10/27/2022 0 Comments Beam hardening artifact meaning![]() Therefore, it is preferable if the start and end position of the tube is aligned with the primary direction of motion, for example, vertically above or below a patient undergoing a chest scan. The sensitivity of the image to motion artifacts depends on the orientation of the motion. Respiratory motion can be minimized if patients are able to hold their breath for the duration of the scan. Using as short a scan time as possible helps minimize artifacts when scanning regions prone to movement. However, in some cases (eg, pediatric patients), it may be necessary to immobilize the patient by means of sedation. Avoidance of Motion Artifacts by the Operator.- The use of positioning aids is sufficient to prevent voluntary movement in most patients. However, there ar e special features on some scanners designed to minimize the resulting artifacts. Steps can be taken to prevent voluntary motion, but some involuntary motion may be unavoidable during body scanning. Motion Artefacts Patient Motion Patient motion can cause misregistration artifacts, which usually appear as shading or streaking in the reconstructed image. ![]() #BEAM HARDENING ARTIFACT MEANING SOFTWARE#Beam hardening correction software should also be used when scanning metal objects to minimize the additional artifacts due to beam hardening. The usefulness of metal artifact reduction software is sometimes limited because, although streaking distant from the metal implants is removed, there still remains a loss of detail around the metal-tissue interface, which is often the main area of diagnostic interest. Manufacturers use a variety of interpolation techniques to substitute the over-range values in attenuation profiles. Streaking caused by over-ranging can be greatly reduced by means of special software corrections. When it is impossible to scan the required anatomy without including metal objects, increasing technique, especially kilovoltage, may help penetrate some objects, and using thin sections will reduce the contribution due to partial volume artifact. For non-removable items, such as dental fillings, prosthetic devices, and surgical clips, it is sometimes possible to use gantry angulation to exclude the metal inserts from scans of nearby anatomy. Patients are normally asked to take off removable metal objects such as jewelry before scanning commences. Additional artifacts due to beam hardening, partial volume, and aliasing are likely to compound the problem when scanning very dense objects. They occur because the density of the metal is beyond the normal range that can be handled by the computer, resulting in incomplete attenuation profiles. Metal ArtefactsThe presence of metal objects in the scan field can lead to severe streaking artifacts. The artefact occurs because the high density anatomy absorbs the lower energy photons while the higher energy photons pass through to the detectors which results in the beam becoming 'harder'. Beam Hardening Artefacts Beam hardening artefacts appear as streaks and shadows adjacent to areas of high density such as the petrous bones, shoulders, and hips. The toolkit is accessible as a module at. ![]() The toolkit is released under the BSD license, imposing minimal restrictions on its use and distribution. Case studies in scan protocol optimization, low dose imaging and iterative algorithm comparison demonstrated its substantial potential in performing scan data based clinical studies. The performance was validated on real patient scans with good agreement with respect to vendor-designed program. Imaging dose in CTDIw is calculated in an empirical formula. Pixel-to-HU mapping is calibrated by a Catphan TM 504 phantom. ![]() Reconstruction is supported by TIGRE with FDK as well as a variety of iterative algorithms. Data conditioning operations including scatter correction, normalization, beam-hardening correction, ring removal are performed sequentially. #BEAM HARDENING ARTIFACT MEANING SERIES#Raw scan data are first decoded to extract X-ray fluoro image series and set up the imaging geometry. The entire imaging chain, module-based architecture, data flow and techniques used in the creation of the toolkit are presented. The aim of this project is to provide not only a tool to bridge the gap between clinical usage of CBCT scan data and research algorithms but also a framework that breaks down the imaging chain into individual processes so that research effort can be focused on a specific part. We presented TIGRE-VarianCBCT, an open-source toolkit Matlab-GPU for Varian on-board cone-beam CT with particular emphasis to address challenges in raw data preprocessing, artifacts correction, tomographic reconstruction and image post-processing. ![]()
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