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doppler principles
basic doppler
| Question | Answer |
|---|---|
| doppler shift | returned frequency - transmitted frequency |
| doppler frequency is between.. | 2-10MHz |
| average speed of sound in tissues | 1540 m/s |
| antegrade flow will be above/below the baseline? | above |
| frequency shift is affected by what? | transmitted doppler frequency, doppler beam "angle to flow", velocity |
| Which angle results in a max frequency shift? | 0 degree |
| advantages of CW doppler? | detect flow in all vessels, useful for obtaining systolic pressures, No aliasing |
| what are some ways to eliminate aliasing? | ^PRF; decrease freq shift (higher angle or decrease transmitted freq); eliminate triplex |
| a large SV/gate is related to | spatial pulse length |
| How to generate a color image? | autocorrelation |
| T/F Frame Rate is affected by the density or number of scan lines | True: the more lines, the more time to generate an image which decreases frame rate |
| Power Doppler can be used for what type of flow? | Trickle flow |
| This artifact has been referred to as a "ghost" artery | mirror-image artifact |
| Increasing focal zones increase lateral/axial resolution? | Lateral |
| when the doppler can not differentiate the main sample voume from those of phantoms | range gate ambiguity |