Computed Tomography Sample Clauses

Computed Tomography. Computed tomography is an imaging technique that utilises computer-processed X-rays to produce tomographic images or 'slices' of specific areas of the body. Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation [347]. Computed tomography produces a volume of data that can be manipulated, through a process known as windowing, in order to demonstrate various bodily structures based on their ability to attenuate the X-xxx xxxx. This information is interpreted as Hounsfield Units (HU). Although historically the images generated were in the axial or transverse plane, perpendicular to the long axis of the body, modern scanners allow this volume of data to be reformatted in various planes or as volumetric (3D) representations of structures. Electron beam computed tomography (EBCT) and multi detector computed tomography (MDCT) are well-validated, non-invasive imaging methods which do not require the administration of radio-opaque contrast dyes [348]. The methods are considered to be the gold-standard for assessing the extent of VC and its progression in the coronary arteries, the aorta and the cardiac valves [349, 350]. Both CT technologies are considered equivalent in accuracy and reproducibility even though they operate on different imaging platforms [351-353]. Electron beam computed tomography employs a rotating fan of X‑rays produced by the impact of a beam of electrons against a tungsten ring. Image acquisition is rapid, limiting patient exposure to radiation [348]. Multi detector computed tomography employs a paired X‑ray source-detector unit revolving in a spiral motion around the patient who lies on a movable bed that advances through the beam of X‑rays [348]. Although MDCT is slower than EBCT and provides a higher radiation dose, it has a higher spatial resolution (better image quality) than EBCT [354]. Despite the advantages of CT imaging techniques for the quantification of calcification, there are also substantial limitations. The method is unable to distinguish intimal from medial calcification and CT methods are expensive and provide increased exposure to ionized radiation. The lack of accessibility of scanners can present a major obstacle to its routine application and more importantly the method requires a clinician or highly trained and experienced reader to interpret the results.
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Computed Tomography. 3. In China and Italy the following bedside medical diagnostic imaging proved to be useful and allowed for less contact with other health care workers a) Chest XRay b) Lung ultrasound c) Respiratory Therapy
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Computed Tomography. Certificate (C45200A) Diploma (D55140) Certificate (C55140C)
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Computed Tomography. The major advantage of CT is increasing the specificity of the diagnosis of TB; therefore, CT is often not necessary in the acute setting, particularly when the disease is already suspected and appropriate precautions and testing are already underway. CT may be able to better show distinct findings such as cavitation or endobronchial spread with tree-in-bud nodules and may be helpful in cases in which the chest radiograph does not show “classic” findings of TB [6]. CT findings can also be helpful in predicting acid-fast bacilli smear positivity [7-9]. Even in acid-fast bacilli smear–negative patients, CT may suggest the risk that a patient will be TB culture positive when findings consistent with active TB are present [10]. CT may be of value in the severely immunocompromised patient with a normal or near-normal radiograph by revealing abnormal lymph nodes or subtle parenchymal disease. Finally, CT may also have a role in identifying patients with latent TB who will be at risk for reactivation disease [4,11]. 1Principal Author and Panel Chair, Medical University of South Carolina, Charleston, South Carolina. 2Panel Vice-chair, National Jewish Health, Denver, Colorado. 3Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts. 4University of Texas MD Xxxxxxxx Cancer Center, Houston, Texas. 5Mayo Clinic, Rochester, Minnesota. 6Mayo Clinic, Phoenix, Arizona. 7Vanderbilt University Medical Center, Nashville, Tennessee, American College of Chest Physicians. 8Mayo Clinic, Jacksonville, Florida. 9Columbia University Medical Center New York and Temple University Health System, Philadelphia, Pennsylvania. 10Specialty Chair, University of Florida College of Medicine, Gainesville, Florida. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: xxxxxxxxxxxx@xxx.xxx Magnetic resonance imaging‌‌ Only 1 study has been performed evaluating magnetic resonance imaging (MRI) for suspected TB. In this study the accuracy of MRI was similar to CT in describing findings related to culture-positive patients [12]. Inferential data regarding the value of MRI can also be derived from its role in cystic fibrosis and the observation in o...
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Computed Tomography. In 1971 Xxxxxxx Xxxxxxxxxx [4] opened a new window for the world with his invention of the computed tomography (CT) machine. CT machines project x-ray beams from a known source through an object, which are then received by detectors. The energy of the source x-ray beams are known, and the detectors measure the energy after they pass through the object. The energy difference between the source and the detector depends on the attenuation properties of the object, and is modeled by the Beer’s law [34]. If enough measurements are obtained, then by solving an inverse problem arising from the Beer’s law, the inner structure of an object can be reconstructed. Because the Beer’s law results in a very challenging nonlinear inverse problem, most image reconstruction algorithms are based on linear approximations. The linear ap- proximations allow for very fast algorithms, and images they produce are often quite good. Thus CT immediately gained popularity for medical diagnostics, but the tech- nique is also used widely in industry to, for example, inspect inanimate objects for defects, or in security to look for weapons and other dangerous materials. Current CT machines mostly use single-energy tubes to conduct scanning. For single-energy CT, we assume that the x-ray tube only emits a uniform energy and this energy is used to estimate the attenuation properties of the object. Using the Radon transform [14], a linear system is constructed to represent an approximation to this physical process. Under certain conditions, an image obtained from solving the corresponding linear system is clear enough to identify necessary information. However, the assumption of single uniform energy is only a simplification of the underlying physics. In actuality, the x-ray beams consist of a spectrum of energies, rather than a single energy. Because of this simplification, precise estimation of the attenuation properties of the object is very challenging, and often leads to appearance of so-called beam-hardening artifacts [45]. In 2006, the invention of dual-source CT machines refreshed this field [19]. Using two x-ray tubes with different voltages, two sets of projected data corresponding to two energy spectra are obtained to conduct image reconstruction. Basically, the attenuation properties of the object can be represented as a function of two variables, position and energy. With an extra energy, we can obtain more information about the object. On the one hand, the beam-hardening artif...
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