Depth resolution in multifocus laser speckle contrast imaging

Zheng, Shuqi; Xiao, Sheng; Kretsge, Lisa N.; Cruz-Martín, Alberto; Mertz, Jérôme

doi:10.1364/ol.436334

Cited by 9 publications

(2 citation statements)

References 23 publications

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“…Factors that are critical to consider are: (i) penetration depth of LSCI when applied to renal imaging, (ii) type of the vessels in the field of view, and (iii) topology of the nephro-vascular network. While in theory, LSCI can collect the blood flow signal from as deep as 300–400 μm, in practice, visually resolvable signal typically comes from top 50 to 150 μm of the vascular structure ( Davis et al, 2014 ; Zheng et al, 2021 ). Considering high vascular density close to the renal surface, it would mean that LSCI is likely limited to imaging vessels originating from ≈10000 nephrons in outer 30% of rat renal cortex ( Letts et al, 2017 ), which would result in ≈40 nephrons in the 1.5 × 1.5 µm field of view.…”

Section: Discussionmentioning

confidence: 99%

Synchronization in renal microcirculation unveiled with high-resolution blood flow imaging

Postnov

Marsh

Cupples

et al. 2022

eLife

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Internephron interaction is fundamental for kidney function. Earlier studies have shown that nephrons signal to each other, synchronise over short distances, and potentially form large synchronised clusters. Such clusters would play an important role in renal autoregulation, but due to the technological limitations, their presence is yet to be confirmed. In the present study, we introduce an approach for high-resolution laser speckle imaging of renal blood flow and apply it to estimate frequency and phase differences in rat kidney microcirculation under different conditions. The analysis unveiled spatial and temporal evolution of synchronised blood flow clusters of various sizes, including the formation of large (>90 vessels) long-lived clusters (>10 periods) locked at the frequency of the tubular glomerular feedback mechanism. Administration of vasoactive agents caused significant changes in the synchronisation patterns and, thus, in nephrons' co-operative dynamics. Specifically, infusion of vasoconstrictor angiotensin II promoted stronger synchronisation, while acetylcholine caused complete desynchronisation. The results confirm the presence of the local synchronisation in the renal microcirculatory blood flow and that it changes depending on the condition of the vascular network and the blood pressure, which will have further implications for the role of such synchronisation in pathologies development.

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Section: Discussionmentioning

confidence: 99%

Synchronization in renal microcirculation unveiled with high-resolution blood flow imaging

Postnov

Marsh

Cupples

et al. 2022

eLife

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“…Moreover, the depth resolution of LSF is limited, making it unsuitable for layer-specific flow measurement. 16,17 In this study, OCTA compensated for technical limitations of other imaging modalities through its high repeatability and reproducibility, exceptionally high spatial resolution, which enabled the assessment of both large vessels and capillaries, being less operator dependent, segmentable 3-dimensional volumetric tissue sampling that allowed isolation of different vascular plexuses and the availability of signal-processing algorithms that can provide velocimetric flow data like SSADA. 10,11 In this study, OCTA-derived biomarkers of ONH and peripapillary area included VD, GFIs, and RFIs.…”

Section: Discussionmentioning

confidence: 99%

Relative Flow Index as a Novel Optical Coherence Tomography Angiography Biomarker in Primary Open Angle Glaucoma

Ameen Ismail,

Hatata,

Sadek

2023

Journal of Glaucoma

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Précis: Relative flow indices, novel optical coherence tomography angiography biomarkers, demonstrated reduced optic nerve head and peripapillary large vessel and capillary perfusion in primary open angle glaucoma. Large vessel perfusion correlated with disease severity and progression. Purpose: To introduce relative flow indices as novel optical coherence tomography angiography (OCTA) biomarkers and their pathological insights in primary open angle glaucoma (POAG). Materials and Methods: This is a retrospective case-control study where 57 POAG and 57 control eyes were included. OCTA 4.5×4.5 mm ONH were analyzed using ImageJ 1.53t to calculate global flow indices (GFIs) and relative flow indices (RFIs) for whole image optic nerve head, isolated radial peripapillary capillary plexus and isolated large vessel angiograms. Results: Retinal nerve fiber layer thickness (RNFLT), optic nerve head (ONH) vascular density (VD), except inside disc and large vessel VD, GFIs and RFIs were lower in POAG than control. There was positive correlation between RNFLT and both VD and GFIs. Among RFIs, only large vessel RFI (ONHLVRFI) demonstrated positive correlation with average RNFLT. Linear regression demonstrated significant positive coefficient for ONHLVRFI with RNFLT as dependent variable. Area under receiver operating characteristic curve (AUC ROC) showed diagnostic accuracy ranging fair, good and excellent for all biomarkers. Inferior RNFLT had highest AUC (0.922) while optic nerve head large vessel density had the lowest (0.523). Conclusions: POAG showed structural loss of RNFL neurovascular unit manifesting as positively correlated reduction of VD and RNFLT. Also, POAG had lower global perfusion of optic nerve head and peripapillary area resulting in positively correlated reduction of GFIs and RNFLT. While RFIs were lower in POAG, only ONHLVRFI demonstrated positive correlation and regression with RNFLT implying that large vessel hypoperfusion was associated with POAG severity and progression.

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Blood flow synchronization in renal microcirculation - a high-resolution imaging study

Postnov

Marsh

Cupples

et al. 2021

Preprint

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Aims: internephron signalling and interaction are fundamental for kidney function. Earlier studies have shown that nephrons signal to each other over short distances and adjust their activity accordingly. Micropuncture experiments revealed synchronous clusters of 2-3 nephrons formed from such interactions, while imaging and modelling results suggested the possibility of larger clusters. Such clusters are expected to play an important role in renal autoregulation, but their presence has not been confirmed and their size has not been estimated. In this study, we present methodology for high resolution renal blood flow imaging and apply it to estimate frequency and phase angle differences in kidney blood vessels under normal conditions and after administration of the vasoactive agents angiotensin II and acetylcholine. Methods and results: to resolve signals from separate arterioles in a sufficiently large field of view, we developed a method for renal laser speckle contrast imaging. Our setup provides imaging of blood flow in the kidney cortex with a limit of image resolution at 0.8 micrometres per pixel and the imaging frequency of 160Hz. We used the method to record from ~1.5x1.5 mm2 sections of the renal surface in anaesthetised Sprague-Dawley rats in unstimulated conditions and during IV infusion of the vasoconstrictor angiotensin II or the vasodilator acetylcholine. In each section, we resolved and segmented 94.8+-15.66 individual arterioles and venules, and analyzed blood flow using wavelet spectral analysis to identify clusters of synchronized blood vessels. Conclusions: we observed spatial and temporal evolution of blood vessel clusters of various sizes, including the formation of large (>90 vessels) long-lived clusters (>10 periods) locked at the frequency of the tubular glomerular feedback (TGF) mechanism. The analysis showed that synchronization patterns and thus the co-operative dynamics of nephrons change significantly when either of the vasoactive agents is administered. On average, synchronization was stronger (larger clusters, longer duration) with angiotensin II administration than in the unstimulated state or with acetyl choline. While it weakens with distance, increased synchronization duration spanned the whole field of view, and likely, beyond it. Neighbouring vessels tend to demonstrate in-phase synchronization, especially in the vasoconstricted condition, which is expected to cause locally increased pressure variation. Our results confirm both the presence of the local synchronization in the renal microcirculatory blood flow and the fact that it changes depending on the condition of the vascular network and the blood pressure, which might have further implications for the role of such synchronization in pathologies development.

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Depth resolution in multifocus laser speckle contrast imaging

Cited by 9 publications

References 23 publications

Synchronization in renal microcirculation unveiled with high-resolution blood flow imaging

Synchronization in renal microcirculation unveiled with high-resolution blood flow imaging

Relative Flow Index as a Novel Optical Coherence Tomography Angiography Biomarker in Primary Open Angle Glaucoma

Blood flow synchronization in renal microcirculation - a high-resolution imaging study

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