Evaluation of macular blood flow after intermittent intravenous infusion of high-dose corticosteroids (pulse therapy) in patients with thyroid-associated orbitopathy (TAO) using angio-OCT

Purpose The aim of this study is to evaluate the changes in macular blood flow index (BFI) in patients with moderate to severe thyroid-associated orbitopathy (TAO) before and after pulse therapy and their relationship with clinical features and disease activity using angio-OCT technology. Methods We analyzed twenty-four eyes. Every patient underwent a complete eye examination and angio-OCT analysis (OCT Topcon ImageNet 6; DRI OCT Triton, Topcon Corporation) before (T0) and two months (T2) after pulse therapy. We analyzed macular vascular blood flow in four angiographic levels: superficial plexus (SP), deep plexus (DP), external retina (ER), and choriocapillaris (CC). We used the clinical activity score (CAS) score to define TAO as moderate or severe. Results Macular BFI significantly increased at T2 in the DP, ER, and CC (p < 0.01). CAS score (5.8 ± 0.8 vs. 3.9 ± 0.9, p < 0.01) and Hertel exophthalmometry values (22.6 ± 2.3 mm vs. 21.2 ± 2,5 mm, p < 0.01) improved for all patients at T2 compared T0. Mean IOP increased from 13.3 ± 2.8 mmHg to 14.3 ± 2.1 mmHg (p < 0.01). No correlation was found between CAS score and macular BFI in all the analyzed levels. Conclusions Pulse therapy treatment can change macular BFI. In particular, two months alter pulse therapy, all the patients show an increase in macular vascular blood flow in each angiographic level. According to our results, angio-OCT analysis of the macular BFI may be a useful tool in the follow-up of TAO patients after pulse therapy.

Impact of Cutaneous Blood Flow on NIR-DCS Measures of Skeletal Muscle Blood Flow Index

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical technique for estimating relative changes in skeletal muscle perfusion during exercise, but may be affected by changes in cutaneous blood flow, as photons emitted by the laser must first pass through the skin. Accordingly, the purpose of this investigation was to examine how increased cutaneous blood flow affects NIR-DCS blood flow index (BFI) at rest and during exercise using a passive whole-body heating protocol that increases cutaneous, but not skeletal muscle, perfusion in the uncovered limb. BFI and cutaneous perfusion (laser Doppler flowmetry) were assessed in 15 healthy young subjects before (e.g., rest) and during 5-minutes of moderate-intensity hand-grip exercise in normothermic conditions and after cutaneous blood flow was elevated via whole-body heating. Hyperthermia significantly increased both cutaneous perfusion (~7.3-fold; p≤0.001) and NIR-DCS BFI (~4.5-fold; p≤0.001). Although relative BFI (i.e., fold-change above baseline) exhibited a typical exponential increase in muscle perfusion during normothermic exercise (2.81±0.95), there was almost no change in BFI during hyperthermic exercise (1.43±0.44). A subset of 8 subjects were subsequently treated with intradermal injection of botulinum toxin-A (Botox) to block heating-induced elevations in cutaneous blood flow, which 1) nearly abolished the hyperthermia-induced increase in BFI, and 2) restored BFI kinetics during hyperthermic exercise to values that were not different from normothermic exercise (p=0.091). Collectively, our results demonstrate that cutaneous blood flow can have a substantial, detrimental impact on NIR-DCS estimates of skeletal muscle perfusion and highlight the need for technical and/or pharmacological advancements to overcome this issue moving forward.

Functional interferometric diffusing wave spectroscopy of the human brain

Cerebral blood flow (CBF) is essential for brain function, and CBF-related signals can inform us about brain activity. Yet currently, high-end medical instrumentation is needed to perform a CBF measurement in adult humans. Here, we describe functional interferometric diffusing wave spectroscopy (fiDWS), which introduces and collects near-infrared light via the scalp, using inexpensive detector arrays to rapidly monitor coherent light fluctuations that encode brain blood flow index (BFI), a surrogate for CBF. Compared to other functional optical approaches, fiDWS measures BFI faster and deeper while also providing continuous wave absorption signals. Achieving clear pulsatile BFI waveforms at source-collector separations of 3.5 cm, we confirm that optical BFI, not absorption, shows a graded hypercapnic response consistent with human cerebrovascular physiology, and that BFI has a better contrast-to-noise ratio than absorption during brain activation. By providing high-throughput measurements of optical BFI at low cost, fiDWS will expand access to CBF.

Guidelines for obtaining an absolute blood flow index with laser speckle contrast imaging

Laser speckle contrast imaging (LSCI) is a technique broadly applied in research and clinical settings for full-field characterization of tissue perfusion. It is based on the analysis of speckle pattern contrast, which can be theoretically related to the decorrelation time - a quantitative measure of dynamics. A direct contrast to decorrelation time conversion, however, requires prior knowledge of specific parameters of the optical system and scattering media and thus is often impractical. For this reason, and because of the nature of some of the most common applications, LSCI is historically used to measure relative blood flow change. Over time, the belief that the absolute blood flow index measured with LSCI is not a reliable metric and thus should not be used has become more widespread. This belief has resulted from the use of LSCI to compare perfusion in different animal models and to obtain longitudinal blood flow index observations without proper consideration given to the stability of the measurement. Here, we aim to clarify the issues that give rise to variability in the repeatability of the quantitative blood flow index and to present guidelines on how to make robust absolute blood flow index measurements with conventional single-exposure LSCI. We also explain how to calibrate contrast to compare measurements from different systems and show examples of applications that are enabled by high repeatability.

Analyzing the Application of Myocardial Blood Flow Index in the Diagnosis of In-Stent Stenosis

Background: In-stent restenosis (ISR) usually develops from stent neointimal hyperplasia (SNH), which will seriously weaken the effect of treatment. In this study, both SNH and ISR were classified as in-stent stenosis (ISS), and a non-invasive parameter – myocardial blood flow index (MBFI) was used to analyze its value in the diagnosis of stent abnormalities. Objectives: Analyzing the application of MBFI in the diagnosis of ISS. Patients and Methods: Clinical follow-up data for 572 patients with drug-eluting stent (DES) was collected continuously. Ninety cases were screened with the protocol of computed coronary tomography angiography (CCTA) and invasive coronary angiography (ICA) for the unrelieved symptoms. In-stent abnormalities included SNH (ISS < 50%) and ISR (ISS ≥ 50%). The ROC curve was analyzed using the optimal cutoff value of MBFI to evaluate the in-stent abnormalities. T-test of independent samples was used for the comparison data with normal distribution, and chi-square test was used for comparison of nominal variables P < 0.05 was considered statistically significant. Results: Frequency of ISS was not statistically different between genders (χ2 = 0.105) (P = 0.7463). The optimal cutoff value was 0.082 with the area under the curve (AUC) of 0.829 (P < 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value were 91.4%, 89.1%, 84.2%, and 94.2%, respectively, and the accuracy was 90.0%. Among 39 cases with MBFI ≤ 0.082, 34 (87.18%, 34/39) were with ISS, including 18 (20%, 18/90) of SNH, and 16 (17.9%, 16/90) of ISR. In the 39 cases with MBFI ≤ 0.082, there were eight (20.5%, 8/39) presented new lesions, and seven (17.9%, 7/39) presented severe lesions. Conclusion: MBFI could be used for evaluating ISS, and more attention should be paid to the new accompanying lesions for the high risk of severe lesions.

Features of cerebral blood flow in patients with chronic obstructive pulmonary disease associated with hypertension

Objective. The aim of the work was to study the features of cerebral blood flow in patients with chronic obstructive pulmonary disease (COPD) associated with hypertension (HTN). Design and methods. A crosssectional study was conducted, which included 90 males 40–60 years old. Of these, 30 patients with chronic COPD associated with HTN (COPD + HTN) were included in the study group, 30 individuals with isolated COPD were in the comparison group, 30 healthy volunteers were included in the control group. All participants underwent physical examination, spirography, 24-hour blood pressure monitoring and ultrasound examination of cerebral vessels. Results. Patients with COPD + HTN in comparison with the control showed an increase in the diameter (p = 0,018) and complex of the intima-media of the common carotid artery (p = 0,003) while the velocities, resistance index (RI) and pulsation index (PI) did not change. In the basin of the internal carotid artery an increase in RI values was noted (p = 0,018). At the intracranial level there was a decrease in the end-diastolic velocity (p = 0,03) and the time-averaged average blood flow velocity (TAV) (p = 0,033) without due changes RI and PI. At the same time no changes in speed indicators and indices were noted in the vertebral artery basin. Among the indicators of cerebral perfusion in patients with COPD + HTN, hydrodynamic resistance (p = 0,0015), intracranial pressure (ICP) (p = 0,0048) significantly increased, and the cerebral blood flow index was comparable with the control. Assessment of venous cerebral blood flow showed an increase in the diameter of the internal jugular vein (p = 0,021) with unchanged TAV together with an increase in ICP indicating the formation of venous dysfunction. It was shown that the body mass index, forced expiratory volume at the first second, systolic and diastolic blood pressure together determine the peak systolic blood flow velocity from the midbrain artery. Conclusions. The cerebral blood flow in patients with COPD + HTN is characterized by a change in arterial blood flow at the level of both intra- and extracranial vessels, while maintaining a normal cerebral blood flow index, as well as the formation of arteriovenous dyshemia against the background of remodeling of the cerebral vascular bed.

Clinical effect of conbercept on improving diabetic macular ischemia by OCT angiography

Background Varying degrees of macular ischemia generally occur in diabetic retinopathy (DR). This study aims to evaluate the effect of conbercept with 3+ pro re nata (PRN) on macular perfusion status in patients with diabetic macular edema (DME) and quantitatively assess changes in foveal avascular zone (FAZ) areas and capillary density in macular regions by applying optical coherence tomography angiography (OCTA). Methods Fifty patients were divided into ischemic (n = 31) and non-ischemic (n = 19) groups according to the presence of ischemia on OCTA at baseline. All patients received intravitreal injections of 0.5 mg of conbercept with 3+ PRN principle. The FAZ areas and macular vessel density measured using OCTA were evaluated at baseline, 3 months, and 6 months after treatment in both groups. Results At months 3 and 6, the FAZ area in the ischemic group changed from 0.510 ± 0.171 mm2 to 0.441 ± 0.158 mm2 then to 0.427 ± 0.153 mm2 (p = 0.003, p = 0.296); in the non-ischemic group, it remained stable (p = 0.269, p = 0.926). The superficial vessel density changed from 41.1 ± 4.1 to 42.5% ± 4.7% then to 42.6% ± 4.6% (p = 0.043, p = 0.812), and the deep vessel density changed from 40.7 ± 4.4 to 42.3% ± 3.6% then to 42.3% ± 4.7% (p = 0.072, p = 0.961) in the ischemic group. In the non-ischemic group, the superficial vessel density changed from 44.8 ± 3.2 to 46.0% ± 3.5% then to 45.7% ± 3.3% (p = 0.108, p = 0.666), whereas the deep vessel density changed from 43.6 ± 3.6 to 43.8% ± 3.2% then to 43.5% ± 4.5% (p = 0.882, p = 0.736). Reperfusion in macular nonperfusion areas was observed. Conclusion Anti–vascular endothelial growth factor treatment may have a positive effect on macular perfusion status. Furthermore, OCTA had advantages in quantifying and calculating blood flow index in the study of macular perfusion status.

Hepatic Arterial Blood Flow Index Is Associated with the Degree of Liver Fibrosis in Patients with Chronic Hepatitis B Virus Infection

Background: Liver fibrosis due to Hepatitis B Virus (HBV) infection is an important public health concern worldwide. An accurate assessment of liver fibrosis is crucial for the identification of susceptible patients to severe clinical conditions and selection of treatment for patients with Chronic Hepatitis B (CHB) infection. Today, the development of simple, accurate, cost-effective, and non-invasive liver fibrosis tests is essential in clinical practice. Methods: According to liver biopsy as the reference standard, we compared the efficacy of hepatic arterial blood flow index (HBI) versus liver stiffness measurement (LSM), aspartate aminotransferase-to-platelet count ratio index (APRI), and fibrosis index based on 4 factors (FIB-4) to predict various degrees of liver fibrosis among 87 patients with CHB infection. Results: Spearman’s rank correlation coefficient of HBI versus the degree of liver fibrosis, according to the METAVIR scoring system, was 0.672 (P < 0.001). The area under the receiver operating characteristic curve (AUROC) of HBI (0.884; 95% CI: 0.806 - 0.961; P = 0.000) was greater than that of LSM (0.807; 95% CI: 0.703 - 0.912; P = 0.00), APRI (0.684; 95% CI: 0.556 - 0.812; P = 0.009), and FIB-4 (0.757; 95% CI: 0.641 - 0.873; P = 0.000) for the diagnostic analysis of significant liver fibrosis (≥ F2); similar results were obtained for the prediction of other liver fibrosis stages. Conclusions: The present findings shed new light on the association of HBI with the degree of liver fibrosis in patients with CHB infection. Hepatic Arterial Perfusion Scintigraphy (HAPS) with the measurement of HBI is a promising diagnostic method of liver fibrosis stage, which can guide therapy in CHB patients, although further large-scale studies are needed.