A blood vessel, from which pulsation artifacts are visible extending horizontally to both sides, is marked by an arrow. MRI axial projections. Pulsation artifacts are visible extending in a horizontal line from the blood vessel marked by circles. Such artifacts emerge from the chemical shift margin between fat and water.
Such artefact manifests as incorrectly registered fat and water pixels in the image. The obtained effect as fat and water rotations in the same voxel are coded as if localized in different voxels.
The artifacts of the chemical shift are most frequently detected in the frequency encoding direction; however, they can also manifest along the cross-cut direction. They are more intensive where the magnetic field is stronger and mostly visible in the bodies of the vertebrae, sockets of the eye and solid bodies surrounded by fat.
Artifacts are more frequently visible in T2, less in T1 sequences [5, 11]. Susceptibility artifacts can be provoked by microscopic gradients or variations in the magnetic field, which forms in the vicinity of interactions between substances with different magnetic susceptibility. Factors that influence the production of metal-related artifacts at MRI imaging include the composition, size, and orientation of the metallic object with regard to the direction of the external magnetic field; the type of pulse sequences applied; and the sequence parameters, including magnetic field strength, voxel size determined by field of view, image matrix, and section thickness , and echo train length .
The nature of the materials varies widely, and distinction must be made between MR-compatible and incompatible materials. A majority of supportive lines, tubes, and catheters are composed of non-ferromagnetic materials, such as polyvinyl chloride plastic and are virtually invisible on MRI . Metallic biomedical implants composed of titanium, tantalum, and nitinol have also been shown to be nonferromagnetic and MR-compatible . However, both ferromagnetic and non-ferromagnetic materials induce artifacts . Artifacts with a high susceptibility are most frequently visible around ferromagnetic objects inside diamagnetic materials such as a human body.
Such gradients cause exit of rotations from the phase and frequency alterations in the surrounding tissues. As a result, light and dark spots with a spatial distortion in the neighoring anatomic structures are seen Figs.
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The magnetic susceptibility effect is increased with the magnetic field strength, leading to a greater impact on image spatial encoding and contrast formation . Such artifacts are the brightest in the long echo and gradient echo GE sequences of the gradient response . The metal artifact triggered by a dental crown is visible marked by a circle. Numerous metal artifacts are visible in the dental projection marked by a circle.
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The broad wave noise corrupts the entire image, meanwhile narrow frequency noise triggers linear bands crosswise to the phase encoding direction . If the interfering signal has a further, low frequency component e. Artifacts triggered by foreign bodies are visible in the vertex projection.
MRI sagittal projection. Artifacts triggered by foreign bodies after the operation marked by a circle. The artifact is visible after a break of the puncture needle marked by a circle. Same artifact visible on another projection marked by a circle. One was left in the vault; the other was inadvertently taken by a patient.
It appears in a TE sequence, when fat and water rotations in the same pixel are outside the phase boundaries — in this way they interrupt the signal of each other. It is very often visible in GE sequences in both directions frequency and phase. In the images made by a magnetic tomography machine of 1.
If slices are produced from different places of the intervertebral disc, they can overlap. If both levels are produced at the same time, e. L4-L5 and L5-S1, then the level, which is second in turn, will contain rotations, which have been already made so a signal loss band is produced, which cross the image horizontally and are the brightest in the back portion Fig.
Slice overlaps should be avoided in the regions which may consist pathology . Visible slice overlap.
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They appear when the field of visibility FOV is lower than the scanned portion of the body, which makes the surplus portion to project on another part of the image Fig. They are triggered by an insufficient selection in the phase period or in some cases by the frequency direction. They may develop making last 3D slices . MRT axial projections. The aliasing artifact is visible. Such artifact is not clearly visible in plain objects. Truncation artifacts are common in the spine due to sharp signal changes.
The artifact in spinal cord can simulate a small fistula. MRT sagittal projections. Ringing artifacts are visible. From the total MRI series examined , artifacts were found on series Fig. Artifact percentages in frequently scanned portions of the body. Artifacts in magnetic resonance imaging: how it can really affect diagnostic image quality and confuse clinical diagnosis? This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Views Reads Downloads What is an artifact? Main reasons behind the artifact formation Technical problems. Artifact types 3. Movement artifacts  A movement is a principal source of MRI image artifacts.
Breathing Breathing movement condition ghosting artifacts and blurring, which can cover or simulate pathological lesions. Extensive movement artifacts are observed due to the patient movement: a 2 years old child, b same child patient, different slice a b. Movement artifacts are observed due to the eye balls movement marked by arrows a MRI coronal projection b MRT axial projection.
Heart movements Heart movements produce series of ghosting artifacts in the phase coding direction, which determine fading of the heart and neighboring structures and signal loss in the images . Pulsation of blood vessels Blood vessels pulsation artifacts can be recognized from their location in the vicinity of a relevant blood vessel in the phase coding direction.
A blood vessel, from which pulsation artifacts are visible extending horizontally to both sides, is marked by an arrow a b. Pulsation artifacts are visible extending in a horizontal line from the blood vessel marked by circles a b. Susceptibility or metal artifact Susceptibility artifacts can be provoked by microscopic gradients or variations in the magnetic field, which forms in the vicinity of interactions between substances with different magnetic susceptibility. Order by , and we can deliver your NextDay items by. In your cart, save the other item s for later in order to get NextDay delivery.
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