Computational fluid dynamic analysis of calcified coronary plaques: Correlation between hemodynamic changes and cardiac image analysis based on left coronary bifurcation angle and lumen assessments

The purpose of this study was to determine the relationship between left coronary bifurcation angle and significant coronary stenosis with use of coronary CT angiography (CCTA)-generated computational fluid dynamics (CFD) analysis when compared to the CCTA analysis of coronary lumen stenosis with invasive coronary angiography (ICA) as the reference method. Eleven patients with calcified plaques at the left coronary artery tree who underwent CCTA and ICA examinations were included in the study. CFD simulation of left coronary models was performed to analyse hemodynamic changes including wall shear stress, wall pressure and flow velocity. The mean bifurcation angle was measured 83.3 ± 17.1° and 83.3 ± 17.0° on CCTA and ICA, respectively, with no significant difference (p=0.99). Of 15 significant stenosis at left anterior descending (LAD) and left circumflex (LCx) on CCTA, only 3 of them were confirmed to be > 50% stenosis on ICA. Wall shear stress was noted to increase in the LAD and LCx models with significant stenosis and wider angulation (> 80°), but remained no change in most of the other coronary models with no significant stenosis and narrower angulation. Wall pressured was decreased at the significant stenotic lesions, while flow velocity was increased with flow turbulence at the post-stenotic sites. This study further clarifies the direct correlation between left coronary bifurcation angle and significant stenosis, with angulation measurement being more accurate than lumen assessment for diagnosing significant stenosis

A novel method of sensitivity analysis testing by applying the DRASTIC and fuzzy optimization methods to assess groundwater vulnerability to pollution: the case of the Senegal River basin in Mali

Abstract. Vulnerability to groundwater pollution in the Senegal River basin was studied by two different but complementary methods: the DRASTIC method (which evaluates the intrinsic vulnerability) and the fuzzy method (which assesses the specific vulnerability by taking into account the continuity of the parameters). The validation of this application has been tested by comparing the connection in groundwater and distribution of different established classes of vulnerabilities as well as the nitrate distribution in the study area. Three vulnerability classes (low, medium and high) have been identified by both the DRASTIC method and the fuzzy method (between which the normalized model was used). An integrated analysis reveals that high classes with 14.64 % (for the DRASTIC method), 21.68 % (for the normalized DRASTIC method) and 18.92 % (for the fuzzy method) are not the most dominant. In addition, a new method for sensitivity analysis was used to identify (and confirm) the main parameters which impact the vulnerability to pollution with fuzzy membership. The results showed that the vadose zone is the main parameter which impacts groundwater vulnerability to pollution while net recharge contributes least to pollution in the study area. It was also found that the fuzzy method better assesses the vulnerability to pollution with a coincidence rate of 81.13 % versus that of 77.35 % for the DRASTIC method. These results serve as a guide for policymakers to identify areas sensitive to pollution before such sites are used for socioeconomic infrastructures

Simulation of blood flow in abdominal aortic aneurysms treated with suprarenal and fenestrated stent grafts

The purpose of this study was to simulate the blood flow features in patients with abdominal aortic aneurysms treated with suprarenal and fenestrated stent grafts, which are two commonly used endovascular techniques to deal with complicated aneurysm necks

Dual Energy CT Angiography of Peripheral Arterial Disease: Feasibility of Using Lower Contrast Medium Volume

Objective: One of the main drawbacks associated with Dual Energy Computed Tomography Angiography (DECTA) is the risk of developing contrast medium-induced nephropathy (CIN). The aim of the present study was firstly, to design an optimal CT imaging protocol by determining the feasibility of using a reduced contrast medium volume in peripheral arterial DECTA, and secondly, to compare the results with those obtained from using routine contrast medium volume. Methods: Thirty four patients underwent DECTA for the diagnosis of peripheral arterial disease. They were randomly divided into two groups: Group 1 (routine contrast volume group) with n = 17, injection rate 4–5 ml/s, and 1.5 ml/kg of contrast medium, and Group 2 ((low contrast volume group), with n = 17, injection rate 4–5ml/s, and contrast medium volume 0.75 ml/kg. A fast kilovoltage—switching 64-slice CT scanner in the dual-energy mode was employed for the study. A total of 6 datasets of monochromatic images at 50, 55, 60, 65, 70 and 75 keV levels were reconstructed with adaptive statistical iterative reconstruction (ASIR) at 50%. A 4-point scale was the tool for qualitative analysis of results. The two groups were compared and assessed quantitatively for image quality on the basis of signal-to-noise ratio (SNR) and contrast-to-noise-ratio (CNR). Radiation and contrast medium doses were also compared.Results: The overall mean CT attenuation and mean noise for all lower extremity body parts was significantly lower for the low volume contrast group (p<0.001), and varied significantly between groups (p = 0.001), body parts (p<0.001) and keVs (p<0.001). The interaction between group body parts was significant with CT attenuation and CNR (p = 0.002 and 0.003 respectively), and marginally significant with SNR (p = 0.047), with minimal changes noticed between the two groups. Group 2 (low contrast volume group) displayed the lowest image noise between 65 and 70 keV, recorded the highest SNR and CNR at 65 keV, and produced significantly lower results with respect to contrast medium volume and duration of contrast injection (p<0.001). The effect of radiation dose was not statistically significant between the two groups. Conclusions: DECTA images created at 65 keV and 50% ASIR with low contrast medium volume protocol, yielded results that were comparable to routine contrast medium volume, with acceptable diagnostic images produced during the evaluation of peripheral arteries

Hemodynamic Effect of Calcifed Plaque on Blood Flow in Carotid Artery Disease: A Preliminary Study

The purpose of the study is to investigate the hemodynamic effect of calcified carotid plaque on blood flow in patients diagnosed with carotid artery disease. Two carotid artery models were generated based on a patient data, with normal and calcified carotid artery appearances. Circular calcified carotid plaque was found at the carotid bifurcation based on 3D computed tomography images. A computational fluid dynamics was performed to analyze the changes of blood flow in different situations. Our results showed that apparent turbulence was found in the diastolic phase at the carotid bifurcation in normal carotid artery geometry. In the presence of the calcified plaque, the flow velocity was increased to some extent, indicating the effect of plaque on hemodynamic changes. Wall shear stress was noticed to be maximal at the aortic bifurcation, and this indicates the potential risk of developing stenosis at this area. Our preliminary study demonstrates fluid structure interaction between calcified plaque and artery in terms of flow changes and wall shear stress

Flow simulation in coronary artery models: An investigation of the effect of variable angulations at left coronary artery

This study was designed to investigate the hemodynamics in the left coronary artery with the aim of identifying the relationship between angulations of left coronary bifurcation and development of atherosclerosis. Six 3D left coronary models were simulated for computational fluid dynamic analysis. The left coronary model was composed of left main stem, left anterior descending and left circumflex branches. The angulations at the left bifurcation weresimulated with angles ranging from 90°, 75°, 60°, 45°, 30° to 15°. The computational fluid dynamic was used for analysis of flow velocity, wall pressure and wall shear stress. Our results showed that apparent low shear stress and high wall pressure was noticed at the left coronary bifurcation regions with wide angled models. Flow pattern was also changed with angled becoming wide in the simulated models. Our analysis shows direction relationship between coronary angulation and development of atherosclerosis. Future studies are required to perform computational fluid dynamic analysis in coronary models from patients' data with different degree of coronary stenosis

Incidental detection of sinus mucosal abnormalities on CT and MRI imaging of the head

Purpose: To investigate the prevalence of incidental sinus abnormalities on CT and MRI imaging of the head, and identify if there is any correlation between patient symptomatology and image findings. Materials and methods: One hundred and fifteen patients who underwent head CT or MRI for non-sinus related indications were included in this study, with image findings being analysed based on the Lund-Mackay Grading System (LMS). These were compared with their symptomatology based on theSNAQ-11 questionnaire. Two reviewers who were blinded to the patients’ SNAQ-11 scores analysed the images. Patients were also referred to an ENT surgeon for anterior rhinoscopy in an attempt to seek a correlation between symptomatology and/or imaging findings against clinical assessment. Results: The prevalence of incidental sinus abnormalities is between 14.8% and 37% for CT and 29.5%and 85.2% for MRI, depending upon the cutoff LMS used. There was no significant difference in the incidence rate between the different age groups or genders. Asymptomatic patients had a significantly lower incidence rate of sinus mucosal abnormalities (8.2-57.1%) when compared to the symptomatic patients (33.3-66.7%) (P<0.01). A significant correlation was found between the MRI sinus findings and patients’ symptoms (r=0.59, P<0.001) with no correlation demonstrated in the CT group. The mean LM score for the patients with clinical sinusitis was 6.2, while the normal patients had a mean LM score of 2.2. Conclusions: MRI is more sensitive than CT to detect sinus mucosal abnormalities. A significant correlation is noticed between MRI findings and patients’ symptomatology

Field application of silicon alleviates drought stress and improves water use efficiency in wheat

Detrimental impacts of drought on crop yield have tripled in the last 50 years with climate models predicting that the frequency of such droughts will intensify in the future. Silicon (Si) accumulation, especially in Poaceae crops such as wheat (Triticum aestivum L.), may alleviate the adverse impacts of drought. We have very limited information, however, about whether Si supplementation could alleviate the impacts of drought under field conditions and no studies have specifically manipulated rainfall. Using field–based rain exclusion shelters, we determined whether Si supplementation (equivalent to 39, 78 and 117 kg ha-1) affected T. aestivum growth, elemental chemistry [Si, carbon (C) and nitrogen (N)], physiology (rates of photosynthesis, transpiration, stomatal conductance, and water use efficiency) and yield (grain production) under ambient and drought (50% of ambient) rainfall scenarios. Averaged across Si treatments, drought reduced shoot mass by 21% and grain production by 18%. Si supplementation increased shoot mass by up to 43% and 73% in ambient and drought water treatments, respectively, and restored grain production in droughted plants to levels comparable with plants supplied with ambient rainfall. Si supplementation increased leaf-level water use efficiency by 32–74%, depending on Si supplementation rates. Water supply and Si supplementation did not alter concentrations of C and N, but Si supplementation increased shoot C content by 39% and 83% under ambient and drought conditions, respectively. This equates to an increase from 6.4 to 8.9 tonnes C ha-1 and from 4.03 to 7.35 tonnes C ha-1 under ambient and drought conditions, respectively. We conclude that Si supplementation ameliorated the negative impacts of drought on T. aestivum growth and grain yield, potentially through its beneficial impacts on water use efficiency. Moreover, the beneficial impacts of Si on plant growth and C storage may render Si supplementation a useful tool for both drought mitigation and C sequestration

Double low-dose computed tomography pulmonary angiography in the diagnosis of pulmonary embolism

The purpose of this study is to investigate the feasibility of double low-dose (low radiation and low contrast medium doses) computed tomography pulmonary angiography (CTPA) in the diagnosis of pulmonary embolism. This retrospective study involved analysis of 59 patients undergoing 64- and 128-slice CTPA examinations which were scanned with a pitch of 0.9 and 100 and 120 kVp, respectively, while flash mode of CTPA was done with a pitch of 3.2 and 120 kVp. There were no significant differences in image quality assessment between the low kVp and standard kVp or high-pitch CTPA protocols (p=0.181-0.186). The mean effective dose for the 100 kVp protocol was significantly lower than that for the120 kVp and the flash mode protocols (p<0.001). The contrast medium was between 35-45 ml for the 100 and 120 kVp protocols, and 20-30 ml for the 120 kVp flash mode protocol. Double low-dose CT pulmonary angiography is feasible for detection of pulmonary embolism with acquisition of diagnostic images