Dopplermodi

Dopplermodi is a German term referring to the different Doppler modes used in ultrasound imaging to assess blood flow and tissue motion. Doppler modes extend ultrasound beyond static gray-scale imaging by measuring frequency shifts caused by moving targets, typically red blood cells, and, in some modes, tissue motion.

Common Doppler modes include:

- Continuous Wave (CW) Doppler: transmits a continuous ultrasound signal and receives echoes from moving targets. It can measure high velocities but does not provide depth information, since it lacks range resolution. It is often used for assessing valves and high-velocity jets.

- Pulsed Wave (PW) Doppler: sends short pulses and samples velocity at a defined depth via a sample volume. It provides depth-specific velocity information but is subject to aliasing at high velocities.

- Color Doppler: overlays color-coded flow information onto a B-mode image, indicating flow direction and relative velocity. It helps localize vessels and assess flow patterns in a real-time anatomical context.

- Power Doppler: displays the amplitude of the Doppler signal, increasing sensitivity to low-velocity flow. It is more prone to motion artifacts and does not indicate flow direction or exact velocity.

- Spectral Doppler: presents velocity versus time as a waveform, enabling quantitative measurements such as peak systolic velocity and blood flow indices.

- Duplex imaging: combines conventional gray-scale imaging with Doppler modes, providing anatomical and hemodynamic information in a single examination.

- Tissue Doppler Imaging (TDI): measures motion of surrounding tissues rather than blood flow, useful in evaluating cardiac function, particularly myocardial velocities.

Applications of Dopplermodi span vascular and cardiac ultrasound, obstetrics and gynecology, and interventional imaging. Limitations include angle dependency, potential for aliasing, and susceptibility to artifacts. Understanding the strengths and weaknesses of each mode is essential for accurate interpretation.