**Doppler**

What is the “Doppler shift”. It boils down to the change in the frequency sent from the machine to the frequency of the returned echo. The difference is the shift.

If the operating frequency is 5 MHz and the returned echo is 4 MHz then the doppler shift is -1 MHz.

The Doppler effect in tissue may be expressed as an equation (shown below). The Doppler shift (Fd) of ultrasound will depend on both the transmitted frequency (Fo) and the velocity (v) of the moving blood. This returned frequency is also called the “frequency shift” and is highly dependent upon the angle between the beam of ultrasound transmitted from the transducer and the moving red blood cells. The propagation speed of sound in tissue is constant (c) and is an important part of the Doppler equation.

**Fd = 2 Fo v / c****Fd**is the Doppler shift**Fo**is the original frequency**v**is the velocity of target**c**is the propagation speed of interrogating beam through soft tissue

**Example: 2 (5MHz) (120 cm/s) / 1540 m/s**

** 120 cm/s = 1.2 m/s (this converts centimeters into meters)**

** 2 x 5MHz = 10 MHz**

** 1.2 m/s x 10MHz = 12MHz**

** / 1540 = 0.0078MHz (this is the doppler shift)**

## Doppler

*Doppler*.You scored %%SCORE%% out of %%TOTAL%%.Your performance has been rated as %%RATING%%

Question 1 |

The difference between the original pulse frequency and the returned pulse frequency. | |

The change between the original pulse frequency and the transducer pulse frequency. | |

The difference between the original pulse velocity and the returned pulse velocity. | |

The difference between the original pulse propagation speed and the returned propagation speed. |

Question 2 |

Fd = 2 Fi v / c | |

Fd = Fr – Fi | |

Fd = 2 Fi c / v | |

v = c ( fi / fo + 1) |

Question 3 |

0, 180 degrees | |

45 degrees | |

30, 60 degrees | |

90 degrees |

Question 4 |

**Fd = 2 Fo v / c**what does Fd stand for?

The Doppler shift | |

The original frequency | |

The velocity of target | |

The propagation speed of interrogating beam through soft tissue |

Question 5 |

**Fd = 2 Fo v / c**what does Fo stand for?

The original frequency | |

The velocity of target | |

The Doppler shift | |

The propagation speed of interrogating beam through soft tissue |

Question 6 |

**Fd = 2 Fo v / c**what does v stand for?

The velocity of target | |

The original frequency | |

The Doppler shift | |

The propagation speed of interrogating beam through soft tissue |

Question 7 |

**Fd = 2 Fo v / c**what does c stand for?

The propagation speed of interrogating beam through soft tissue | |

The Doppler shift | |

The velocity of target | |

The original frequency |

Question 8 |

Higher | |

Lower | |

The same | |

Color in an Ultrasound is unrelated to frequency. |

Question 9 |

The medium | |

The frequency of the beam | |

The source | |

The velocity of the interrogated object |

Question 10 |

0 | |

1 | |

100 | |

Unable to determine |

Question 11 |

1,540 m/s - The speed of sound in soft tissue. | |

1,570 m/s - The speed of sound in blood. | |

4,080 m/s - The speed of sound in bone. | |

330 m/s - The speed of sound in gas. |

List |

#### Franco

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This is really great i take my spi on sept 28 IM SO NERVOUS

Good luck, let us know how your test went. We are all rooting for you.

Good job!

Thanks