| 1. |
- Saager, Rolf B., 1974-, et al.
(författare)
-
From theory to practice : the broadening role of polydimethylsiloxane phantoms as an intermediary between model validation and instrument performance testing (Conference Presentation)
- 2016
-
Ingår i: Proceedings Volume 9700, Design and Quality for Biomedical Technologies IX; 97000G (2016). - : SPIE - International Society for Optical Engineering.
-
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.
|
|
| 2. |
- Ponticorvo, Adrien, et al.
(författare)
-
Quantitative long term measurements of burns in a rat model using spatial frequency domain imaging and laser speckle imaging (Conference Presentation)
- 2016
-
Ingår i: Proceedings Volume 9711, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues IX; 971102 (2016). - : SPIE - International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- The ability to accurately assess burn wound severity in a timely manner is a critical component of wound management as it dictates the course of treatment. While full thickness and superficial burns can be easily diagnosed through visual inspection, burns that fall in between these categories are difficult to classify. Additionally, the ability to better quantify different stages of wound healing from a burn of any severity would be important for evaluating the efficacy of different treatment options. Here we present a longitudinal (28 day) study that employs spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI) as non-invasive technologies to characterize in-vivo burn wounds and healing in a murine model. Burn wounds were created using an established technique of a brass comb heated to a given temperature and applied for a set amount of time. They were imaged immediately after the initial injury and then at 2, 4, 7, 14, 21, and 28 days following the injury. Biopsies were taken on the day of the injury in order to verify the extent of the burn damage as well as at different time points after the injury in order to visualize different stages of inflammation and healing. The results of this study suggest that the reduced scattering coefficient measured using SFDI and blood flow as measured using LSI have the potential to provide useful metrics for quantifying the severity of burn injuries as well as track the different stages associated with wound healing progression.
|
|
| 3. |
- Saager, Rolf B., 1974-, et al.
(författare)
-
In vivo isolation of the effects of melanin from underlying hemodynamics across skin types using spatial frequency domain spectroscopy
- 2016
-
Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 21:5
-
Tidskriftsartikel (refereegranskat)abstract
- Skin is a highly structured tissue, raising concerns as to whether skin pigmentation due to epidermal melanin may confound accurate measurements of underlying hemodynamics. Using both venous and arterial cuff occlusions as a means of inducing differential hemodynamic perturbations, we present analyses of spectra limited to the visible or near-infrared regime, in addition to a layered model approach. The influence of melanin, spanning Fitzpatrick skin types I to V, on underlying estimations of hemodynamics in skin as interpreted by these spectral regions are assessed. The layered model provides minimal cross-talk between melanin and hemodynamics and enables removal of problematic correlations between measured tissue oxygenation estimates and skin phototype.
|
|
| 4. |
- Saager, Rolf B., 1974-, et al.
(författare)
-
Low-cost tissue simulating phantoms with adjustable wavelength-dependent scattering properties in the visible and infrared ranges
- 2016
-
Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 21:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present a method for low-cost fabrication of polydimethylsiloxane (PDMS) tissue simulating phantoms with tunable scattering spectra, spanning visible, and near-infrared regimes. These phantoms use optical polishing agents (aluminum oxide powders) at various grit sizes to approximate in vivo tissue scattering particles across multiple size distributions (range: 17 to 3 μm). This class of tunable scattering phantoms is used to mimic distinct changes in wavelength-dependent scattering properties observed in tissue pathologies such as partial thickness burns. Described by a power-law dependence on wavelength, the scattering magnitude of these phantoms scale linearly with particle concentration over a physiologic range [μ's=(0.5 to 2.0 mm−1)] whereas the scattering spectra, specific to each particle size distribution, correlate to distinct exponential coefficients (range: 0.007 to 0.32). Aluminum oxide powders used in this investigation did not detectably contribute to the absorption properties of these phantoms. The optical properties of these phantoms are verified through inverse adding-doubling methods and the tolerances of this fabrication method are discussed.
|
|
| 5. |
- Saager, Rolf B., 1974-, et al.
(författare)
-
Low-cost tissue simulating phantoms with tunable, wavelength-dependent scattering properties (Conference Presentation)
- 2016
-
Ingår i: Proceedings Volume 9700, Design and Quality for Biomedical Technologies IX; 970005 (2016). - : SPIE - International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- Tissue-simulating phantoms provide the opportunity to evaluate the performance of optical and spectroscopic instruments under controlled experimental conditions. Recent efforts have advanced phantom fabrication methods to provide more tissue realistic phantoms, both in terms of a) incorporating absorbing agents that more faithfully mimic in vivo tissue chromophores spanning visible and near infrared regimes and b) accounting for multi-layer tissue structures with distinct optical properties. The spectral scattering properties in these phantoms, however, are typically based only on a single scattering agent, thereby locking the spectral scattering properties to a single particle size distribution. However, in both healthy tissue as well as pathologic tissue, regions of distinct and differentiated scattering may be present. With differing mean size and distribution of scattering objects in these tissue regions, the relative wavelength-dependent scattering spectra may vary. For example, partial thickness burns exhibit significant cellular damage and collagen denaturation that will significantly alter the wavelength-dependent scattering properties resembling large Mie-like scatterer distributions in both visible and near infrared regimes. We present a low-cost method to fabricate silicone tissue-simulating phantoms with tunable scattering spectra properties that span visible and near infrared wavelengths. We use optical polishing agents (white aluminum oxides powders) at various grit sizes to approximate Mie scattering across multiple mean particle sizes. Mean particle sizes used in this study range from 17-3 micron. The optical properties of these phantoms are verified using an integrating sphere in combination with inverse adding-doubling methods. The tolerances of this fabrication method will be discussed.
|
|
| 6. |
- Vasefi, Fartash, et al.
(författare)
-
Multimode optical dermoscopy (SkinSpect) analysis for skin with melanocytic nevus
- 2016
-
Ingår i: Proceedings Volume 9711, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues IX; 971110 (2016). - : SPIE - International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- We have developed a multimode dermoscope (SkinSpect™) capable of illuminating human skin samples in-vivo with spectrally-programmable linearly-polarized light at 33 wavelengths between 468nm and 857 nm. Diffusely reflected photons are separated into collinear and cross-polarized image paths and images captured for each illumination wavelength. In vivo human skin nevi (N = 20) were evaluated with the multimode dermoscope and melanin and hemoglobin concentrations were compared with Spatially Modulated Quantitative Spectroscopy (SMoQS) measurements. Both systems show low correlation between their melanin and hemoglobin concentrations, demonstrating the ability of the SkinSpect™ to separate these molecular signatures and thus act as a biologically plausible device capable of early onset melanoma detection.
|
|
| 7. |
- Vasefi, Fartash, et al.
(författare)
-
Separating melanin from hemodynamics in nevi using multimode hyperspectral dermoscopy and spatial frequency domain spectroscopy
- 2016
-
Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 21:11
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in the pattern and distribution of both melanocytes (pigment producing) and vasculature (hemoglobin containing) are important in distinguishing melanocytic proliferations. The ability to accurately measure melanin distribution at different depths and to distinguish it from hemoglobin is clearly important when assessing pigmented lesions (benign versus malignant). We have developed a multimode hyperspectral dermoscope (SkinSpect™) able to more accurately image both melanin and hemoglobin distribution in skin. SkinSpect uses both hyperspectral and polarization-sensitive measurements. SkinSpect’s higher accuracy has been obtained by correcting for the effect of melanin absorption on hemoglobin absorption in measurements of melanocytic nevi. In vivo human skin pigmented nevi (N=20) were evaluated with the SkinSpect, and measured melanin and hemoglobin concentrations were compared with spatial frequency domain spectroscopy (SFDS) measurements. We confirm that both systems show low correlation of hemoglobin concentrations with regions containing different melanin concentrations (R=0.13 for SFDS, R=0.07 for SkinSpect).
|
|
