![]() Both modules were reset in the motherboard, and the bad-detector test was repeated. Because the first cause would have required replacing the detector module, we tried to rule out the second cause-a loose connection. Two possibilities for the defect were suspected, either an electronic issue within the detector module or a loose connection between the module and the motherboard. The service engineer performed the bad-detector test to rule out the possibility that the artifact was caused by defective detector modules. 1B, arrows) and remained even after cleaning of the Mylar (DuPont Teijin Films) window with warm water. The artifact persisted on the CT scan of the uniformity phantom ( Fig. We encountered the ring artifact on a transaxial CT image while performing routine PET/CT on a 64-slice time-of-flight Gemini TF 64 scanner (Philips) ( Fig. Scanner-based artifacts may appear because of a sudden breakdown of the system. Non–scanner-based CT artifacts are caused mainly by improper selection of acquisition parameters and by metallic implants, patient motion, and improper patient preparation ( 2, 3). Artifacts on CT images, though independent of PET image acquisition, can still degrade the quality of PET images during processing and interpretation ( 2). Hence, quality control testing of PET/CT equipment, both at acceptance and periodically, is mandatory to achieve the best results ( 1). To our knowledge, this particular cause of the ring artifact has not been described in literature.Ī diagnostic outcome from PET/CT imaging is the product of images that combine quality, reliability, and reproducibility. We describe a rare cause of the ring artifact that appeared on a transaxial CT image because of a loose electronic contact. The ring artifact is scanner-based and caused mainly by either a miscalibrated element or a defective element of a detector row. So, each will exhibit different characteristics in your images.Artifacts and image quality are two sides of the same coin. ![]() JPEG Artifacts and digital noise are both side effects of digital photography that can have negative affects on your photos such as:Ĭompression artifacts are different than digital noise and are caused by different processes involved with the capturing and saving of an image. So, it is always best to start with a clean image before making any creative or corrective enhancements – this will ensure optimal quality of your final image. Applying creative and corrective enhancements to an image plagued with compression artifacts will cause your adjustments to not be as clean and crisp as they should be. Dark color degradation around sharp edgesĮvery single JPEG image exhibits these characteristics to some degree, and the more compressed your image is the worse it will be.īesides lowering image quality, the presence of jpeg compression artifacts can have negative effects on your post processing. Color degradation – false color or color changes 4. ![]() The degradation of image detail can appear as:ġ. ![]() This is also very common with images taken on mobile devices such as camera phones and for many point-and-shoot cameras. In addition, each time you save your image more data is lost and image quality reduced. The quality that is lost (discarded) from your image can not be recovered. jpg some of the data from the original image file is discarded and your image is saved with a reduced file size. This means that when you save your image as a. The JPEG format uses a lossy compression method during saving. However, despite the usefulness it can have, saving an image in the jpeg format also comes with some not-so-great side effects. It’s great for small files used on websites and for emailing because it can load and send faster. The jpg format is a very popular and widely used format. Understanding the cause and effects of JPEG Artifacts (as well as being able to recognize them) is very important to the quality of your images.
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