SignificanceTracking changes in the vasculature of patients with peripheral arterial disease (PAD) may identify the need for follow-up treatment within only weeks after an initial intervention, enabling timely support and improving patient outcomes.AimWe aim to evaluate dynamic vascular optical spectroscopy’s (DVOS’s) ability to accurately monitor the hemodynamics of affected arteries in patients with PAD after a surgical intervention and predict long-term clinical outcomes.ApproachA DVOS system non-invasively monitored the blood flow through 256 lower extremity arteries in 80 PAD patients immediately before, immediately after, and 3 to 4 weeks after they underwent a surgical intervention.ResultsHemodynamic changes measured by DVOS after a revascularization procedure (RP) classified patient long-term (6.2±4.4 months) outcomes with high accuracy [81.6% for patients with ulcers (n=31); 81.1% for patients without ulcers (n=54)] by 3 to 4 weeks after the RP, outperforming available ankle-brachial index and ultrasound measurements. In addition, DVOS parameters distinguished between patients who underwent only a catheter angiography (CA) and patients who underwent both a CA and RP (P<0.05).ConclusionsThe DVOS system was able to classify patient long-term clinical outcomes with high accuracy within one month after an RP and distinguish among different interventions. DVOS may be a promising alternative or adjunct to existing monitoring approaches.
Monitoring the carotid artery in patients who are at high-risk for stroke is crucial for early detection of abnormalities and may improve personalized, point-of-care diagnostics. We have developed a flexible 3-D printed patch for dynamic optical spectroscopy to evaluate the total blood oxygenation within the carotid artery. Each patch consists of a sensing module and detection module measuring 25 mm × 20 mm and 21 mm × 20 mm, respectively, placed a maximum distance of 32 mm apart. The sensing module contains four sources at wavelengths of 670 nm, 750 nm, 808 nm, and 850 nm placed in a square configuration, and the detection module contains two photodiodes in a parallel orientation. During data acquisition, two probes were applied proximally to both the left and right carotid arteries in the neck, and two probes were also placed proximally to the right and left radial arteries in the wrists. Six healthy participants were instructed to perform breathing exercises, such as a single deep breath, continuous deep breaths, and a timed breath hold, with intervals of routine breathing between each activity. Blood oxygenation was continuously measured during the data acquisition protocol. Our study demonstrated consistent blood oxygen content between the left and right carotid and radial arteries across all breathing exercises. Additionally, during a breath hold, we observed a 0.3% and a 0.1% decrease in oxygen saturation in the radial and carotid arteries, respectively. These findings underscore the system's potential to detect disease-related variations in individual carotid arteries, facilitating early detection.
Peripheral arterial disease (PAD) affects over 8.5 million people in the United States. Diagnostic tools to identify PAD continue to have low sensitivity for patients with diabetes and/or with poor vascular health in the small vessels of the lower extremities. A handheld device developed in our laboratory may address these limitations. The device combines dynamic vascular optical spectroscopy (DVOS) with pressure sensing to monitor the relationship between applied pressure and blood volume changes in tissues of interest, which is expected to differ between healthy and PAD subjects. Our probe is 20mm in diameter with the bottom face housing two infrared sources (wavelength λ = 780nm and 850nm) and one silicon photodetector located around 10mm from each source. The DVOS system continuously records the reflected light intensity from the local tissue at a frame rate of 10.24 frames per second. Simultaneously, the load applied by the probe to the tissue surface is measured continuously with a force sensor at the same frame rate. During data acquisition, the applied load is gradually increased, resulting in dynamic changes of the monitored DVOS signals. These recorded signals provide information on the response of the local tissue perfusion to changes in applied pressure. Here, we report on a preclinical study monitoring 3 vascular locations in the lower extremities of 3 healthy volunteers. Preliminary results suggest that on average there is a 0.03% change in total hemoglobin concentration per 10 mmHg change in applied pressure. We expect these changes to be significantly smaller in PAD patients.
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.
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