Presentation is loading. Please wait.

Presentation is loading. Please wait.

IMAGE QUALITY. SPATIAL RESOLUTION CONTRAST RESOLUTION NOISE IMAGE ARTIFACTS RADIATION DOSE.

Similar presentations


Presentation on theme: "IMAGE QUALITY. SPATIAL RESOLUTION CONTRAST RESOLUTION NOISE IMAGE ARTIFACTS RADIATION DOSE."— Presentation transcript:

1 IMAGE QUALITY

2 SPATIAL RESOLUTION CONTRAST RESOLUTION NOISE IMAGE ARTIFACTS RADIATION DOSE

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

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

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

6 Spatial frequency Lp/cm

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

8 SPATIAL FREQUENCY 1 5

9 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

10 Resolution in CT Spatial ResolutionContrast Resolution

11 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

12

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

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

15 # of projections S. resolution

16 ALGORITHM vs NOISE DETAIL NOISE STANDARD SMOOTHING EDGE-ENHANCEMENT

17 SPATIAL RESOLUTION AT HIGH CONTRAST HIGH CONTRAST RESOLUTION

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

19

20 DISPLAY RESOLUTION

21

22

23 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)

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

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

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

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

28 CONTRAST RESOLUTION PHANTOM

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

30 PATIENT SIZE PHOTON FLUX PATIENT SIZE C. RESOLUTION

31 SLICE THICKNESS C. RESOLUTION SLICE THICKNESS C. RESOLUTION

32 DETECTOR SENSITIVITY C. RESOLUTION DETECTOR SENSITIVITY C. RESOLUTION

33 LOW CONTRAST RESOLUTION LOW SPATIAL FREQUENCY ALGORITHM

34 ALGORITHM vs NOISE DETAIL NOISE STANDARD SMOOTHING EDGE-ENHANCEMENT

35 QUANTUM NOISE C. RESOLUTION QUANTUM NOISE C. RESOLUTION

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

37


Download ppt "IMAGE QUALITY. SPATIAL RESOLUTION CONTRAST RESOLUTION NOISE IMAGE ARTIFACTS RADIATION DOSE."

Similar presentations


Ads by Google