UltrasoUnd Physics & instrUmentation - Pegasus Lectures

22.4 Color Display and Velocity Interpretation .................................................................................571
22.4.1 Toward and Away.........................................................................................................571
22.4.2 How the System Applies a Color Map .........................................................................571
23. Time Correlated Color .........................................................................................................................572
24. Color Gain ..........................................................................................................................................572
24.1 Setting the Appropriate Color Gain ...........................................................................................572
25. Interpreting the Color Bar Relative to Spectral Doppler .....................................................................573
26. Color Invert and Aliasing ....................................................................................................................573
27. Color Wall Filters ................................................................................................................................574
27.1 Wall Filter and Color Scale Integrated ......................................................................................574
27.2 The Absence of Color ................................................................................................................574
27.3 Interpreting the Color Bar Relative to Nyquist and the Wall Filters .........................................575
28. Determining Flow Direction in Color Doppler ...................................................................................576
28.1 Why Colors Change Even When Velocity Doesn’t ...................................................................576
28.2 Defining the Insonification Angle ..............................................................................................577
28.3 Cosine Revisited ........................................................................................................................577
28.4 Step-by-Step Approach ..............................................................................................................578
29. Color Persistence .................................................................................................................................582
29.1 The Purpose and Effects of Color Persistence ...........................................................................582
29.2 Persistence and Temporal Distortion .........................................................................................582
29.3 Important Points about Persistence ...........................................................................................582
30. Color Priority .......................................................................................................................................583
30.1 How Color Priority Works .........................................................................................................583
30.2 Important Points about Color Priority: ......................................................................................583
31. Understanding Color Wall Filters Behavior ........................................................................................584
31.1 Digital Filtering .........................................................................................................................584
31.2 Comparing Spectral Doppler Wall FIlters with the Color Wall Filter .......................................584
31.3 Color Wall Filters and Nyquist ..................................................................................................585
31.4 Effect of Signal Strength on Color Wall Filtering .....................................................................585
31.5 Angle Correction Error (10 degree error) ..................................................................................588
32. Conceptual Questions ..........................................................................................................................589
CHaPTeR 8 - artifacts
Introduction ................................................................................................................................................593
1. Categorizing Artifacts ..........................................................................................................................594
1.1 Image Detail Resolution Related ...............................................................................................594
1.2 Locational Artifacts ...................................................................................................................594
1.3 Attenuation Artifacts..................................................................................................................594
1.4 Doppler Artifacts .......................................................................................................................594
2. Detail Resolution .................................................................................................................................595
2.1 Lateral and Axial Resolution .....................................................................................................595
2.2 Elevation Resolution..................................................................................................................596
3. “Locational” Artifacts ...........................................................................................................................596
3.1 Refraction ..................................................................................................................................596
3.2 Reverberation ...........................................................................................................................598
3.2.1 A Simple Case: Between a Specular Reflector and the Transducer Face ...................598
3.2.2 A More Complex Case: Between Multiple Specular Reflectors ..................................600
3.2.3 A Very Complex Case: “Ghosting” or “Mirrored” Arteries ........................................600
3.2.4 Be Vigilant Not to Confuse a Reverberation Artifact with a Thrombus ......................601
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Pegasus Lectures, Inc.