Peripheral arterial disease (PAD) affects an estimated 8.5 million people in the United States. PAD is caused by atherosclerosis, which is a narrowing of the arteries due to plaque build-up. Patients with a severe presentation of the disease often require a surgical intervention to reopen the arteries and restore blood flow to the affected areas. During the intervention, physicians often monitor the progress of the intervention using contrast angiography. The process requires a contrast agent and high radiation doses. Our lab has proposed the use of dynamic vascular optical spectroscopy (DVOS) as a non-invasive, non-iodizing method to track changes in the arteries during an intervention. In this preliminary study, we found that the DVOS signal changes in response to intervention techniques such as balloon inflations and deflations. For our trial subject, we saw on average a 19.5% change in total hemoglobin concentration (HbT) due to injection of a contrast agent prior to balloon inflation and on average a 26.6% change in HbT due to injection of a contrast agent after a sequence of balloon inflations and deflations. The data suggest that DVOS can monitor vascular health and blood perfusion in arteries in real-time during a surgical intervention.
KEYWORDS: Wound healing, Arteries, Data acquisition, Diseases and disorders, Vascular diseases, Lab on a chip, Blood, Optical spectroscopy, Animal model studies, Optical sensing
SignificanceDue to the persistence of chronic wounds, a second surgical intervention is often necessary for patients with peripheral arterial disease (PAD) within a year of the first intervention. The dynamic vascular optical spectroscopy system (DVOS) may assist physicians in determining patient prognosis only a month after the first surgical intervention.AimWe aim to assess the DVOS utility in characterizing wound healing in PAD patients after endovascular intervention.ApproachThe DVOS used near-infrared light (670 < λ < 850 nm) to record hemodynamic response to a cuff inflation in 14 PAD patients with lower limb ulcers immediately before, immediately after, and at a first follow-up 3 to 4 weeks after intervention. Ankle-brachial index (ABI) and arterial duplex ultrasound (A-DUS) measurements were obtained when possible.ResultsThe total hemoglobin plateau time differed significantly between patients with ulcers that reduced in size (N = 9) and patients with ulcers that did not (N = 5) 3 to 4 weeks after intervention (p value < 0.001). Data correlated strongly (89% sensitivity, 100% specificity, and AUC = 0.96) with long-term wound healing. ABI and A-DUS measurements were not statistically associated with wound healing.ConclusionsThis pilot study demonstrates the potential of the DVOS to aid physicians in giving accurate long-term wound healing prognoses 1 month after intervention.
Ulcers are a common occurrence in diabetic patients with peripheral arterial disease (PAD). Early prognosis of ulcer healing can help patients avoid prolonged pain and future amputation by alerting physicians to intervention efficacy. However, monitoring of ulcers and predicting intervention success remains a challenge. We have developed a so-called vascular optical tomography imaging system (VOTIS) to address this problem. The system consists of patches with infrared sources and silicon photodiodes. The patches are placed on areas of interest in the lower extremities and light attenuation data is obtained at multiple frames per second. During data acquisition, a thigh cuff is inflated and deflated to affect blood flow to the lower extremities, resulting in dynamic changes of the recorded signals. Features such as maximum change in total absorption, response time to cuff inflation, and plateau time (PT) between cuff inflation and deflation can be extracted. Here we report on a pilot study of 10 PAD patients (70% diabetic) with ulcers, who had a surgical intervention to improve blood flow. VOTIS measurements were obtained immediately after the intervention, and again three weeks later. Prognosis was determined from EHR and classified as improvement (N=7) - when an ulcer reduces in size - or no improvement (N=3). In an ROC analysis, the VOTIS-derived biomarker PT demonstrated high classification potential (Sn=86%, Sp=100%, AUC=0.95).
Approximately 12 million people in the United States are affected by peripheral artery disease (PAD), characterized by an accumulation of plaque in the arteries of the lower extremities. In advanced stages, treating physicians often recommend a surgical intervention to improve blood flow to the feet. However, about 50% of patients require a second intervention within 12 months. Here we report on the potential of dynamic optical imaging (DOI) to predict the long-term outcome of such surgery. Our DOI system consists of four detection patches, each configured with two SI-detectors and four laser diodes at different wavelengths (678 nm, 780 nm, 808 nm and 850 nm). These patches are placed on four different angiosomes of the foot to record the dynamical responses to inflations and deflations of a thigh cuff. Inflating a cuff causes blood to accumulate in the foot, while deflating the cuff reduces the amount of blood. DOI measurements can be characterized by a response time to cuff inflation (rise time), and a plateau time between cuff inflation and deflation. For this study 16 patients with no previous history of interventions were enrolled, and DOI data was collected before and after the intervention. 4 of the 16 patients needed a second intervention within 6 months. We found a strong correlation between the changes in pre-and post-intervention rise time and the 6 months treatment outcome. A ROC analysis showed that it was possible to categorize outcomes correctly with an AUC (Area Under the Curve) of about 83%, and corresponding specificity of 100% and sensitivity of 75%.
In patients with peripheral artery disease (PAD), plaque is accumulating in arteries which leads to a reduction in blood supply to the extremities. In advanced stages, surgical intervention is required to reopen the arteries and restore limb perfusion. During this procedure, it is important to correctly identify which areas of the foot lack perfusion. The standard procedure to obtain this information is X-ray angiography, which is performed repeatedly during the intervention. The disadvantage of this procedure is the relatively high radiation dose and extensive use of contrast agents. To reduce this problem, we evaluate in this pilot study (involving 4 patients) the ability of vascular optical spectroscopy (VOS) to detect the X-ray contrast agent permeating the angiosomes in the foot. We show that the contrast agent can be detected by optical measurements as it temporarily replaces the blood in the different angiosomes, which leads to a 1% to 5% change in the signal amplitude. In addition, measurements of the blood pooling in the foot were performed before the intervention. We observed a strong correlation between the angiosomes that showed a worsen state in the measurement done before the intervention and the absence of angiographic contrast agent signals during the intervention itself. Among the 4 patients monitored, 2 showed a response to the contrast agent in their angiosomes and they corresponded to the patients with a relatively better perfusion in the pre-intervention measurements.
Peripheral artery disease (PAD) affects approximately 12 million people in the US. The disease is caused by an accumulation of plaque in arteries, which leads to stenosis and reduction in blood flow. In advanced cases, surgery or endovascular interventions are required to re-establish blood flow to the extremities. In over 40% of these cases a second intervention is required within 12 months. Therefore, accurate monitoring the blood flow in the feet of these patients is crucial. In this study, dynamic vascular optical spectroscopy was used to assess perfusion in 4 different angiosomes of 25 patients who underwent a surgical intervention. Imaging was performed just before the intervention, 4 hours later and 1 month later. Each optical spectroscopy session consisted in inflating a thigh pressure cuff to 60 mmHg, maintaining the pressure for 60 seconds and releasing it, then repeating the procedure while inflating the cuff to 100 mmHg. Totalhemoglobin [THb] time traces for each angiosome were calculated. We found a strong correlation between the dynamic shapes of the THb-signals obtained before the intervention, 3 hours after the intervention and 1 month later and the longterm outcome of the procedure.
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