Strain Patterns With Ultrasound for Assessment of Abdominal Aortic Aneurysm Vessel Wall Biomechanics.

BACKGROUND: Abdominal aortic aneurysms (AAAs) are an important cause of death. Small AAAs are surveyed with ultrasound (US) until a defined diameter threshold, often triggering a computer tomography scan and surgical repair. Nevertheless, 5%-10% of AAA ruptures are below threshold, and some large AAAs never rupture. AAA wall biomechanics may reveal vessel wall degradation with potential for patient-centred risk assessment. This clinical study investigated AAA vessel wall biomechanics and deformation patterns, including reproducibility. METHODS: In 50 patients with AAA, 183 video clips were recorded by two sonographers. Prototype software extracted AAA vessel wall principal strain characteristics and patterns. Functional principal component analysis (FPCA) derived strain pattern statistics. RESULTS: Strain patterns demonstrated reduced AAA wall strains close to the spine. The strain pattern "topography" (i.e., curve phases or "peaks" and "valleys") had a 3.9 times lower variance than simple numeric assessment of strain amplitudes, which allowed for clustering in two groups with FPCA. A high mean reproducibility of these clusters of 87.6% was found. Median pulse pressure-normalised mean principal strain (PPPS) was 0.038%/mm Hg (interquartile range: 0.029-0.051%/mm Hg) with no correlation to AAA size (Spearman's ρ = 0.02, false discovery rate-p = 0.15). Inter-operator reproducibility of PPPS was poor (limits of agreement: ±0.031%/mm Hg). DISCUSSION: Strain patterns challenge previous numeric stiffness measures based on anterior-posterior-diameter and are reproducible for clustering. This study's PPPS aligned with prior findings, although clinical reproducibility was poor. In contrast, US-based strain patterns hold promising potential to enhance AAA risk assessment beyond traditional diameter-based metrics.

Automated 3D ultrasound bridges the gap between novices and experts in diameter assessment of abdominal aortic aneurysms.

BACKGROUND: The current management of abdominal aortic aneurysm (AAA) hinges upon assessing diameter using ultrasound (US). Diameter reproducibility with conventional two-dimensional ultrasound (2D-US) is challenging and requires experienced operators. A novel automatic three-dimensional ultrasound (3D-US) system enables on-cart software-assisted diameter estimation (3D-SAUS), potentially facilitating more precise diameter measurements than 2D-US. This study aimed to assess the variance of AAA diameter measurements among US novices and experts by comparing 2D-US with 3D-SAUS in a clinical setting. METHODS: A total of 580 US scans were scheduled by 29 US operators (13 experts and 16 novices) on 10 patients with AAAs. Experts and novices measured all patients' AAA anterior-posterior (AP) diameters with 2D-US and 3D-SAUS. Outcomes were limits of agreement (LoA) using a mixed-effects model. RESULTS: In total, 564 of 580 planned US scans were performed. 500 US scans were automatically analyzed by the software and included. When using 3D-SAUS instead of 2D-US, novices reduced their LoA from ±16.5% to ±10.2% (P<0.001), reaching the experts' LoA of ±10.5% (P=0.782 for difference). The experts' LoA was ±10.5% for 2D-US and ±9.7% for 3D-SAUS, with no statistically significant difference between the two modalities (P=0.423). CONCLUSIONS: Clinical implementation of the 3D-SAUS demonstrates a substantial reduction in variance in AAA diameter measurements among novice sonographers, surpassing the performance of conventional 2D-US techniques. Additionally, using the 3D-SAUS tool enables novice sonographers to achieve proficiency levels comparable to those of experts employing conventional 2D-US.

PODO/TERT256 - A promising human immortalized podocyte cell line and its potential use for in vitro research at different oxygen levels.

Podocytes are of key interest for the prediction of nephrotoxicity as they are especially sensitive to toxic insults due to their central role in the glomerular filtration apparatus. However, currently, prediction of nephrotoxicity in humans remains insufficiently reliable, thus highlighting the need for advanced in vitro model systems using human cells with improved prediction capacity. Recent approaches for refining in vitro model systems focus on closely replicating physiological conditions as observed under the in vivo situation typical of the respective nephron section of interest. PODO/TERT256, a human immortalized podocyte cell line, were employed in a semi-static transwell system to evaluate its potential use as a human podocyte in vitro system for modelling potential human glomerular toxicity. Furthermore, the impact of routinely employed excessive oxygen tension (21 % - AtmOx), when compared to the physiological oxygen tensions (10 % - PhysOx) observed in vivo, was analyzed. Generally, cultured PODO/TERT256 formed a stable, contact-inhibited monolayer with typical podocyte morphology (large cell body, apical microvilli, finger-like cytoplasmic projections (reminiscent of foot processes), and interdigitating cell-cell junctions) and developed a size-selective filtration barrier. PhysOx, however, induced a more pronounced in vivo like phenotype, comprised of significantly larger cell bodies, significantly enhanced filtration barrier size-selectivity, and a remarkable re-localization of nephrin to the cell membrane, thus suggesting an improved in vitro replication of in vivo characteristics. Preliminary toxicity characterization with the known glomerulotoxin doxorubicin (DOX) suggested an increasing change in filtration permeability, already at the lowest DOX concentrations tested (0.01 µM) under PhysOx, whereas obvious changes under AtmOx were observed as of 0.16 µM and higher with a near all or nothing effect. The latter findings suggested that PODO/TERT256 could serve as an in vitro human podocyte model for studying glomerulotoxicity, whereby culturing at PhyOx tension appeared critical for an improved in vivo-like phenotype and functionality. Moreover, PODO/TERT256 could be incorporated into advanced human glomerulus systems in vitro, recapitulating microfluidic conditions and multiple cell types (endothelial and mesenchymal cells) that can even better predict human glomerular toxicity.

One-year volume growth of abdominal aortic aneurysms measured by extended field-of-view ultrasound.

BACKGROUND: Measurement of volume has the potential to detect subtle growth not recognized in the current surveillance paradigm of abdominal aortic aneurysms (AAAs). Currently available three-dimensional ultrasound allows for estimation of AAA volume, but for most patients, the AAA extends beyond the ultrasound field-of-view and only allows visualization of a partial AAA volume. A new extended field-of-view three-dimensional ultrasound protocol (XFoV US) has been found to improve the proportion of patients with visualization of the full AAA volume. METHODS: To investigate the applicability of the XFoV US protocol in estimating AAA volume growth in follow-up, 86 patients with AAAs were recruited from the surveillance program at a university hospital. All were imaged by XFoV US at baseline and at one-year follow-up. RESULTS: Assessment of full volume, based on visualization of the AAA neck and bifurcation at both baseline and one-year follow-up, was achieved in 67/86 (78%) of patients. One-year mean growth in maximum diameter was 2.8 mm (6%/year), in centerline length 2.9 mm (4%/year), and in volume 15.9 mL (19%/year). In 17/67 (25%) of patients, volume growth was detected in diameter-stable AAAs. Baseline XFoV US volume was associated with one-year AAA volume growth, while, conversely, maximum baseline diameter was not associated with one-year AAA diameter growth. CONCLUSIONS: This study concludes that the XFoV US protocol provides a safe and repeatable modality for assessing AAA volume growth, and that AAA volume is a promising predictive measure of AAA growth.

Endoleak following endovascular repair of popliteal artery aneurysm: clinical outcome and contrast-enhanced ultrasound detection.

BACKGROUND: Continued blood flow in the aneurysm sac after repair, also known as endoleak, can occur after both open and endovascular popliteal aneurysm repair (EPAR) with risk for aneurysm sac enlargement. Primary aims were to investigate aneurysm sac growth and the presence and classification of endoleak after EPAR using contrast-enhanced ultrasound (CEUS). METHODS: Cross-sectional study of patients receiving EPAR with expanded polytetrafluorethylene (ePTFE) covered stent-grafts between 1st of January 2009 and 1st of February 2019 at a tertiary referral endovascular center. Patients were re-invited in 2021 and 31 legs were examined for endoleak using CEUS. Endoleaks were classified by a core-lab consisting of three CEUS-experienced physicians. RESULTS: Median follow-up was 57 months (range 33-143 months). Endoleak was detected in 16 PAA, and categorized as type I (N.=3), type II (N.=10), type III (N.=1) or indeterminate (N.=2). Median maximal PAA diameter was 24 mm (range 15-55 mm) at the time of EPAR compared to 17 mm (range 6-43 mm) at follow-up (P<.001). Maximal aneurysm sac diameter was smaller at follow-up than at the index procedure in both PAAs with and without endoleak on CEUS (P=0.005 vs. P<0.001, respectively). There was no difference in PAA sac shrinkage at follow-up between patients with or without endoleak (P=0.28). Freedom from aneurysm sac growth was 97%. CONCLUSIONS: CEUS was sensitive in endoleak detection after EPAR. Shrinkage of the PAA sac was found in both patients with and without endoleaks. CEUS appears useful for targeted examinations rather than routine surveillance after EPAR.

Anticoagulants and reduced thrombus load in abdominal aortic aneurysms assessed with three-dimensional contrast-enhanced ultrasound examination.

OBJECTIVE: The relationship between intraluminal thrombus (ILT) and abdominal aortic aneurysm (AAA) growth and rupture risk remains ambiguous. Studies have shown a limited effect of antiplatelet therapy on ILT size, whereas the impact of anticoagulant therapy on ILT is unresolved. This study aims to evaluate an association between antithrombotic therapy and ILT size assessed with three-dimensional contrast-enhanced ultrasound (3D-CEUS) examination in a cohort of patients with AAA. METHODS: In a cross-sectional study, 309 patients with small AAAs were examined with 3D-CEUS. Patients were divided into three groups based on prescribed antithrombotic therapy: anticoagulant (n = 36), antiplatelet (n = 222), and no antithrombotic therapy (n = 51). Patient ILT size was calculated in volume and thickness and compared between the three groups. RESULTS: Patients on anticoagulants had a significantly lower estimated marginal mean ILT volume of 16 mL (standard error [SE], ±3.2) compared with 28 mL (SE, ±2.7) in the no antithrombotic group and 30 mL (SE, ±1.3) in the antiplatelet group when adjusting for AAA volume (P < .001) and comorbidities (P < .001). In addition, patients on anticoagulant therapy had significantly lower estimated marginal mean ILT thickness of 10 mm (SE, ±1.1) compared with 13 mm (SE, ±0.9) in the no antithrombotic group of and 13mm (SE, ±0.4) in the antiplatelet group when adjusting for AAA diameter (P = .03) and comorbidities (P = .035). CONCLUSIONS: A 3D-CEUS examination is applicable for ILT assessment and demonstrates that patients with AAA on anticoagulant therapy have lower ILT thickness and volume than patients with AAA on antiplatelet therapy and those without antithrombotic therapy. Causality between anticoagulants and ILT size, and extrapolation to AAA growth and rupture risk, is unknown and merits further investigations, to further nuance US-based AAA surveillance strategy.

Ultrasound Transducer Pressure: An Unexplored Source of Abdominal Aortic Aneurysm Measurement Error.

This study was aimed at quantifying the abdominal aortic aneurysm (AAA) compression phenomenon and assessing the use of a new tool to estimate transducer pressure in vivo. In this cross-sectional study, 47 participants with AAA and a median anterior-to-posterior (AP) AAA diameter of 46 mm (range: 30-76 mm) were included. The majority of the patients were overweight with body mass indexes >25 (33/47, 70%). A standardized ultrasound (US)-compatible gel pad, with a pre-defined thickness (15 mm) and mass (150 g), was interposed between the US transducer and participant to estimate the applied transducer pressure. A firm transducer pressure significantly lowered the median AP diameter from 46.1 mm (range: 29.7-76.3) to 39.4 mm (range: 21.7-67.5) (p = 0.001). The mean diameter bias between light and firm transducer pressure was 6.1 mm (95% confidence interval: 4.9-7.3). The applied transducer pressure varied significantly and could be measured by translating the deformation of a low-tech gel pad interposed between the US transducer and the participant.

Full-Volume Assessment of Abdominal Aortic Aneurysm by Improved-Field-of-View 3-D Ultrasound Performs Comparably to Computed Tomographic Angiography.

Three-dimensional ultrasound (US) of abdominal aortic aneurysms (AAAs) is limited by the field-of-view of the 3D-US transducer. To obtain an extended field-of-view (XFoV), two transducer navigation system-assisted US protocols have been developed: XFoV-2D and XFoV-3D. In this study, the XFoV US protocols were compared with the currently available 3D-US protocol with standard field-of-view (FoV-st) and the established gold standard, computed tomography angiography (CTA). A total of 65 patients with AAA were included, and AAA imaging was processed offline with prototype software. The novel XFoV-2D and XFoV-3D protocols allowed for assessment of full AAA volume in significantly more patients (45/65 [69%] and 43/65 [66%], respectively), compared with the current 3D-US standard, FoV-st (30/65 [46%] patients). The mean difference in AAA volume estimation between each XFoV US protocol and 3-D CTA differed significantly (XFoV-2D: 16.9 mL, XFoV-3D: 7.6 mL, p = 0.002), indicating that XFoV-3D agreed best with 3D-CTA. No significant difference was found in the variance of full AAA volume quantification between each XFoV US protocol and CTA (p = 0.49). It is concluded that the XFoV US protocols improved the generation of full AAA volumes compared with the currently available 3D-US technology, with AAA volume estimates comparable to CTA estimates.

Profiling abdominal aortic aneurysm growth with three-dimensional ultrasound.

BACKGROUND: Profiling is a new method based on three-dimensional ultrasound (3D-US) allowing for direct comparison of baseline and follow-up diameters along the AAA length. This study aimed to evaluate the feasibility of profiling to visualize AAA changes at submaximum diameters, and to categorize the growth profiles. METHODS: This is a retrospective analysis of prospectively and consecutively included patients under AAA surveillance at a tertiary referral center. 3D-US images of AAAs at baseline and at one-year follow-up were segmented, generating a centerline and a mesh of the aneurysm geometry. The mesh was processed to illustrate diameter changes of a given AAA. Three growth profiles were identified: 1) peak growth (the largest, significant [≥3.6 mm] diameter difference occurred within a 10 mm margin to either side of the maximum baseline diameter); B) edge growth (at least one significant diameter difference and the criteria for peak growth did not apply); and 3) no growth (all diameter differences were nonsignificant). A centerline length of ≥60 mm was assumed to capture a comparable segment of the wall geometry at baseline and follow-up. Cohen's kappa and Kaplan Meier analysis were used to analyze data. RESULTS: In total, 186 patients had growth profiles generated. Of these, 28 (15%) were discarded, mainly based on inadequate centerline lengths (N.=21, 11.3%). The remaining patients were categorized into edge growth (N.=83, 52%), no growth (N.=47, 30%), and peak growth (N.=28, 18%). CONCLUSIONS: Profiling interprets AAA growth at submaximum diameters. Half of the cohort had edge growth. These AAAs risk being classified as stable.

Validation of an assessment tool for estimation of abdominal aortic aneurysm compression in diagnostic ultrasound.

The study investigated ultrasound (US) transducer push, tantamount to applied transducer pressure, during abdominal aortic aneurysm (AAA) US scanning in a simulated non-clinical setup. During an assessment of maximal AAA diameter on a three-dimensional print-based AAA phantom, US transducer push varied as much as 2000% (range: 0.52-12.45 kPa) amongst 16 experienced sonographers. The mean transducer push was 5.54 ± 3.91 kPa (CV = 0.71). Deformation of a standardized gel-pad allowed for transducer push calculation based on US images; Young's modulus of the gel-pad was estimated to 44,26 N/m2. The method is theoretically validated in a safe and non-clinical environment. Future investigations with the aim of clinical validation of the gel-pad principle on AAA patients are suggested, including the objectification of the magnitude of an eventual transducer push-related error during US AAA diameter measurement.

Full-Volume Assessment of Abdominal Aortic Aneurysms by 3-D Ultrasound and Magnetic Tracking.

Volume assessment of abdominal aortic aneurysms (AAAs) using 3-D ultrasound (US) is an innovative technique reporting good agreement with computed tomography angiography. One major limitation of the current 3-D US technique is a limited field of view, allowing full AAA acquisition in only 60% of patients. This study presents two new US acquisition protocols using magnetic field tracking, providing an "extended field of view" (XFoV-2-D and XFoV-3-D) with the aim of including both the aortic bifurcation and neck for full-volume assessment, and compares these methods with the current standard 3-D US protocol and with computed tomography angiography. A total of 20 AAA patients were included and underwent the current standard 3-D US protocol and the two novel 3-D US "extended field of view" protocols. Four patients were excluded from further analysis because of low image quality, leaving 16 patients eligible for analysis. Full AAA volume was achieved in 8 patients (50%) using the standard 3-D US protocol, in 11 patients (69%) with the XFoV-2-D protocol and in 13 patients (81%) with the XFoV-3-D protocol. In conclusion, this article describes two new and feasible US protocols applicable for full-AAA-volume estimation in most patients and should initiate further research into the added value of full volume in AAA surveillance.

An exploratory investigation of the effect of naturalistic light on fatigue and subjective sleep quality in stroke patients admitted for rehabilitation: A randomized controlled trial.

BACKGROUND: Daylight entrains the central circadian pacemaker to the 24-hour day and is crucial for optimal alertness and sleep-quality. Rehabilitation patients tend to lack exposure to sufficient natural light. OBJECTIVE: Installed diurnal naturalistic light may reduce the known disrupted sleep quality and fatigue seen in post stroke patients. METHODS: Stroke patients were randomized to either an intervention rehabilitation unit (IU) equipped with naturalistic lighting (artificial sunlight spectrum) or to a control rehabilitation unit (CU) with standard indoor lighting. At inclusion and discharge, fatigue and subjective sleep quality were measured. RESULTS: Ninety stroke patients were included between May 2014, and June 2015. At discharge, patients from the IU experienced less fatigue than the CU patients, based on the Multidimensional Fatigue Inventory questionnaire general (IU, n = 28; CU, n = 30; diff - 20.6%, 95% confidence interval (CI) [- 35.0%; - 3.0%]; P = 0.025) and the Rested Statement (IU, n = 28; CU, n = 30; diff + 41.6%, 95% CI [+4.6%; +91.8%]; P =  0.025). No differences were detected between groups in sleepiness or subjective sleep quality by the Pittsburgh Sleep Quality Index. CONCLUSIONS: Fatigue was significantly reduced in rehabilitation patients exposed to naturalistic lighting during admission.

An exploratory investigation of the effect of naturalistic light on depression, anxiety, and cognitive outcomes in stroke patients during admission for rehabilitation: A randomized controlled trial.

BACKGROUND: Patients admitted for rehabilitation often lack sufficient natural light to entrain their circadian rhythm. OBJECTIVE: Installed diurnal naturalistic light may positively influence the outcome of depressive mood, anxiety, and cognition in such patients. METHODS: A quasi-randomized controlled trial. Ninety stroke patients in need of rehabilitation were randomized between May 1, 2014, and June 1, 2015 to either a rehabilitation unit equipped entirely with always on naturalistic lighting (IU), or to a rehabilitation unit with standard indoor lighting (CU).Examinations were performed at inclusion and discharge. The following changes were investigated: depressive mood based on the Hamilton Depression scale (HAM-D6) and Major Depression Inventory scale (MDI), anxiety based on the Hospital Anxiety and Depression Scale (HADS), cognition based on the Montreal Cognitive Assessment (MoCA) and well-being based on the Well-being Index (WHO-5). RESULTS: Depressive mood (MDI p = 0.0005, HAM-D6 p = 0.011) and anxiety (HADS anxiety p = 0.045) was reduced, and well-being (WHO-5 p = 0.046) was increased, in the IU at discharge compared to the CU. No difference was found in cognition (MoCA p = 0.969). CONCLUSIONS: This study is the first to demonstrate that exposure to naturalistic light during admission may significantly improve mental health in rehabilitation patients. Further studies are needed to confirm these findings.

Unbiased pattern analysis reveals highly diverse responses of cytoskeletal systems to cyclic straining.

In mammalian cells, actin, microtubules, and various types of cytoplasmic intermediate filaments respond to external stretching. Here, we investigated the underlying processes in endothelial cells plated on soft substrates from silicone elastomer. After cyclic stretch (0.13 Hz, 14% strain amplitude) for periods ranging from 5 min to 8 h, cells were fixed and double-stained for microtubules and either actin or vimentin. Cell images were analyzed by a two-step routine. In the first step, micrographs were segmented for potential fibrous structures. In the second step, the resulting binary masks were auto- or cross-correlated. Autocorrelation of segmented images provided a sensitive and objective measure of orientational and translational order of the different cytoskeletal systems. Aligning of correlograms from individual cells removed the influence of only partial alignment between cells and enabled determination of intrinsic cytoskeletal order. We found that cyclic stretching affected the actin cytoskeleton most, microtubules less, and vimentin mostly only via reorientation of the whole cell. Pharmacological disruption of microtubules had barely any influence on actin ordering. The similarity, i.e., cross-correlation, between vimentin and microtubules was much higher than the one between actin and microtubules. Moreover, prolonged cyclic stretching slightly decoupled the cytoskeletal systems as it reduced the cross-correlations in both cases. Finally, actin and microtubules were more correlated at peripheral regions of cells whereas vimentin and microtubules correlated more in central regions.

The Effects of Naturalistic Light on Diurnal Plasma Melatonin and Serum Cortisol Levels in Stroke Patients during Admission for Rehabilitation: A Randomized Controlled Trial.

Background: Stroke patients admitted for rehabilitation often lack sufficient daytime blue light exposure due to the absence of natural light and are often exposed to light at unnatural time points. We hypothesized that artificial light imitating daylight, termed naturalistic light, would stabilize the circadian rhythm of plasma melatonin and serum cortisol levels among long-term hospitalized stroke patients. Methods: A quasi-randomized controlled trial. Stroke patients in need of rehabilitation were randomized between May 1, 2014, and June 1, 2015 to either a rehabilitation unit equipped entirely with always on naturalistic lighting (IU), or to a rehabilitation unit with standard indoor lighting (CU). At both inclusion and discharge after a hospital stay of at least 2 weeks, plasma melatonin and serum cortisol levels were measured every 4 hours over a 24-hour period. Circadian rhythm was estimated using cosinor analysis, and variance between time-points. Results: A total of 43 were able to participate in the blood collection. Normal diurnal rhythm of melatonin was disrupted at both inclusion and discharge. In the IU group, melatonin plasma levels were increased at discharge compared to inclusion (n = 23; median diff, 2.9; IQR: -1.0 to 9.9, p = 0.030) and rhythmicity evolved (n = 23; p = 0.007). In the CU group, melatonin plasma levels were similar between discharge and inclusion and no rhythmicity evolved. Overall, both patient groups showed normal cortisol diurnal rhythms at both inclusion and discharge. Conclusions: This study is the first to demonstrate elevated melatonin plasma levels and evolved rhythmicity due to stimulation with naturalistic light.

Reorientation dynamics and structural interdependencies of actin, microtubules and intermediate filaments upon cyclic stretch application.

Any cell within a tissue is constantly confronted with a variety of mechanical stimuli. Sensing of these diverse stimuli plays an important role in cellular regulation. Besides shear stress, cells of the vascular endothelium are particularly exposed to a permanent cyclic straining originating from the interplay of outwards pushing blood pressure and inwards acting contraction by smooth musculature. Perpendicular alignment of cells as structural adaptation to this condition is a basic prerequisite in order to withstand deformation forces. Here, we combine live cell approaches with immunocytochemical analyses on single cell level to closely elucidate the mechanisms of cytoskeletal realignment to cyclic strain and consolidate orientation analyses of actin fibres, microtubules (MTs) and vimentin. We could show that strain-induced reorientation takes place for all cytoskeletal systems. However, all systems are characterized by their own, specific reorientation time course with actin filaments reorienting first followed by MTs and finally vimentin. Interestingly, in all cases, this reorientation was faster than cell body realignment which argues for an active adaptation mechanism for all cytoskeletal systems. Upon actin destabilization, already smallest alterations in actin kinetics massively hamper cell morphology under strain and therefore overall reorientation. Depolymerization of MTs just slightly influences actin reorientation velocity but strongly affects cell body reorientation.