| 1. |
- Moy, Austin J., et al.
(författare)
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Optical properties of mouse brain tissue after optical clearing with FocusClear™
- 2015
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Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 20:9
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence microscopy is commonly used to investigate disease progression in biological tissues. Biological tissues, however, are strongly scattering in the visible wavelengths, limiting the application of fluorescence microscopy to superficial (<200 μm) regions. Optical clearing, which involves incubation of the tissue in a chemical bath, reduces the optical scattering in tissue, resulting in increased tissue transparency and optical imaging depth. The goal of this study was to determine the time- and wavelength-resolved dynamics of the optical scattering properties of rodent brain after optical clearing with FocusClear™. Light transmittance and reflectance of 1-mm mouse brain sections were measured using an integrating sphere before and after optical clearing and the inverse adding doubling algorithm used to determine tissue optical scattering. The degree of optical clearing was quantified by calculating the optical clearing potential (OCP), and the effects of differing OCP were demonstrated using the optical histology method, which combines tissue optical clearing with optical imaging to visualize the microvasculature. We observed increased tissue transparency with longer optical clearing time and an analogous increase in OCP. Furthermore, OCP did not vary substantially between 400 and 1000 nm for increasing optical clearing durations, suggesting that optical histology can improve ex vivo visualization of several fluorescent probes.
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| 2. |
- 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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| 3. |
- 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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| 4. |
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| 5. |
- Saager, Rolf B., 1974-, et al.
(författare)
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From theory to practice : the broadening role of polydimethylsiloxane phantoms as an intermediary between model validation and instrument performance testing (Conference Presentation)
- 2016
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Ingår i: Proceedings Volume 9700, Design and Quality for Biomedical Technologies IX; 97000G (2016). - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)abstract
- Polydimethylsiloxane (PDMS) has been a popular medium to fabricate tissue simulating optical phantoms. Recently, its use has significantly expanded in instrument calibration and performance testing, validation of advanced models of light transport of complex tissue geometries and evaluation of novel measurement modalities. To meet these demands, fabrication methods of these optical phantoms have become more refined and its structure and constituent components (i.e. dyes and scattering agents) have evolved to better mimic optical properties of tissue spanning both visible and near infrared regimes. We present efforts at the Beckman Laser Institute that address these challenges through PDMS phantoms.
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| 6. |
- Saager, Rolf B., 1974-, et al.
(författare)
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Impact of hemoglobin breakdown products in the spectral analysis of burn wounds using spatial frequency domain spectroscopy
- 2019
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Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 24:2
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Tidskriftsartikel (refereegranskat)abstract
- Burn wounds and wound healing invoke several biological processes that may complicate the interpretation of spectral imaging data. Through analysis of spatial frequency domain spectroscopy data (450 to 1000 nm) obtained from longitudinal investigations using a graded porcine burn wound healing model, we have identified features in the absorption spectrum that appear to suggest the presence of hemoglobin breakdown products, e.g., methemoglobin. Our results show that the calculated concentrations of methemoglobin directly correlate with burn severity, 24 h after the injury. In addition, tissue parameters such as oxygenation (StO2) and water fraction may be underestimated by 20% and 78%, respectively, if methemoglobin is not included in the spectral analysis.
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| 7. |
- Saager, Rolf B., 1974-, et al.
(författare)
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In vivo measurements of cutaneous melanin across spatial scales : using multiphoton microscopy and spatial frequency domain spectroscopy
- 2015
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Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 20:6
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Tidskriftsartikel (refereegranskat)abstract
- The combined use of nonlinear optical microscopy and broadband reflectance techniques to assess melanin concentration and distribution thickness in vivo over the full range of Fitzpatrick skin types is presented. Twelve patients were measured using multiphoton microscopy (MPM) and spatial frequency domain spectroscopy (SFDS) on both dorsal forearm and volar arm, which are generally sun-exposed and non-sun-exposed areas, respectively. Both MPM and SFDS measured melanin volume fractions between ∼5% (skin type I non-sun-exposed) and 20% (skin type VI sun exposed). MPM measured epidermal (anatomical) thickness values ∼30–65 μm, while SFDS measured melanin distribution thickness based on diffuse optical path length. There was a strong correlation between melanin concentration and melanin distribution (epidermal) thickness measurements obtained using the two techniques. While SFDS does not have the ability to match the spatial resolution of MPM, this study demonstrates that melanin content as quantified using SFDS is linearly correlated with epidermal melanin as measured using MPM (R2=0.8895). SFDS melanin distribution thickness is correlated to MPM values (R2=0.8131). These techniques can be used individually and/or in combination to advance our understanding and guide therapies for pigmentation-related conditions as well as light-based treatments across a full range of skin types.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Torabzadeh, Mohammad, et al.
(författare)
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hyperspectral characterization of tissue simulating phantoms using a supercontinuum laser in a spatial frequency domain imaging instrument
- 2018
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Ingår i: Proceedings Volume 10486, Design and Quality for Biomedical Technologies XI; 104860G (2018). - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)abstract
- Hyperspectral Imaging (HSI) is a growing field in tissue optics due to its ability to collect continuous spectral features of a sample without a contact probe. Spatial Frequency Domain Imaging (SFDI) is a non-contact wide-field spectral imaging technique that is used to quantitatively characterize tissue structure and chromophore concentration. In this study, we designed a Hyperspectral SFDI (H-SFDI) instrument which integrated a supercontinuum laser source to a wavelength tuning optical configuration and a sCMOS camera to extract spatial (Field of View: 2cm×2cm) and broadband spectral features (580nm-950nm). A preliminary experiment was also performed to integrate the hyperspectral projection unit to a compressed single pixel camera and Light Labeling (LiLa) technique.
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