This work demonstrates a non-contact diffuse reflectance approach with a working distance of ~1.1... more This work demonstrates a non-contact diffuse reflectance approach with a working distance of ~1.1 meters for the potential of glucose sensing. Non-contact diffuse reflectance over 1.1-1.3 µm was developed according to a center-illumination-area-detection (CIAD) geometry. The modeled response of diffuse reflectance in the CIAD geometry was examined with phantoms by altering independently the size of the collection geometry and the reduced scattering and absorption properties of the medium. When applied to aqueous turbid medium containing glucose control solutions with the cumulative volume varying over three orders of magnitude, a linear relationship expected for the diffuse reflectance as a function of the medium absorption/reduced-scattering property was observed for four conditions of the glucose-medium composition that differed either in the effective glucose concentration or the host medium scattering property. The cumulation of glucose up to 17.8mg/dL and 8.9mg/dL in the host medium having the same optical properties resulted in linear regression slopes of 0.0032 and 0.0030, respectively. The cumulation of the glucose up to 17.8mg/dL in an aqueous host medium that differed two folds in the reduced scattering property caused the linear regression slope to differ between 0.0032 and 0.0019. The R 2 values of all cases were all greater than 0.987.
The clinical prospect of treating spinal cord injury by photobiomodulation therapy (PBMT) is uncl... more The clinical prospect of treating spinal cord injury by photobiomodulation therapy (PBMT) is unclear as the spinal dosimetry of transcutaneous laser application is unknown, yet essential for clinical recommendations. Light irradiances at 9 sites over an 8cm length along the thoracic to lumbar segment of the spinal canal were measured in 6 cadaver dogs using a flexible intra-spinal probe, under a surface irradiance of 3.14W/cm2. The skin transmits 4-12% of 980nm PBMT light. On-contact technique is ~5 times more efficient than off-contact technique. Transcutaneous transmission of photobiomodulatory irradiance to the spinal canal will benefit from contact-probe technique and skin-clearing approaches.
We present a model regarding laparoscopic detectability of a long absorbing tubular inclusion par... more We present a model regarding laparoscopic detectability of a long absorbing tubular inclusion parallel to the medium surface and bisecting the source-detector-pair. The model agrees with measurements in an aqueous medium using a 10mm probe.
We demonstrate diffuse reflectance spectroscopy (DRS) of a subsurface tubular inclusion by using ... more We demonstrate diffuse reflectance spectroscopy (DRS) of a subsurface tubular inclusion by using a fiber probe having a single source-detector pair attached to a laparoscopic bipolar device. A forward model was also developed for DRS sensing of an underlying long absorbing tubular inclusion set in parallel to the tissue surface, normal to the line of sight of the source-detector pair, and equidistant from the source and the detector. The model agreed with measurements performed at 500 nm and using a 10 mm source-detector separation (SDS) on an aqueous tissue phantom embedding a tubing of 2 or 4 mm inner diameter that contained 9.1% to 33.3% red dye at a depth of up to 11.5 mm. When tested on solid phantoms using the 10 mm SDS, a tubular inclusion of $ \ge 3\;{\rm mm}$≥3mm inner diameter containing 0.05% red dye at a background absorption coefficient of $ 0.021\;{\rm mm}^{-1} $0.021mm-1 caused $ \ge 8\% $≥8% change of the signal at 500 nm versus the baseline when the inclusion was shallower than 5 mm. When assessed on avian muscle tissue having a 4 mm tubular inclusion embedded at an edge depth of 2 mm, DRS with the 10 mm SDS differentiated the following contents of the inclusion: 33.3% red dye (mimicking blood), 33.3% green dye, 33.3% yellow dye (mimicking bile), water (mimicking urine), and air.
Journal of the Optical Society of America, Jun 29, 2012
Part IV examines frequency-domain photon diffusion in a homogeneous medium enclosed by a "concave... more Part IV examines frequency-domain photon diffusion in a homogeneous medium enclosed by a "concave" circular cylindrical applicator or enclosing a "convex" circular cylindrical applicator, both geometries being infinite in the longitudinal dimension. The aim is to assess by analogical and finite-element methods the changes of AC amplitude, modulation depth, and phase with respect to the line-of-sight source-detector distance for a source and a detector located along the azimuthal or longitudinal direction on the concave or convex medium-applicator interface. By comparing to their counterparts along a straight line on a semi-infinite medium-applicator interface, for the same line-of-sight source-detector distance, it is found that: (1) the decay-rate of AC photon fluence is smaller along the azimuthal direction and greater along the longitudinal direction on the concave interface, (2) the decay-rate of AC photon fluence is greater along the azimuthal direction and smaller along the longitudinal direction on the convex interface, (3) the modulation depth along both azimuthal and longitudinal directions decays more slowly on the concave interface and faster on the convex interface, and (4) the phase along both azimuthal and longitudinal directions increases more slowly on the concave interface and faster on the convex interface.
Abstract Nondestructive tomographic identification of underlying moldy lesions of apple is demons... more Abstract Nondestructive tomographic identification of underlying moldy lesions of apple is demonstrated experimentally, for the first time, by using frequency domain diffuse optical tomography (FD-DOT). The custom applicator-probe had 18 optodes distributed on a spheroid apple-size imaging domain. The 12 source channels were time-multiplexed to a laser source modulated at 110 MHz, and the 6 detector channels were individually conditioned for parallel heterodyning at 10 kHz. The iterative image reconstruction was performed without priors in an open-source finite-element-method (FEM) package with custom meshing of the imaging domain. Cylindrical moldy lesions in apple at controlled center depths ranging from 10 mm to 35 mm were established using 10 mm diameter cylinder inclusions harvested from mildew flesh, and freeform lesions in apple were developed by injecting colonies of Alternaria alternate. The moldy lesions not deeper than 20 mm from the peel were resolvable on the absorption images. The moldy lesions were unremarkable on the reduced scattering images. Contrast-detail-analysis is also performed in simulation to assess the condition of identifying a moldy-core lesion by FD-DOT.
Model approximation is necessary for reflectance assessment of tissue at sub-diffusive to non-dif... more Model approximation is necessary for reflectance assessment of tissue at sub-diffusive to non-diffusive scale. For tissue probing over a sub-diffusive circular area centered on the point of incidence, we demonstrate simple analytical steady-state total diffuse reflectance from a semi-infinite medium with the Henyey-Greenstein (HG) scattering anisotropy (factor $g$g). Two physical constraints are abided to: (1) the total diffuse reflectance is the integration of the radial diffuse reflectance; (2) the radial and total diffuse reflectance at $g \gt {0}$g>0 analytically must resort to their respective forms corresponding to isotropic scattering as $g$g becomes zero. Steady-state radial diffuse reflectance near the point of incidence from a semi-infinite medium of $g \approx 0$g≈0 is developed based on the radiative transfer for isotropic scattering, then integrated to find the total diffuse reflectance for $g \approx 0$g≈0. The radial diffuse reflectance for $g \ge 0.5$g≥0.5 is semi-empirically formulated by comparing to Monte Carlo simulation results and abiding to the second constraint. Its integration leads to a total diffuse reflectance for $g \ge 0.5$g≥0.5 that is also bounded by the second constraint. Over a collection diameter of the reduced-scattering pathlength ($1/\mu _s^{ \prime}$1/μs') scaled size of [${{10}^{ - 5}}$10-5, ${{10}^{ - 1}}$10-1] for $g = [{0.5},{0.95}]$g=[0.5,0.95] and the absorption coefficient as strong as the reduced scattering coefficient, the simple analytical total diffuse reflectance is found to be accurate, with an average error of 16.1%.
The large liver transplant waitlists and increasing of marginal donor organs call for a rapid, no... more The large liver transplant waitlists and increasing of marginal donor organs call for a rapid, non-destructive method of evaluating organ quality for transplantation. We demonstrate a diffuse optical non-destructive organ risk (DONOR) indexing method for identifying significant liver pathology, in particular unacceptable fibrosis and necrosis. Measurements were acquired from 27 human livers not meeting the clinical criteria for transplantation (OUHSC IRB #8155). A portable lab-on-a-crate diffuse optical spectroscopy (DOS) device with a hands-free probe of 3mm source-detector separation was used for measurements on liver surface and cross-section. The DOS measurements were obtained from a total of five sites, including the right anterior, right posterior, and left anterior liver surfaces and the right and left cut sections, and corresponding tissue sections were obtained for formalin-fixed paraffin embedded (FFPE) H&E controls of 8 types of liver pathology. Due to the difficulty of obtaining a control liver, a clinically inconspicuous and histologically unremarkable liver number 24 was used as the baseline for DONOR index processing. For the measurements at the cross-sectional parenchyma of the right lobe alone, a single threshold of the DONOR index at 1.5 identified all six livers with fibrosis stage ≥2 and one liver with necrosis=5, in the presence of mixed pathologies. A prime pattern of altering the DOS profile by the fibrosis alone is identified. The surface measurements differ from the parenchyma measurements at various levels, due to the shielding effect of the thin collagen-rich capsule. DONOR indexing of liver pathology is promising, but requiring unsheilding the capsular effect.
A semi-empirical model initiated in 2009 has facilitated clinical investigations of steady-state ... more A semi-empirical model initiated in 2009 has facilitated clinical investigations of steady-state single-fiber reflectance spectroscopy (SfRS). We demonstrate an integration model for steady-state SfRS. Our model treats the single-fiber diffuse reflectance as the integration of a lever-set spatially resolved diffuse reflectance associated with a light incidence at the center of the fiber over the entire fiber facet. The integration over the collection area with a diameter ݀dfib reproduces the steady-state features of SfRS over the dimensionless reduced scattering μsdfib= [10-2, 103], absorption coefficient μa=[0.001, 1.0] mm-1 and an anisotropy factor ݃g= 0.9 for the Henyey-Greenstein scattering phase function.
Detecting important anatomic structures including ureters and mesenteric vessels is of utmost imp... more Detecting important anatomic structures including ureters and mesenteric vessels is of utmost importance to preventing unintended injury, facilitating intraoperative decision making, and potentially reducing operative time, in minimally invasive procedures performed in the abdomen. Diffuse reflectance spectroscopy (DRS) has been investigated previously for augmenting surgeon’s knowledge of tissue types intraoperatively. The potential of detecting a hollow structure by DRS is not only bounded by the parametric differences between that hollow structure and peripheral tissues including solid organs, but also determined by the relative scale between the hollow structure and the sampling depth of the probe. We have developed an applicator-probe with a 10mm source-detector distance that can be mounted on an 8mm laparoscopic instrument and passed through a 12mm trocar port for laparoscopic operability. The 10mm source-detector separation of this laparoscopically adaptable applicator probe renders sampling depth of a few millimeters for the potential of better discrimination between a hollow structure and a solid tissue parenchyma. DRS using this applicator-probe was performed on a number of hollow structures and solid organs intraoperatively in pigs. The hollow structures included urinary bladder, ureter, large intestine, small intestine, stomach, gallbladder, and mesenteric vessel. The solid organs or tissues included kidney, liver, and ovary. The ratio between the model-based normalized DRS signals at 700nm and 800nm was used as an index. An index value of 1 separates the hollow structures including ureter, bladder, and stomach (between 1 and 2) from other hollow structures including intestines and mesenteric vessel and solid organs (less than 0.7).
Surface diffuse optical spectroscopy was used to assess 12 livers rejected from transplantation. ... more Surface diffuse optical spectroscopy was used to assess 12 livers rejected from transplantation. A quantitation method correctly distinguished all 3 livers with the Ishak fibrosis stages >= 2 in the presence of various other pathologies.
The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic... more The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic-pressure wave from magnetic nanoparticle (MNP) when thermally mediated under an alternating magnetic field (AMF) at a pulsed or frequency-chirped application. Several independent experimental studies have since validated magneto-thermoacoustic effect, and a latest report has discovered acoustic-wave generation from MNP at the second-harmonic frequency of the AMF when operating continuously. We propose that applying two AMFs with differing frequencies to MNP will produce acoustic-pressure wave at the summation and difference of the two frequencies, in addition to the two second-harmonic frequencies. Analysis of the specific absorption dynamics of the MNP when exposed to two AMFs of differing frequencies has shown some interesting patterns of acoustic-intensity at the multiple frequency components. The ratio of the acoustic-intensity at the summation-frequency over that of the difference-frequency is determined by the frequency-ratio of the two AMFs, but remains independent of the AMF strengths. The ratio of the acoustic-intensity at the summation- or difference-frequency over that at each of the two second-harmonic frequencies is determined by both the frequency-ratio and the field-strength-ratio of the two AMFs. The results indicate a potential strategy for localization of the source of a continuous-wave magneto-thermalacoustic signal by examining the frequency spectrum of full-field non-differentiating acoustic detection, with the field-strength ratio changed continuously at a fixed frequency-ratio. The practicalities and challenges of this magnetic spatial localization approach for magneto-thermo-acoustic imaging using a simple envisioned set of two AMFs arranged in parallel to each other are discussed.
In vivo single-fiber reflectance spectroscopy (SfRS) was performed on an orthotopic AY-27 rat bla... more In vivo single-fiber reflectance spectroscopy (SfRS) was performed on an orthotopic AY-27 rat bladder urothelial cell carcinoma model to explore potential spectroscopic features revealing neoplastic changes. AY-27 bladder tumor cells were intravesically instilled in four rats and allowed to implant and grow for one week, with two additional rats as the control. A total of 107 SfRS measurements were taken from 27 sites on two control bladders and 80 from four AY-27 treated bladders. The spectral profiles obtained from AY-27 treated bladders revealed various levels of a methemoglobin (MetHb) characteristic spectral feature around 635nm. A multisegment spectral analysis method estimated concentrations of five chromophore compositions including oxyhemoglobin, deoxyhemoglobin, MetHb, lipid and water. The total hemoglobin concentration ([HbT]), the MetHb proportion in the total hemoglobin and the lipid volume content showed possible correlations. The 80 measurements from the AY-27 treated bladders could separate to three sub-sets according to the MetHb proportion. Specifically, 72 were in subset 1 with low proportion (5.3%<[MetHb]<7%), 6 in subset 2 with moderate proportion (7%<[MetHb]<30%), and 2 in subset 3 with significant proportion (>30%). When grouped according to [MetHB], the [HbT] increased from 368 μM of subset 1 to 488 μM of subset 2 to 541 μM of subset 3, in comparison to the 285 μM of the control. The increased total hemoglobin and the elevation of MetHb proportion may signify angiogenesis and degradation in hemoglobin oxygen-transport. Additionally, the lipid volume content decreased from 2.58% in the control to <0.2% in the tumor groups, indicating disruption of subepithelium tissue architecture.
We present an empirical master-slave dual-source configuration within the diffusion approximation... more We present an empirical master-slave dual-source configuration within the diffusion approximation that enhances modeling of spatially resolved diffuse reflectance at short-path and with low scattering from a semi-infinite homogeneous medium when irradiated by a pencil beam. An isotropic virtual source positioned at a depth of 1/(reduced scattering coefficient) is used as the master source. A second isotropic virtual source whose depth and intensity depend upon those of the master source and tissue property according to a set of simple empirical formulas is added as the slave source. When tested for a semi-infinite homogeneous medium, this master-slave dual-source model consistently produces the aggressive peaking of the diffuse reflectance toward the point of entry, which is significantly underestimated by the model prediction that involves only the master source. Monte Carlo simulations have shown the effectiveness of this empirical model at a short source-detector separation of 1/100 of 1/(reduced scattering coefficient) and an absorption to reduced scattering ratio as strong as 1, with an error within 20% in the near field (1/10 of 1/(reduced scattering coefficient)).
This work demonstrates a non-contact diffuse reflectance approach with a working distance of ~1.1... more This work demonstrates a non-contact diffuse reflectance approach with a working distance of ~1.1 meters for the potential of glucose sensing. Non-contact diffuse reflectance over 1.1-1.3 µm was developed according to a center-illumination-area-detection (CIAD) geometry. The modeled response of diffuse reflectance in the CIAD geometry was examined with phantoms by altering independently the size of the collection geometry and the reduced scattering and absorption properties of the medium. When applied to aqueous turbid medium containing glucose control solutions with the cumulative volume varying over three orders of magnitude, a linear relationship expected for the diffuse reflectance as a function of the medium absorption/reduced-scattering property was observed for four conditions of the glucose-medium composition that differed either in the effective glucose concentration or the host medium scattering property. The cumulation of glucose up to 17.8mg/dL and 8.9mg/dL in the host medium having the same optical properties resulted in linear regression slopes of 0.0032 and 0.0030, respectively. The cumulation of the glucose up to 17.8mg/dL in an aqueous host medium that differed two folds in the reduced scattering property caused the linear regression slope to differ between 0.0032 and 0.0019. The R 2 values of all cases were all greater than 0.987.
The clinical prospect of treating spinal cord injury by photobiomodulation therapy (PBMT) is uncl... more The clinical prospect of treating spinal cord injury by photobiomodulation therapy (PBMT) is unclear as the spinal dosimetry of transcutaneous laser application is unknown, yet essential for clinical recommendations. Light irradiances at 9 sites over an 8cm length along the thoracic to lumbar segment of the spinal canal were measured in 6 cadaver dogs using a flexible intra-spinal probe, under a surface irradiance of 3.14W/cm2. The skin transmits 4-12% of 980nm PBMT light. On-contact technique is ~5 times more efficient than off-contact technique. Transcutaneous transmission of photobiomodulatory irradiance to the spinal canal will benefit from contact-probe technique and skin-clearing approaches.
We present a model regarding laparoscopic detectability of a long absorbing tubular inclusion par... more We present a model regarding laparoscopic detectability of a long absorbing tubular inclusion parallel to the medium surface and bisecting the source-detector-pair. The model agrees with measurements in an aqueous medium using a 10mm probe.
We demonstrate diffuse reflectance spectroscopy (DRS) of a subsurface tubular inclusion by using ... more We demonstrate diffuse reflectance spectroscopy (DRS) of a subsurface tubular inclusion by using a fiber probe having a single source-detector pair attached to a laparoscopic bipolar device. A forward model was also developed for DRS sensing of an underlying long absorbing tubular inclusion set in parallel to the tissue surface, normal to the line of sight of the source-detector pair, and equidistant from the source and the detector. The model agreed with measurements performed at 500 nm and using a 10 mm source-detector separation (SDS) on an aqueous tissue phantom embedding a tubing of 2 or 4 mm inner diameter that contained 9.1% to 33.3% red dye at a depth of up to 11.5 mm. When tested on solid phantoms using the 10 mm SDS, a tubular inclusion of $ \ge 3\;{\rm mm}$≥3mm inner diameter containing 0.05% red dye at a background absorption coefficient of $ 0.021\;{\rm mm}^{-1} $0.021mm-1 caused $ \ge 8\% $≥8% change of the signal at 500 nm versus the baseline when the inclusion was shallower than 5 mm. When assessed on avian muscle tissue having a 4 mm tubular inclusion embedded at an edge depth of 2 mm, DRS with the 10 mm SDS differentiated the following contents of the inclusion: 33.3% red dye (mimicking blood), 33.3% green dye, 33.3% yellow dye (mimicking bile), water (mimicking urine), and air.
Journal of the Optical Society of America, Jun 29, 2012
Part IV examines frequency-domain photon diffusion in a homogeneous medium enclosed by a "concave... more Part IV examines frequency-domain photon diffusion in a homogeneous medium enclosed by a "concave" circular cylindrical applicator or enclosing a "convex" circular cylindrical applicator, both geometries being infinite in the longitudinal dimension. The aim is to assess by analogical and finite-element methods the changes of AC amplitude, modulation depth, and phase with respect to the line-of-sight source-detector distance for a source and a detector located along the azimuthal or longitudinal direction on the concave or convex medium-applicator interface. By comparing to their counterparts along a straight line on a semi-infinite medium-applicator interface, for the same line-of-sight source-detector distance, it is found that: (1) the decay-rate of AC photon fluence is smaller along the azimuthal direction and greater along the longitudinal direction on the concave interface, (2) the decay-rate of AC photon fluence is greater along the azimuthal direction and smaller along the longitudinal direction on the convex interface, (3) the modulation depth along both azimuthal and longitudinal directions decays more slowly on the concave interface and faster on the convex interface, and (4) the phase along both azimuthal and longitudinal directions increases more slowly on the concave interface and faster on the convex interface.
Abstract Nondestructive tomographic identification of underlying moldy lesions of apple is demons... more Abstract Nondestructive tomographic identification of underlying moldy lesions of apple is demonstrated experimentally, for the first time, by using frequency domain diffuse optical tomography (FD-DOT). The custom applicator-probe had 18 optodes distributed on a spheroid apple-size imaging domain. The 12 source channels were time-multiplexed to a laser source modulated at 110 MHz, and the 6 detector channels were individually conditioned for parallel heterodyning at 10 kHz. The iterative image reconstruction was performed without priors in an open-source finite-element-method (FEM) package with custom meshing of the imaging domain. Cylindrical moldy lesions in apple at controlled center depths ranging from 10 mm to 35 mm were established using 10 mm diameter cylinder inclusions harvested from mildew flesh, and freeform lesions in apple were developed by injecting colonies of Alternaria alternate. The moldy lesions not deeper than 20 mm from the peel were resolvable on the absorption images. The moldy lesions were unremarkable on the reduced scattering images. Contrast-detail-analysis is also performed in simulation to assess the condition of identifying a moldy-core lesion by FD-DOT.
Model approximation is necessary for reflectance assessment of tissue at sub-diffusive to non-dif... more Model approximation is necessary for reflectance assessment of tissue at sub-diffusive to non-diffusive scale. For tissue probing over a sub-diffusive circular area centered on the point of incidence, we demonstrate simple analytical steady-state total diffuse reflectance from a semi-infinite medium with the Henyey-Greenstein (HG) scattering anisotropy (factor $g$g). Two physical constraints are abided to: (1) the total diffuse reflectance is the integration of the radial diffuse reflectance; (2) the radial and total diffuse reflectance at $g \gt {0}$g>0 analytically must resort to their respective forms corresponding to isotropic scattering as $g$g becomes zero. Steady-state radial diffuse reflectance near the point of incidence from a semi-infinite medium of $g \approx 0$g≈0 is developed based on the radiative transfer for isotropic scattering, then integrated to find the total diffuse reflectance for $g \approx 0$g≈0. The radial diffuse reflectance for $g \ge 0.5$g≥0.5 is semi-empirically formulated by comparing to Monte Carlo simulation results and abiding to the second constraint. Its integration leads to a total diffuse reflectance for $g \ge 0.5$g≥0.5 that is also bounded by the second constraint. Over a collection diameter of the reduced-scattering pathlength ($1/\mu _s^{ \prime}$1/μs') scaled size of [${{10}^{ - 5}}$10-5, ${{10}^{ - 1}}$10-1] for $g = [{0.5},{0.95}]$g=[0.5,0.95] and the absorption coefficient as strong as the reduced scattering coefficient, the simple analytical total diffuse reflectance is found to be accurate, with an average error of 16.1%.
The large liver transplant waitlists and increasing of marginal donor organs call for a rapid, no... more The large liver transplant waitlists and increasing of marginal donor organs call for a rapid, non-destructive method of evaluating organ quality for transplantation. We demonstrate a diffuse optical non-destructive organ risk (DONOR) indexing method for identifying significant liver pathology, in particular unacceptable fibrosis and necrosis. Measurements were acquired from 27 human livers not meeting the clinical criteria for transplantation (OUHSC IRB #8155). A portable lab-on-a-crate diffuse optical spectroscopy (DOS) device with a hands-free probe of 3mm source-detector separation was used for measurements on liver surface and cross-section. The DOS measurements were obtained from a total of five sites, including the right anterior, right posterior, and left anterior liver surfaces and the right and left cut sections, and corresponding tissue sections were obtained for formalin-fixed paraffin embedded (FFPE) H&E controls of 8 types of liver pathology. Due to the difficulty of obtaining a control liver, a clinically inconspicuous and histologically unremarkable liver number 24 was used as the baseline for DONOR index processing. For the measurements at the cross-sectional parenchyma of the right lobe alone, a single threshold of the DONOR index at 1.5 identified all six livers with fibrosis stage ≥2 and one liver with necrosis=5, in the presence of mixed pathologies. A prime pattern of altering the DOS profile by the fibrosis alone is identified. The surface measurements differ from the parenchyma measurements at various levels, due to the shielding effect of the thin collagen-rich capsule. DONOR indexing of liver pathology is promising, but requiring unsheilding the capsular effect.
A semi-empirical model initiated in 2009 has facilitated clinical investigations of steady-state ... more A semi-empirical model initiated in 2009 has facilitated clinical investigations of steady-state single-fiber reflectance spectroscopy (SfRS). We demonstrate an integration model for steady-state SfRS. Our model treats the single-fiber diffuse reflectance as the integration of a lever-set spatially resolved diffuse reflectance associated with a light incidence at the center of the fiber over the entire fiber facet. The integration over the collection area with a diameter ݀dfib reproduces the steady-state features of SfRS over the dimensionless reduced scattering μsdfib= [10-2, 103], absorption coefficient μa=[0.001, 1.0] mm-1 and an anisotropy factor ݃g= 0.9 for the Henyey-Greenstein scattering phase function.
Detecting important anatomic structures including ureters and mesenteric vessels is of utmost imp... more Detecting important anatomic structures including ureters and mesenteric vessels is of utmost importance to preventing unintended injury, facilitating intraoperative decision making, and potentially reducing operative time, in minimally invasive procedures performed in the abdomen. Diffuse reflectance spectroscopy (DRS) has been investigated previously for augmenting surgeon’s knowledge of tissue types intraoperatively. The potential of detecting a hollow structure by DRS is not only bounded by the parametric differences between that hollow structure and peripheral tissues including solid organs, but also determined by the relative scale between the hollow structure and the sampling depth of the probe. We have developed an applicator-probe with a 10mm source-detector distance that can be mounted on an 8mm laparoscopic instrument and passed through a 12mm trocar port for laparoscopic operability. The 10mm source-detector separation of this laparoscopically adaptable applicator probe renders sampling depth of a few millimeters for the potential of better discrimination between a hollow structure and a solid tissue parenchyma. DRS using this applicator-probe was performed on a number of hollow structures and solid organs intraoperatively in pigs. The hollow structures included urinary bladder, ureter, large intestine, small intestine, stomach, gallbladder, and mesenteric vessel. The solid organs or tissues included kidney, liver, and ovary. The ratio between the model-based normalized DRS signals at 700nm and 800nm was used as an index. An index value of 1 separates the hollow structures including ureter, bladder, and stomach (between 1 and 2) from other hollow structures including intestines and mesenteric vessel and solid organs (less than 0.7).
Surface diffuse optical spectroscopy was used to assess 12 livers rejected from transplantation. ... more Surface diffuse optical spectroscopy was used to assess 12 livers rejected from transplantation. A quantitation method correctly distinguished all 3 livers with the Ishak fibrosis stages >= 2 in the presence of various other pathologies.
The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic... more The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic-pressure wave from magnetic nanoparticle (MNP) when thermally mediated under an alternating magnetic field (AMF) at a pulsed or frequency-chirped application. Several independent experimental studies have since validated magneto-thermoacoustic effect, and a latest report has discovered acoustic-wave generation from MNP at the second-harmonic frequency of the AMF when operating continuously. We propose that applying two AMFs with differing frequencies to MNP will produce acoustic-pressure wave at the summation and difference of the two frequencies, in addition to the two second-harmonic frequencies. Analysis of the specific absorption dynamics of the MNP when exposed to two AMFs of differing frequencies has shown some interesting patterns of acoustic-intensity at the multiple frequency components. The ratio of the acoustic-intensity at the summation-frequency over that of the difference-frequency is determined by the frequency-ratio of the two AMFs, but remains independent of the AMF strengths. The ratio of the acoustic-intensity at the summation- or difference-frequency over that at each of the two second-harmonic frequencies is determined by both the frequency-ratio and the field-strength-ratio of the two AMFs. The results indicate a potential strategy for localization of the source of a continuous-wave magneto-thermalacoustic signal by examining the frequency spectrum of full-field non-differentiating acoustic detection, with the field-strength ratio changed continuously at a fixed frequency-ratio. The practicalities and challenges of this magnetic spatial localization approach for magneto-thermo-acoustic imaging using a simple envisioned set of two AMFs arranged in parallel to each other are discussed.
In vivo single-fiber reflectance spectroscopy (SfRS) was performed on an orthotopic AY-27 rat bla... more In vivo single-fiber reflectance spectroscopy (SfRS) was performed on an orthotopic AY-27 rat bladder urothelial cell carcinoma model to explore potential spectroscopic features revealing neoplastic changes. AY-27 bladder tumor cells were intravesically instilled in four rats and allowed to implant and grow for one week, with two additional rats as the control. A total of 107 SfRS measurements were taken from 27 sites on two control bladders and 80 from four AY-27 treated bladders. The spectral profiles obtained from AY-27 treated bladders revealed various levels of a methemoglobin (MetHb) characteristic spectral feature around 635nm. A multisegment spectral analysis method estimated concentrations of five chromophore compositions including oxyhemoglobin, deoxyhemoglobin, MetHb, lipid and water. The total hemoglobin concentration ([HbT]), the MetHb proportion in the total hemoglobin and the lipid volume content showed possible correlations. The 80 measurements from the AY-27 treated bladders could separate to three sub-sets according to the MetHb proportion. Specifically, 72 were in subset 1 with low proportion (5.3%<[MetHb]<7%), 6 in subset 2 with moderate proportion (7%<[MetHb]<30%), and 2 in subset 3 with significant proportion (>30%). When grouped according to [MetHB], the [HbT] increased from 368 μM of subset 1 to 488 μM of subset 2 to 541 μM of subset 3, in comparison to the 285 μM of the control. The increased total hemoglobin and the elevation of MetHb proportion may signify angiogenesis and degradation in hemoglobin oxygen-transport. Additionally, the lipid volume content decreased from 2.58% in the control to <0.2% in the tumor groups, indicating disruption of subepithelium tissue architecture.
We present an empirical master-slave dual-source configuration within the diffusion approximation... more We present an empirical master-slave dual-source configuration within the diffusion approximation that enhances modeling of spatially resolved diffuse reflectance at short-path and with low scattering from a semi-infinite homogeneous medium when irradiated by a pencil beam. An isotropic virtual source positioned at a depth of 1/(reduced scattering coefficient) is used as the master source. A second isotropic virtual source whose depth and intensity depend upon those of the master source and tissue property according to a set of simple empirical formulas is added as the slave source. When tested for a semi-infinite homogeneous medium, this master-slave dual-source model consistently produces the aggressive peaking of the diffuse reflectance toward the point of entry, which is significantly underestimated by the model prediction that involves only the master source. Monte Carlo simulations have shown the effectiveness of this empirical model at a short source-detector separation of 1/100 of 1/(reduced scattering coefficient) and an absorption to reduced scattering ratio as strong as 1, with an error within 20% in the near field (1/10 of 1/(reduced scattering coefficient)).
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Papers by Daqing Piao