verify the phase/frequency directions IDEAL artifact distortion due to too large of a FOV with a too high acceleration rate with parallel imaging IDEAL artifact appearance moiré pattern on the periphery with mid-sagittal pixilation How do you compensate for IDEAL artifact? 1. use a dedicated coil rather than a body coil Annefact detection of signals being generated outside the desired FOV, aka cusp artifacts Annefact appearance bright, ghosting signal smeared across the phase direction of an image How do you compensate for annefact? 1. use a different pulse sequence localizer other than a gradient 2. increase gapping Moiré pattern wave-like pattern at the periphery of an image due to too large of a FOV while using gradient pulse sequence and magnet body coil Moiré pattern appearance severe banding or wave-like pattern at the periphery of an image, aka moiré fringes or zebra artifact How do you compensate for moiré pattern? 1. motion correction imaging technique (Propeller/BLADE) Partial volume averaging a loss of resolution due to excessively large voxels causing more area to be sampled which drops signal contrast in certain pieces of anatomy, typically caused by slices that are too thick partial volume averaging appearance decrease in signal contrast of thicker slices how do you compensate for partial volume averaging? use thinner slices Crosstalk artifact Excitation into an adjacent slice due to multiple overlapping slices or acquisitions, aka slice overlap artiface Crosstalk artifact appearance loss of signal on area of overlapping slices or acquisitions How do you compensate for crosstalk artifact? 1. sponges to help the patient stay still 2. select " flow compensation" option movement motion artifact movement on the image being sampled by patient motion Movement motion artifact appearance anatomy in the phase directionīlurry How do you compensate for movement motion artifact? 1. flow band inferior or superior to the area of interest 2. removing any mobile devices from the vicinity of the control room Flow motion artifact movement on the image by blood or CFS flow Flow motion artifact appearance pulsation artifact along the phase direction How do you compensate for flow motion artifact 1. metal suppression sequences (GE= MAVRIC Siemens= WARP) RF zipper artifact stray RF waves entering the room from mobile or navigation devices RF zipper artifact appearance severe distortion with signal disorientation in the phase direction How do you compensate for RF zipper artifact 1. do a metallic protocol w/ increased bandwidth, increased FOV, and tailored RF 3. Chemical shift appearance shifting of fat-based tissue over water-based tissue in the frequency direction, shadowing appearance How do you compensate for chemical shift? increase bandwidth Metallic susceptibility extreme localized dephasing due to different areas being magnetized, happens with gradient echo due to lack of 180 degree refocusing pulse Metallic susceptibility appearance signal loss which can appear dark or light and geometric distortion How do you compensate for metallic susceptibility? 1.
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