo reflectance images of dysplastic lesions from 12 patients at 31 wavelengths from 500 to 950 nm. Based on these image data, we developed a parallel Monte Carlo code to simulate reflectance images from a heterogeneous skin tissue model. With this tool, we have investigated the dependence of the lesion contrast in the reflectance image on the heterogeneous distribution of tissue optical parameters. The Monte Carlo model is currently used to generate multispectral reflectance imaging data for multivariate analysis of the in vivo imaging data. DOI: 10.2529/PIERS061020122702 It has been estimated that Caucasians may develop up to 50 clinically benign nevi by age 40. Patients with more than 100 nevi were estimated to have a 3-fold to 10-fold increased risk of developing malignant melanomas and pigmented basal cell carcinomas in comparison to the general population [1]. Diagnosis of MM is currently established by histopathology of biopsied tissues from the suspicious-appearing nevi or pigmented lesions. These patients often present a difficult dilemma to primary-care physicians and dermatologists. A physician has to either prescribe painful and costly excision biopsy with likely cosmetic disfigurement with limited information on the lesion or leave untouched with the risk of MM developing in the patients. Therefore, cost-effective pre-biopsy methods of examination could greatly improve patient care and reduce medical cost with better specificity and sensitivity than what are available now. In this report, we present multispectral reflectance image data acquired from 12 patients with dysplastic lesions at 31 wavelengths from 500 to 950 nm and results of numerical studies of reflectance imaging method by a Monte Carlo (MC) code. A multispectral imaging system employing a thermoelectrically cooled CCD camera has been constructed to acquire polarimetric images [2]. Fig. 1 presents a schematic of the imaging system. We used a xenon fiber optic light source and a collimating lens to produce a parallel light beam of
The problem of determining optical parameters from one reflectance image has been solved for homogeneous tissue phantoms within the radiative transfer theory. We further extend this method for depth-resolving in heterogeneous phantoms of pigmented lesions.
We introduce an inverse method for determining simultaneously the real and imaginary refractive indices of microspheres based on integrating sphere measurements of diffuse reflectance and transmittance, and Monte Carlo modelling in conjunction with the Mie theory. The results for polystyrene microspheres suspended in water are presented.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)