IMAGE QUALITY

SPATIAL RESOLUTION CONTRAST RESOLUTION NOISE IMAGE ARTIFACTS RADIATION DOSE

QUALITY MEASUREMENT METHODS PSF- POINT SPREAD FUNCTION LSF- LINE SPREAD FUNCTION CTF – CONTRAST SPREAD FUNCTION MTF- MODULATION TRANSFER FUNCTION

MTF MODULATION TRANSFER FUNCTION MOST COMMONLY USED TO DESCRIBE SPATIAL RESOLUTION IN CT

MTF MTF OF 1 – 100% TRANSFER OF OBJECT TO IMAGE MTF OF 0 – 0% TRANSFER OF OBJECT TO IMAGE

Spatial frequency Lp/cm

Spatial Frequency LARGE OBJECTS – LOW S.F. SMALL OBJECTS – HIGH S.F.

SPATIAL FREQUENCY 1 5

ABSOLUTE SIZE OF AN OBJECT IN CT IT’S EQUAL TO THE RECIPROCAL OF THE SPATIAL FREQUENCY CT SCANNER SPATIAL FREQUENCY- 15 lp/cm. WHAT SIZE OF AN OBJECT CAN THE SCANNER RESOLVE 1/15 = 0.06 cm/lp= 0.6 mm/lp 0.6 /2 = 0.3 mm object

Resolution in CT Spatial ResolutionContrast Resolution

SPATIAL RESOLUTION DEGREE OF BLURRING IN THE IMAGE MEASURE OF THE ABILITY TO DISCRIMINATE OBJECTS OF VARYING DENSITY A SMALL DISTANCE APART AGAINST A UNIFORM BACKGROUND

GEOMETRIC FACTORS F. SPOT SIZE BLURR APERTURE SIZE ( COLLIMATION) BLURR SLICE THICKNESS BLURR

PARTIAL VOLUME EFFECT 10MM SLICE THICKNESS SPREADS 2MM OBJECT OVER THE ENTIRE SLICE THICKNESS

# of projections S. resolution

ALGORITHM vs NOISE DETAIL NOISE STANDARD SMOOTHING EDGE-ENHANCEMENT

SPATIAL RESOLUTION AT HIGH CONTRAST HIGH CONTRAST RESOLUTION

DISPLAY RESOLUTION THE # OF PIXELS PER HORIZONTAL AND VERTICAL DIMENSIONS OF THE MATRIX ON THE MONITOR SCREEN OR FILM SHEET MATRIX SIZE DISPLAY RESOLUTION

DISPLAY RESOLUTION

HIGH RESOLUTION CT SLICE- 1 – 2 MM REDUCTION OF PARTIAL VOLUME ARTIFACT USE OF HIGH SPATIAL FREQ. ALGORITHM ( GOOD DETAIL) USE OF SMALL FOV ( SMALLER PIXEL)

RECONSTRUCTION ( TARGETING) vs MAGNIFICATION IN SPATIAL RESOLUTION RECONSTRUCTION - VERY LITTLE DIFFERENCE MAGNIFICATION – SIGNIFICANT DIFFERENCE, SPATIAL RESOLUTION

CONTRAST RESOLUTION SENSITIVITY OF THE SYSTEM LOW CONTRAST RESOLUTION LOW CONTRAST DETECTIBILITY

LOW CONTRAST RESOLUTION ( TISSUE RESOLUTION) THE ABILITY OF AN IMAGING SYSTEM TO DEMONSTRATE SMALL CHANGES IN TISSUE CONTRAST

FACTORS AFFECTING LOW CONTRAST RESOLUTION PHOTON FLUX SLICE THICKNESS PATIENT SIZE DETECTOR SENSITIVITY RECONSTRUCTION ALGORITHM IMAGE DISPLAY IMAGE RECORDING QUANTUM NOISE

CONTRAST RESOLUTION PHANTOM

PHOTON FLUX (P.F.) kVp P.F. mAs P.F. KVP, mAs C. RESOLUTION

PATIENT SIZE PHOTON FLUX PATIENT SIZE C. RESOLUTION

SLICE THICKNESS C. RESOLUTION SLICE THICKNESS C. RESOLUTION

DETECTOR SENSITIVITY C. RESOLUTION DETECTOR SENSITIVITY C. RESOLUTION

LOW CONTRAST RESOLUTION LOW SPATIAL FREQUENCY ALGORITHM

ALGORITHM vs NOISE DETAIL NOISE STANDARD SMOOTHING EDGE-ENHANCEMENT

QUANTUM NOISE C. RESOLUTION QUANTUM NOISE C. RESOLUTION

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