Arterial pulsation dependence of perivascular cerebrospinal fluid flow measured by dynamic diffusion tensor imaging in the human brain.

Perivascular cerebrospinal fluid (pCSF) flow is a key component of the glymphatic system. Arterial pulsation has been proposed as the main driving force of pCSF influx along the superficial and penetrating arteries; however, evidence of this mechanism in humans is limited. We proposed an experimental framework of dynamic diffusion tensor imaging with low b-values and ultra-long echo time (dynDTIlow-b) to capture pCSF flow properties during the cardiac cycle in human brains. Healthy adult volunteers (aged 17-28 years; seven men, one woman) underwent dynDTIlow-b using a 3T scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) with simultaneously recorded cardiac output. The results showed that diffusion tensors reconstructed from pCSF were mainly oriented in the direction of the neighboring arterial flow. When switching from vasoconstriction to vasodilation, the axial and radial diffusivities of the pCSF increased by 5.7 % and 4.94 %, respectively, suggesting that arterial pulsation alters the pCSF flow both parallel and perpendicular to the arterial wall. DynDTIlow-b signal intensity at b=0 s/mm2 (i.e., T2-weighted, [S(b=0 s/mm2)]) decreased in systole, but this change was ∼7.5 % of a cardiac cycle slower than the changes in apparent diffusivity, suggesting that changes in S(b=0 s/mm2) and apparent diffusivity arise from distinct physiological processes and potential biomarkers associated with perivascular space volume and pCSF flow, respectively. Additionally, the mean diffusivities of white matter showed cardiac-cycle dependencies similar to pCSF, although a delay relative to the peak time of apparent diffusivity in pCSF was present, suggesting that dynDTIlow-b could potentially reveal the dynamics of magnetic resonance imaging-invisible pCSF surrounding small arteries and arterioles in white matter; this delay may result from pulse wave propagation along penetrating arteries. In conclusion, the vasodilation-induced increases in axial and radial diffusivities of pCSF and mean diffusivities of white matter are consistent with the notion that arterial pulsation can accelerate pCSF flow in human brain. Furthermore, the proposed dynDTIlow-b technique can capture various pCSF dynamics in artery pulsation.

Reducing blood flow pulsation artifacts in 3D time-of-flight angiography by locally scrambling the order of the acquisition at 3 T and 7 T.

PURPOSE: Non-contrast-enhanced time of flight (TOF) is a standard method for magnetic resonance angiography used to depict vessel morphology. TOF is commonly performed with a 3D steady-state acquisition, employing a short repetition time to support high resolution imaging. At 7 T, TOF exhibits substantial increase in SNR and contrast, improving its clinical value. However, one of the remaining challenges, exacerbated at 7 T, is the presence of artifacts due to pulsatile blood flow, especially near major blood vessels. In this study we examine a method to significantly reduce these artifacts. METHODS: We recently introduced a new "local-scrambling" approach that semi-randomizes the acquisition order of the phase encodes, to achieve a controllable cutoff frequency above which the artifacts are drastically reduced. With this approach, artifacts resulting from fast local fluctuations such as cardiac pulsation are significantly reduced. In this study, we explore the ability of this local-scrambling approach to reduce pulsatile blood flow artifacts in a 3D TOF acquisition. Cartesian line-by-line and center-out ordering, with and without local-scrambling, were compared in simulations and in human brain imaging at 3 and 7 T scanners. RESULTS: In the simulations the artifact intensity showed a 10-fold reduction using local-scrambling compared to line-by-line and 4-fold compared to center-out ordering. In vivo results show that artifacts are much more pronounced at 7 T compared to 3 T, and in both cases they are effectively reduced by local-scrambling. CONCLUSION: Local-scrambling improves image quality for both line-by-line and center-out ordering. This approach can easily be implemented in the scanner without any changes to the reconstruction.

Measurement of changes in cerebrospinal fluid pulsation after traumatic brain injury using echo-planar imaging-based functional MRI.

Traumatic brain injury (TBI) is a major public health concern worldwide, with a high incidence and a significant impact on morbidity and mortality. The alteration of cerebrospinal fluid (CSF) dynamics after TBI is a well-known phenomenon; however, the underlying mechanisms and their implications for cognitive function are not fully understood. In this study, we propose a new approach to studying the alteration of CSF dynamics in TBI patients. Our approach involves using conventional echo-planar imaging-based functional MRI with no additional scan, allowing for simultaneous assessment of functional CSF dynamics and blood oxygen level-dependent-based functional brain activities. We utilized two previously suggested indices of (i) CSFpulse, and (ii) correlation between global brain activity and CSF inflow. Using CSFpulse, we demonstrated a significant decrease in CSF pulsation following TBI (p < 0.05), which was consistent with previous studies. Furthermore, we confirmed that the decrease in CSF pulsation was most prominent in the early months after TBI, which could be explained by ependymal ciliary loss, intracranial pressure increment, or aquaporin-4 dysregulation. We also observed a decreasing trend in the correlation between global brain activity and CSF inflow in TBI patients (p < 0.05). Our findings suggest that the decreased CSF pulsation after TBI could lead to the accumulation of toxic substances in the brain and an adverse effect on brain function. Further longitudinal studies with larger sample sizes, TBI biomarker data, and various demographic information are needed to investigate the association between cognitive decline and CSF dynamics after TBI. Overall, this study sheds light on the potential role of altered CSF dynamics in TBI-induced neurologic symptoms and may contribute to the development of novel therapeutic interventions.

Relationship between the natural cessation time of umbilical cord pulsation in full-term newborns delivered vaginally and maternal-neonatal outcomes: a prospective cohort study.

BACKGROUND: To analyze the impact of the time of natural cessation of the umbilical cord on maternal and infant outcomes in order to explore the time of clamping that would be beneficial to maternal and infant outcomes. METHODS: The study was a cohort study and pregnant women who met the inclusion and exclusion criteria at the Obstetrics and Gynecology Department of Qilu Hospital of Shandong University from September 2020 to September 2021. Analysis using Kruskal-Wallis rank sum test, Pearson's Chi-squared test, generalized linear mixed model (GLMM) and repeated measures ANOVA. If the difference between groups was statistically significant, the Bonferroni test was then performed. A two-sided test of P < 0.05 was considered statistically significant. RESULTS: A total of 345 pregnants were included in this study. The subjects were divided into the ≤60 seconds group (n = 134), the 61-89 seconds group (n = 106) and the ≥90 seconds group (n = 105) according to the time of natural arrest of the umbilical cord. There was no statistically significant difference in the amount of postpartum hemorrhage and the need for iron, medication, or supplements in the postpartum period between the different cord spontaneous arrest time groups for mothers (P > 0.05). The weight of the newborns in the three groups was (3316.27 ± 356.70) g, (3387.26 ± 379.20) g, and (3455.52 ± 363.78) g, respectively, and the number of days of cord detachment was 12.00 (8.00, 15.75) days, 10.00 (7.00, 15.00) days and 9.00 (7.00, 13.00) days, respectively, as the time of natural cessation of the cord increased. The neonatal lymphocyte ratio, erythrocyte pressure, and hemoglobin reached a maximum in the 61-89 s group at (7.41 ± 2.16) %, (61.77 ± 8.17) % and (194.52 ± 25.84) g/L, respectively. Lower incidence of neonatal hyperbilirubinemia in the 61-89 s group compared to the ≥90s group 0 vs 4.8 (P < 0.05). CONCLUSIONS: In full-term singleton vaginal births, maternal and infant outcomes are better when waiting for 61-89 s after birth for the cord to stop pulsating naturally, suggesting that we can wait up to 90s for the cord to stop pulsating naturally, and if the cord does not stop pulsating after 90s, artificial weaning may be more beneficial to maternal and infant outcomes.

Increased pulsation ratio in rear quarters reduces machine-on time and milking on empty teats.

Dairy cows usually store more milk in rear than in front quarters. At conventional machine milking this leads to an earlier cessation of milk flow in front than in rear quarters and hence unavoidable milking on empty front teats. We tested the hypothesis that an increased pulsation ratio in rear quarters reduces both milking on empty front teats and machine-on time. We have also tested if the different amplitude of cyclic vacuum fluctuations during milking with simultaneous vs. alternate pulsation within front and rear quarters, respectively, impacts milking characteristics. Ten Holstein dairy cows were milked twice daily at 14-h and 10-h milking intervals. Pulsation ratio in front quarters was 65:35, but was either set at 65:35, 70:30, 75:25 or 80:20 in rear quarters. Whole udder milk flow, claw vacuum, and mouthpiece chamber vacuum of all 4 quarters were recorded during milking. Teat tissue thickness of all 4 teats was measured with a cutimeter at 5 and 30 min after cluster detachment. Total milk yield did not differ among treatments, indicating complete udder emptying. The time of quarter milk flow (tQMF) of front quarters did not differ among treatments but decreased with increasing pulsation ratio in rear quarters. In addition, the faster milking of rear quarters at higher pulsation ratio caused higher peak and average milk flow rates, a shorter duration of milk flow decline, and a reduced machine-on time. The increased milk flow at a higher pulsation ratio did not cause a significant reduction of the claw vacuum at the used sample size. Teat tissue thickness did not significantly differ among treatments, likely because milking on empty teats did almost not occur in the rear quarters, and treatment settings did not differ in front quarters. Simultaneous pulsation caused higher amplitudes of cyclic vacuum fluctuation than alternate pulsation. However, milking characteristics did not differ between simultaneous and alternate pulsation. In conclusion, an increased pulsation ratio in rear quarters reduces machine-on time, increases milking performance, and reduces the time of milking on empty teats in front quarters, without an increased impact on teat tissue thickness.

Reduction in the risk of contrast-induced nephropathy using enhanced external counter-pulsation in patients with chronic kidney disease.

OBJECTIVE: To evaluate the efficacy of EECP in the prevention of contrast-induced nephropathy (CIN) in patients with chronic kidney disease (CKD). METHODS: A prospective trial was undertaken in the participants. A total of 280 patients with an estimated glomerular filtration rate (eGFR) of <60 ml/min/1.73 m2 who underwent percutaneous coronary artery procedures were enrolled and divided into two groups: the control group (n = 100) and the EECP group (n = 180). All patients received extracellular fluid volume expansion therapy with 0.9% normal saline, and patients in the EECP groups were also treated with EECP. The renal function indexes of the two groups were determined 48-72 h after coronary artery procedures. RESULTS: In the EECP group, the BUN and serum creatinine (Scr) after coronary artery procedures were significantly lower than those before coronary artery procedures (BUN: 8.4 ± 3.5 vs. 6.6 ± 2.7 mmol/L, p < 0.001; Scr: 151.9 ± 44.7 vs. 144.5 ± 48.3 µmol/L, p < 0.001), while the eGFR was significantly increased (43.6 ± 11.4 vs. 47.1 ± 13.9 ml/min/1.73 m2, p < 0.001). The degree of Scr elevation was lower in the EECP group than in the control group (12.4 ± 15.0 vs. 20.9 ± 24.8 µmol/L, p = 0.026). Additionally, the EECP group had a lower incidence of post-procedures Scr elevation than the control group (36.5 vs. 48.0%, p = 0.042), a higher incidence of post-procedures eGFR elevation (62.2 vs. 48.0%, p = 0.021), and a lower risk of CIN (1.1 vs. 6.0%, p = 0.019). CONCLUSION: EECP therapy has a protective effect on renal function and can reduce the risk of CIN in patients with CKD.

Research into Prediction Method for Pressure Pulsations in a Centrifugal Pump Based on Variational Mode Decomposition-Particle Swarm Optimization and Hybrid Deep Learning Models.

Centrifugal pump pressure pulsation contains various signals in different frequency domains, which interact and superimpose on each other, resulting in characteristics such as intermittency, non-stationarity, and complexity. Computational Fluid Dynamics (CFD) and traditional time series models are unable to handle nonlinear and non-smooth problems, resulting in low accuracy in the prediction of pressure fluctuations. Therefore, this study proposes a new method for predicting pressure fluctuations. The pressure pulsation signals at the inlet of the centrifugal pump are processed using Variational Mode Decomposition-Particle Swarm Optimization (VMD-PSO), and the signal is predicted by Convolutional Neural Networks-Long Short-Term Memory (CNN-LSTM) model. The results indicate that the proposed prediction model combining VMD-PSO with four neural networks outperforms the single neural network prediction model in terms of prediction accuracy. Relatively high accuracy is achieved by the VMD-PSO-CNN-LSTM model for multiple forward prediction steps, particularly for a forward prediction step of 1 (Pre = 1), with a root mean square error of 0.03145 and an average absolute percentage error of 1.007%. This study provides a scientific basis for the intelligent operation of centrifugal pumps.

Reduction of the cardiac pulsation artifact and improvement of lesion conspicuity in flow-compensated diffusion images in the liver-A quantitative evaluation of postprocessing algorithms.

PURPOSE: To enhance image quality of flow-compensated diffusion-weighted liver MRI data by increasing the lesion conspicuity and reducing the cardiac pulsation artifact using postprocessing algorithms. METHODS: Diffusion-weighted image data of 40 patients with liver lesions had been acquired at 1.5 T. These data were postprocessed with 5 different algorithms (weighted averaging, p-mean, percentile, outlier exclusion, and exception set). Four image properties of the postprocessed data were evaluated for optimizing the algorithm parameters. These properties were the lesion to tissue contrast-to-noise ratio (CNR), the reduction of the cardiac pulsation artifact, the data consistency, and the vessel darkness. They were combined into a total quality score ( Q total , $$ {Q}_{\mathrm{total}}, $$ set to 1 for the trace-weighted reference image), which was used to rate the image quality objectively. RESULTS: The weighted averaging algorithm performed best according to the total quality score ( Q total = 1.111 ± 0.067 $$ {Q}_{\mathrm{total}}=1.111\pm 0.067 $$ ). The further ranking was outlier exclusion algorithm ( Q total = 1.086 ± 0.061 $$ {Q}_{\mathrm{total}}=1.086\pm 0.061 $$ ), p-mean algorithm ( Q total = 1.045 ± 0.049 $$ {Q}_{\mathrm{total}}=1.045\pm 0.049 $$ ), percentile algorithm ( Q total = 1.012 ± 0.049 $$ {Q}_{\mathrm{total}}=1.012\pm 0.049 $$ ), and exception set algorithm ( Q total = 0.957 ± 0.027 $$ {Q}_{\mathrm{total}}=0.957\pm 0.027 $$ ). All optimized algorithms except for the exception set algorithm corrected the pulsation artifact and increased the lesion CNR. Changes in Q total $$ {Q}_{\mathrm{total}} $$ were significant for all optimized algorithms except for the percentile algorithm. Liver ADC was significantly reduced (except for the exception set algorithm), particularly in the left lobe. CONCLUSION: Postprocessing algorithms should be used for flow-compensated liver DWI. The proposed weighted averaging algorithm seems to be suited best to increase the image quality of artifact-corrupted flow-compensated diffusion-weighted liver data.

Messing up to clean up: Semi-randomized frequency selective space-filling curves to suppress physiological signal fluctuations in MRI.

PURPOSE: Rapid 3D steady-state sequences are widely used but are also known to be sensitive to semi-periodic physiological signal fluctuations due to, for example, cardiac pulsation, breathing, and eye/eyelids movement. This semi-periodicity results in repeating artifacts in the image whose intensity depends on the scan parameters. The purpose of this study is to design a reordering of the 2D phase encodes (within the 3D acquisition) that reduces these artifacts. METHODS: A randomized order of the phase encodes can suppress repeating artifact but may also introduce its own apparent noise, for example, in cases of slow subject movement or gradual changes in eddy currents. In a new design a semi-randomized space-filling curve is generated by scrambling the local order of the phase encodes to achieve a controlled frequency selective effect, that is, eliminating artifacts above a chosen (fluctuation) frequency threshold while leaving lower frequencies untouched, thus overcoming the limitations of a randomized order. The method was characterized in simulations and substantiated by human brain imaging at 7 T using two steady-state gradient echo variants that suffer from pulsation, either near blood vessels or near the ventricles. RESULTS: The simulations with a point source show that the maximum artifact intensity can be reduced by factors of 10-50 depending on the scan parameters. In human scanning, the new approach drastically reduced physiologically induced artifacts and was superior in this regard to both full randomization and a generalized Hilbert curve, another semi-randomized approach. CONCLUSION: The phase-encodes reordering presented here effectively removes artifacts arising from local fluctuations.

Thermal Pulsation in the Management of Meibomian Gland Dysfunction and Dry Eye: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the literature to determine the efficacy and safety of thermal pulsation technologies in improving signs or symptoms of meibomian gland dysfunction (MGD) and dry eye compared with no therapy or with conventional warm compress therapy or eyelid hygiene. METHODS: A literature search was conducted in the PubMed database in June 2022 and again in March 2023 to identify all studies in the English language on the use of thermal pulsation to treat MGD or dry eye. The search yielded 59 citations, and 11 articles met all of the inclusion criteria. The panel methodologist then assigned a level of evidence rating for each study; 8 studies were rated level I evidence and 3 studies were rated level II evidence. RESULTS: All included studies evaluated a single 12-minute session using the LipiFlow automated thermal pulsation system (TearScience, Inc, or Johnson & Johnson). Improvements were detected in subjective and objective metrics of MGD or dry eye in patients within 1 to 12 months of thermal pulsation treatment compared with nontreatment. Most of the studies (9/11) reported greater efficacy with thermal pulsation than with standard warm compress therapy and eyelid hygiene. Four of these studies showed relevant industry conflicts of interest. Two of the 4 level I studies without direct industry participation concluded that thermal pulsation treatment was not significantly different from conventional hygiene or warm compress therapy control treatments (in symptoms in one of the studies and in objective findings in the second study). No serious adverse events were reported in any of the 11 studies. CONCLUSIONS: According to the current literature, a single thermal pulsation session may improve subjective or objective parameters of MGD and dry eye safely. However, industry support and participation were present in 4 of the 8 level I studies. The durability beyond several months and cost efficacy remain uncertain. Because the inclusion parameters of this assessment captured only the LipiFlow system, the conclusions are limited to that product. High-quality independent studies are needed to assess the long-term benefits of this intervention. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Separate effect of turbulent pulsation on internal mass transfer in porous biofilms.

Turbulence is considered to be the result of coupled time-averaged and pulsating velocities, making it difficult to distinguish the respective effects, and the quantitative effect of turbulent pulsation alone on mass transfer within biofilms has not been discussed in the literature. In this study, we constructed a special oscillating grid biofilm reactor combining Particle Image Velocimetry (PIV) measurements and Computational Fluid Dynamics (CFD) simulations to achieve nearly isotropic turbulence in a designed ambient without time-averaged velocity and shear stress. Subsequently, velocity and contaminant concentration distributions were obtained by solving a mass transfer model with a k-ε turbulence model, combined with measurements of biofilm structure parameters. The results showed that the increase in turbulent pulsation intensity led to a significant stratification of the percolation velocity gradient in biofilms, which enhanced convective mass transfer. The changes of biofilm density and porosity under turbulent pulsation were more strongly correlated with convective mass transfer. When the turbulent intensity (q) increased to 2.50 cm s-1, the removal rate reached the highest value of 96.93%, accelerating the migration of contaminant concentration and the diffusive mass transfer effect was obvious. In addition, the trend of biofilm thickness under turbulent pulsation was consistent with the change of contaminant concentration distribution, and the correlation between them was greater. In summary, at q of 2.50 cm s-1, there was a positive effect on both convection and diffusion mechanisms in biofilms, and the contaminant removal rate and biofilm thickness reached the maximum, which was the recommended turbulent pulsation conditions.

Meibomian gland dysfunction patients benefit in ocular parameters and tear chemokines after thermal pulsation treatment.

Objectives: To investigate the effect of thermal pulsation treatment on meibomian gland function, ocular parameters and tear inflammatory cytokines compared with the warm compress group. Methods: Twenty-five participants with MGD underwent a 12-minute thermal pulsation treatment, while 25 participants with MGD underwent manual warm compress treatment. MGD related parameters, including meibomian gland function (MGE, MQ and lid margin), tear stability (NIKBUT, FBUT and LLT), tear secretion (SIT, and TMH), were examined and OSDI questionnaire was also obtained. Tear chemokines (MIG, IFN-γ, IL-8, IP-10 and MCP-1) were examined and analyzed the correlations with MGD related parameters and OSDI. Results: Compared with warm compress subjects, OSDI, lid margin and tear stability were found improved more in thermal pulsation treatment at 3 months (OSDI: *p = 0.014, lid margin: *p = 0.021, LLT: **p = 0.008, CFS: *p = 0.028). The level of IP-10 and MIG decreased more in thermal pulsation group than in warm compress group (IP-10: *p = 0.021, MIG: *p = 0.039). IP-10 was positively correlated with MQ (r = 0.522, *p = 0.037) and negatively correlated with tear stability (r = -0.613, **p = 0.002), and OSDI was only positively correlated with IL-8 (r = 0.679, ***p < 0.001). The decrease of MIG was positively correlated with less corneal epithelium injury (r = 0.557, **p = 0.006) and meibograde (r = 0.49, *p = 0.019). Conclusions: Thermal pulsation treatment obviously improved MGD probably by attenuating tear CXCL chemokines in ocular surface of MGD patients, which demonstrated an efficacy and well-tolerated therapy in clinical.

Relationship between pulsation of posterior vortex vein, choroidal thickness, and choroidal vascular hyperpermeability in polypoidal choroidal vasculopathy.

PURPOSE: Posterior vortex vein pulsation on Heidelberg indocyanine green angiography (HRA-IA) video is reported to indicate the presence of congestion in these vessels. This study aimed to determine the relationship between posterior vortex vein pulsation, choroidal thickness, and choroidal vascular hyperpermeability (CVH) in polypoidal choroidal vasculopathy (PCV). METHODS: Forty-three eyes of 43 patients who had not received previous treatment and were diagnosed with PCV using multimodal imaging were included and retrospectively investigated. On initial visit, presence or absence of pulsation in the posterior vortex vein was analysed using HRA-IA. Subfoveal choroidal thickness (SFCT) was assessed, and patients were divided into the SFCT ≥ 200 µm and < 200 µm (P and NP, respectively) groups. Presence or absence of CVH was investigated using IA in the late phase, and the associations between the three parameters were analysed. RESULTS: Posterior vortex vein pulsation was detected in 24/43 eyes (55%). There were 27 eyes in the P group (mean SFCT, 286 ± 48 µm) and 16 eyes in the NP group (mean SFCT, 143 ± 41 µm). Pulsation was detected in 10 eyes (37%) in the P group and 14 eyes (88%) in the NP group. Incidence of pulsation was significantly higher in the NP group (P < 0.05). There were 17 (40%) patients with CVH-13 (48%) and four (25%) in the P and NP groups, respectively (P = 0.1994). There was no correlation between the presence or absence of pulsation and CVH (P = 0.1994). CONCLUSION: Congestion of the vortex vein is potentially associated with the pathogenesis of PCV with a thin choroid.

Magnetic resonance imaging of the pulsing brain: a systematic review.

OBJECTIVE: To perform a systematic review of the literature exploring magnetic resonance imaging (MRI) methods for measuring natural brain tissue pulsations (BTPs) in humans. METHODS: A prospective systematic search of MEDLINE, SCOPUS and OpenGrey databases was conducted by two independent reviewers using a pre-determined strategy. The search focused on identifying reported measurements of naturally occurring BTP motion in humans. Studies involving non-human participants, MRI in combination with other modalities, MRI during invasive procedures and MRI studies involving externally applied tests were excluded. Data from the retrieved records were combined to create Forest plots comparing brain tissue displacement between Chiari-malformation type 1 (CM-I) patients and healthy controls using an independent samples t-test. RESULTS: The search retrieved 22 eligible articles. Articles described 5 main MRI techniques for visualisation or quantification of intrinsic brain motion. MRI techniques generally agreed that the amplitude of BTPs varies regionally from 0.04 mm to ~ 0.80 mm, with larger tissue displacements occurring closer to the centre and base of the brain compared to peripheral regions. Studies of brain pathology using MRI BTP measurements are currently limited to tumour characterisation, idiopathic intracranial hypertension (IIH), and CM-I. A pooled analysis confirmed that displacement of tissue in the cerebellar tonsillar region of CM-I patients was + 0.31 mm [95% CI 0.23, 0.38, p < 0.0001] higher than in healthy controls. DISCUSSION: MRI techniques used for measurements of brain motion are at an early stage of development with high heterogeneity across the methods used. Further work is required to provide normative data to support systematic BTPs characterisation in health and disease.

Dynamic evaluation of unruptured intracranial aneurysms by 4D-CT angiography: comparison with digital subtraction angiography (DSA) and surgical findings.

BACKGROUND: This study was to prospectively investigate the feasibility of four-dimensional computed tomography angiography (4D-CTA) with electrocardiogram-gated (ECG) reconstruction for preoperative evaluation of morphological parameters, and compared with digital subtraction angiography (DSA). We also aimed to detect pulsation in unruptured intracranial aneurysms (UIAs) by using 4D-CTA, as a potential predicting factor of growth or rupture. MATERIALS: 64 patients with 64 UIAs underwent ECG-gated dynamic 4D-CTA imaging before treatment, of which 46 patients additionally underwent DSA. Original scanning data were reconstructed to produce 20 data sets of cardiac cycles with 5%-time intervals. The extent of agreement on UIAs morphological features assessed with 4D-CTA and DSA was estimated using the k coefficient of the Kappa test. The radiation doses were also calculated and compared between 4D-CTA and DSA. In the aneurysmal surgically treated in our institution, we were able to compare the surgical findings of the aneurysm wall with 4D-CTA images. We performed long-term follow-up on untreated patients. RESULTS: The morphological characteristics detected by 4D-CTA and DSA were consistent in aneurysm location (k = 1.0), shape (k = 0.76), maximum diameter (k = 0.94), aneurysm neck (k = 0.79) and proximity to parent and branch vessels (k = 0.85). 4D-CTA required lower radiation doses (0.32 ± 0.11 mSv) than DSA (0.84 ± 0.37 mSv, P < 0.001). Pulsation was detected in 26 of the 64 unruptured aneurysms, and all underwent neurosurgical clipping or interventional embolization. In aneurysms surgically treated in our hospital, we observed a significant correlation between 4D-CTA findings and surgical evaluation of the aneurysmal wall, in particular the irregular pulsations detected on 4D-CTA have demonstrated to correspond to dark-reddish thinner wall at surgery. CONCLUSIONS: In this proof-of-concept study, 4D-CTA provided real-time, non-invasive preoperative assessments of UIAs comparable to DSA. Moreover, optimal correlation between the irregular pulsation detected by 4D-CTA and the surgical findings support a possible role of this technique to identify aneurysms with a higher risk of rupture.

Effect of mechanical premilking stimulation on milking duration in late lactation.

This study documents the effect of mechanical prestimulation on the milking duration of pasture-based cows in late lactation to better harness increased capacity of automation in the milk harvesting process. Premilking stimulation, provided via manual or mechanical means, has been shown to promote the milk letdown reflex and assist in achieving quick, comfortable, and complete milk removal from the udder. The literature is lacking knowledge on the effect of mechanical premilking stimulation on milking duration, especially in late lactation and in pasture-based systems, and many pasture-based farms do not practice a full premilking routine because of a lack of labor availability. The current study addresses this gap in knowledge. In this study, we tested 2 treatments: (1) the No Stim treatment used normal farm milking settings with no premilking preparation and (2) the Stim treatment used 60 s of mechanical premilking stimulation, with a rate of 120 cycles per minute and a pulsator ratio of 30:70 on cluster attachment. Once the 60 s of stimulation had elapsed, normal milking settings resumed for the remainder of the milking. Sixty cows were enrolled in the study, which ran for 20 d. The effect of treatment on a.m. milking duration was significant, a.m. milking duration for Stim was 12 s shorter than that of No Stim. The effect of treatment on p.m. milk duration was not significant. Treatment had no effect on a.m./p.m. milk yields, average milk flowrates or peak milk flowrates. Significant differences emerged between treatments on a.m. and p.m. dead time (time from cluster attachment to reach a milk flowrate of 0.2 kg/min). The a.m. and p.m. dead times were 6 s shorter for Stim compared with No Stim. The time taken to achieve peak milk flowrate (time to peak) at morning milking was 7 s shorter for Stim compared with No Stim, and treatment yielded no significant effects on time to peak at p.m. milkings. Treatment also had no significant effect on log10 somatic cell count. Although the percentage of congested teat-ends and teat-barrels was numerically lower for Stim versus No Stim, no statistical differences were detected across these measures. Based on the results of the study, we found merit in applying 60 s of mechanical pre-stimulation at a.m. milking from a milking duration perspective. However, the strategy was not as successful for the p.m. milking. Analysis of the milk flowrate profiles recorded during the study suggest potential utility in employing different machine settings for various milkings based on anticipated yield and level of udder fill.

Impact of Thermal Pulsation System Therapy on Pre-Operative Intraocular Lens Calculations before Cataract Surgery in Patients with Meibomian Gland Disfunction.

In patients with eye surface disorders such as dry eye syndrome or Meibomian gland dysfunction (MGD) it is necessary to improve the tear film condition in order to obtain visual system measurements before cataract surgery. The aim of the project was to analyze the Thermal Pulsation System (TPS) impact on the visual system parameters used in cataract surgery qualification. The study included six patients (11 eyes) with MGD diagnosis. All patients were treated with TPS. The obtained results were compared and used to calculate the power and type of the intraocular lens (IOL). As a treatment result, the power of astigmatism has changed in 64% of the eyes. Planned surgical treatment type has changed in 27% of cases. TPS also affected the cylinder axis in three eyes, which was 27% of cases. Based on the calculations, power of the recommended IOL has changed in five eyes (46%). Stabilization of visual system parameters after TPS allowed to improve the accuracy of the results. It also ensured the proper astigmatism treating method during cataract surgery and allowed selection of the proper IOL power and type.

Measurement of CSF pulsation from EPI-based human fMRI.

It is recently discovered that the glymphatic system and meningeal lymphatic system are the primary routes for the clearance of brain waste products. The CSF flow is part of these systems, facilitating the clearance procedure. Nonetheless, the relationship between CSF flow and brain functional activity has been underexplored. To investigate CSF dynamics and functional brain activity simultaneously, recent studies have proposed a CSF inflow index measured on edge slices (CSFedge) of echo-planar imaging (EPI) based functional magnetic resonance imaging (fMRI), however, it lacks the quantitative aspect of the CSF pulsation. We proposed a new method for quantifying CSF pulsation (CSFpulse) based on an interslice CSF pulsation model in the 4th ventricle of EPI-based fMRI. The proposed CSFpulse successfully detected the higher CSF flow during the resting state than the typical task states (visual and motor) (p<.05), which is consistent with previous studies based on phase contrast (PC) MRI and CSF volume MRI, while it was not detected in CSFedge based indices or baseline CSF signals in various regions of interest (ROIs). Moreover, CSFpulse demonstrated dynamic functional changes in CSF pulsation: it decreased during the activation-on blocks while it increased during the activation-off blocks. CSFpulse significantly correlated with stroke volume measured using PC MRI, a standard method for CSF pulsation quantification, under the same functional state, while CSFedge based indices or CSF ROIs showed no correlation with the PC MRI stroke volume. Lastly, the correlation of CSFpulse with global BOLD was weaker than that of CSFedge, suggesting that CSFpulse may reflect distinct CSF physiological information that is less affected by global BOLD effects. Based on these results, the proposed CSFpulse provides CSF pulsatility information more accurately in a quantitative manner than CSFedge based indices from the recent CSF studies or the conventional ROI-based analysis. In addition to the high correlation with PC MRI, CSFpulse is much faster than PC MRI and provides information of functional brain activations simultaneously, advantageous over PC MRI or CSF volume MRI. Accordingly, the suggested CSFpulse can be used for investigating intra-subject functional changes in BOLD and CSF pulsation simultaneously and inter-subject CSF pulsation variations based on conventional EPI-based fMRI, which warrants further investigation.

Physiological instability is linked to mortality in primary central nervous system lymphoma: A case-control fMRI study.

Primary central nervous system lymphoma (PCNSL) is an aggressive brain disease where lymphocytes invade along perivascular spaces of arteries and veins. The invasion markedly changes (peri)vascular structures but its effect on physiological brain pulsations has not been previously studied. Using physiological magnetic resonance encephalography (MREGBOLD ) scanning, this study aims to quantify the extent to which (peri)vascular PCNSL involvement alters the stability of physiological brain pulsations mediated by cerebral vasculature. Clinical implications and relevance were explored. In this study, 21 PCNSL patients (median 67y; 38% females) and 30 healthy age-matched controls (median 63y; 73% females) were scanned for MREGBOLD signal during 2018-2021. Motion effects were removed. Voxel-by-voxel Coefficient of Variation (CV) maps of MREGBOLD signal was calculated to examine the stability of physiological brain pulsations. Group-level differences in CV were examined using nonparametric covariate-adjusted tests. Subject-level CV alterations were examined against control population Z-score maps wherein clusters of increased CV values were detected. Spatial distributions of clusters and findings from routine clinical neuroimaging were compared [contrast-enhanced, diffusion-weighted, fluid-attenuated inversion recovery (FLAIR) data]. Whole-brain mean CV was linked to short-term mortality with 100% sensitivity and 100% specificity, as all deceased patients revealed higher values (n = 5, median 0.055) than surviving patients (n = 16, median 0.028) (p < .0001). After adjusting for medication, head motion, and age, patients revealed higher CV values (group median 0.035) than healthy controls (group median 0.024) around arterial territories (p ≤ .001). Abnormal clusters (median 1.10 × 105 mm3 ) extended spatially beyond FLAIR lesions (median 0.62 × 105 mm3 ) with differences in volumes (p = .0055).

Correlated noise in brain magnetic resonance elastography.

PURPOSE: Magnetic resonance elastography (MRE) uses phase-contrast MRI to generate mechanical property maps of the in vivo brain through imaging of tissue deformation from induced mechanical vibration. The mechanical property estimation process in MRE can be susceptible to noise from physiological and mechanical sources encoded in the phase, which is expected to be highly correlated. This correlated noise has yet to be characterized in brain MRE, and its effects on mechanical property estimates computed using inversion algorithms are undetermined. METHODS: To characterize the effects of signal noise in MRE, we conducted 3 experiments quantifying (1) physiomechanical sources of signal noise, (2) physiological noise because of cardiac-induced movement, and (3) impact of correlated noise on mechanical property estimates. We use a correlation length metric to estimate the extent that correlated signal persists in MRE images and demonstrate the effect of correlated noise on property estimates through simulations. RESULTS: We found that both physiological noise and vibration noise were greater than image noise and were spatially correlated across all subjects. Added physiological and vibration noise to simulated data resulted in property maps with higher error than equivalent levels of Gaussian noise. CONCLUSION: Our work provides the foundation to understand contributors to brain MRE data quality and provides recommendations for future work to correct for signal noise in MRE.