Colorimetry has been used as an objective measure of perceived skin color by human eye to document and
score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the
most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for
erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the
amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance
spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were
recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and
on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements
was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light
complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness
of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution
at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance
of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in
comparison to colorimetry assessment.
The stratum corneum (SC) serves a primary function of skin barrier and its maintenance is vital for the existence of
terrestrial life. Few studies have been performed for evaluation of human SC repair in vivo, non-invasively. In the
present study tape stripping was performed on the arms and legs of seven volunteers until all the SC was removed. The
injured site and a control adjacent site were measured over a period of 10 days after the injury to assess functionality and
repair. Transepidermal water loss (TEWL), tryptophan fluorescence and reflectance confocal microscopy were used to
determine permeability of the skin barrier, cell turnover and epidermis morphology, respectively. The results show an
exponential rate of recovery for the skin permeability (TEWL) which contrasted with a linear increase in the thickness of
the SC as determined by confocal microscopy. Cell turnover increased rapidly immediately after the injury to 2.5 times
the levels of the control site, attaining a maximum of 3.5-4 times greater levels after three days and slowly returned to
baseline levels after the ten days. Correlation of the cell turnover to the thickness of the viable epidermis was observed
and further studies are under way to interpret these results.
The minimal erythema dose induced by solar-simulated radiation is a useful measure of UV sensitivity of
skin. Most skin phototests have been conducted by projecting a flat field of UV radiation onto the skin in
an area greater than 15 cm × 15 cm with an increment of radiation doses. In this study, we investigated the
responses of human skin to solar-simulated radiation of different field sizes. Twelve human subjects of skin
phototype I-IV were exposed to solar-simulated radiation (SSR) on their upper inner arm or on their lower
back with a series of doses in increments of 20% in order to determine the threshold dose to induce a minimal
perceptible erythema response (MED). Each dose was delivered with a liquid light guide (8 mm diameter on
the back or 6 mm on the upper inner arm) and with quartz optical fibers of 200 μm diameter. The resulting
skin responses were evaluated visually and investigated with a reflectance confocal microscope and imaging.
The erythema response to the microscopic challenge was always diffuse with no clear boundaries extending to
several times the exposed site diameter at doses greater than 2 MED. The skin returned to normal appearance
from the microscopic challenge after two weeks of exposure while change in appearance for the larger areas
persisted for several weeks to months. This new modality of testing provides the possibility to study skin at
the microscopic level with a rapid recovery following challenge.
We present a simple and cost-effective optical technique for the simultaneous assessment of pulsating and total blood noninvasively in an inflammatory skin lesion. Acquisitions of diffuse reflectance spectra in the visible range at 6 Hz are used to trace the oscillating components of reflectance. Measurements on erythematous lesions from a UV insult show slow changing signal at about 0.1 Hz and heart-driven regular oscillations at about 1 Hz simultaneously. The results demonstrate the potential of the technique in monitoring both pulsating and steady components of the blood in inflammatory lesions of the skin.
The stratum corneum provides a vital physical barrier that protects against external insults and excessive internal water loss. Water activity is thought as a key factor to maintain proper skin barrier integrity via regulating enzyme activities and lipid phase behavior. Consequently, maintenance of an optimal hydration level in SC becomes an important clinical and cosmetic concern.
The objective methods to assess SC hydration are based on either electrical or optical measurements. Electrical techniques used in the current study include high frequency conductance (Skicon), impedance (Nova DPM) and DC I-V curve (Skinsensor). Confocal Raman Microscopy was utilized to document water profile versus depth, and this technique is based on inelastic scattering of monochromatic light from different chemical species of skin.
Water patches were applied on the 14 subjects' forearm for 20 minutes and 1.5 hrs. Skin hydration levels for individuals
were documented by utilizing the mentioned above instruments in vivo. Results show that patterns of water profiles upon the hydration are significantly different among the individuals and these differences may be related to skin barrier function integrity. The intrinsic water content and water absorption upon the hydration were summed corresponding to different depths (3 μm and 15 μm) from the data obtained by confocal Raman microscopy. These results were correlated to the readings from electrical approaches. Superficial (3 μm) but not deeper layer (15 μm) water contents correlated well with the readings from SkinSensor. Neither depth measurements correlate well with the Skicon. There is strong
correlation between the data acquired with Skicon and SkinSensor.
Measurement of cutaneous microcirculation is of great importance for clinical evaluations as many biological processes (i.e. inflammation) activate superficial vessels. Diffuse Reflectance Spectroscopy (DRS) is a widely used method to assess cutaneous microcirculation since it is based on the spectral characteristics of skin chromophores, particularly the strong absorption bands of blood in the visible spectral range. However, the DRS system only provides a snapshot of the blood content in tissue from the reflectance detected at a single exposure time, and it fails to demonstrate dynamic changes of blood flow inside the tissues. In the present study, a prototype system for functional DRS (fDRS) has been developed for the sequential acquisition of multiple reflectance spectra in the visible range at sub-second intervals. Twelve healthy subjects with skin phototype I-III were recruited for a UV skin phototest where the subject's back was exposed to an increasing
dose of solar-simulated radiation at a maximum of 3 minimum erythema dose (MED). Evaluations included conventional DRS, functional DRS, and a laser Doppler flowmeter/imaging system. In a frequency analysis
results, there were two distinctive frequency components. A low-frequency component was found near 0.03-0.1 Hz, and another high-frequency component near 0.9-1.2 Hz which is synchronous with heart pulsations.
The magnitude of the high-frequency and the steady-state components of the fDRS signal increased with
increase in exposure dose. These results demonstrate the potential of this technique for noninvasive
assessment of cutaneous microcirculation.
In rhytidectomy the postoperative edema (swelling) and ecchymosis (bruising) can influence the cosmetic results. Evaluation of edema has typically been performed by visual inspection by a trained physician using a fourlevel or, more commonly, a two-level grading(1). Few instruments exist capable of quantitatively assessing edema and ecchymosis in skin. Here we demonstrate that edema and ecchymosis can be objectively quantitated in vivo by a multispectral clinical imaging system (MSCIS). After a feasibility study of induced stasis to the forearms of
volunteers and a benchtop study of an edema model, five subjects undergoing rhytidectomy were recruited for a clinical study and multispectral images were taken approximately at days 0, 1, 3, 6, 8, 10, 15, 22 and 29 (according with the day of their visit). Apparent concentrations of oxy-hemoglobin, deoxy-hemoglobin (ecchymosis), melanin, scattering and water (edema) were calculated for each pixel of a spectral image stack. From the blue channel on
cross-polarized images bilirubin was extracted. These chromophore maps are two-dimensional quantitative representations of the involved skin areas that demonstrated characteristics of the recovery process of the patient after the procedure. We conclude that multispectral imaging can be a valuable noninvasive tool in the study of edema and ecchymosis and can be used to document these chromophores in vivo and determine the efficacy of treatments in a clinical setting.
It is known that effectiveness of acne treatment increases when the lesions are detected earlier, before they could progress into mature wound-like lesions, which lead to scarring and discoloration. However, little is known about the evolution of acne from early signs until after the lesion heals. In this work we computationally characterize the evolution of inflammatory acne lesions, based on analyzing cross-polarized images that document acne-prone facial skin over time. Taking skin images over time, and being able to follow skin features in these images present serious challenges,
due to change in the appearance of skin, difficulty in repositioning the subject, involuntary movement such as breathing.
A computational technique for automatic detection of lesions by separating the background normal skin from the acne lesions, based on fitting Gaussian distributions to the intensity histograms, is presented. In order to track and quantify the evolution of lesions, in terms of the degree of progress or regress, we designed a study to capture facial skin images from an acne-prone young individual, followed over the course of 3 different time points. Based on the behavior of the lesions between two consecutive time points, the automatically detected lesions are classified in four categories: new lesions, resolved lesions (i.e. lesions that disappear completely), lesions that are progressing, and lesions that are regressing (i.e. lesions in the process of healing). The classification our methods achieve correlates well with visual inspection of a trained human grader.
Currently, most investigations of wound healing rely on invasive biopsy followed by histology and
immunohistochemistry staining. There is a great need to develop non-invasive techniques for in vivo diagnostic, clinical
and scientific evaluation. Here, we performed a comprehensive investigation on the dynamic wound healing process as
a response to laser-induced microinjuries using non-invasive imaging techniques such as reflectance laser-scanning
confocal microscopy and video microscopy. Eight healthy subjects ranging from Fitzpatrick skin type II-VI with age
from 27 to 57 years were recruited. The volar forearm of each subject was treated with a laser device that generates an
array of microbeams with an infrared wavelength. The microscopic changes of epidermal cells and collagen during the
wound healing process were assessed non-invasively using confocal microscopy. We also developed a quantitative
method to evaluate the dynamic wound healing process at the microscopic level in three areas of interest: (1) treated
micro-wounding zone, (2) surrounding collateral damage zone and (3) normal area. The depth-dependent intensity
profile derived from reflectance confocal microscope images clearly distinguishes the three areas of interest and
quantitatively measures the cellular structure-associated changes. A progressive change in depth-dependent intensity
profiles in subjects with different ages parallels the clinical observation of wound healing rate. The quantitative analysis
developed in this study may find broad applications in assessing the skin response to treatment at a microscopic level.
Nowadays, documenting the face appearance through imaging is prevalent in skin research, therefore detection
and quantitative assessment of the degree of facial wrinkling is a useful tool for establishing an objective baseline
and for communicating benefits to facial appearance due to cosmetic procedures or product applications. In this
work, an algorithm for automatic detection of facial wrinkles is developed, based on estimating the orientation and
the frequency of elongated features apparent on faces. By over-filtering the skin texture image with finely tuned
oriented Gabor filters, an enhanced skin image is created. The wrinkles are detected by adaptively thresholding
the enhanced image, and the degree of wrinkling is estimated based on the magnitude of the filter responses.
The algorithm is tested against a clinically scored set of images of periorbital lines of different severity and we
find that the proposed computational assessment correlates well with the corresponding clinical scores.
The activity of certain bacteria in skin is known to correlate to the presence of porphyrins. In particular
the presence of coproporphyrin produced by P.acnes inside plugged pores has been correlated to acne vulgaris.
Another porphyrin encountered in skin is protoporphyrin IX, which is produced by the body in the pathway for
production of heme.
In the present work, a fluorescence spectroscopy system was developed to measure the characteristic spectrum
and quantify the two types of porphyrins commonly present in human facial skin. The system is comprised of
a Xe lamp both for fluorescence excitation and broadband light source for diffuse reflectance measurements. A
computer-controlled filter wheel enables acquisition of sequential spectra, first excited by blue light at 405 nm
then followed by the broadband light source, at the same location. The diffuse reflectance spectrum was used
to correct the fluorescence spectrum due to the presence of skin chromophores, such as blood and melanin. The
resulting fluorescence spectra were employed for the quantification of porphyrin concentration in a population of
healthy subjects. The results show great variability on the concentration of these porphyrins and further studies
are being conducted to correlate them with skin conditions such as inflammation and acne vulgaris.
Determination of tissue optical properties is fundamental for application of light in either therapeutical or diagnostics procedures. In the present work we implemented a spatially resolved steady-state diffuse reflectance method where only two fibers (one source and one detector) spaced 2.5 mm apart are used for the determination of the optical properties. The method relies on the spectral characteristics of the tissue chromophores (water, dry tissue, and blood) and the assumption of a simple wavelength dependent expression for the determination of the reduced scattering coefficient. Because of the probe dimensions the method is suited for endoscopic measurements. The method was validated against more traditional models, such as the diffusion theory combined with adding doubling for in vitro measurements of bovine muscle. Mean and standard deviation of the absorption coefficient and the reduced scattering coefficient at 630 nm for normal mucosa were 0.87±0.22 cm–1 and 7.8±2.3 cm–1, respectively. Cancerous mucosa had values 1.87±1.10 cm–1 and 8.4±2.3 cm–1, respectively. These values are similar to data presented by other authors. Blood perfusion was the main variable accounting for differences in the absorption coefficient between the studied tissues.
Background: Subjective measures are considered the gold standard in palliative care evaluation, but no studies have evaluated palliative photodynamic therapy (PDT) subjectively. If PDT is to be accepted as a palliative therapy for later-stage obstructing esophageal and lung cancer, evidence of its effectiveness and acceptability to patients must be made known. Study Design/Materials and Methods: This ongoing study's major aim is to evaluate subjective outcomes of PDT in patients with obstructing esophageal and lung cancer. Existing measures of health status, dysphagia and performance status were supplemented with an instrument developed to evaluate PDT symptom relief and side effect burden, the PDT Side Effects Survey (PSES). Results: PDT patients treated with porfimer sodium (Photofrin) and 630-nm light experienced reduced dysphagia grade and stable performance status for at least one month after PDT (N= 10-17), but these effects did not necessarily persist at three months. Fatigue, appetite and quality of life may be the most burdensome issues for these patients. Conclusions: Preliminary data suggest that the PSES is an acceptable and valid tool for measuring subjective outcomes of palliative PDT. This study is the first attempt to systematically evaluate subjective outcomes of palliative PDT. Multi-center outcomes research is needed to draw generalizable conclusions that will establish PDT's effectiveness in actual clinical practice and enhance the wider adoption of PDT as a cancer symptom relief modality.
The FDA has approved PDT using Photofrin for certain esophageal and lung cancers, specifying an approved prescription of administered drug (mg/kg body weight) and administered light (J/linear cm of cylindrical fiber). This paper describes our development of a multi-optical fiber catheter for endoscopic use which documents the drug accumulated in the target tissues and the light penetration into the target tissues. The catheter uses reflectance to specify the light penetration depth and uses reflectance- corrected fluorescence to document drug accumulation. The goal is to document the variation in drug and light received by patients who are administered the FDA-approved prescription.
KEYWORDS: Oxygen, Photodynamic therapy, In vivo imaging, In vitro testing, Absorbance, Chemical species, Argon ion lasers, Molecules, Quantum efficiency, Oxidation
This paper considers the fraction PDT-induced oxidizing radicals that react with a specific oxidizable target within a cell rather than with all possible oxidizable sites. There are many oxidizable sites within the cell, each with a different efficiency of oxidation (Y_ox_j) and a different in vivo concentration (C_iv_j). One measures the efficiency of oxidation of a single ith chemical species in vitro (Y_it_i), then measures the oxidation of the same species in vivo (Y_iv_i). The concentration of this ith species in vivo must be measured (C_iv_i). A convenient test chemical species is chosen, such as a photobleachable fluorophore. Then the in vivo yield is approximately: Y_iv_i = (C_iv_i*Y_it_i)/sum_all_j(C_iv_j*Y_iv_j) (eq.1). Rearranging to solve for the total oxidation: Sum_all_j(C_iv_j*Y_iv_j) = (C_iv_i*Y_it_i)/Y_iv_I (Eq.2) Once the sum_all_j() in Eq.2 is specified, one can measure the in vitro oxidation efficiency and the in vivo concentration of any ith species and use Eq.1 to predict the fraction of PDT_generated singlet oxygen that will attack that ith species in vivo. Of course, the above is only a first approximation toward a complex problem but is a beginning. This paper illustrates the experimental specification of the Y_ox_j for NADPh oxidation in a cuvette using the photosensitizer Photofrin.
Photo-oxidation was studied during PDT in a model system using NADPH as the target substrate and Photofrin II as the photosensitizer. The efficiency of NADPH oxidation per photon absorbed by photosensitizer was determined as a function of substrate concentration. The kinetics of changes in absorbance was measured to assay oxidation of NADPH. The efficiency of oxidation increased with increasing NADPH concentration and approached a stable value of 0.0048. Using typical values for the quantum efficiency of the Photofrin triplet state generation and the efficiency of singlet oxygen production we obtained a value of the efficiency of interaction between singlet oxygen and NADPH. Efficiency of diffusion of singlet oxygen was modeled with molecular diffusion theory using typical values for the singlet oxygen lifetime and the diffusion coefficient in aqueous solutions.
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