Wrap-around artefacts in magnetic resonance imaging (MRI) are common, typically caused by anatomical structures outside the Field of View (FOV) overlapping into the imaging area. This paper reports a rare source of wrap-around artifact, a wet cotton ball, whose image was inadvertently included in cranial imaging, potentially leading to misdiagnosis as pathological conditions such as otomastoiditis, postoperative changes, or intracranial hemorrhage. Hence, there is a need to enhance MRI technologists' awareness of such artifacts. We analyzed four consecutive cases of cranial MRI scans with similar artifacts, all located on the right side of the brain but in different regions. On axial T2-weighted images (T2WI) and T2 fluid-attenuated inversion recovery (T2FLAIR) sequences, the artifacts appeared as oval-shaped, relatively well-defined heterogeneous high signals. On axial T1-weighted images (T1WI), signal intensity and border clarity varied, with artifact locations slightly more lateral compared to T2WI and T2FLAIR. The artifacts in the first three cases were not identified by the MRI technologists. However, in the fourth case, a patient with head trauma, the MRI technologist noticed inconsistencies in the artifact characteristics across different sequences, as well as similarities to a previous case of cranial trauma, which raised suspicion of an artifact. Systematic image analysis and equipment inspection subsequently revealed a wet cotton ball attached to the outer surface of the head-and-neck coil, inadvertently left there by a radiology nurse during preparation for a previous case. Upon removal of the cotton ball and rescanning the sequences with artifacts in cases 3 and 4, the artifacts disappeared, confirming the wet cotton ball as the source. Additionally, upon review, similar artifacts were found in the first two cases but overlooked due to various reasons. The aim of this study is to improve MRI technologists' recognition of artifacts caused by non-metallic foreign objects, avoiding misdiagnosis, and to prompt us to refine our examination protocols and enhance radiology nurses' awareness of MRI safety.
Keywords: cotton ball; misdiagnosis; mri artifact; pediatric imaging; quality control.
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