Diffuse near-infrared spectroscopy prediction of healing in diabetic foot ulcers: a human study and cost analysis.

Wound size reduction has been the standard benchmark for determination of efficacy for diabetic ulcer treatments but due to interclinician error and difficulty measuring irregular wound shapes, this method is unreliable with a positive predictive value of less than 60%. Diffuse near-infrared spectroscopy (DNIRS) uses 70-MHz modulated light in the diagnostic window (650-900 nm) noninvasively to quantify levels of oxy- and deoxy-hemoglobin in the wound bed, which when measured over time, can show a trend toward or away from healing based on the changes in oxy-hemoglobin concentration from week to week. In this study, DNIRS was used to monitor 24 human diabetic foot ulcers longitudinally over the course of 20 weekly or biweekly measurement sessions. In just 4 weeks, the DNIRS system has an 82% positive predictive value (sensitivity of 0.9 and specificity of 0.86; p < 0.002). These data indicate that it could be possible to predict healing in 4 weeks using DNIRS, which can provide objective guidance toward the continuation of costly treatments. Discontinuing ineffective treatments after 4 weeks could have potentially saved over $12,600 per patient, based on the treatment regimen of patients in this study.

Multifunctional carbon-nanotube cellular endoscopes.

Glass micropipettes, atomic force microscope tips and nanoneedles can be used to interrogate cells, but these devices either have conical geometries that can damage cells during penetration or are incapable of continuous fluid handling. Here, we report a carbon-nanotube-based endoscope for interrogating cells, transporting fluids and performing optical and electrochemical diagnostics at the single organelle level. The endoscope, which is made by placing a multiwalled carbon nanotube (length, 50-60 µm) at the tip of a glass pipette, can probe the intracellular environment with a spatial resolution of ∼100 nm and can also access organelles without disrupting the cell. When the nanotube is filled with magnetic nanoparticles, the endoscope can be remotely manoeuvered to transport nanoparticles and attolitre volumes of fluids to and from precise locations. Because they are mounted on conventional glass micropipettes, the endoscopes readily fit standard instruments, creating a broad range of opportunities for minimally invasive intracellular probing, drug delivery and single-cell surgery.

Biopolymer encapsulated live influenza virus as a universal CD8+ T cell vaccine against influenza virus.

Current influenza virus vaccines primarily elicit antibodies and can be rendered ineffective by antigenic drift and shift. Vaccines that elicit CD8+ T cell responses targeting less variable proteins may function as universal vaccines that have broad reactivity against different influenza virus strains. To generate such a universal vaccine, we encapsulated live influenza virus in a biopolymer and delivered it to mice subcutaneously. This vaccine was safe, induced potent CD8+ T cell immunity and protected mice against heterosubtypic lethal challenge. Safety of subcutaneous (SQ) vaccination was tested in Rag-/-γc-/- double knockout mice which we show cannot control intranasal infection. Biopolymer encapsulation of live influenza virus could be used to develop universal CD8+ T cell vaccines against heterosubtypic and pandemic strains.

Near infrared wound monitor helps clinical assessment of diabetic foot ulcers.

BACKGROUND: The efficacy of using diffuse near infrared spectroscopy (NIRS) in predicting wound healing in diabetic foot ulcers was demonstrated by conducting a pilot human study. METHOD: Sixteen chronic diabetic wounds were followed and assessed for subsurface oxyhemoglobin concentration using the NIRS device. Weekly measurements were conducted until there was wound closure, limb amputation, or 20 completed visits without healing. Wound size and degree of wound contraction were measured by image analysis of digital photographs, and results were compared to NIRS results. RESULTS: In the 16 patients followed, seven wounds healed, six limbs were amputated, and three wounds remained opened after 20 visits. Initial values of subsurface hemoglobin concentration, in all wounds, were higher than in nonwound control sites. Healed wounds exhibited a consistent reduction of hemoglobin concentration several weeks prior to closure, and the absolute hemoglobin concentration approached the value at the control site. In wounds that did not heal or ended in amputations, the hemoglobin concentration remained elevated throughout the study. A negative slope for the rate of change of hemoglobin concentration was indicative of healing across all wounds. CONCLUSIONS: Evaluation of diabetic foot ulcers using NIRS may provide an effective and more complete measurement of wound healing compared to current clinical approaches.

Image analysis of chronic wounds for determining the surface area.

Progress in wound healing is primarily quantified by the rate of change of the wound's surface area. The most recent guidelines of the Wound Healing Society suggest that a reduction in wound size of <40% within 4 weeks necessitates a reevaluation of the treatment. However, accurate measurement of wound size is challenging due to the complexity of a chronic wound, the variable lighting conditions of examination rooms, and the time constraints of a busy clinical practice. In this paper, we present our methodology to quantify a wound boundary and measure the enclosed wound area reproducibly. The method derives from a combination of color-based image analysis algorithms, and our results are validated with wounds in animal models and human wounds of diverse patients. Images were taken by an inexpensive digital camera under variable lighting conditions. Approximately 100 patient images and 50 animal images were analyzed and a high overlap was achieved between the manual tracings and the calculated wound area by our method in both groups. The simplicity of our method combined with its robustness suggests that it can be a valuable tool in clinical wound evaluations. The basic challenge of our method is in deep wounds with very small surface areas where color-based detection can lead to erroneous results and which could be overcome by texture-based detection methods. The authors are willing to provide the developed MATLAB code for the work discussed in this paper.

Prediction of wound healing in human diabetic foot ulcers by diffuse near-infrared spectroscopy: a pilot study.

A human study was conducted in which the efficacy of in vivo diffuse near-infrared (NIR) spectroscopy was demonstrated in predicting wound healing in diabetic foot ulcers. Sixteen chronic diabetic wounds were followed and assessed for subsurface oxy-hemoglobin concentration using the NIR device. Weekly measurements were conducted until there was wound closure, limb amputation, or 20 completed visits without healing. Digital photography measured wound size, and the degree of wound contraction was compared with the NIR results. In the 16 patients followed, seven wounds healed, six limbs were amputated, and three wounds remained opened after 20 visits. The initial values in subsurface hemoglobin concentration in all wounds were higher than the nonwound control sites. Healed wounds showed a consistent reduction of hemoglobin concentration several weeks before closure that approached control site values. In wounds that did not heal or resulted in amputation of the limb, the hemoglobin concentration remained elevated. In some cases, these nonhealing wounds appeared to be improving clinically. A negative slope for the rate of change of hemoglobin concentration was indicative of healing across all wounds. In conclusion, evaluation of wounds using NIR may provide an effective measurement of wound healing. NIR spectroscopy can determine wound healing earlier than that visibly assessed by current clinical approaches.

Noninvasive assessment of diabetic foot ulcers with diffuse photon density wave methodology: pilot human study.

A pilot human study is conducted to evaluate the potential of using diffuse photon density wave (DPDW) methodology at near-infrared (NIR) wavelengths (685 to 830 nm) to monitor changes in tissue hemoglobin concentration in diabetic foot ulcers. Hemoglobin concentration is measured by DPDW in 12 human wounds for a period ranging from 10 to 61 weeks. In all wounds that healed completely, gradual decreases in optical absorption coefficient, oxygenated hemoglobin concentration, and total hemoglobin concentration are observed between the first and last measurements. In nonhealing wounds, the rates of change of these properties are nearly zero or slightly positive, and a statistically significant difference (p<0.05) is observed in the rates of change between healing and nonhealing wounds. Differences in the variability of DPDW measurements over time are observed between healing and nonhealing wounds, and this variance may also be a useful indicator of nonhealing wounds. Our results demonstrate that DPDW methodology with a frequency domain NIR device can differentiate healing from nonhealing diabetic foot ulcers, and indicate that it may have clinical utility in the evaluation of wound healing potential.

Changes in optical properties of tissue during acute wound healing in an animal model.

Changes of optical properties of wound tissue in hairless rats were quantified by diffuse photon density wave methodology at near-infrared frequencies. The diffusion equation for semi-infinite media was used to calculate the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain device. There was an increase in the absorption and scattering coefficients and a decrease in blood saturation of the wounds compared with the nonwounded sites. The changes correlated with the healing stage of the wound. The data obtained were supported by immunohistochemical analysis of wound tissue. These results verified now by two independent animal studies could suggest a noninvasive method to detect the progress of wound healing.

Correlation of near infrared absorption and diffuse reflectance spectroscopy scattering with tissue neovascularization and collagen concentration in a diabetic rat wound healing model.

The objective of this paper was to correlate optical changes of tissue during wound healing measured by near infrared (NIR) and diffuse reflectance spectroscopy (DRS) with histologic changes in an animal model. Amplitude and phase of scattered light were obtained in a diabetic rat and control model and biopsies were taken for blood vessel ingrowth and collagen concentration. NIR absorption coefficient correlated with blood vessel ingrowth over time, in both the control and diabetic animals. DRS data correlated with collagen concentration. Previous publications by this group documented only the NIR changes during the wound healing process but this is the first reported correlation with histology data. The ability to correlate DRS scattering with collagen concentration during healing is another important and novel finding. This technology may play an important role clinically in assessing the efficacy of wound healing agents in diabetics.

Near infrared diffuse optical tomography: improving the quality of care in chronic wounds of patients with diabetes.

A frequency domain diffuse optical tomography instrument operating in the Near Infrared region (680-830nm) has been designed and used to monitor healing in diabetic wounds in a rat animal model. Instrument design and calibration are described and preliminary data of the in vivo experiment are reported. Excellent discrimination capability between the control and the diabetic population is possible, while the time course of impaired healing in diabetic animals appears to have different optical coefficients from the normal healing in the control group.

Optical properties of wounds: diabetic versus healthy tissue.

Diffuse photon density wave (DPDW) methodology at Near Infrared frequencies has been used to calculate absorption and scattering from wounds of healthy and diabetic rats. The diffusion equation for semi-infinite media is being used for calculating the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain device. Differences observed during the course of healing in the two populations can be correlated to the delayed healing observed in diabetics. These results are encouraging and further work will focus on the implementation of this device to the clinical setting as a monitoring tool in chronic diabetic wounds.

Monitoring diabetic wound healing by NIR spectroscopy.

Chronic wounds represent one of the most serious complications of diabetes. Lack of quantitative assessment of healing progress makes diabetic wound management a clinical challenge. We constructed an optical device based on near infrared diffuse optical spectroscopy and monitored the change in wound optical properties during healing. A single source, four detector frequency domain instrument with multiple wavelengths was employed in a streptozotocin induced diabetic rat animal model. Optical properties including absorption and reduced scattering coefficients were measured. Our results show that there is significant difference in the absorption and reduced scattering coefficient of the wounds between diabetic and controls rats, and such difference persists throughout the healing period. Our technique would be highly useful in monitoring and quantifying the wound healing process.