Azita Tajaddini

Evaluation of Diabetic Foot Ulcer Healing With Hyperspectral Imaging of Oxyhemoglobin and Deoxyhemoglobin

OBJECTIVE Foot ulceration remains a major health problem for diabetic patients and has a major impact on the cost of diabetes treatment. We tested a hyperspectral imaging technology that quantifies cutaneous tissue hemoglobin oxygenation and generated anatomically relevant tissue oxygenation maps to assess the healing potential of diabetic foot ulcers (DFUs). RESEARCH DESIGN AND METHODS A prospective single-arm blinded study was completed in which 66 patients with type 1 and type 2 diabetes were enrolled and followed over a 24-week period. Clinical, medical, and diabetes histories were collected. Transcutaneous oxygen tension was measured at the ankles. Superficial tissue oxyhemoglobin (oxy) and deoxyhemoglobin (deoxy) were measured with hyperspectral imaging from intact tissue bordering the ulcer. A healing index derived from oxy and deoxy values was used to assess the potential for healing. RESULTS Fifty-four patients with 73 ulcers completed the study; at 24 weeks, 54 ulcers healed while 19 ulcers did not heal. When using the healing index to predict healing, the sensitivity was 80% (43 of 54), the specificity was 74% (14 of 19), and the positive predictive value was 90% (43 of 48). The sensitivity, specificity, and positive predictive values increased to 86, 88, and 96%, respectively, when removing three false-positive osteomyelitis cases and four false-negative cases due to measurements on a callus. The results indicate that cutaneous tissue oxygenation correlates with wound healing in diabetic patients. CONCLUSIONS Hyperspectral imaging of tissue oxy and deoxy may predict the healing of DFUs with high sensitivity and specificity based on information obtained from a single visit.

Automated three-dimensional assessment of coronary artery anatomy with intravascular ultrasound scanning

BACKGROUND Angiography allows the definition of advanced, severe stages of coronary artery disease, but early atherosclerotic lesions, which do not lead to luminal stenosis, are not identified reliably. In contrast, intravascular ultrasound scanning allows the precise characterization and quantification of a wide range of atherosclerotic lesions, independent of the severity of luminal stenosis. METHODS Three-dimensional (3-D) reconstruction of entire coronary segments is possible with the integration of sequential 2-dimensional tomographic images and allows volumetric analysis of coronary arteries. RESULTS Automated systems able to recognize lumen and vessel borders and to display 3-D images are becoming available. CONCLUSION These systems have the potential for on-line 3-D image reconstruction for clinical decision-making and fast routine volumetric analysis in research studies. This review describes 3-D intravascular ultrasound scanning acquisition, analysis, and processing, and the associated technical challenges.

A novel experimental method to estimate stress-strain behavior of intact coronary arteries using intravascular ultrasound (IVUS).

Most arterial mechanics studies have focused on excised non-coronary vessels, with few studies validating the application of ex-vivo results to in-vivo conditions. A method was developed for testing the mechanical properties of intact left anterior descending coronary arteries under a variety of conditions. Vascular deformation and pressure were simultaneously measured with intravascular ultrasound and a pressure transducer guidewire, respectively. Results suggest the importance of understanding in-vivo factors such as myocardial support, vascular tone and local pressure fluctuations when applying ex-vivo coronary characterization data. With further development, this method can more accurately characterize the true in-vivo constitutive behavior in normal and atherosclerotic coronaries.

Simulation of lower limb axial arterial length change during locomotion

The effect of external forces on axial arterial wall mechanics has conventionally been regarded as secondary to hemodynamic influences. However, arteries are similar to muscles in terms of the manner in which they traverse joints, and their three-dimensional geometrical requirements for joint motion. This study considers axial arterial shortening and elongation due to motion of the lower extremity during gait, ascending stairs, and sitting-to-standing motion. Arterial length change was simulated by means of a graphics based anatomic and kinematic model of the lower extremity. This model estimated the axial shortening to be as much as 23% for the femoropopliteal arterial region and as much as 21% for the iliac artery. A strong correlation was observed between femoropopliteal artery shortening and maximum knee flexion angle (r²=0.8) as well as iliac artery shortening and maximum hip angle flexion (r²=0.9). This implies a significant mechanical influence of locomotion on arterial behavior in addition to hemodynamics factors. Vascular tissue has high demands for axial compliance that should be considered in the pathology of atherosclerosis and the design of vascular implants.

Skin microcirculation in feet of healthy subjects after short-term intermittent pneumatic compression (IPC)

INTRODUCTION Approximately 10-20% of individuals older than 70 years have peripheral arterial disease (PAD). In PAD, atherosclerotic narrowing of the leg arteries limits the blood flow to the extremities, which is associated with considerable morbidity, and increased cardiovascular risk. Intermittent pneumatic compression (IPC) is promising as a conservative means of maintaining the lower extremity circulation (1). A number of studies have shown improvement in skin microcirculation as well as in arterial blood flow after using long term use of IPC (2). However, the physiological mechanism of action and efficiency of the devices are still under investigation (3). This study will provide preliminary data for quantifying the benefits that could result from short term use of IPC with the Perfect Touch® device.

Fat pad volume in the forefoot of diabetic patients with recurrent ulcers

Plantar ulcers are a major complication of diabetes, often leading to amputation. Multiple factors are known to contribute to the etiology of ulcers, including neuropathy, plantar pressures, and vascular changes. This study focused on another factor that is thought to play a role, namely fat pad thickness under the metatarsal heads. Both non-diabetic (n = 10) and diabetic patients with a history of ulceration (n = 14) were recruited for this study. These groups were matched in terms of age and body mass index. Each subject had MRI data collected on each foot (once every 2 months for 1 year for diabetic patients, and once every 6 months for control subjects). The Tl-weighted images spanned the entire midand forefoot regions. Post-processing involved segmenting the images into fat volumes using an in-house image processing routine (Slice-o-matic, CCF), followed by 3D reconstruction using Rhinocerous 3.0. Percentage of fat in the plantar soft tissues was calculated by scaling the overall fat volume to the number of slices needed to span the length of the metatarsals. The results showed that, as expected, fat pad volume decreased as a function of duration of diabetes (p < 0.05). However diabetic subjects who re-ulcerated during the course of this study (n =6) surprisingly had a higher fat volume in their metatarsal region (p<0.05) compared with patients who did not reulcerate. This finding casts doubt on the notion that repeat ulceration in diabetic patients is due to a fat pad that is too thin to provide adequate cushioning. It is still possible, however, that there may be localized changes in fat pad thickness, or altered material properties, in patients who are prone to re-ulceration. The authors would like to acknowledge support of the Cleveland Clinics General Clinical Research Center (funded by the National Institutes of Health) and funding provided by the Diabetes Association of Greater Cleveland and the Juvenile Diabetes Research Foundation.