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

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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 Resolution in CT Spatial ResolutionContrast Resolution

4 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

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

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

7 HIGH CONTRAST PHANTOM

8

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10 FACTORS AFFECTING SPATIAL RESOLUTION SLICE THICKNESS FOCAL SPOT SIZE DETECTOR WIDTH TYPE OF CONVOLUTION FILTER (KERNEL) MATRIX SIZE FOV

11 SLICE THICKNESS SLICE THICKNESS S. RESOLUTION 5 MM 1 MM

12 FOCAL SPOT SIZE FOCAL SPOT SIZE S. RESOLUTION LARGE FOCAL SPOT = LARGE PENUMBRA (BLURR)

13 DETECTOR WIDTH DETECTOR WIDTH S. RESOLUTION

14 TYPE OF CONVOLUTION FILTER SHARP KERNEL S. RESOLUTION SMOOTHSHARP

15 MATRIX SIZE MATRIX SIZE S. RESOLUTION 80 X X 512

16 DFOV SIZE DFOV S. RESOLUTION 20CM 10CM

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

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

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

20 CONTRAST RESOLUTION PHANTOM

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

22 PHOTON FLUX (INTENSITY) PHOTON FLUX C. RESOLUTION mAs P. FLUX kVp P. FLUX

23 LOW TECHNIQUEADEQUATE TECHNIQUE

24 SLICE THICKNESS SLICE THICKNESS C. RESOLUTION 8 mm 5 mm

25 10 mm – 100 PHOTONS5 mm – 50 PHOTONS

26 PATIENT SIZE PATIENT SIZE C. RESOLUTION NORMALLARGE

27 DETECTOR SENSITIVITY DETECTOR SENSITIVITY C. RESOLUTION

28 TYPE OF CONVOLUTION FILTER SMOOTH KERNEL C. RESOLUTION SMOOTHSHARP

29 IMAGE DISPLAY MONITOR RESOLUTION C. RESOLUTION

30 QUANTUM NOISE QUANTUM NOISE C. RESOLUTION HIGH NOISELOW NOISE

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

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33 NOISE SOURCES IN CT QUANTUM NOISE – X-RAY INTENSITY AT THE DETECTORS MATRIX SIZE DFOV SLICE THICKNESS CONVOLUTION FILTER TYPE PITCH

34 QUANTUM NOISE – CONTROLLED BY THE TECHNOLOGIST mA Time kVp NOISE

35 QUANTUM (STATISTICAL) – CONTROLLED BY THE TECHNOLOGIST ELECTRONIC – INHERENT IN THE EQUIPMENT

36 QUANTUM NOISE – CONTROLLED BY THE TECHNOLOGIST DFOV MATRIX COLLIMATION FILTER SPATIAL FREQUENCY PITCH NOISE

37 DOSE vs IMAGE QUALITY RADIATION DOSE IMAGE QUALITY


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