Background and aims: MRI-based haemodynamics have been applied to study the relationship between time-averaged wall shear stresses (TAWSS), oscillatory shear index (OSI) and atherosclerotic lesions in the coronary art...
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Background and aims: MRI-based haemodynamics have been applied to study the relationship between time-averaged wall shear stresses (TAWSS), oscillatory shear index (OSI) and atherosclerotic lesions in the coronary arteries, carotid artery and human aorta. However, the role of TAWSS and OSI is poorly understood in lower extremity arteries. The aim of this work was to investigate the feasibility of haemodynamic assessment of the superficial femoral artery (SFA) in patients with peripheral artery disease (PAD) and we hypothesised that there is an association between TAWSS and OSI, respectively, and atherosclerotic burden expressed as a normalised wall index (NWI). Methods: Six cases of 3D vascular geometries of the SFA and related inlet/outlet flow conditions were extracted from patient-specific MRI data including baseline, 12 and 24 months. Blood flow simulations were performed to compute flow descriptors, including TAWSS and OSI, and NWI. Results: NWI was correlated positively with TAWSS (correlation coefficient: r = 0.592;p < 0.05). NWI was correlated negatively with OSI (correlation coefficient: r = -0.310, p < 0.01). Spatially averaged TAWSS and average NWI increased significantly between baseline and 24 months, whereas OSI decreased over two years. Conclusions: In this pilot study with a limited sample size, TAWSS was positively associated with NWI, a measure of plaque burden, whereas OSI showed an inverse relationship. However, our findings need to be verified in a larger prospective study. MRI-based study of haemodynamics is feasible in the superficial femoral artery.
Background: A talar body prosthetic implant may be indicated after a severe fracture in the talus bone resulting in avascular necrosis with collapse. This process is patient-specific, in which the geometry is copied f...
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Background: A talar body prosthetic implant may be indicated after a severe fracture in the talus bone resulting in avascular necrosis with collapse. This process is patient-specific, in which the geometry is copied from the healthy talus of the opposite foot to create the implant. More recently, an 'off-the-shelf' non-custom talar prosthetic was proposed, consisting of a standardised shape in 10 different sizes. Methods:The generic-shaped talus was determined by creating 3D models via image processing software MIMICS and further refined using Geomagic, from raw data of CT scan imaging. This study evaluated the intra- and inter-operator reliability in 3D modelling of talus bone from CT scan imaging. Results: Four operators created 3D models using CT scans of four subjects via the documented protocol. The average deviations were well within the acceptable value, and although the extreme values were large, the distributions showed that the critical deviations were either few points, or small areas. Intra- and inter-operator differences were not statistically significant in most cases. The talus bone was found to have larger deviations than the tibia due to rougher surface. Conclusions: From our results, the method of converting 2D CT images to 3D models used to develop generic talus implant is reliable within the acceptable tolerances.
Coronary artery disease (CAD) is currently one of the most prevalent diseases in the world population and calcium deposits in coronary arteries are one direct risk factor. These can be assessed by the calcium score (C...
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Coronary artery disease (CAD) is currently one of the most prevalent diseases in the world population and calcium deposits in coronary arteries are one direct risk factor. These can be assessed by the calcium score (CS) application, available via a computed tomography (CT) scan, which gives an accurate indication of the development of the disease. However, the ionising radiation applied to patients is high. This study aimed to optimise the protocol acquisition in order to reduce the radiation dose and explain the flow of procedures to quantify CAD. The main differences in the clinical results, when automated or semiautomated post-processing is used, will be shown, and the epidemiology, imaging, risk factors and prognosis of the disease described. The software steps and the values that allow the risk of developing CAD to be predicted will be presented. A64-row multidetector CT scan with dual source and two phantoms (pig hearts) were used to demonstrate the advantages and disadvantages of the Agatston method. The tube energy was balanced. Two measurements were obtained in each of the three experimental protocols (64, 128, 256 mAs). Considerable changes appeared between the values of CS relating to the protocol variation. The predefined standard protocol provided the lowest dose of radiation (0.43 mGy). This study found that the variation in the radiation dose between protocols, taking into consideration the dose control systems attached to the CT equipment and image quality, was not sufficient to justify changing the default protocol provided by the manufacturer.
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