Aksone Nouvong

Hyperspectral imaging in diabetic foot wound care.

Diabetic foot ulceration is a major complication of diabetes and afflicts as many as 15 to 25% of type 1 and 2 diabetes patients during their lifetime. If untreated, diabetic foot ulcers may become infected and require total or partial amputation of the affected limb. Early identification of tissue at risk of ulcerating could enable proper preventive care, thereby reducing the incidence of foot ulceration. Furthermore, noninvasive assessment of tissue viability around already formed ulcers could inform the diabetes caregiver about the severity of the wound and help assess the need for amputation. This article reviews how hyperspectral imaging between 450 and 700 nm can be used to assess the risk of diabetic foot ulcer development and to predict the likelihood of healing noninvasively. Two methods are described to analyze the in vivo hyperspectral measurements. The first method is based on the modified Beer-Lambert law and produces a map of oxyhemoglobin and deoxyhemoglobin concentrations in the dermis of the foot. The second is based on a two-layer optical model of skin and can retrieve not only oxyhemoglobin and deoxyhemoglobin concentrations but also epidermal thickness and melanin concentration along with skin scattering properties. It can detect changes in the diabetic foot and help predict and understand ulceration mechanisms

Assessing diabetic foot ulcer development risk with hyperspectral tissue oximetry

Foot ulceration remains a serious health concern for diabetic patients and has a major impact on the cost of diabetes treatment. Early detection and preventive care, such as offloading or improved hygiene, can greatly reduce the risk of further complications. We aim to assess the use of hyperspectral tissue oximetry in predicting the risk of diabetic foot ulcer formation. Tissue oximetry measurements are performed during several visits with hyperspectral imaging of the feet in type 1 and 2 diabetes mellitus subjects that are at risk for foot ulceration. The data are retrospectively analyzed at 21 sites that ulcerated during the course of our study and an ulceration prediction index is developed. Then, an image processing algorithm based on this index is implemented. This algorithm is able to predict tissue at risk of ulceration with a sensitivity and specificity of 95 and 80%, respectively, for images taken, on average, 58 days before tissue damage is apparent to the naked eye. Receiver operating characteristic analysis is also performed to give a range of sensitivity/specificity values resulting in a Q-value of 89%.

In vivo time-resolved autofluorescence measurements to test for glycation of human skin.

We present an evaluation of time-resolved fluorescence measurements on human skin for screening type 2 diabetes. In vivo human skin is excited with a pulse diode at 375 nm and pulse width of 700 ps. Fluorescence decays are recorded at four different emission wavelengths: 442, 460, 478, and 496 nm. Experiments are performed at various locations, including the palms, arms, legs, and cheeks of a healthy Caucasian subject to test single-subject variability. The fluorescence decays obtained are modeled using a three-exponential decay. The variations in the lifetimes and amplitudes from one location to another are minimal, except on the cheek. We compare the fluorescent decays of 38 diabetic subjects and 37 nondiabetic subjects, with different skin complexions and of ages ranging from 6 to 85 yr. The average lifetimes for nondiabetic subjects were 0.5, 2.6, and 9.2 ns with fractional amplitudes of 0.78, 0.18, and 0.03, respectively. The effects of average hemoglobin A1c (HbA1c) from the previous 4 yr and diabetes duration are evaluated. While no significant differences between the fluorescence lifetimes of nondiabetic and diabetic subjects are observed, two of the fractional amplitudes are statistically different. Additionally, none of the six fluorescence parameters correlated with diabetes duration or HbA1c. One of the lifetimes as well as two of the fractional amplitudes differ between diabetic subjects with foot ulcers and nondiabetic subjects.

Monitoring temporal development and healing of diabetic foot ulceration using hyperspectral imaging

This study combines non-invasive hyperspectral imaging with an experimentally validated skin optical model and inverse algorithm to monitor diabetic feet of two representative patients. It aims to observe temporal changes in local epidermal thickness and oxyhemoglobin concentration and to gain insight into the progression of foot ulcer formation and healing. Foot ulceration is a debilitating comorbidity of diabetes that may result in loss of mobility and amputation. Inflammation and necrosis preempt ulceration and can result in changes in the skin prior to ulceration and during ulcer healing that affect oxygen delivery and consumption. Previous studies estimated oxyhemoglobin and deoxyhemoglobin concentrations around pre-ulcerative and ulcer sites on the diabetic foot using commercially available hyperspectral imaging systems. These measurements were successfully used to detect tissue at risk of ulceration and predict the healing potential of ulcers. The present study shows epidermal thickening and decrease in oxyhemoglobin concentration can also be detected prior to ulceration at pre-ulcerative sites. The algorithm was also able to observe reduction in the epidermal thickness combined with an increase in oxyhemoglobin concentration around the ulcer as it healed and closed. This methodology can be used for early prediction of diabetic foot ulceration in a clinical setting.

The Top 10 Things Foot and Ankle Specialists Wish Every Primary Care Physician Knew

Foot and ankle problems are common complaints of patients presenting to primary care physicians. These problems range from minor disorders, such as ankle sprains, plantar fasciitis, bunions, and iIngrown toenails, to more serious conditions such as Charcot arthropathy and Achilles tendon rupture. Early recognition and treatment of foot and ankle problems are imperative to avoid associated morbidities. Primary care physicians can address many of these complaints successfully but should be cognizant of which patients should be referred to a foot and ankle specialist to prevent common short-term and long-term complications. This article provides evidence-based pearls to assist primary care physicians in providing optimal care for their patients with foot and ankle complaints.

Two-Layer Optical Model of Skin for Early, Non-Invasive Detection of Wound Development on the Diabetic Foot

Foot ulceration is a debilitating comorbidity of diabetes that may result in loss of mobility and amputation. Optical detection of cutaneous tissue changes due to inflammation and necrosis at the preulcer site could constitute a preventative strategy. A commercial hyperspectral oximetry system was used to measure tissue oxygenation on the feet of diabetic patients. A previously developed predictive index was used to differentiate preulcer tissue from surrounding healthy tissue with a sensitivity of 92% and specificity of 80%. To improve prediction accuracy, an optical skin model was developed treating skin as a two-layer medium and explicitly accounting for (i) melanin content and thickness of the epidermis, (ii) blood content and hemoglobin saturation of the dermis, and (iii) tissue scattering in both layers. Using this forward model, an iterative inverse method was used to determine the skin properties from hyperspectral images of preulcerative areas. The use of this information in lowering the false positive rate was discussed.

Reactive oxygen species and bacterial biofilms in diabetic wound healing

Chronic wounds are a common and debilitating complication for the diabetic population. It is challenging to study the development of chronic wounds in human patients; by the time it is clear that a wound is chronic, the early phases of wound healing have passed and can no longer be studied. Because of this limitation, mouse models have been employed to better understand the early phases of chronic wound formation. In the past few years, a series of reports have highlighted the importance of reactive oxygen species and bacterial biofilms in the development of chronic wounds in diabetics. We review these recent findings and discuss mouse models that are being utilized to enhance our understanding of these potentially important contributors to chronic wound formation in diabetic patients.

Evaluation of diabetic foot ulcer development using hyperspectral imaging

The World Health Organization estimates that more than 180 million people worldwide have diabetes. This number is expected to double by 2030. In 2008, diabetes affected over 21 million Americans corresponding to an estimated 7.9% of the population. Foot ulceration is a debilitating comorbidity of diabetes and a leading cause of hospitalization that can result in loss of mobility and amputation. Studies have shown that (i) 15% of all diabetic patients develop a foot ulcer at least once in their life and (ii) foot ulcers precede about 85% of all lower limb amputations among diabetic patients. In the United States alone, more than 88,000 amputations are performed annually on diabetic patients. Treatment of infected and/or ischemic diabetic foot ulcers accounts for about 25% of all hospital days and the costs of foot disorder diagnosis and management are estimated at several billion dollars annually. Thus, early detection of foot ulcer formation could reduce the human and financial costs of the disease. It can assist clinicians in early preventive therapy including unloading or prescribing appropriate orthotics or footgear. Predictions of healing probability could also increase the limb salvation rate.