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IMAGE QUALITY NOISE LINEARITY CROSS-FIELD UNIFORMITY IMAGE ARTIFACTS NOISE IN CT FLUCTUATION OF CT# BETWEEN POINTS IN THE IMAGE FOR A SCAN OF UNIFORM MATERIAL SUCH WATER. NOISE IN CT NOISE LEVEL 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: 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 PHOTON FLUX ( # OF DETECTED PHOTONS) MATRIX SIZE (PIXEL SIZE) SLICE THICKNESS ALGORITHM ELECTRONIC NOISE ( DETECTOR ELECTRONICS) SCATTER RADIATION NOISE WIDTH OF PIXEL SLICE THICKNESS DOSE NOISE SPATIAL R. NOISE SPATIAL R. NOISE LINEARITY RELATIONSHIP OF CT# TO THE LINEAR ATTENUATION COEFFICIENT CROSS-FIELD UNIFORMITY THE UNIFORMITY OF CT # THROUGHOUT THE ENTIRE SCAN FIELD OF VIEW IS ONE INDICATION THAT CT SCANNER IS PERFORMANCE IS ACCEPTABLE. 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 A DISTORTION OR ERROR IN AN IMAGE THAT IS UNRELATED TO THE SUBJECT BEING STUDIED IMAGE ARTIFACTS STREAKS RING CT# DISTORTION SOURCES OF ARTIFACTS PATIENT IMAGING PROCESS EQUIPMENT TYPES AND CAUSES OF ARTIFACTS STREAKS IMPROPER SAMPLING OF DATA PARTIAL VOLUME AVERAGING PATIENT MOTION METAL & BEAM HARDENING NOISE SPIRAL SCANNING MECHANICAL FAILURE TYPES AND CAUSES OF ARTIFACTS SHADING PART. VOLUME AVG. BEAM HARDENING SPIRAL SCANNING SCATTER OFF-FOCUS RADIATION INCOMPLETE PROJECTION TYPES AND CAUSES OF ARTIFACTS RINGS AND BANDS BAD DETECTOR IN III GENERATION CT MOTION ARTIFACT- VOLUNTARY & INVOLUNTARY CORRECTION: IMMOBILIZATION PROPER EXPLANATION OF PROCEDURE SHORT SCAN TIME MOTION REDUCTION SOFTWARE (SHIMADZU –MAC) I MOTION METAL ARTIFACTS INCOMPLETE PROJECTION PROFILES STAR SHAPED ARTIFACTS METAL ARTIFACTS METAL ARTIFACT MAR BEAM HARDENING ARTIFACTCUPPING ARTIFACT INCREASE IN THE MEAN ENERGY OF THE X-RAY BEAM AS IT PASSES THROUGH THE PATIENT IT CAN OCCUR WHEN RADIATION BEAMS HAVE DIFFERENT PATH LENGTHS BEAM HARDENING BEAM HARDENING ARTIFACT STREAKS OR BROAD DARK BANDS REDUCTION OF BEAM HARDENING BOW TIE FILTER UTILIZATION SPECIAL CORRECTION SOFTWARE CORRECTED PARTIAL VOLUME ARTIFACT AVERAGE CT NUMBERS IN SLICE CORRECTING PARTIAL VOLUME ARTIFACT THIN SLICES NOISE – PHOTON STARVATION OUT OF FIELD ARTIFACT EQUIPMENT INDUCED ARTIFACTS STREAK ARTIFACTS 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 DETECTOR RECALIBRATION BALANCING ALGORITHM UTILIZATION ALIASING ARTIFACT NOT ENOUGH SAMPLES CORRECTION OF ALIASING ARTIFACT INCREASE NUMBER OF VIEWS OR RAY SAMPLES PER VIEW. CONVOLUTION FILTER (SOFTWARE METHOD) ALIASING ARTIFACT TUBE ARCING SPIRAL ARTIFACTS WINDMILL MOTION STAIRCASE SHADING WINDMILL MOTION MOTION STAIRCASE