Transcript IMAGE QUALITY

IMAGE QUALITY
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NOISE
LINEARITY
CROSS-FIELD UNIFORMITY
IMAGE ARTIFACTS
NOISE IN CT
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FLUCTUATION OF
CT# BETWEEN
POINTS IN THE
IMAGE FOR A SCAN
OF UNIFORM
MATERIAL SUCH
WATER.
NOISE IN CT
NOISE LEVEL
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PERCENTAGE OF CONTRAST OR IN CT
NUMBERS
NOISE LEVEL %= STANDARD DEVIATION /CT # RANGE
NOISE CAN BE MEASURED BY
SCANNING
A WATER PHANTOM
AND COMPUTING THE MEAN
AND STANDARD DEVIATION
FOR FOR A REGION OF
INTEREST. (ROI)
THE NOISE LEVELS FOR CT
SCANNERS VARY AND DEPEND
ON:
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MAS
SCAN TIME
KVP
SLICE THICKNESS
OBJECT SIZE
ALGORITHM
MAS
KVP
SCAN TIME
SLICE T.
NOISE
OBJECT SIZE
NOISE
ALGORITHM vs NOISE
DETAIL
EDGE-ENHANCEMENT
STANDARD
SMOOTHING
NOISE
NOISE IN CT IS MAINLY RELATED
TO
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PHOTON FLUX ( # OF DETECTED
PHOTONS)
MATRIX SIZE (PIXEL SIZE)
SLICE THICKNESS
ALGORITHM
ELECTRONIC NOISE ( DETECTOR
ELECTRONICS)
SCATTER RADIATION
NOISE
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WIDTH OF PIXEL
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SLICE THICKNESS
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DOSE
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NOISE
SPATIAL R.
NOISE
SPATIAL R.
NOISE
LINEARITY
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RELATIONSHIP OF CT# TO THE LINEAR
ATTENUATION COEFFICIENT
CROSS-FIELD UNIFORMITY
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THE UNIFORMITY OF CT # THROUGHOUT
THE ENTIRE SCAN FIELD OF VIEW IS
ONE INDICATION THAT CT SCANNER IS
PERFORMANCE IS ACCEPTABLE.
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IT REFERS TO THE VALUES OF THE
PIXELS IN THE RECONSTRUCTED IMAGE
THEY SHOULD BE CONSTANT AT ANY POINT IN THE IMAGE OF PHANTOM
CROSS-FIELD UNIFORMITY
CROSS-FIELD UNIFORMITY
IMAGE ARTIFACTS
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A DISTORTION OR ERROR IN AN IMAGE
THAT IS UNRELATED TO THE SUBJECT
BEING STUDIED
IMAGE ARTIFACTS
STREAKS
RING
CT# DISTORTION
SOURCES OF ARTIFACTS
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PATIENT
IMAGING PROCESS
EQUIPMENT
TYPES AND CAUSES OF ARTIFACTS
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STREAKS
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IMPROPER
SAMPLING OF DATA
PARTIAL VOLUME
AVERAGING
PATIENT MOTION
METAL & BEAM
HARDENING
NOISE
SPIRAL SCANNING
MECHANICAL
FAILURE
TYPES AND CAUSES OF ARTIFACTS
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SHADING
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PART. VOLUME AVG.
BEAM HARDENING
SPIRAL SCANNING
SCATTER
OFF-FOCUS
RADIATION
INCOMPLETE
PROJECTION
TYPES AND CAUSES OF ARTIFACTS
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RINGS AND BANDS
BAD DETECTOR IN III
GENERATION CT
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MOTION ARTIFACT- VOLUNTARY &
INVOLUNTARY
CORRECTION:
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IMMOBILIZATION
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PROPER EXPLANATION OF
PROCEDURE
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SHORT SCAN TIME
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MOTION REDUCTION
SOFTWARE (SHIMADZU –MAC)
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MOTION
METAL ARTIFACTS
INCOMPLETE PROJECTION PROFILES
STAR SHAPED ARTIFACTS
METAL ARTIFACTS
METAL ARTIFACT
MAR
BEAM HARDENING ARTIFACTCUPPING ARTIFACT
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INCREASE IN THE MEAN ENERGY OF
THE X-RAY BEAM AS IT PASSES
THROUGH THE PATIENT
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IT CAN OCCUR WHEN RADIATION BEAMS
HAVE DIFFERENT PATH LENGTHS
BEAM HARDENING
BEAM HARDENING ARTIFACT
STREAKS OR BROAD DARK BANDS
REDUCTION OF BEAM
HARDENING
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BOW TIE FILTER UTILIZATION
SPECIAL CORRECTION SOFTWARE
CORRECTED
PARTIAL VOLUME
ARTIFACT
AVERAGE CT NUMBERS IN SLICE
CORRECTING PARTIAL VOLUME
ARTIFACT
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THIN SLICES
NOISE – PHOTON STARVATION
OUT OF FIELD ARTIFACT
EQUIPMENT INDUCED ARTIFACTS
STREAK ARTIFACTS
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MECHANICAL FAILURE
POOR GANTRY RIGIDITY
MECHANICAL ASSIGNMENT
TUBE ROTOR WOBBLE
POOR SAMPLING OF THE DETECTOR
BAD DETECTOR-RING ARTIFACTS ( III GEN.)
TUBE ARCING
RING ARTIFACTS- III GENERATION
CORRECTION OF RING ARTIFACT
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DETECTOR RECALIBRATION
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BALANCING ALGORITHM UTILIZATION
ALIASING ARTIFACT
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NOT ENOUGH SAMPLES
CORRECTION OF ALIASING
ARTIFACT
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INCREASE NUMBER OF VIEWS OR RAY
SAMPLES PER VIEW.
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CONVOLUTION FILTER (SOFTWARE
METHOD)
ALIASING ARTIFACT
TUBE ARCING
SPIRAL ARTIFACTS
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WINDMILL
MOTION
STAIRCASE
SHADING
WINDMILL
MOTION
MOTION
STAIRCASE