![]() ![]() ![]() The volume of the artifacts and the computed relative differences in mean and max standardized uptake value (SUV) between the two PET images are reported. The reconstructed PET images were evaluated visually and quantitatively using regions of interests in reference regions. Our inpainting algorithm delineates the outer contour of signal voids breaching the anatomical volume using the non-attenuation-corrected PET image and classifies the inner air regions based on an aligned template of likely dental artifact areas. MR-AC was based on either standard MR-AC DIXON or MR-AC INPAINTED where the susceptibility-induced signal voids were substituted with soft tissue information. The PET/MR data were acquired over a single-bed position of 25.8 cm covering the head and neck. Patients were injected with -FDG, -PiB, -FET, or -DOTATATE. MethodsĪ total of 148 PET/MR patients with clear visual signal voids on the attenuation map in the dental region were included in this study. The purpose of this study was to assess the frequency and magnitude of subsequent PET image distortions following MR-AC. The susceptibility effects due to metal implants challenge MR-AC in the neck region of patients with dental implants. slice-overlap artifact a.k.a.In the absence of CT or traditional transmission sources in combined clinical positron emission tomography/magnetic resonance (PET/MR) systems, MR images are used for MR-based attenuation correction (MR-AC).propylene glycol peak: resonates at 1.13 ppm.N-acetylaspartate (NAA) peak: resonates at 2.0 ppm.glutamine-glutamate peak: resonates at 2.2-2.4 ppm.gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm.2-hydroxyglutarate peak: resonates at 2.25 ppm.arterial spin labeling (ASL) MR perfusion.dynamic contrast enhanced (DCE) MR perfusion.dynamic susceptibility contrast (DSC) MR perfusion.metal artifact reduction sequence (MARS).turbo inversion recovery magnitude (TIRM).fluid attenuation inversion recovery (FLAIR).diffusion tensor imaging and fiber tractography.MRI pulse sequences ( basics | abbreviations | parameters).iodinated contrast-induced thyrotoxicosis.iodinated contrast media adverse reactions.clinical applications of dual-energy CT.as low as reasonably achievable (ALARA).One can observe this when observing the shadow cast by the light source onto the anatomy. The closer the anatomy is to the detector the less magnification/distortion. The object to image receptor distance (OID) is the distance between the object to the detector. Although 100 cm is the universally accepted SID, studies have shown that apart from improving distortion issues, increasing the SID from 100 cm to 122 cm decreases entrance skin dose despite any need for an increase in mAs 1. The greater the SID, the less magnification the image will suffer. The source image receptor distance (SID), is the distance of the tube from the image receptor, affecting magnification. The point of the central ray is the focal spot on the x-ray tube therefore one can angle the tube on a stationary axis and maintain the central ray at the level of the joint, seldom applied but useful for imaging that requires longer radiographs e.g. tibia/fibula x-ray. CenteringĬentering the anatomy to the central ray on the image receptor will limit beam distortion due to divergence. The amount of distortion can be limited via three factors. All regions peripheral to the central ray will then suffer from some degree of distortion. As the beam exits the x-ray tube the beam will 'diverge' while the center point (central ray) of the beam will not suffer from any divergence. It is due to this point source nature that x-ray beams will all possess 'beam divergence'. The x-ray beam originates from a point source within the x-ray tube. Several factors contribute to radiographic distortion whereby the anatomy examined is misrepresenting on the plain radiograph. ![]()
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