Non-invasive evaluation of therapeutic response in keloid scar using diffuse reflectance spectroscopy

Noninvasive hemoglobin quantification across different cohorts using a wearable diffuse reflectance spectroscopy system

Quantifying hemoglobin is vital yet invasive through blood draws. We developed a wearable diffuse reflectance spectroscopy device comprising control and sensor boards with photodiodes and light-emitting diodes to noninvasively determine hemoglobin. Neural networks enabled recovery of optical parameters for chromophore fitting to calculate hemoglobin. Testing healthy and elderly subjects revealed strong correlation (r=0.9) between our system and invasive methods after data conversion. Bland-Altman analysis demonstrated tight 95% limits of agreement from -1.98 to 1.98 g/dL between the DRS and invasive hemoglobin concentrations. By spectroscopically isolating hemoglobin absorption, interference from melanin was overcome. Our device has the potential for future integration into wearable technology, enabling hemoglobin level tracking.

Effect of skin color on optical properties and the implications for medical optical technologies: a review

Significance

Skin color affects light penetration leading to differences in its absorption and scattering properties. COVID-19 highlighted the importance of understanding of the interaction of light with different skin types, e.g., pulse oximetry (PO) unreliably determined oxygen saturation levels in people from Black and ethnic minority backgrounds. Furthermore, with increased use of other medical wearables using light to provide disease information and photodynamic therapies to treat skin cancers, a thorough understanding of the effect skin color has on light is important for reducing healthcare disparities.

Aim

The aim of this work is to perform a thorough review on the effect of skin color on optical properties and the implication of variation on optical medical technologies.

Approach

Published in vivo optical coefficients associated with different skin colors were collated and their effects on optical penetration depth and transport mean free path (TMFP) assessed.

Results

Variation among reported values is significant. We show that absorption coefficients for dark skin are ∼ 6 % to 74% greater than for light skin in the 400 to 1000 nm spectrum. Beyond 600 nm, the TMFP for light skin is greater than for dark skin. Maximum transmission for all skin types was beyond 940 nm in this spectrum. There are significant losses of light with increasing skin depth; in this spectrum, depending upon Fitzpatrick skin type (FST), on average 14% to 18% of light is lost by a depth of 0.1 mm compared with 90% to 97% of the remaining light being lost by a depth of 1.93 mm.

Conclusions

Current published data suggest that at wavelengths beyond 940 nm light transmission is greatest for all FSTs. Data beyond 1000 nm are minimal and further study is required. It is possible that the amount of light transmitted through skin for all skin colors will converge with increasing wavelength enabling optical medical technologies to become independent of skin color.

Non-invasive assessment of skin hydration and sensation with diffuse reflectance spectroscopy

The skin is a vital organ in the human body, providing essential functions such as protection, sensation, and metabolism. Skin hydration is one of the crucial factors in maintaining normal skin function. Insufficient skin hydration can lead to dryness, shedding of the stratum corneum, a decrease in skin barrier function, and may cause skin inflammation. Therefore, maintaining or improving skin hydration is critical in promoting healthy skin. Currently, the commonly used method for measuring skin hydration is bioelectrical capacitance analysis, which is often affected by environmental humidity and can only provide limited information. To overcome these limitations, this study used diffuse reflectance spectroscopy (DRS) in the wavelength range of 400-1000 nm to quantify skin absorption and scattering modulation caused by changes in skin hydration states. The advantages of this technique include rapid measurements, non-invasiveness, a straightforward optical setup, and suitability for prolonged skin monitoring. We found that DRS-derived skin absorption coefficients had a correlation coefficient of 0.93 with the skin capacitance at various skin hydration states. In addition, our findings reveal that absorption and scattering coefficients may be useful in discerning skin hydration enhancement induced by applying soaked cotton pads or cosmeceutical facial masks, as well as evaluating skin sensation. This study verifies that the DRS method could be a convenient and effective tool for evaluating skin hydration related information.

Noninvasive transcutaneous bilirubin measurement in adults using skin diffuse reflectance

Accurate measurement of bilirubin concentration in adults is crucial for the diagnosis and management of liver and biliary tract diseases. Traditional methods relying on central laboratory testing pose challenges such as invasiveness, patient discomfort, and time consumption. Non-invasive alternatives have been explored, but their applicability to adult populations remains uncertain. This study aimed to develop and validate a portable non-invasive optical system based on spatially resolved diffuse reflectance spectroscopy (DRS) specifically tailored for adult transcutaneous bilirubin measurement. Forty-two adult patients with various underlying conditions were included in the study. Comparisons between transcutaneous bilirubin values measured by the DRS system and total serum bilirubin concentrations obtained through blood tests revealed strong correlations, particularly at the neck (r = 0.872) and the medial side of the right upper arm (r = 0.940). Bland-Altman analyses demonstrated substantial agreement between the transcutaneous bilirubin values and total serum bilirubin concentrations. The results highlight the potential of the non-invasive DRS system as a convenient and reliable tool for monitoring bilirubin values in adults.

Relevance and utility of the in-vivo and ex-vivo optical properties of the skin reported in the literature: a review [Invited]

Imaging non-invasively into the human body is currently limited by cost (MRI and CT scan), image resolution (ultrasound), exposure to ionising radiation (CT scan and X-ray), and the requirement for exogenous contrast agents (CT scan and PET scan). Optical imaging has the potential to overcome all these issues but is currently limited by imaging depth due to the scattering and absorption properties of human tissue. Skin is the first barrier encountered by light when imaging non-invasively, and therefore a clear understanding of the way that light interacts with skin is required for progress on optical medical imaging to be made. Here we present a thorough review of the optical properties of human skin measured in-vivo and compare these to the previously collated ex-vivo measurements. Both in-vivo and ex-vivo published data show high inter- and intra-publication variability making definitive answers regarding optical properties at given wavelengths challenging. Overall, variability is highest for ex-vivo absorption measurements with differences of up to 77-fold compared with 9.6-fold for the in-vivo absorption case. The impact of this variation on optical penetration depth and transport mean free path is presented and potential causes of these inconsistencies are discussed. We propose a set of experimental controls and reporting requirements for future measurements. We conclude that a robust in-vivo dataset, measured across a broad spectrum of wavelengths, is required for the development of future technologies that significantly increase the depth of optical imaging.

The Efficacy of Intense Pulsed Light in the Treatment of Keloids and Hypertrophic Scars

Introduction: Different therapies have been applied to keloids and hypertrophic scars. Intense pulsed light (IPL) has recently been used but the evidence is limited. This study was to evaluate the effectiveness and safety of IPL as monotherapy for keloids and hypertrophic scars. Methods: This was a before-and-after interventional study on 16 patients with 50 scars who underwent IPL. Seven scars receive one IPL session, seven received two sessions, and 36 received three sessions. Outcomes were evaluated by the Vancouver Scar Scale (VSS), Patient and Observer Scar Assessment Scale (POSAS), scar ultrasound, colorimeter for pigmentation and erythema, and side effects. Results: After the treatment, most outcomes significantly improved except that the pigmentation of the scars did not change. Scar thickness significantly reduced by nearly 10% after the first IPL session, 15% after the second session, and>20% after the third session. All side effects were mild with crust (33.3-46%), blisters (8.3-40%), and hyperpigmentation around the scar (0-14%); the pain was moderate as assessed by the patients. Conclusion: IPL is a safe and effective treatment for keloids and hypertrophic scars. More studies are required to confirm our results.

VIS-NIR Diffuse Reflectance Spectroscopy System with Self-Calibrating Fiber-Optic Probe: Study of Perturbation Resistance

We report on the comparative analysis of self-calibrating and single-slope diffuse reflectance spectroscopy in resistance to different measurement perturbations. We developed an experimental setup for diffuse reflectance spectroscopy (DRS) in a wide VIS-NIR range with a fiber-optic probe equipped with two source and two detection fibers capable of providing measurements employing both single- and dual-slope (self-calibrating) approaches. In order to fit the dynamic range of a spectrometer in the wavelength range of 460-1030 nm, different exposure times have been applied for short (2 mm) and long (4 mm) source-detector distances. The stability of the self-calibrating and traditional single-slope approaches to instrumental perturbations were compared in phantom and in vivo studies on human palm, including attenuations in individual channels, fiber curving, and introducing optical inhomogeneities in the probe-tissue interface. The self-calibrating approach demonstrated high resistance to instrumental perturbations introduced in the source and detection channels, while the single-slope approach showed resistance only to perturbations introduced into the source channels.

Relative perfusion index: An objective, quantitative and noninvasive method for evaluating the severity of keloids

BACKGROUND

Keloids are the result of abnormal wound healing, and they differ from the normal skin of the patient in the level of blood perfusion and the degrees of inflammation, hypoxia, regeneration of vessels, and expression of sensory receptors. However, there is no objective assessment method to accurately characterize the severity of keloids.

OBJECTIVES

The purpose of this study was to evaluate the perfusion levels of keloids and the expression levels of various internal cytokines, including hypoxia-induced factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), interleukin-17 (IL-17), HT_2A receptor subtype (5-HT_2A R), and H1R, in keloids and nonadjacent normal skin and to propose a laser speckle contrast imaging (LSCI)-based relative perfusion index (RPI), through which keloids can be divided into five grades to objectively characterize their severity.

METHODS

This population-based cross-sectional study included 70 untreated keloid patients who each had only one keloid on the chest. LSCI was used to measure the area of each patient's keloid ( K area ${K}_{\mathrm{area}}$ ) and the perfusion level of each patient's keloid ( K perfusion ${K}_{\mathrm{perfusion}}$ ) and normal skin ( N perfusion ${N}_{\mathrm{perfusion}}$ ). The Vancouver Scar Scale (VSS) and Visual Analog Scale (VAS) for pain and pruritus were also used to assess each keloid. Immunohistochemistry and Western blot were used to detect the expression levels of various internal cytokines in keloids and normal skin. We compared the perfusion and expression levels of intrinsic cytokines between keloids and normal skin. We established the RPI to grade the severity of keloids and applied different methods to test the utility of the RPI.

RESULTS

The mean perfusion level of keloids was significantly higher than that of normal skin (p < 0.001). The expression levels of HIF-1α, VEGF, IL-17, 5-HT_2A R, and H1R in keloids were significantly higher than those in normal skin (p < 0.05). RPI was defined as: [ ( K perfusion - N perfusion ) × 0.03 + K area × 0.001 ] . $[({K}_{\mathrm{perfusion}}-{N}_{\mathrm{perfusion}})\times 0.03+{K}_{\mathrm{area}}\times 0.001].$ The severity of keloids could be divided into five grades based on RPI. The RPI had a higher correlation with the pain-VAS, pruritus-VAS, and the expression levels of internal cytokines in keloids than blood perfusion levels and the VSS. T-SNE (t-distributed stochastic neighbor embedding) was also used to verify the clinical discriminatory abilities of this RPI model.

CONCLUSIONS

The proposed RPI based on LSCI showed the highest accuracy, unlike the VSS and assessment of perfusion, and can be utilized as a reliable, objective, quantitative, and noninvasive tool to evaluate the severity of keloids.

Investigating the clinical implication of corneometer and mexameter readings towards objective, efficient evaluation of psoriasis vulgaris severity

In clinical settings, although Psoriasis Area and Severity Index (PASI) scoring system can provide a quick visual assessment of the severity of psoriasis vulgaris, there is still a strong demand for higher efficiency and accuracy in quantifying the inflammation status of psoriatic lesions. Currently, there are already commercial systems, such as the Courage + Khazaka Corneometer and Mexameter that measure skin capacitance and optical reflectance, for conveniently quantifying the status of skin barrier function and erythema of skin. Despite numerous comparisons of the Courage + Khazaka system with the PASI scoring system, they are rarely compared on parity with diffuse reflectance spectroscopy (DRS) based systems. In this study, we employed a custom-built DRS system shown to be able to determine the skin water-protein binding status and the hemoglobin concentration, and we performed cross-validation of the DRS measurement results with the readings derived from the Corneometer and Mexameter as well as a portion of the PASI scores. Our results revealed that the erythema readings from the Mexameter were a good representation of skin oxygenated hemoglobin but not the deoxygenated hemoglobin. On the other hand, the dermatologists recruited in this study were inclined to rate higher scores on the “erythema” category as skin’s deoxygenated hemoglobin level was higher. Thus, the Mexameter derived erythema readings may not be coherent with the PASI erythema scores. Further, the Corneometer derived skin capacitance readings were well correlated to the PASI “desquamation” and “thickness” scores, while the PASI “desquamation” evaluation was a dominating factor contributing to the DRS deduced water-protein binding status. We conclude that the DRS method could be a valuable addition to existing skin capacitance/reflectance measurement systems and the PASI scoring system toward achieving a more efficient and objective clinical psoriasis vulgaris severity evaluation.

Potential Use of Novel Image and Signal Processing Methods to Develop a Quantitative Assessment of the Severity of Acute Radiation Dermatitis in Breast Cancer Radiotherapy

More than 95% of patients who undergo radiotherapy report symptoms of radiation dermatitis, which is a side effect of this therapy. Erythema, edema, dry and moist desquamation intensify with each fraction of irradiation and can significantly reduce a patient's quality of life. Therefore, an effective skin care procedure is needed for skin that has been exposed to ionizing radiation in order to avoid unplanned treatment interruptions. The methods that are currently used to assess the severity of an acute radiation reaction are based on visual scales (RTOG, EORTC, NCI CTCAE, LENT-SOMA). Because the assessment is made subjectively, the results depend on the researchers, their experience and perceptiveness. Until now, several studies have been carried out to check the possibility of using an objective methods like hyperspectral imaging, thermal imaging, laser Doppler flowmetry, dielectric and electrochemical methods, reflection spectrophotometry and Courage-Khazaka Multi-skin instrument to radiation-induced dermatitis assessment. Unfortunately, due to various limitations that occurred in the research, none of these techniques was successfully implement as alternative for visual assessment. The continuous development of technology enables researchers to access new techniques that might constitute useful diagnostic and cognitive tools. Infrared thermal imaging, hyperspectral imaging and reflectance spectroscopy are examples of the visual techniques that have been used for many years in various fields of medicine, including dermatology and chronic wound or burn care. They provide information on the skin parameters, such as the temperature, concentration and distribution of chromophores (eg, hemoglobin and melanin), saturation or perfusion changes. The aim of this study is to review the available literature on the use of imaging methods in the clinical assessment of skin with lesions of various origins, evaluation of their suitability for the assessment of radiation reaction and consideration the possibility of creating a quantitative scale for assessing severity of acute radiation dermatitis.

Laser fluorescence spectroscopy in predicting the formation of a keloid scar: preliminary results and the role of lipopigments

Keloid scars, in contrast to other scar types, significantly reduce the patient's quality of life. To develop a nondestructive optical diagnostic technique predicting the keloid scars formation in vivo, laser-induced fluorescence spectroscopy (LFS) was used to study the autofluorescence in skin of patients with various types of head and neck cicatricial deformities. The unexpected results were obtained for the endogenous fluorescence of lipofuscin. Significantly reduced autofluorescence of lipofuscin was registered both in the intact and in the keloid scar tissues in comparison with the intact and scar tissues in patients with hypertrophic and normotrophic scars. Sensitivity and specificity achieved by LFS in keloid diagnosis are 81.8% and 93.9% respectively. It could take place due to the changes in the reductive-oxidative balance in cells, as well as due to the proteolysis processes violation. Therefore, we suppose that the evaluation of the lipofuscin autofluorescence in skin before any surgical intervention could predict the probability of the subsequent keloid scars formation.

Optical characteristics of human skin with hyperpigmentation caused by fluorinated pyrimidine anticancer agent

The fluorinated pyrimidine anticancer agent has several side effects that degrade the quality of life of patients, including hyperpigmentation. Hyperpigmentation differs in color from common pigmentation such as a suntan, giving rise to dramatic skin appearance changes. In this study, we measured the optical properties of the skin of patients with hyperpigmentation by using the reflection spatial profile method (RSPM). The absorption coefficient in hyperpigmentation increased ~1.5-2.5 times and pheomelanin significantly increased compared to the normal skin. In addition, the scattering coefficient of skin with hyperpigmentation was about 65.9-76.5% of that of normal skin.

Noninvasive transcutaneous bilirubin assessment of neonates with hyperbilirubinemia using a photon diffusion theory-based method

Transcutaneous bilirubinometers are widely used to screen neonatal jaundice. However, it was reported that their accuracy is compromised at low and high bilirubin levels. We used a photon diffusion theory-based method valid in the 450-600 nm wavelength region to overcome this obstacle. Our clinical study results showed that our system could properly determine the transcutaneous bilirubin concentrations at total serum bilirubin levels higher than 14 mg/dL, where a commercial bilirubinometer failed to provide proper results in several cases. These findings suggested that photon diffusion theory could be employed to improve the core algorithm of modern bilirubinometers and enhance their applicability.

Novel Stereoscopic Optical System for Objectively Measuring Above-Surface Scar Volume-First-Time Quantification of Responses to Various Treatment Modalities

BACKGROUND

Current approaches use subjective semiquantitative or cumbersome objective methodologies to assess physical characteristics of hypertrophic and keloid scars.

OBJECTIVE

This pilot study aimed to evaluate the accuracy and feasibility of a new stereoscopic optical and high-resolution 3-dimensional imaging system, for objectively measuring changes in above-surface scar volume after various interventions.

METHODS

Feasibility and accuracy were assessed by monitoring the above-surface scar volume of 5 scars in 2 patients for 5 successive months. Above-surface scar volume and Vancouver Scar Scale scores and the investigator and patient volume improvement assessment scores were assessed before and 12 weeks after last intervention.

RESULTS

Scar volume measured by the imaging system correlated significantly with the gold standard (actual weight). The greatest volume reduction followed a combination of cryotherapy and intralesional triamcinolone acetonide and 5-fluorouracil injections in Patient 1 and a combination of pulse dye laser and intralesional triamcinolone acetonide injections in Patient 2.

CONCLUSION

The new stereoscopic optical system is a valid, accurate, and practical objective method for assessing scar volume and for monitoring treatment response. It is more sensitive and accurate than semiquantitative objective scales. Further studies with a higher number of patients and scars are required to increase the measurement validity of the system.

Skin collagen can be accurately quantified through noninvasive optical method: Validation on a swine study

BACKGROUND/PURPOSE

Diffuse reflectance spectroscopy (DRS) is a noninvasive optical technology characterized by relatively low system cost and high efficiency. In our previous study, we quantified the relative concentration of collagen for the individual keloid patient. However, no actual value of collagen concentration can prove the reliability of collagen detection by our DRS system.

METHODS

Skin-mimicking phantoms were prepared using different collagen and coffee concentrations, and their chromophore concentrations were quantified using the DRS system to analyze the influence of collagen and other chromophores. Moreover, we used the animal study to compare the DRS system with the collagen evaluation of biopsy section by second-harmonic generation (SHG) microscopy at four different skin parts.

RESULTS

In the phantom study, the result showed that coffee chromophore did not severely interfere with collagen concentration recovery. In the animal study, a positive correlation (r=.902) between the DRS system and collagen evaluation with SHG microscopy was found.

CONCLUSIONS

We have demonstrated that the DRS system can quantify the actual values of collagen concentration and excluded the interference of other chromophores in skin-mimicking phantoms. Furthermore, a high positive correlation was found in the animal study with SHG microscopy. We consider that the DRS is a potential technique and can evaluate skin condition objectively.

Light distribution modulated diffuse reflectance spectroscopy

Typically, a diffuse reflectance spectroscopy (DRS) system employing a continuous wave light source would need to acquire diffuse reflectances measured at multiple source-detector separations for determining the absorption and reduced scattering coefficients of turbid samples. This results in a multi-fiber probe structure and an indefinite probing depth. Here we present a novel DRS method that can utilize a few diffuse reflectances measured at one source-detector separation for recovering the optical properties of samples. The core of innovation is a liquid crystal (LC) cell whose scattering property can be modulated by the bias voltage. By placing the LC cell between the light source and the sample, the spatial distribution of light in the sample can be varied as the scattering property of the LC cell modulated by the bias voltage, and this would induce intensity variation of the collected diffuse reflectance. From a series of Monte Carlo simulations and phantom measurements, we found that this new light distribution modulated DRS (LDM DRS) system was capable of accurately recover the absorption and scattering coefficients of turbid samples and its probing depth only varied by less than 3% over the full bias voltage variation range. Our results suggest that this LDM DRS platform could be developed to various low-cost, efficient, and compact systems for in-vivo superficial tissue investigation.

A systematic review of objective burn scar measurements

BACKGROUND

Problematic scarring remains a challenging aspect to address in the treatment of burns and can significantly affect the quality of life of the burn survivor. At present, there are few treatments available in the clinic to control adverse scarring, but experimental pharmacological anti-scarring strategies are now beginning to emerge. Their comparative success must be based on objective measurements of scarring, yet currently the clinical assessment of scars is not carried out systematically and is mostly based on subjective review of patients. However, several techniques and devices are being introduced that allow objective analysis of the burn scar. The aim of this article is to evaluate various objective measurement tools currently available and recommend a useful panel that is suitable for use in clinical trials of anti-scarring therapies.

METHODS

A systematic literature search was done using the Web of Science, PubMed and Cochrane databases. The identified devices were then classified and grouped according to the parameters they measured. The tools were then compared and assessed in terms of inter- and intra-rater reproducibility, ease of use and cost.

RESULTS

After duplicates were removed, 5062 articles were obtained in the search. After further screening, 157 articles which utilised objective burn scar measurement systems or tools were obtained. The scar measurement devices can be broadly classified into those measuring colour, metric variables, texture, biomechanical properties and pathophysiological disturbances.

CONCLUSIONS

Objective scar measurement tools allow the accurate and reproducible evaluation of scars, which is important for both clinical and scientific use. However, studies to evaluate their relative performance and merits of these tools are scarce, and there remain factors, such as itch and pain, which cannot be measured objectively. On reviewing the available evidence, a panel of devices for objective scar measurement is recommended consisting of the 3D cameras (Eykona/Lifeviz/Vectra H1) for surface area and volume, DSM II colorimeter for colour, Dermascan high-frequency ultrasound for scar thickness and Cutometer for skin elasticity and pliability.

Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation

Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm.

Portable handheld diffuse reflectance spectroscopy system for clinical evaluation of skin: a pilot study in psoriasis patients

Diffuse reflectance spectroscopy (DRS) has been utilized to study biological tissues for a variety of applications. However, many DRS systems are not designed for handheld use and/or relatively expensive which limit the extensive clinical use of this technique. In this paper, we report a handheld, low-cost DRS system consisting of a light source, optical switch, and a spectrometer, that can precisely quantify the optical properties of tissue samples in the clinical setting. The handheld DRS system was employed to determine the skin chromophore concentrations, absorption and scattering properties of 11 patients with psoriasis. The measurement results were compared to the clinical severity of psoriasis as evaluated by dermatologist using PASI (Psoriasis Area and Severity Index) scores. Our statistical analyses indicated that the handheld DRS system could be a useful non-invasive tool for objective evaluation of the severity of psoriasis. It is expected that the handheld system can be used for the objective evaluation and monitoring of various skin diseases such as keloid and psoriasis.

Toward reliable retrieval of functional information of papillary dermis using spatially resolved diffuse reflectance spectroscopy

Spatially resolved diffuse reflectance spectroscopy (SRDRS) has been employed to quantify tissue optical properties and its interrogation volume is majorly controlled by the source-to-detector separations (SDSs). To noninvasively quantify properties of dermis, a SRDRS setup that includes SDS shorter than 1 mm is required. It will be demonstrated in this study that Monte Carlo simulations employing the Henyey-Greenstein phase function cannot always precisely predict experimentally measured diffuse reflectance at such short SDSs, and we speculated this could be caused by the non-negligible backward light scattering at short SDSs that cannot be properly modeled by the Henyey-Greenstein phase function. To accurately recover the optical properties and functional information of dermis using SRDRS, we proposed the use of the modified two-layer (MTL) geometry. Monte Carlo simulations and phantom experiment results revealed that the MTL probing geometry was capable of faithfully recovering the optical properties of upper dermis. The capability of the MTL geometry in probing the upper dermis properties was further verified through a swine study, and it was found that the measurement results were reasonably linked to histological findings. Finally, the MTL probe was utilized to study psoriatic lesions. Our results showed that the MTL probe was sensitive to the physiological condition of tissue volumes within the papillary dermis and could be used in studying the physiology of psoriasis.