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Assessing the infinitely expanding intersection region for the development of large-scale multipoint laser Doppler velocimetry
摘要： Multipoint laser Doppler velocimetry (MLDV) has been effective for non-invasively measuring the flow velocity distribution with a high-spatial and high-time resolution. The flow velocity can be estimated using a scattered light signal by seeding particles passing through a fringe pattern formed in the intersection region of two laser beams. The shape of this intersection region can be easily changed by changing the optical components and positions of the lasers. An infinitely expanding intersection region is proposed in the present paper. A wide intersection region was indicated by the measurement results of flow velocity. The intersection region is evaluated using a flow channel (1.4 mm ? 1.4 mm). The area of the operating measurement region exceeds 150 mm in the horizontal direction and is less than ?10 mm in the vertical direction. This new MLDV is referred to as a large-scale MLDV.
关键词： flow velocity distribution,high-spatial resolution,large-scale MLDV,intersection region,high-time resolution,Multipoint laser Doppler velocimetry,MLDV
更新于2025-09-12 10:27:22
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Chronic Hindlimb Ischemia Assessment; Quantitative Evaluation Using Laser Doppler in a Rodent Model of Surgically Induced Peripheral Arterial Occlusion
摘要： Therapeutic neoangiogenesis (TNA) holds promise as a treatment for peripheral arterial disease. Nevertheless, proper tools for in vivo pre-clinical investigation of different TNA approaches and their effects are still lacking. Here we describe a chronic ischemic hindlimb model in rats using laser Doppler quantitative evaluation of tissue perfusion. Male Wistar rats (n = 20), aged between 6–8 months, with an average weight of 287 ± 26.74 g, were used. Animals were divided into two experimental groups: group A (n = 17; hindlimb chronic ischemia model) and group B (n = 3; control). Hindlimb ischemia was induced by concomitant ligation of the right femoral and popliteal artery. Evaluation of tissue perfusion was quantified in perfusion units (PU) on a scale from 0 to 500 (500 PU = maximal detectable perfusion) by laser Doppler analysis at day 0, day 15 and day 30 after induction of ischemia. Induction of chronic ischemia in the rat hindlimb by concomitant ligation of the femoral and popliteal artery can be readily obtained but requires basic microsurgical skills. Laser Doppler analysis has shown unaltered ischemia levels throughout the study (129,17 PU ± 3.13 day 0 vs. 130,33 PU day 30 ± 3,27, p = not significant (n.s.)). We demonstrate a simple and reproducible model of chronic hindlimb ischemia in rats, with stable tissue perfusion levels that are accurately quantified using laser Doppler technology. Hence, this model can represent a valid tool for further studies involving therapeutic neoangiogenesis.
关键词： laser Doppler,chronic ischemia,experimental model,hindlimb
更新于2025-09-12 10:27:22
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Gastroscopy assisted laser Doppler flowmetry and visible light spectroscopy in patients with chronic mesenteric ischemia
摘要： Mucosal pathology due to chronic mesenteric ischemia (CMI) is rarely seen during upper endoscopy. Combining Laser Doppler Flowmetry (LDF) and Visible Light Spectroscopy (VLS) may aid in detection of CMI at an early stage. We aimed to investigate the utility of LDF and VLS in detecting microcirculatory changes in patients with CMI during upper endoscopy. In a single center, prospective study, 104 patients were evaluated for mesenteric ischemia during a 24 months period. Patients with a consensus diagnosis of CMI (n ? 40) were examined with LDF and VLS. Thirty-two were successfully treated and had a definitive diagnosis of CMI. Results were compared with controls (n ? 38) with normal intestinal circulation evaluated with duplex ultrasonography (DUS). Treatment response was evaluated clinically and with DUS at 1 month and with VLS and LDF at 3 months. A significant reduction in mucosal capillary hemoglobin oxygen saturation (SO2) was found in CMI patients compared to controls before treatment: mean ± SD: 67 ± 9%, 81 ± 4%, respectively (p < .001). A significant reduction was also seen for the relative hemoglobin (rHb) amount, flow and velocity (p < .001). The sensitivity of SO2 measured by VLS for diagnosing CMI was 94% and the specificity 72% (cut-off 78%), calculated with ROC curve analysis. A combination of SO2 and rHb increased the test sensitivity and specificity to 97% and 79%, respectively. Conclusion: CMI patients have significantly reduced microcirculation in the stomach and duodenum compared to controls. The results suggest that VLS should be included when performing an upper endoscopy in patients with suspected CMI.
关键词： laser doppler flowmetry,acute mesenteric ischemia,Chronic mesenteric ischemia,upper endoscopy,visible light spectroscopy
更新于2025-09-12 10:27:22
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Diagnostic accuracy of laser Doppler imaging for the assessment of burn depth: a meta-analysis and systematic review
摘要： An overall assessment of the diagnostic value of laser Doppler imaging (LDI) to assess burn depth in patients is presented based on relevant studies. Both eligible research and relevant articles were identified through specific index searches of Embase, Cochrane and PubMed databases. The latest study included was published in March 2019 and all eligible publications reported on cohort or cross-sectional research. All articles were tested for heterogeneity by using a suitable effect model to calculate amalgamative values of sensitivity, specificity and the diagnostic odds ratio (DOR). Analyses of summary receiver operating characteristic (SROC) are given for burn depth values. After rigorous screening, 14 studies with a total cohort of 1,818 patients were chosen for the meta-analysis to explore the validity of LDI diagnosis to assess the depth of burns. The burn depth overall sensitivity for LDI was 91% (95% CI: 86-95%) and global specificity was 96% (95% CI: 92-98%). The overall positive likelihood ratio of LDI was 20.35 (95% CI: 10.71-38.69) and the overall negative likelihood ratio was 0.09 (95% CI: 0.05-0.15). The overall DOR was 152.93 (95% CI: 69.44-336.81) of LDI. The acreage under the SROC was not low for LDI (AUC = 0.98; 95% CI: 0.96-0.99). In conclusion, the present analysis reviewed the literature and meta-analysis of studies to validate LDI for the diagnosis of burn depth. The results indicated that LDI has a high accuracy for this diagnostic function.
关键词： diagnostic accuracy,burn depth,meta-analysis,laser Doppler imaging (LDI)
更新于2025-09-12 10:27:22
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Quantitative Analysis of Heel Skin Microcirculation Using Laser Doppler Flowmetry and Tissue Spectrophotometry
摘要： OBJECTIVE: To examine perfusion changes in the heel skin of individuals with and without diabetes mellitus to understand how skin is pathologically affected by diabetes mellitus. METHODS: This case-control study was conducted at an academic hospital in Tuebingen, Germany. A total of 30 subjects were enrolled in the study: 15 with known type 2 diabetes mellitus and 15 without. Each subject was asked to lie in a supine position on a hard lateral transfer mat for 10 minutes. MAIN OUTCOME MEASURES: Heel perfusion was quantitatively assessed directly after relief of pressure and after 3 and 6 minutes after relief of pressure using laser Doppler flowmetry and tissue spectrophotometry. MAIN RESULTS: Directly after relief of pressure, blood flow increased in the superficial skin layers (2 mm below the surface of the skin) in both groups. However, in deep skin layers (8 mm below the surface of the skin), blood flow increased in patients with diabetes mellitus and decreased in healthy patients. Oxygen saturation (SO2) was higher in healthy subjects directly after pressure relief. CONCLUSIONS: The increase in blood flow in superficial skin layers indicates reactive hyperemia after exposure in both groups. The prolonged hyperemia in deep skin layers in patients with diabetes indicates increased tissue vulnerability. Despite the increase in blood flow in deep skin layers, the SO2 and thus supply of tissue in patients with diabetes were reduced.
关键词： diabetes mellitus,pressure injury,oxygen saturation,blood flow,perfusion,diabetic foot ulcers,laser Doppler flowmetry,pressure ulcer,microcirculation
更新于2025-09-12 10:27:22
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Laser-based Techniques for Microcirculatory Assessment in Orthopedics and Trauma Surgery
摘要： Microcirculatory integrity and proper function are the cornerstones to tissue nourishment and viability. In the clinical environment extended immobility, injuries, and inflammatory reactions demand local microcirculatory adaption to provide adequate supply. Assessment of endothelial adjustment capability and microcirculatory perfusion status, as direct or surrogate markers of disease, are therefore of uttermost interest to the treating physician. Given the simple, noninvasive, nonradiating nature of laser-based techniques for bedside or intraoperative microcirculatory perfusion assessment, this article’s objective is to present a comprehensive overview of available techniques, their technological aspects, and current application. Advantages of individual methods are pointed out and compared with each other. The areas of medical utilization relevant to orthopedics and trauma surgery are exemplified and their available evidence elaborated. A particular focus is put on laser speckle contrast imaging, with its current and future influence on medical practice.
关键词： noninvasive cutaneous microcirculatory perfusion assessment,laser Doppler flowmetry,laser Doppler imaging,Laser speckle contrast imaging
更新于2025-09-11 14:15:04
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Wavelet Analysis of the Temporal Dynamics of the Laser Speckle Contrast in Human Skin
摘要： Objective: Spectral analysis of laser Doppler ?owmetry (LDF) signals has been widely used in studies of physiological vascular function regulation. An alternative to LDF is the laser speckle contrast imaging method (LSCI), which is based on the same physical principle. In contrast to LDF, LSCI provides non-scanning full-?eld imaging of a relatively wide skin area and offers high spatial and temporal resolutions, which allows visualization of microvascular structure. This circumstance, together with a large number of works which had shown the effectiveness of temporal LSCI analysis, gave impetus to experimental studies of the relation between LDF and LSCI used to monitor the temporal dynamics of blood ?ow. Methods: Continuous wavelet transform was applied to construct a time-frequency representation of a signal. Results: Analysis of 10 minute LDF and LSCI output signals recorded simultaneously revealed rather high correlation between oscillating components. It was demonstrated for the ?rst time that the spectral energy of oscillations in the 0.01-2 Hz frequency range of temporal LSCI recordings carries the same information as the conventional LDF recordings and hence it re?ects the same physiological vascular tone regulation mechanisms. Conclusion: The approach proposed can be used to investigate speckle pattern dynamics by LSCI in both normal and pathological conditions. Signi?cance: The results of research on the in?uence of spatial binning and averaging on the spectral characteristics of perfusion monitored by LSCI are of considerable interest for the development of LSCI systems optimized to evaluate temporal dynamics.
关键词： laser Doppler ?owmetry,oscillations,blood microcirculation,wavelets,laser speckle contrast imaging
更新于2025-09-11 14:15:04
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Revascularization of Free Skin Grafts Overlying Modified Hughes Tarsoconjunctival Flaps Monitored Using Laser-Based Techniques
摘要： Purpose: It has recently been shown that the flap pedicle does not supply blood to a tarsoconjunctival graft in the modified Hughes procedure in patients. This raises questions concerning the rate of revascularization of the free skin graft commonly used to reconstruct the anterior lamella. The aim of this study was, thus, to monitor the course of revascularization in free skin grafts overlying modified Hughes tarsoconjunctival flaps, using laser-based techniques. Methods: Free skin grafts from the upper eyelid or upper arm in 9 patients were used to cover a tarsoconjunctival flap according to the modified Hughes procedure. Blood perfusion was monitored using laser speckle contrast imaging, and vascular reactivity was studied with laser Doppler velocimetry after heating the tissue to 44°C. Measurements were made at the time of surgery (baseline) and at 1, 3, 8, and 16 weeks postoperatively. Results: The gradual increase in perfusion of the free skin grafts during the healing process indicates revascularization. A slight increase in perfusion was seen already after 1 week. Perfusion reached 50% of the baseline after 3 weeks, and complete restoration of perfusion was seen after 8 weeks. The vascular function monitored with heat-induced hyperemia increased in a similar fashion. Conclusions: Full-thickness skin grafts revascularize within 3 to 8 weeks, despite overlying a tarsoconjunctival flap, which has recently been reported to be avascular. This provides further evidence that it should be possible to repair large eyelid defects using free full-thickness eyelid grafts.
关键词： laser Doppler velocimetry,revascularization,laser speckle contrast imaging,free skin grafts,modified Hughes tarsoconjunctival flaps
更新于2025-09-11 14:15:04
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Preclinical vascular alterations in obese adolescents detected by Laser-Doppler Flowmetry technique
摘要： Background and aims: Childhood obesity promotes adverse changes in cardiovascular structure and function. This study evaluated whether alterations in skin microcirculation were already present in obese adolescents in a pre-clinical phase of cardiovascular disease. Methods and results: After an overnight fasting 22 obese adolescents and 24 normal-weight controls of similar age and gender distribution underwent clinical and blood examination and assessment of microvascular function by using two non-invasive techniques such as Peripheral Artery Tonometry (PAT) and Laser-Doppler Flowmetry (LDF). As compared to normal weight subjects, obese children had higher blood pressure, were significantly more hyper-insulinemic and insulin resistant, showing significantly higher plasma total cholesterol, LDL cholesterol, triglycerides and alanine aminotransferase (ALT). LDF showed lower pre- and post-occlusion forearm skin perfusion (perfusion units/second (PU/sec); median [IQR]) in obese than in normal weight subjects (pre-occlusion: 1633.8 [1023.5] vs. 2281.1 [1344.2]; p Z 0.015. Post-occlusion: 4811.3 [4068.9] vs. 7072.8 [7298.8]; p Z 0.021), while PAT revealed similar values of reactive hyperemia index (RHI). In entire population, fat mass % (FM%) was an independent determinant of both pre-and post-occlusion skin perfusion. Finally, being obese was associated with a higher risk to have a reduction of both pre- and post-occlusion skin perfusion (OR Z 5,82 and 9,27, respectively). Conclusion: LDF showed very early, pre-clinical, vascular involvement in obese adolescents, characterized by impaired skin microcirculation, possibly reflecting a more diffuse microvascular dysfunction to other body tissues. Whether changing life style and improving weight may reverse such pre-clinical alterations remains to be established.
关键词： Microcirculation,Obesity,Skin,Peripheral artery tonometry,Laser-Doppler flowmetry
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Assessment of Accelerometer Versus LASER for Board Level Vibration Measurements
摘要： The ongoing trend to deploy ICs in more complex and harsher applications, entails precise evaluation of solder joint reliability of components subjected to vibration loads. For this, a good understanding of the PCB vibrational motion during a board level vibration test is essential. This can only be achieved by a well characterized vibration test setup. The vibration motion can be recorded by using a contact-based measurement approach, using an accelerometer, or a contactless measurement configuration, i.e. using a Laser Doppler Vibrometer (LDV). This paper evaluates both measurement techniques by recording the PCB dynamic response, i.e. the resonance frequency and peak-to-peak displacement, in a board level vibration test set up. Bare and assembled printed circuit boards (PCBs) are investigated using different PCB form factors and package outlines (Wafer Level Chip Scale Package (WLCSP) and Ball Grid Array (BGA)), showing that LDV enables better lateral resolution and a more accurate measurement solution. Especially when the weight of the accelerometer cannot be neglected compared to the weight of the component on the PCB. An accelerometer is shown to perturb the PCB vibration motion. It is found that depending upon the test objectives and PCB electronic system involved, both techniques can be used as complementary to one another. The accelerometer weight may give rise to substantial modification of vibration response which can be used to simulate the presence of a component on a bare PCB. In addition, both methods are expected to recognize the same trends when e.g. studying the environmental impact during vibration tests. Finally, the experimental observations are also confirmed using a Finite Element Model (FEM).
关键词： board level reliability,LASER Doppler Vibrometer,Wafer Level Chip Scale Package,vibration test,modal analysis,PCB dynamic response
更新于2025-09-11 14:15:04