o_1977r8vv9vk1ts2ms0kd8pksa.pdf

XII
Contents
Determination of Vascular Luminal Area 40
Determination of the Angle
of Insonation ................... 40
Alternative Methods of Doppler
Flowmetry ..................... 41
Non-Doppler Flowmetry ± Time Domain
Processing Velocity Measurement .... 41
Doppler Waveform Analysis and Doppler
Indices ......................... 43
Comprehensive Waveform Analysis ... 44
Choice of Indices .................. 45
Sources of Variance of the Doppler
Indices ....................... 46
Hemodynamic Basis of Doppler Waveform
Analysis ........................ 46
Experimental Approaches to Hemodynamic
Validation of Doppler Indices . 47
Arterial Input Impedance: Basic
Concepts and Relevance to Doppler
Waveform Analysis ............... 47
Doppler Indices and Peripheral
Resistance ..................... 49
Doppler Indices and Input Impedance . 49
Doppler Indices and Central Circulation 52
Placental Vascular Changes and
Abnormal Doppler Waveforms ...... 54
Summary ....................... 54
References .................... 55
5 Venous Haemodynamics ........... 57
Torvid Kiserud
Velocity Profile in Veins ............. 57
Parabolic Blood Velocity Profile and Flow
Calculation .................... 57
Factors Modifying the Velocity Profile . 58
Pulsation in Veins ............... 59
Cardiac Function and Waveform ..... 59
Transmission Lines ............... 59
Wave Reflections ................ 60
Compliance and Reservoir Function
of the Umbilical Vein ............. 61
Direction of Pulse and Blood Velocity .. 63
Source of Pulse ................. 64
References .................... 65
6 Sonographic Color Flow Mapping:
Basic Principles .................. 69
Dev Maulik
Principles of Doppler Color Flow Mapping 69
Multigated Doppler Interrogation .... 69
Color Doppler Signal Analysis ....... 70
Instrumentation ................... 71
Color Flow Processor ............. 71
Transducers for Doppler Color Flow
Mapping ...................... 72
Color Mapping ................... 72
Color Classification ............... 72
Color Perception ................ 73
Color Encoding of Doppler Flow Signals 73
Color Mapping of Direction of Flow ... 73
Color Mapping of Velocity and the Color
Bar .......................... 73
Color Mapping of Variance ......... 74
Formation of a Color Frame .......... 74
Two-Dimensional Color Frame
Formation ..................... 74
Persistence .................... 75
Frame Rate .................... 75
M-Mode Color Frame Formation ..... 75
Operational Considerations ........... 76
Transducer Frequency ............ 76
Pulse Repetition Frequency ......... 76
Doppler Color Flow Gain .......... 77
High-Pass Filter (Wall Filter) ......... 77
Limitations of Doppler Color
Flow Mapping .................... 78
Aliasing ...................... 78
Range Ambiguity ................ 80
Temporal Ambiguity ............. 80
Angle of Insonation .............. 80
Wall Motion Ghost Signals ......... 81
Mirroring ..................... 81
Color Mapping of Doppler Amplitude
(Doppler Power or Doppler Energy) ... 81
Summary ....................... 83
References .................... 84
7 Three-dimensional Color and Power
Doppler Ultrasonography
of the Fetal Cardiovascular System .... 85
Rabih Chaoui, Karim D. Kalache
Introduction ..................... 85
Technical Background ............... 85
Equipment .................... 85
Advantages of Power Doppler for 3D
Rendering ..................... 85
Principle of Data Acquisition, Image
Rendering, and Display ............ 85
Limitations of 3D Power Doppler
in Prenatal Ultrasound ............ 87
Clinical Application ................ 87
Umbilical Cord and Placenta ........ 87
Intraabdominal Vessels ............ 87
Renal Vessels ................... 89
Intracranial Vessels ............... 90
Lung Vessels ................... 91
Fetal Tumors or Aberrant Vessels ..... 91