Electromagnetic interference (EMI) artifact usually results from electrical power lines, electrical equipment, and mobile telephones. In the United States this is sometimes referred to as 60 cycle interference (or 60 Hz pickup).

Local Stuff ar·te·fact-An object produced or shaped by human craft, especially a tool, weapon, or ornament of archaeological or historical interest.

Physiologic Artifacts

• Muscle (electromyogram) activity. Myogenic potentials are the most common artifacts (see images below).
• Glossokinetic artifact.
• Eye movements.
• ECG artifact.
• Pulse.
• Respiration artifacts.
• Skin artifacts.

Reducing Motion Artifacts

1. Minimize the degree of motion. a. The importance of simple instruction/education of the patient to hold still while the scanner is making noise should not be underestimated.
2. Suppress signal from moving tissues. a.
3. Adjust imaging sequences and parameters. a.
4. Detect and compensate for motion.

Forehead, jaw, and eyelid muscle movements can cause artifacts by moving the electrodes. Movements in the surroundings produce disturbances by altering the ambient electrical fields. Moreover, the tongue and eyes have their own dipole electric charge. Therefore, their movement can get recorded by the electrodes.

Muscle artifacts are characterized by surges in high frequency activity and are readily identified because of their outlying high values relative to the local background activity. Within and across REM sleep episodes muscle artifacts were evenly distributed.

Electrocardiographic artifacts are defined as electrocardiographic alterations, not related to cardiac electrical activity. As a result of artifacts, the components of the electrocardiogram (ECG) such as the baseline and waves can be distorted. Motion artifacts are due to shaking with rhythmic movement.

Physiologic artifacts are caused by patient movement, including breathing, heartbeat, and blood flow. Artifacts can arise from the inherent physics of the MRI, such as the presence of metal or chemical shift. Finally, the hardware and software involved in constructing MRI images can cause artifacts.

Flow artifacts are caused by flowing blood or fluids in the body. A liquid flowing through a slice can experience an RF pulse and then flow out of the slice by the time the signal is recorded. Picture the following example. We are using a spin-echo sequence to image a slice.

Physics-based artifacts result from the physical processes involved in the acquisition of CT data. Patient-based artifacts are caused by such factors as patient movement or the presence of metallic materials in or on the patient. Scanner-based artifacts result from imperfections in scanner function.

Motion artifact is a patient-based artifact that occurs with voluntary or involuntary patient movement during image acquisition. Misregistration artifacts, which appear as blurring, streaking, or shading, are caused by patient movement during a CT scan.

magnetic resonance imaging

Causes of electrical artifacts on ECGs are manifold. External artifacts are usually caused by line current, which has a frequency of 50 Hz or 60 Hz. Internal electrical artifacts can be caused by tremors, muscle shivering, hiccups or, as in the present case, medical devices.

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.

What causes susceptibility? Susceptibility is caused by interactions of electrons and nuclei with the externally applied magnetic field. Nuclei and electrons each possess spin, a quantum mechanical property with no exact analogue in classical physics.

Magnetic susceptibility is the degree to which a material can be magnetized in an external magnetic field. If the ratio between the induced magnetization and the inducing field is expressed per unit volume, volume susceptibility (k) is defined as.

Gibbs artifact, also known as truncation artifact or ringing artifact, is a type of MRI artifact. It refers to a series of lines in the MR image parallel to abrupt and intense changes in the object at this location, such as the CSF-spinal cord and the skull-brain interface.

Abstract. Background and purpose: CSF pulsation artifact is a pitfall of fast fluid-attenuated inversion-recovery (FLAIR) brain MR imaging. We studied ventricular CSF pulsation artifact (VCSFA) on axial FLAIR images and its relationship to age and ventricular size.

Herringbone artifact, also known as spike artifact, crisscross artifact, or corduroy artifact, is an MRI artifact related to one or few aberrant data point(s) in k-space. In image space, the regularly spaced stripes resemble the appearance of a fabric with a herringbone pattern.

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.

Ghosting is usually caused by the slow response time of certain types of LCD panels. This is because when the image is refreshed the physical pixels cannot update as fast as the image causing a smearing image effect on the display. Cheaper IPS monitors can also show ghosting artifacts but to a much smaller degree.

In television, a ghost is a replica of the transmitted image, offset in position, that is superimposed on top of the main image. It is often caused when a TV signal travels by two different paths to a receiving antenna, with a slight difference in timing.

The chemical shift phenomenon refers to the signal intensity alterations seen in magnetic resonance (MR) imaging that result from the inherent differences in the resonant frequencies of precessing protons. Chemical shift was first recognized as a misregistration artifact of image data.

In MRI bandwidth is defined as the amount of frequencies or wavelengths that can be transmitted or received in a limited amount of time. Bandwidth is measured in cycles per second or Hertz (Hz). An MRI sequence is designed with two types of bandwidths: transmitter bandwidth (tBW) and receiver bandwidth (rBW).

Chemical shift is due to the differences between resonance frequencies of fat and water. It occurs in the frequency-encode direction where a shift in the detected anatomy occurs because fat resonates at a slightly lower frequency than water.

A chemical shift is defined as the difference in parts per million (ppm) between the resonance frequency of the observed proton and that of the tetramethylsilane (TMS) hydrogens. From: Spin Resonance Spectroscopy, 2018.