W11 Artifacts PDF

ARTIFACTS On completion of this section, the student should be able to know the following: Image Artifacts Beam-Hardening Artifa...

ARTIFACTS On completion of this section, the student should be able to know the following: Image Artifacts Beam-Hardening Artifacts Partial Volume Artifacts Motion Artifacts Metallic Artifacts Ring Artifacts TUBE ARCING artifact S. Jastaniah, J. Al-Ghamdi, A. Aref (KAU), A. Musa (KKU), K. Hassan (BMC) 4/29/24 1  IMAGE ARTIFACTS DEFINED AS ANYTHING APPEARING ON THE IMAGE THAT IS NOT PRESENT IN THE OBJECT SCANNED. HAVE MANY DIFFERENT PRESENTATIONS AND CAUSES. THEY CAN BE BROADLY CLASSIFIED AS: PHYSICS-BASED: INCLUDE BEAM HARDENING AND PHOTON STARVATION PATIENT-BASED : INCLUDE METALLIC AND MOTION ARTIFACTS. EQUIPMENT-INDUCED : ARTIFACTS CAUSED BY DETECTOR SENSITIVITY AND MECHANICAL INSTABILITY.  BEAM-HARDENING ARTIFACTS WHEN THE X-RAY BEAM TRAVELS THROUGH AN OBJECT, THE LOW-ENERGY PHOTONS ARE ABSORBED MORE THAN THE HIGH-ENERGY PHOTONS MANIFEST AS DARK BANDS OR STREAKS SAME SLICE WITH IMPROVEMENT USING BEAM-HARDENING CORRECTION  PARTIAL VOLUME EFFECT OCCURS WHEN MORE THAN ONE TYPE OF TISSUE IS CONTAINED WITHIN A VOXEL..  PARTIAL VOLUME ARTIFACTS…CONT. OCCURS WHEN MORE THAN ONE TYPE OF TISSUE IS CONTAINED WITHIN A VOXEL (SMALL STRUCTURES CAN BE MISSED) BEST STRATEGY TO REDUCE THESE ARTIFACTS ; Ø THIN SLICES. Ø AVAILABLE VOLUME ARTIFACT REDUCTION SOFTWARE. IMAGES BELOW IS SAME SLICE BUT USING THIN SLICE :  MOTION ARTIFACTS TWO TYPES; VOLUNTARY MOTION IS DIRECTLY CONTROLLED BY THE PATIENT, SUCH AS SWALLOWING OR RESPIRATORY MOTION, INVOLUNTARY MOTION IS NOT UNDER THE DIRECT CONTROL OF THE PATIENT, SUCH AS CARDIAC MOTION. ARTIFACTS FROM PATIENT MOTION APPEAR AS SHADING, STREAKING, BLURRING, OR GHOSTING.  PATIENT MOTION IS REDUCED BY ADEQUATELY PREPARING THE PATIENT INVOLUNTARY MOTION IS REDUCED USING SHORTEST SCAN TIME POSSIBLE MOTION…CONT.  METALLIC ARTIFACTS ; OBJECTS IN THE FOV WILL CREATE STREAK ARTIFACTS BEST REDUCED BY REMOVING THE METAL. NON REMOVABLE OBJECTS CAN BE AVOIDED BY ANGLING THE GANTRY, INCREASE KVP , CORRECTION SOFTWARE AND USE SMOOTHING ALGORITHM. METAL ARTIFACT…CONT  Avoiding Dental Artifacts Aygun, N., & Zinreich, S. (2015, April 21). Overview of Diagnostic Imaging of the Head and Neck [Digital image]. Retrieved March 27, 2016, from http://clinicalgate.com/overview-of-diagnostic-imaging-of-the-head-and-neck/  RING ARTIFACTS CAUSED BY IMPERFECT DETECTOR ELEMENTS. APPEAR ON THE IMAGE AS A RING CAN SOMETIMES BE ELIMINATED BY RECALIBRATING THE SCANNER.  RING ARTIFACT …CONT. ONE OF THE DETECTORS IS OUT OF CALIBRATION ON A THIRD- GENERATION (ROTATING X-RAY TUBE AND DETECTOR ASSEMBLY) SCANNER  TUBE ARCING ARTIFACT CAUSED BY A TEMPORARY SHORT CIRCUIT IN THE X-RAY TUBE CAUSING MOMENTARY LOSS OF X-RAY OUTPUT IT IS SEEN AS NEAR-PARALLEL AND AN EQUIDISTANT STREAK PATTERN ON REMEDY TUBE REPLACEMENT