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ARTIFACTS IN COMPUTED TOMOGRAPHY
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ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

Mar 26, 2015

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Seth Holmes
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Page 1: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

ARTIFACTS IN COMPUTED TOMOGRAPHY

Page 2: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

ARTIFACT

• Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear attenuation coefficient

Page 3: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

APPEARANCE OF ARTIFACTS

STREAKS

SHADING

BANDS

RINGS

Page 4: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

SOURCES OF ARTIFACTS

• PATIENT

• IMAGING PROCESS AND EQUIPMENT

Page 5: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

PATIENT INDUCED ARTIFACTS

• MOTION

• BEAM HARDENING

• METAL ARTIFACT

• OUT OF FIELD ARTIFACT

Page 6: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

MOTION ARTIFACT CAUSED BY:

• VOLUNTARY MOTION• INVOLUNTARY MOTION

IT PRODUCES “GHOSTING” EFFECT OBJECT CT IMAGE APPEARS– AS IF COMPOSED OF

SUPERIMPOSED IMAGES

Page 7: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

MOTION

Page 8: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

MOTION

Page 9: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

MOTION

Page 10: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

MOTION

Page 11: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY:

• VOLUNTARY MOTION: EXPLANATION OF THE PROCEDURE AND GOOD COMMUNICATION WITH A PATIENT

• INVOLUNTARY MOTION: SHORT SCAN TIME

Page 12: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

BEAM HARDENING

• IT OCCURS WHEN THE AVERAGE ENERGY OF AN X-RAY BEAM PASSING THROUGH THE PATIENT INCREASES. BEAM IS “HARDENED” HIGH ENERGY PHOTONS ARE ATTENUATED LESS BY THE TISSUE. AS A RESULT, THEY ARE PASS THROUGH THE PATIENT AND REACH THE DETECTORS. THIS ARTIFACT IS ALSO CALLED “CUPPING” ARTIFACT BEACAUSE THE HARDENING IS MOST PRONOUNCED IN THE CENTER AND LESS AT THE PERIPHERY. IT RESAMBLES A CUP.

Page 13: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

COMMON AREAS OF MANIFESTATION:

• SKULL – PETROUS PYRAMIDS

• UPPER CHEST AND SHOULDERS

• HIPS

Page 14: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

BEAM HARDENING

Page 15: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

BEAM HARDENING - CONTRAST

Page 16: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

BEAM HARDENING

Page 17: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• INCREASE kVp

• DECREASE SLICE THICKNESS

• INCREASE FILTRATION – BOWTIE FILTER

Page 18: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

METAL ARTIFACT

• MANIFEST ITSELF AS “STAR STREAKING” ARTIFACT. IT’S CAUSED BY PRESENCE OF METALLIC OBJECTS INSIDE OR OUTSIDE THE PATIENT. METALLIC OBJECT ABSORBS THE PHOTONS CAUSING AN INCOMPLETE PROFILE

Page 19: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

METAL ARTIFACT

Page 20: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

METAL ARTIFACT

Page 21: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• REMOVAL OF EXTERNAL METALLIC OBJECTS

• MAR SOFTWARE

• GANTRY ANGULATION

Page 22: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

OUT OF FIELD ARTIFACT

• PATIENT IS NOT ENTIRELY ENCLOSED IN THE SCANNING FIELD OF VIEW. PATIENTS BODY CAN OBSTRUCT DETECTORS. IN ADDITION, PATIENT TISSUE OUTSIDE THE SFOV WILL FURTHER HARDEN THE X-RAY BEAM. ARTIFACT APPEARS AS STREAKS AND SHADING.

Page 23: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

OUT OF FIELD ARTIFACT

Page 24: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

OUT OF FIELD ARTIFACT

Page 25: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

OUT OF FIELD ARTIFACT

Page 26: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY:

• SELECTION OF LARGER SFOV

• TAPING PATIENT TISSUE

• RAISING PATIENTS ARMS ABOVE THEIR HEAD ON THE SCAN OF CHEST AND ABDOMEN

Page 27: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

EQUIPMENT IMAGING PROCESS ARTIFACTS

• PARTIAL VOLUME EFFECT• AILIASING• PHOTON STARVATION (NOISE)• AIR-CONTRAST INTERFACE• RING• TUBE ARCING• LINE IN TOPOGRAM• STAIRCASE

Page 28: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

PARTIAL VOLUME EFFECT

• Mechanism of partial volume artifacts, which occur when a dense object lying off-center protrudes part of the way into the x-ray beam.

Page 29: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.
Page 30: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• THIN SLICE SELECTION

• THIN SLICE INREMMENTATION

Page 31: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

AILIASING

FINE LINE ON AN IMAGE

Page 32: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.
Page 33: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

•INCREASE SCAN TIME

•USE COMPLETE ARC SCAN

Page 34: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

PHOTON STARVATION - NOISE

• FLUCTUATION OF CT# BETWEEN POINTS IN THE IMAGE FOR A SCAN OF UNIFORM MATERIAL SUCH WATER.

Page 35: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

NOISE

Page 36: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

NOISE

Page 37: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

NOISE

Page 38: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• kVp INCREASE

• mAs INCREASE

• SLICE THICKNESS INCREASE

Page 39: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

AIR-CONTRAST INTERFACE

STREAKING

Page 40: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.
Page 41: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• CHANGE THE PATIENT POSITION

Page 42: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

RING

• MALFUNCTION OF A DETECTOR IN A THIRD GENERATION SCANNER

Page 43: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

RING

Page 44: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

RING

Page 45: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• DETECTOR CALIBRATION

• DETECTOR REPLACEMENT

Page 46: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

TUBE ARCING

• TUNGSTEN VAPOR FROM ANODE AND CATHODE INTERCEPTS THE PROJECTILE ELECTRONS INTENDED FOR COLLISIONS WITH THE TARGET. CRACKLING SOUND!!!!

Page 47: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

TUBE ARCING

Page 48: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• GAS BURNOFF

• TUBE REPLACEMENT

Page 49: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

LINE IN TOPOGRAM

• BAD DETECTOR CAUSES CONTINUOUS LINE ON THE TOPOGRAM

Page 50: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.
Page 51: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• DETECTOR REPLACEMENT

Page 52: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

STAIRCASE

• IMPROPER SELECTION OF SLICE THICKNESS AND SLICE INCREMENTATION WHEN GENERATION MPR AND 3-D IMAGES

Page 53: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

STAIRCASE

Page 54: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

STAIRCASE

Page 55: ARTIFACTS IN COMPUTED TOMOGRAPHY. ARTIFACT Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear.

REMEDY

• THIN SLICE USE

• 50% OVERLAP ON RECON SLICE INCREMENTATION