Quantitative Flow Analysis Research Articles

Numerical simulations of conductive heating vacuum membrane distillation: Quantitative analysis of shunted heat flows and preventive strategy of salt crystallization

Numerical simulations of conductive heating vacuum membrane distillation: Quantitative analysis of shunted heat flows and preventive strategy of salt crystallization

Quantitative analysis of Maxwell fluid flow with dual diffusion through the variable porous canonical gap using artificial neural network approach

Quantitative analysis of Maxwell fluid flow with dual diffusion through the variable porous canonical gap using artificial neural network approach

Applying material and energy flow analysis to assess urban metabolism in the context of the circular economy

AbstractWith the circular economy (CE) gaining more traction worldwide, local authorities are engaging in efforts to develop circular strategies at the urban level. Developing and monitoring such strategies require detailed quantitative information on material and energy flows, which can be obtained through an urban metabolism (UM) analysis. This study demonstrates a bottom‐up approach to analyze UM at the sectoral level based on material and energy flow analysis (MEFA), aiming to examine its utility within the context of the CE. The analysis is performed for Umeå urban area (Sweden) with a 5‐year timeframe (2017–2021). The application of MEFA provides a detailed quantitative description of material and energy flows per sector, indicating the critical sectors in terms of resource consumption and waste generation and the most significant flows. More specifically, it reveals that the construction sector and households are key sectors within Umeå’s UM and that construction materials, food products, fossil fuels, and drinking water are significant metabolic flows. Furthermore, the application of MEFA with a multi‐year timeframe uncovers trends in consumption rates of materials and generation rates of waste and emissions, revealing, for example, the correlation of material consumption and waste generation with the level of construction activity. Overall, by illustrating the potential of MEFA to provide a detailed quantitative analysis of material and energy flows, this study emphasizes its utility in supporting the design and monitoring of circular strategies at the urban level. At the same time, it highlights limitations of the method and suggests areas for future research.

Intraoperative Transit-Time Flow as a Predictor of Failure after Infrainguinal Revascularization with Heparin-Bonded Expanded Polytetrafluoroethylene Graft

The heparin-bonded expanded polytetrafluoroethylene (He-ePTFE) conduit is an option for patients requiring infrainguinal revascularization (iIR), but the risk of failure may be unpredictable, especially in cases with poor run-off. Intraoperative transit-time flow (TTF) provides an automated and quantitative analysis of flow and may serve as an adjunct evaluation during surgical revascularization. The aim of this study was to assess TTF in patients undergoing iIR with He-PTFE at 3 referral hospitals and to establish a predictive flow threshold for graft occlusion. A prospective registry initiated in 2020 enrolled patients undergoing iIR using He-PTFE for critical limb ischemia or severe claudication, and TTF measurement was analyzed. Preoperative assessments of anatomical and clinical characteristics were available for all patients. The HT353 Optima Meter (Transonic Systems Inc., Ithaca, NY, USA) was used in all procedures according to a standardized protocol. The institutional ethics committee approved the study. A predictive model using receiver operating characteristic curve analysis was utilized to establish the threshold of flow, and variables were compared. Anatomical and clinical evaluation were reported according to Rutherford grade, Global Limb Anatomic System and Wound, Ischemia, and foot Infection classification. The main outcome considered was the correlation between TTF and graft occlusion. Secondary outcomes included survival, other predictors of graft occlusion, freedom from major adverse cardiovascular events, and freedom from major amputation. Among 68 patients, 55.8% had Rutherford 5-6, 45.6% had Global Limb Anatomic System 3 and 73.5% had Wound, Ischemia, and foot Infection 3-4. Distal anastomosis was at tibial level in 23.5% and mean diameter of conduit was 6.4mm. Basal and postoperative TTF were 27.8±15.6ml/min and 109.0±53.0 ml/min, respectively. After a mean follow-up of 18±13months, 7 (10.9%) patients presented graft occlusion and 5 (7.8%) required major amputation. TTF threshold=80ml/min revealed a sensitivity and specificity of 81.8% (95% confidence interval 48.2-97.7) and 80.7% (95% confidence interval 68.1-90.0) respectively, and it was selected as cut-off for graft occlusion. Freedom from graft occlusion in patients with TTF >80ml/min vs. TTF ≤80ml/min at 6, 12, and 24months was 95.7% (standard error (SE)=0.030) vs. 65.5% (SE=0.115), 95.7% (SE=0.030) vs. 58.9% (SE=0.120) and 90.9% (SE=0.054) vs. 51.6% (SE=0.126), P=0.0003. No statistical difference in primary patency, secondary patency and limb salvage was observed. At multivariate analysis, distal anastomosis at tibial vessel (odds ratio 8.50) and TTF ≤80ml/min (odds ratio 9.39) were independent predictors of graft occlusion. These results suggest that TTF may serve as a valuable tool in the management of iIR. A TTF measurement of ≤80ml/min should be regarded as a predictor of graft occlusion, prompting consideration of additional intraoperative maneuvers to enhance arterial flow. Caution should be exercised in patients requiring direct tibial artery revascularization, as it represents a predictor of failure independent of TTF levels. Larger cohorts of patients and longer follow-up periods are necessary to confirm these findings.

Tracking the consumption-based CO2 emissions of typical Chinese megacities in multiscale economies

Accurately tracking consumption-based CO2 emissions of megacities is crucial for clarifying regional mitigation responsibility. However, without a general emission framework, it's challenging to accomplish comparative studies of multi-megacities by quantitative carbon flow analyses. Here, we constructed a megacity-centred multilevel emission accounting framework and developed a methodology based on the revised multiscale multi-regional input-output model. Our approach integrates in-boundary and trans-boundary carbon flow driven by final demand and thus constructs urban classifications based on self-constructed consumption degree. The results indicate heterogeneity and commonality of megacities' consumption-based emissions in spatial and industrial distribution. Trans-boundary consumption-based emissions account for 81%–93% of the total in megacities, mainly from mainland China. While the majority of megacities are net importers overall, for relatively developed regions, megacities with low consumption degrees remain net exporters. At sector-level, 3 key sectors of other manufacturing, construction and services drive more than 75% of emissions. Inspired by the results, we propose differentiated carbon governance implications based on urban emission pattern classification, exploring priorities for emission reduction. Our research indicated the need for megacities as pioneers to consider consumption-side emission reductions.

Quantitative analysis of abdominal aortic blood flow by 99mTc-DTPA renal scintigraphy in patients with heart failure.

This study aimed to explore the characteristics of abdominal aortic blood flow in patients with heart failure (HF) using 99mTc-diethylenetriaminepentaacetic acid (DTPA) renal scintigraphy. We investigated the ability of renal scintigraphy to measure the cardiopulmonary transit time and assessed whether the time-to-peak of the abdominal aorta (TTPa) can distinguish between individuals with and without HF. We conducted a retrospective study that included 304 and 37 patients with and without HF (controls), respectively. All participants underwent 99mTc-DTPA renal scintigraphy. The time to peak from the abdominal aorta's first-pass time-activity curve was noted and compared between the groups. The diagnostic significance of TTPa for HF was ascertained through receiver operating characteristic (ROC) analysis and logistic regression. Factors influencing the TTPa were assessed using ordered logistic regression. The HF group displayed a significantly prolonged TTPa than controls (18.5 [14, 27] s vs. 11 [11, 13] s). Among the HF categories, HF with reduced ejection fraction (HFrEF) exhibited the longest TTPa compared with HF with mildly reduced (HFmrEF) and preserved EF (HFpEF) (25 [17, 36.5] s vs. 17 [15, 23] s vs. 15 [11, 17] s) (P < 0.001). The ROC analysis had an area under the curve of 0.831, which underscored TTPa's independent diagnostic relevance for HF. The diagnostic precision was enhanced as left ventricular ejection fraction (LVEF) declined and HF worsened. Independent factors for TTPa included the left atrium diameter, LVEF, right atrium diameter, velocity of tricuspid regurgitation, and moderate to severe aortic regurgitation. Based on 99mTc-DTPA renal scintigraphy, TTPa may be used as a straightforward and non-invasive tool that can effectively distinguish patients with and without HF.

Quantitative analysis of systemic perfusion and cerebral blood flow in the modeling of aging and orthostatic hypotension.

Introduction: Orthostatic hypotension (OH) is common among the older population. The mechanism hypothesized by OH as a risk factor for cognitive decline and dementia is repeated transient cerebral blood flow deficiency. However, to our knowledge, quantitative evaluation of cardiac output and cerebral blood flow due to acute blood pressure changes resulting from postural changes is rare. Methods: We report a new fluid-structure interaction model to analyze the quantitative relationship of cerebral blood flow during OH episodes. A device was designed to simulate the aging of blood vessels. Results and Discussion: The results showed that OH was associated with decreased transient cerebral blood flow. With the arterial aging, lesions, the reduction in cerebral blood flow is accelerated. These findings suggest that systolic blood pressure regulation is more strongly associated with cerebral blood flow than diastolic blood pressure, and that more severe OH carries a greater risk of dementia. The model containing multiple risk factors could apply to analyze and predict for individual patients. This study could explain the hypothesis that transient cerebral blood flow deficiency in recurrent OH is associated with cognitive decline and dementia.

Kiosk 3R-TB-01 - Improved Quantitative Flow Analysis of Main and Branch Pulmonary Arteries Distal to the Vortex in Repaired Tetralogy of Fallot- a Single Center 4D Flow Cardiovascular Magnetic Resonance Study

Kiosk 3R-TB-01 - Improved Quantitative Flow Analysis of Main and Branch Pulmonary Arteries Distal to the Vortex in Repaired Tetralogy of Fallot- a Single Center 4D Flow Cardiovascular Magnetic Resonance Study

Quantitative analysis of myocardial blood flow in surgically revascularized and not revascularized myocardial segments. A pilot PET study.

To prospectively compare changes in myocardial blood flow (MBF) and myocardial flow reserve (MFR) in multivessel coronary artery disease (MVCAD) patients undergoing incomplete revascularization (IR) versus complete revascularization (CR) by coronary artery bypass grafting (CABG). Seven male patients (age 68 ± 9years) with MVCAD underwent myocardial perfusion PET/CT with [13N]ammonia before and at least 4months after CABG. Segmental resting and stress MBF as well as MFR were measured. Resting and during stress left ventricle ejection fraction (LVEF) were also calculated. Three patients (43%) underwent CR and four (57%) IR. Among 119 myocardial segments, 101 (85%) were revascularized, and 18 (15%) were not. After CABG, stress MBF (mL/min/gr) and MFR are significantly increased in all myocardial segments, with a greater increase in the revascularized segments (p = 0.013). In both groups, LVEF significantly decreased during stress at baseline PET (p = 0.04), but not after CABG. Stress MBF and MFR significantly improve after CABG in both revascularized and not directly revascularized myocardial segments. IR strategy may be considered in patients with high surgical risk for CR.

Quantitative analysis and modeling of groundwater flow using visual MODFLOW: a case from subtropical coal mine, northwest Bangladesh

Quantitative analysis and modeling of groundwater flow using visual MODFLOW: a case from subtropical coal mine, northwest Bangladesh

Quantitative analysis of colloid retention and pore fluid flow in monolithic, open-porous media by X-ray computed microtomography and magnetic resonance velocimetry

X-ray computed microtomography (μCT) is a state-of-the-art technique for the experimental investigation of colloidal transport and retention in porous media. However, quantitative analysis of the amount of retained particles in laboratory CT scanners is problematic due to the polychromatic spectrum of the X-ray sources used, so such investigations are predominantly carried out in synchrotron based scanners. Synchrotron sources are expensive to operate and the measurement time at these facilities is severely limited, so that extensive parameter studies cannot usually take place here.In this work, we present an experimental investigation of deep bed filtration processes in a laboratory scale, conducted in porous, monolithic ceramics, including the quantification of retained particles. Experimental insights were given by an innovative combination of μCT and magnetic resonance velocimetry (MRV). Image analysis was carried using a novel approach for detection and quantification of even very low concentrated colloidal depositions, hereby correcting for beamhardening artifacts. Axial deposition profiles are presented, revealing a hyper-exponential behavior, thus indicating unfavorable attachment conditions and a transport-length dependent distribution of the filter efficiency kf. Due to the monolithic, porous media, further evaluation of colloid deposition is based on individual pore objects. It was found that not all pores contributed equally to colloid deposition, numerous pores even remained empty. It is very likely, that those pores are not well incorporated in the porous network and thus cannot be reached by fluid flow. The structural data of the porous media and colloidal depositions was correlated with 3D velocity information. It could be shown that the filter efficiency for particle retention is a function of time and axial position of the individual pore, and changes over the duration of the process. At a certain point in the filtration process, the rate of change of the volumetric particle fraction per pore becomes negative, predominantly at the media's inlet, while it remains positive throughout deeper pore layers. Thus, the rate of change is governed by a complex relocation process along the porous medium.

Multi-scale modelling of multi-physics flow in coal seams

The understanding and quantitative analysis of multi-physics flow in coal seam gas reservoirs are of importance for estimating potential gas production or assessing the feasibility of carbon dioxide sequestration and hydrogen storage projects. Thus, such phenomena as two-phase flow, gas and rock compressibility, as well as sorption and diffusion and their relative contributions to flow characteristics, should be quantitatively analysed. At the pore-scale, direct numerical simulations and pore-network modelling are used for micro-CT based flow simulations. However, there is a lack of modelling tools available for modelling fluid flow on micro-CT images of coal. Therefore, we develop an appropriate hybrid numerical solution for image-based flow simulations in coal, where the two-phase Darcy–Brinkman flow model is employed as a basis. This model tends towards the Navier–Stokes solution in the resolved regions of the image and towards the continuum Darcy flow in the sub-resolved zones. The gas phase is considered compressible, while the other phase represents water. The sorption processes are introduced by the Langmuir isotherm, while the transient nature of sorption is captured by the implicit combination of the Langmuir and pressure equations in the Darcy–Brinkman model. The surface diffusion is explicitly embedded in the proposed hybrid model by using the second Fick’s law. The impact of matrix swelling-shrinkage phenomenon on the coal porosity and absolute permeability is accounted for by using the Palmer–Masoori analytical model. The proposed hybrid numerical solution is implemented by using the OpenFoam open-source software. Moreover, several illustrative synthetic and realistic simulations are presented to demonstrate the capability of the developed solver to capture complex coal multi-physics. Furthermore, the employment of numerical irregular meshes for saving computational resources is also exemplified.

Comparison of the diagnostic accuracy of dynamic CT perfusion and cardiac CMR with quantitative perfusion: a subanalysis of ADVANTAGE II study

Abstract Funding Acknowledgements Type of funding sources: None. Background The ADVANTAGE II study has evaluated the performance of dynamic myocardial perfusion assessed by CT (CTP) in stented patient using ICA and in particular invasive coronary physiology (FFR and IMR) as gold-standard. Recently, quantitative myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been showed to detect obstructive coronary artery disease (CAD) and coronary microvascular dysfunction (CMD). In a substudy of ADVANTAGE II we aimed to evaluate the performance of quantitative stress CMR in comparison to CTP. Methods We present data from 39 subjects with clinically indicated ICA who underwent both vasodilator stress CMR using 1.5T MR scanner (General Electric) and dynamic stress myocardial CTP using a last generation scanner characterized by a 16-cm Z-axis coverage. In CMR Quantitative myocardial perfusion imaging was performed using the dual sequence technique (i.e. low-resolution slice for arterial input function and 2–3 short axis slices for myocardial perfusion). Resting MBF (rMBF), Stress MBF (sMBF), and myocardial perfusion reserve (MPR) were measured using Fermi deconvolution (Circle Cvi42). Quantitative perfusion results were displayed on color-encoded pixel-wise maps and on a 16-segment plot with segmental values listed. Results When FFR was used as gold standard the diagnostic accuracy of CTP was higher than those of CCTA (84.7% vs. 61.5%, p&amp;lt;0.001). When IMR was used as gold standard, diagnostic accuracy of CTP was higher than CCTA (82.9% vs. 59.3%, p&amp;lt;0.01, respectively). When the presence of at least one abnormal physiological parameter among FFR and IMR was used as gold standard, the diagnostic accuracy of CTP was higher than that of CCTA (90.8%vs 68%). Quantitative stress CMR using 2.2 ml/min/g as cut-off has a sensitivity of 83.3%, 77.7% and 100% vs QCA, FFR and IMR, respectively with higher performance of dynamic CTP in comparison to quantitative stress CMR. Conclusions In this substudy of ADVANTAGE II, we showed that global sMBF in MRI can accurately identify patients with CAD. Dynamic CTP seems to offer higher value of diagnostic performance in comparison to quantitative CMR that seems to be very promising, but more data are needed.

Quantitative Analysis of Parenchymal Effects and Flow of Large Arteriovenous Malformations Managed With Stereotactic Radiosurgery.

Stereotactic radiosurgery (SRS) of larger arteriovenous malformations (AVM) is associated with an elevated incidence of adverse radiation effects (ARE). To date, volume-response and dose-response models have been used to predict such effects. To understand radiological outcomes and their hemodynamic effects on the regional brain. A retrospective analysis was conducted at our institution using a prospective registry of patients managed between 2014 and 2020. We included patients with AVM with a nidus larger than 5 cc who received either single-session or volume-staged Gamma Knife radiosurgery. AVM volume changes, volumes of parenchymal response, and obliteration were analyzed and correlated with transit times and diameters of feeding arteries and draining veins. Sixteen patients underwent single-session SRS, and 9 patients underwent volume-staged SRS. The average AVM volume was 12.6 cc (5.5-23). The AVM locations were predominantly lobar (80%) and 17 (68%) were in critical locations. The mean margin dose was 17.2 Gy (15-21), and the median V12Gy was 25.5 cc. Fourteen (56%) AVMs had a transit time shorter than 1 second. The median vein-artery ratio (sum diameter of the veins/sum diameter of feeding arteries) was 1.63 (range, 0.60-4.19). Asymptomatic parenchymal effects were detected in 13 (52%) patients and were symptomatic in 4 (16%) patients. The median time to ARE was 12 months (95% CI 7.6-16.4). On univariate analysis, significant predictors of ARE were lower vein-artery ratio ( P = .024), longer transit time ( P = .05), higher mean dose ( P = .028), and higher D95 ( P = .036). Transit times and vessel diameters are valuable predictors of the subsequent parenchymal response after SRS. A more quantitative understanding of blood flow is critical for predicting the effects on the regional brain after AVM radiosurgery.

Enhancement of flow boiling in the microchannel with a bionic gradient wetting surface

Flow boiling in microchannels is promising to enhance electronic heat dissipation (urgently required). However, vigorous boiling in a narrow space can trigger serious flow reversal and heat transfer deterioration, restraining further performance enhancement. In this work, a bionic gradient wetting surface was developed to overcome the challenge. The upstream hydrophobicity and surface variation induced flowing bubble expansion and frequent interface fluctuation, benefiting the backflow suppression and churn flow appearance. While the downstream hydrophilicity improved liquid supply and vapor venting, preventing partial dry-out and pressure drop increase. The flow regimes on the bionic surface were demonstrated by the quantitative analysis of two-phase flow, exhibiting the shortest backflow duration time and the second-high frequency of churn flow appearance. Moreover, the gradient wettability showed negligible oscillations in average wall temperature and pressure drop and achieved the maximum enhancement rate of 50.1% and 63.2% for the heat transfer coefficient and performance evaluation criterion, respectively. The surface combination scheme incorporated the merits of different wetting surfaces and significantly enhanced the integrated performance, showing immense potential in high-efficient thermal management applications.

Quantitative Measurements of Macular and Optic Nerve Head Blood Flow Parameters Following Cataract Surgery in Eye Department, Red Cross Tertiary General Hospital, Athens, Greece

Objective: To evaluate the effect of uncomplicated cataract surgery on macular and optic nerve head blood flow with Optical Coherence Tomography Angiography (OCT-A). Retinal vascular changes and macular vessel remodeling following cataract surgery is an area of interest, as the effect, cause and duration of such changes remain debatable.&#x0D; Setting: Eye Department, Red Cross Tertiary General Hospital, Athens, Greece.&#x0D; Methods: In this study, we recruited cataract surgery candidates who had regular post operative visits and underwent longitudinal OCT-A examinations before and after surgery.&#x0D; Results: Macular vessel density increased in the post operative visits both in the superficial (SCP) and deep capillary network (DCP) (P&lt;0.001) and showed a persistent effect over 3 months follow-up. Macular thickness increased over the first postoperative month, but returned to preoperative values at 3 months. Foveal avascular zone (FAZ) measurements and vessel density at radial peripapillary capillaries (RPC) were unaffected.&#x0D; Conclusions: OCT-A enables a quantitative analysis of blood flow by regular patient monitoring. In this study, we found that after cataract surgery, macular blood flow increased significantly. The reason for this could be attributed to post operative inflammatory process or vascular remodeling due to change in retinal metabolic demands.

Abstract 14447: Multi-Center Evaluation of Stress Myocardial Blood Flow by Cardiac Magnetic Resonance in Known and Suspected Ischemic Heart Disease: Preliminary Findings From the AQUA-MBF Initiative

Introduction: Quantitative myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been shown to detect obstructive coronary artery disease (CAD) and coronary microvascular dysfunction (CMD) in several mostly small, single-center studies. The AQUA-MBF ( A ssessment of QUA ntitative MBF ) study is a multicenter initiative involving 16 centers. Hypothesis: The goal of this sub-study is to determine if MBF can differentiate CAD, CMD, and normal volunteers in this multicenter setting. Methods: We present data from 53 subjects (15 with CAD, 20 at risk for CMD and 18 controls) who underwent vasodilator stress CMR (Figure) using 1.5T and 3.0T MR scanners (General Electric). At risk for CMD was defined as having diabetes and 2 other risk factors in absence of ≥50% stenosis based on coronary CT. CAD was defined as the presence of stenosis ≥70% based on invasive coronary angiography. Stress perfusion images were acquired using the dual sequence technique. Stress MBF was measured in each of the 16 AHA segments using Fermi deconvolution (Circle Cvi42). In the CAD group, each segment was further classified as having late gadolinium enhancement (LGE), supplied by CAD, or a normal remote territory. The means of the 5 groups were compared using one-way analysis of variance. Results: The segmental stress MBF (ml/g/min) for the 5 groups are shown in figure. Compared to the normal group, segmental stress MBF in 4 disease groups were significantly lower (p&lt;0.001). Segmental MBF in those at risk for CMD was lower than normal segments and greater than CAD segments (p&lt;0.001). LGE and CAD segments had the lowest stress MBF but similar to each other (p=0.9). Conclusions: In this multicenter study, we show that quantification of MBF using the dual sequence stress perfusion CMR technique can differentiate diseased from healthy myocardium and also between obstructive CAD and those at risk for CMD.

A Numerical Model for Heat and Moisture Transfer in Porous Media of Building Envelopes

This study presents a one-dimensional quantitative analysis of unsaturated flow in natural stones using a numerical model (Finite Difference Method) and a mass balance for the heat flow. For that, we considered heat and moisture transfer between the external environment and a porous media (sandstone and limestone) with homogeneous characteristics. For unsaturated water flow, Richards’ equation and the formulation proposed by Gardner for volumetric water content and hydraulic conductivity were considered. The results of the numerical analysis showed that the evaporation of porewater throughout summer days (January 3rd and 4th) considerably reduced the temperature of the roof by about 8°C. The accumulated conductive heat flow and the volumetric water content were also reduced due to the evaporation process. This fact indicates that evaporation can be useful in providing thermal comfort and, consequently, in improving the energy efficiency of buildings with natural stones as envelopes.

Influence of the area of the aqueduct and region of interest on quantification of stroke volume in healthy volunteers using phase-contrast cine magnetic resonance imaging.

Phase-contrast cine magnetic resonance imaging (PC-MRI) has been used to measure cerebrospinal fluid (CSF) flow dynamics, but the influence of the area of the aqueduct and region of interest (ROI) on quantification of stroke volume (SV) has not been assessed. To assess the influence of the area of the ROI in quantifying the aqueductal SV measured with PC-MRI within the cerebral aqueduct. Nine healthy volunteers (mean age = 29.6 years) were enrolled in the study, and brain MRI examinations were performed on a 3.0-T system. Quantitative analysis of the aqueductal CSF flow was performed using manual ROI placement. ROIs were separately drawn for each of the 12 phases of the cardiac cycle, and changes in aqueduct size during the cardiac cycle were determined. The SV was calculated using 12 different aqueductal ROIs and compared with the SV calculated using a fixed ROI size. There was variation in the size of the aqueduct during the cardiac cycle. In addition, the measured SV increased with a greater area of the ROI. A significant difference in the calculated SVs with the 12 variable ROIs was observed compared with that using a fixed ROI throughout the cardiac cycle. To establish reliable reference values for the SV in future studies, a variable ROI should be considered.

Preoperative flow analysis of arteriovenous malformations and obliteration response after stereotactic radiosurgery.

Morphological and angioarchitectural features of cerebral arteriovenous malformations (AVMs) have been widely described and associated with outcomes; however, few studies have conducted a quantitative analysis of AVM flow. The authors examined brain AVM flow and transit time on angiograms using direct visual analysis and a computer-based method and correlated these factors with the obliteration response after Gamma Knife radiosurgery. A retrospective analysis was conducted at a single institution using a prospective registry of patients managed from January 2013 to December 2019: 71 patients were analyzed using a visual method of flow determination and 38 were analyzed using a computer-based method. After comparison and validation of the two methods, obliteration response was correlated to flow analysis, demographic, angioarchitectural, and dosimetric data. The mean AVM volume was 3.84 cm3 (range 0.64-19.8 cm3), 32 AVMs (45%) were in critical functional locations, and the mean margin radiosurgical dose was 18.8 Gy (range 16-22 Gy). Twenty-seven AVMs (38%) were classified as high flow, 37 (52%) as moderate flow, and 7 (10%) as low flow. Complete obliteration was achieved in 44 patients (62%) at the time of the study; the mean time to obliteration was 28 months for low-flow, 34 months for moderate-flow, and 47 months for high-flow AVMs. Univariate and multivariate analyses of factors predicting obliteration included AVM nidus volume, age, and flow. Adverse radiation effects were identified in 5 patients (7%), and 67 patients (94%) remained free of any functional deterioration during follow-up. AVM flow analysis and categorization in terms of transit time are useful predictors of the probability of and the time to obliteration. The authors believe that a more quantitative understanding of flow can help to guide stereotactic radiosurgery treatment and set accurate outcome expectations.