What is a zipper artifact on an MRI?
Zipper artifacts appear as dashed lines. There are various causes for this MRI artifact. Most of zipper artifact s result from inhomogeneities of the magnetic field caused by interferences with radio frequency from various sources ('your radio is working in the scanner room means your shielding is not working').
What causes zipper lines in magnetic resonance imaging?
Most of zipper artifact s result from inhomogeneities of the magnetic field caused by interferences with radio frequency from various sources ('your radio is working in the scanner room means your shielding is not working'). Software and equipment problems can also cause zipper lines in both directions.
What causes the zipper artifact in image processing?
Zipper artifact due to RF-feedthrough Annefact (cusp) artifact due to stimulated echoes outside FOV The annefact (cusp) artifact closely resembles the zipper artifact in that it is a featherlike ribbon of bright signal smeared through the center of the image in the phase-encode direction.
Why does MRI have such a wide variety of image artifacts?
Why does MRI have such a wide variety of image artifacts? • MRI requires seamless integration and interplay of magnet, gradient coil system, RF system, and pulse sequence computer, each of which is a complicated subsystem. • Human body also interacts with RF and B
What is zipper artifact MRI?
Zipper artifacts are a type of MRI artefact where one or more spurious bands of electronic noise extends across the image. There are various causes for zipper artifacts in images and no single solution exists. These artefacts can be related to hardware or software problems either of the scanner itself or the shielding.
What causes artifacts in MRI?
Artifacts are caused by a variety of factors that may be patient-related such as voluntary and physiologic motion, metallic implants or foreign bodies. Finite sampling, k-space encoding, and Fourier transformation may cause aliasing and Gibbs artifact.
Which MRI artifact is the most common?
Motion artifactsMotion artifacts A motion artifact is one of the most common artifacts in MR imaging. Motion can cause either ghost images or diffuse image noise in the phase-encoding direction.
How does aliasing artifacts occur in MRI?
Aliasing artifacts occur in the phase encoding direction when the dimensions of the imaged object exceeds the field of view. Signal generated from outside the field of view appears as a superimposed object at the opposite edge of the image.
What is zipper artifact?
Zipper artifacts are a type of MRI artefact where one or more spurious bands of electronic noise extends across the image. There are various causes for zipper artifacts in images and no single solution exists. These artefacts can be related to hardware or software problems either of the scanner itself or the shielding.
What are 3 examples of artifacts?
Examples include stone tools, pottery vessels, metal objects such as weapons and items of personal adornment such as buttons, jewelry and clothing. Bones that show signs of human modification are also examples.
What causes ghosting in MRI?
Ghosting is a type of structured noise appearing as repeated versions of the main object (or parts thereof) in the image. They occur because of signal instability between pulse cycle repetitions. Ghosts are usually blurred, smeared, and shifted and are most commonly seen along the phase encode direction.
What causes susceptibility artifact?
The most likely source of the artifact is microscopic metal fragments from the burr, suction tip or other surgical instruments, but other possible causes include hemorrhage or paramagnetic suture material. These artifacts may cause difficulty in interpretation or suggest a clinical problem.
What causes moire effect in MRI?
The combination of aliasing artifacts and field inhomo- geneity can lead to Moire fringes or zebra artifacts (Fig. 5). Basically these are interference patterns of superimposed images with different phases from one side of the body to the other that alternatively add and cancel [1].
What causes aliasing artifact?
It is caused by a corruption in the spatial encoding of objects outside the FOV which cannot be distinguished from objects inside the FOV. It results in a spatial mismapping to the opposite side of the image.
How do you reduce aliasing artifacts?
The artifact can be quickly remedied by lowering the baseline (if display of flow away from the transducer is not required), or increasing the PRF.
What is aliasing and how do you prevent it?
The solution to prevent aliasing is to band limit the input signals—limiting all input signal components below one half of the analog to digital converter's (ADC's) sampling frequency. Band limiting is accomplished by using analog low-pass filters that are called anti-aliasing filters.
Zipper Artifact
An MRI room has to be shielded to contain the static magnetic field and to protect from rogue radio frequencies. This is done by a faraday cage. By surrounding the room in a conductive material (commonly copper), radio frequencies will contact this material and run through it.
Common Causes
This artifact is found in the frequencies direction of our image. This is because when we are collected patient frequencies in the patient, we place them in the frequency direction of our K space. This will represent this contamination in the frequency direction.
Remedies
Make sure the scan door is closed and if you see a compromised area of the faraday cage, call the field engineer.
What are the sources of artifacts in MRI?
There are many sources of artifacts in MRI. These are summarized as follows: Image processing artifact. Aliasing.
What causes a bright band toward the lower frequencies?
Chemical shift effect between fat and water causes a bright band toward the lower frequencies (due to overlap of fat and water at lower frequencies) and a dark band toward the higher frequencies (due to lack of fat and water signals).
