| 1. |
- Nguyen, John Quan, et al.
(författare)
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Effects of motion on optical properties in the spatial frequency domain
- 2011
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Ingår i: Journal of Biomedical Optics. - : OSA Publishing. - 1083-3668 .- 1560-2281. ; 16:12, s. 126009-1-126009-9
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Tidskriftsartikel (refereegranskat)abstract
- Spatial frequency domain imaging (SFDI) is a noncontact and wide-field optical imaging technology currently being used to study the optical properties and chromophore concentrations of in vivo skin including skin lesions of various types. Part of the challenge of developing a clinically deployable SFDI system is related to the development of effective motion compensation strategies, which in turn, is critical for recording high fidelity optical properties. Here we present a two-part strategy for SFDI motion correction. After verifying the effectiveness of the motion correction algorithm on tissue-simulating phantoms, a set of skin-imaging data was collected in order to test the performance of the correction technique under real clinical conditions. Optical properties were obtained with and without the use of the motion correction technique. The results indicate that the algorithm presented here can be used to render optical properties in moving skin surfaces with fidelities within 1.5% of an ideal stationary case and with up to 92.63% less variance. Systematic characterization of the impact of motion variables on clinical SFDI measurements reveals that until SFDI instrumentation is developed to the point of instantaneous imaging, motion compensation is necessary for the accurate localization and quantification of heterogeneities in a clinical setting.
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| 2. |
- Nguyen, John Quan, et al.
(författare)
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Motion correction in spatial frequency domain imaging$\mathsemicolon$ optical property determination in pigmented lesions
- 2011
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Ingår i: Proceedings Volume 7883 SPIE BIOS, 22-27 JANUARY 2011 Photonic Therapeutics and Diagnostics VII. - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)abstract
- Background and Objective: Spatial Frequency Domain Imaging (SFDI) is a non-contact wide-field optical imaging technology currently being used to study the optical properties and chromophore concentrations of in-vivo malignant melanomas and benign pigmented lesions. Our objective is to develop a motion correction procedure in order to assess the concerns of subject-motion related variables during clinical measurements.Study Design/Materials and Methods: SFDI motion-correction is a two-part procedure which utilizes a fiduciary marker and canny-edge detection in order to reposition and align the frame-to-frame regions-of-interest (ROI). Motioninduced phase-shifts are subsequently sampled before the entire image-set is processed by a modified demodulation formula. By comparing the results of the adjusted processing method with data gathered from the current non-corrected method, we were able to systematically characterize the impact of motion variables on SFDI measurements.Results: Motion-corrected SFDI data from moving phantom measurements and clinical patient measurements showed up to 84.58% decrease in absorption (μa) variance and up to 92.63% decrease in reduced-scattering (μs') variance. Stationary phantom test-measurements showed almost no difference between motion corrected and standard processing. Conclusion: SFDI motion correction is necessary for obtaining high-fidelity in-vivo optical property measurements of pigmented lesions in a clinical setting.
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| 3. |
- Saager, Rolf B., 1974-, et al.
(författare)
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Method for depth-resolved quantitation of optical properties in layered media using spatially modulated quantitative spectroscopy
- 2011
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Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 16:7
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated that spatially modulated quantitative spectroscopy (SMoQS) is capable of extracting absolute optical properties from homogeneous tissue simulating phantoms that span both the visible and near-infrared wavelength regimes. However, biological tissue, such as skin, is highly structured, presenting challenges to quantitative spectroscopic techniques based on homogeneous models. In order to more accurately address the challenges associated with skin, we present a method for depth-resolved optical property quantitation based on a two layer model. Layered Monte Carlo simulations and layered tissue simulating phantoms are used to determine the efficacy and accuracy of SMoQS to quantify layer specific optical properties of layered media. Initial results from both the simulation and experiment show that this empirical method is capable of determining top layer thickness within tens of microns across a physiological range for skin. Layer specific chromophore concentration can be determined to <±10% the actual values, on average, whereas bulk quantitation in either visible or near infrared spectroscopic regimes significantly underestimates the layer specific chromophore concentration and can be confounded by top layer thickness.
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| 4. |
- Saager, Rolf B., 1974-, et al.
(författare)
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Quantitative fluorescence imaging of protoporphyrin IX through determination of tissue optical properties in the spatial frequency domain
- 2011
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Ingår i: Journal of Biomedical Optics. - : OSA Publishing. - 1083-3668 .- 1560-2281. ; 16:12, s. 126013-1-126013-5
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Tidskriftsartikel (refereegranskat)abstract
- The ability to quantitatively determine tissue fluorescence is of interest for the purpose of better understanding the details of photodynamic therapy of skin cancer. In particular, we are interested in quantifying protoporphyrin IX (PpIX) in vivo. We present a method of correcting fluorescence for effects of native tissue absorption and scattering properties in a spatially resolved manner that preserves the resolution of the fluorescence imaging system, based off a homogeneous representation of tissue. Validation was performed using a series of liquid turbid phantoms having varying concentrations of absorber, scatterer, and fluorophore (PpIX). Through the quantification of tissue optical properties via spatial frequency domain imaging, an empirical model based on Monte Carlo simulations was deployed to successfully decouple the effects of absorption and scattering from fluorescence. From this we were able to deduce the concentration of the PpIX to within 0.2 μg/ml of the known concentration. This method was subsequently applied to the determination of PpIX concentration from in vivo normal skin where the model-based correction determined a concentration of 1.6 μg/ml, which is in agreement with literature.
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| 5. |
- Yafi, Amr, et al.
(författare)
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Postoperative Quantitative Assessment of Reconstructive Tissue Status in a Cutaneous Flap Model Using Spatial Frequency Domain Imaging
- 2011
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Ingår i: Plastic and reconstructive surgery (1963). - : Ovid Technologies (Wolters Kluwer Health). - 0032-1052 .- 1529-4242. ; 127:1, s. 117-130
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Tidskriftsartikel (refereegranskat)abstract
- Background:The purpose of this study was to investigate the capabilities of a novel optical wide-field imaging technology known as spatial frequency domain imaging to quantitatively assess reconstructive tissue status.Methods:Twenty-two cutaneous pedicle flaps were created on 11 rats based on the inferior epigastric vessels. After baseline measurement, all flaps underwent vascular ischemia, induced by clamping the supporting vessels for 2 hours (either arteriovenous or selective venous occlusions); normal saline was injected into the control flap and hypertonic-hyperoncotic saline solution was injected into the experimental flap. Flaps were monitored for 2 hours after reperfusion. The spatial frequency domain imaging system was used for quantitative assessment of flap status over the duration of the experiment.Results:All flaps demonstrated a significant decline in oxyhemoglobin and tissue oxygen saturation in response to occlusion. Total hemoglobin and deoxyhemoglobin were increased markedly in the selective venous occlusion group. After reperfusion and the administration of solutions, oxyhemoglobin and tissue oxygen saturation in those flaps that survived gradually returned to baseline levels. However, flaps for which oxyhemoglobin and tissue oxygen saturation did not show any signs of recovery appeared to be compromised and eventually became necrotic within 24 to 48 hours in both occlusion groups.Conclusions:Spatial frequency domain imaging technology provides a quantitative, objective method of assessing tissue status. This study demonstrates the potential of this optical technology to assess tissue perfusion in a very precise and quantitative way, enabling wide-field visualization of physiologic parameters. The results of this study suggest that spatial frequency domain imaging may provide a means for prospectively identifying dysfunctional flaps well in advance of failure.
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