Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
Technical developments are ongoing in CT, and there has been a continually\nincreasing trend in patient prescription, resulting in increased exposure.\nCurrently, doses delivered during CT are generally evaluated using computed\ntomography dose index (CTDI), which is measured with a 10 cm pencil ionization\nchamber placed in a 14 cm PMMA phantom. However, shortfalls in\nCTDI have been identified by the American Association of Physicists in\nMedicine (AAPM) who have proposed a new method, dose equilibrium\n(DEq). In this paper, the dose equilibrium was used to estimate the dose in\ntwo protocols (thoracic and abdominopelvic) and compared to CTDI values.\nIn addition, a retrospective correction was applied to 20 patient CTDIâ??s by\ncharacterizing the specific DEq profile of the system scans. The results indicated\nthe dose equilibrium estimations of two protocols, thoracic and abdominopelvic,\nwere 29% and 30% respectively, higher than those informed by\nthe CT scanner. In addition, a retrospective dose correction estimation of a\nrandom sample of twenty patients demonstrated an annual underestimation\nin absorbed dose by between 26% and 28%. Continued use of the CTDI method\nin quality assurance of modern CT could result in greater patient risk.\nAAPM Task Group 111 presents a more accurate, safer method to estimate\ndose and its adoption is paramount....
Blood oxygenation level dependence signal (BOLD) for functional magnetic\nresonance imaging (FMRI), is the use of blood magnetization depending on\nthe oxygenation state of hemoglobin. Susceptibility gradient can shift and\nskew k -space trajectories and it leads to echo time shift and BOLD sensitivity\nchange. FMRI can be used to detect the signal, the change of the susceptibility\ngradient of the signal and the distortion of k space trajectory, resulting\nin echo time shift and BOLD sensitivity change. Using the percentage signal\nchange (PSC) and calibration function, it can be applied to many different\nfields, such as age-related research. In this paper, the performance of BOLD\nsignal change correction based on sensitivity gradient was verified by real data\ngroup calculation, and methods of further improving the calculation speed\nwere analyzed. This paper also analyzed the performance of correcting the\nvariations of BOLD Signal due to susceptibility gradients with real data set,\nand identified the computational issues that need to be improved for further\nresearch....
X-ray computed tomography (CT) is widely used in clinical practice. The involved ionizing\nX-ray radiation, however, could increase cancer risk. Hence, the reduction of the radiation dose\nhas been an important topic in recent years. Few-view CT image reconstruction is one of the main\nways to minimize radiation dose and potentially allow a stationary CT architecture. In this paper,\nwe propose a deep encoder-decoder adversarial reconstruction (DEAR) network for 3D CT image\nreconstruction from few-view data. Since the artifacts caused by few-view reconstruction appear in\n3D instead of 2D geometry, a 3D deep network has a great potential for improving the image quality\nin a data driven fashion. More specifically, our proposed DEAR-3D network aims at reconstructing\n3D volume directly from clinical 3D spiral cone-beam image data. DEAR is validated on a publicly\navailable abdominal CT dataset prepared and authorized by Mayo Clinic. Compared with other\n2D deep learning methods, the proposed DEAR-3D network can utilize 3D information to produce\npromising reconstruction results....
Purpose: Knowledge of the hemodynamics in the vascular system is important to understand\nand treat vascular pathology. The present study aimed to evaluate the hemodynamics in the human\ncarotid artery bifurcation measured by four-dimensional (4D) flow magnetic resonance imaging\n(MRI) as compared to computational fluid dynamics (CFD). Methods: This protocol used MRI data of\n12 healthy volunteers for the 3D vascular models and 4D flow MRI measurements for the boundary\nconditions in CFD simulation. We compared the velocities measured at the carotid bifurcation and\nthe 3D velocity streamlines of the carotid arteries obtained by these two methods. Results: There was\na good agreement for both maximum and minimum velocity values between the 2 methods for\nvelocity magnitude at the bifurcation plane. However, on the 3D blood flow visualization, secondary\nflows, and recirculation regions are of poorer quality when visualized through the 4D flow MRI.\nConclusion: 4D flow MRI and CFD show reasonable agreement in demonstrated velocity magnitudes\nat the carotid artery bifurcation. However, the visualization of blood flow at the recirculation regions\nand the assessment of secondary flow characteristics should be enhanced for the use of 4D flow MRI\nin clinical situations....
Background: functional gastrointestinal disorders (FGID) are common conditions in\nchildren and adults, often associated with abnormalities of whole gut transit. Currently, transit tests\ncan be performed using several imaging methods, including tracking of radiopaque markers, gamma\nscintigraphy with the use of radioisotopes, magnetic tracking methods, tracking of movement of\nwireless motility capsules, and emerging magnetic resonance imaging (MRI) approaches. Objectives:\nto review recent literature on diagnostic imaging techniques used to investigate whole gut transit\nin FGIDs. Methods: a systematic review was carried out. The different techniques are described\nbriefly, with particular emphasis on contemporary literature and new developments, particularly in\nthe field of MRI. Conclusions: emerging MRI capsule marker methods are promising new tools to\nstudy whole gut transit in FGIDs....
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