Lesson 12: Doppler Principles. This lesson contains 50 slides plus 26 multiple-choice questions.

Lesson 12: Doppler Principles This lesson contains 50 slides plus 26 multiple-choice questions. Accompanying text for the slides in this lesson can be found on pages 59 through 80 in the textbook:

DOPPLER DOPPLER PRINCIPLES

DOPPLER TRANSDUCER SAME FREQUENCY During Doppler operation, the reflected sound has the same frequency as the transmitted sound if the blood is stationary.

DOPPLER TRANSDUCER LOWER FREQUENCY During Doppler operation, the reflected sound has a lower frequency if the blood is moving away from the sound source.

DOPPLER TRANSDUCER HIGHER FREQUENCY During Doppler operation, the reflected sound has a higher frequency if the blood is moving toward the sound source.

DOPPLER SHIFT f

DOPPLER SHIFT FORMULA

BLOOD VELOCITY FORMULA

DOPPLER RELATIONSHIPS TRANSMITTED FREQUENCY f o DOPPLER ANGLE q BLOOD VELOCITY V DOPPLER SHIFT f Increase Increase Decrease Decrease Increase Decrease Decrease Increase Increase Increase Decrease Decrease

DOPPLER CALCULATIONS Doppler shifts ( f) for V = 100 cm per second c = 1550 meters per second q cos q f o = 2.5 MHz f o = 5.0 MHz 0 1 3226 Hz 6452 Hz 30 0.867 2794 Hz 5588 Hz 45 0.707 2281 Hz 4562 Hz 60 0.5 1613 Hz 3226 Hz 75 0.259 835 Hz 1670 Hz 90 0 0 Hz 0 Hz

DOPPLER SHIFT EXAMPLE TRANSMITTED FREQUENCY RECEIVED FREQUENCY DOPPLER SHIFT f DIRECTION OF FLOW TO SOUND 5 MHz 4.995 MHz 5 khz Away 5 MHz 5.005 MHz 5 khz Toward

SPECTRAL DOPPLER FFT DISPLAY: POSITIVE DOPPLER SHIFT WITHOUT SPECTRAL BROADENING FREQUENCY SCALES FFT DISPLAY: POSITIVE DOPPLER SHIFT WITH SPECTRAL BROADENING

CW SPECTRAL DOPPLER NON-IMAGING CW B-MODE IMAGING AND CW

CW SPECTRAL DOPPLER NON-IMAGING CARDIAC CW DOPPLER TRANSDUCER

CW SPECTRAL DOPPLER CW DOPPLER DETECTING SHIFTS FROM MORE THAN ONE VESSEL

CW SPECTRAL DOPPLER B-MODE AND CW DOPPLER WITH SPECTRUM ANALYZER DISPLAY

PW SPECTRAL DOPPLER PW TRANSMITTING PW RECEIVING

PW SPECTRAL DOPPLER NON-IMAGING PW B-MODE IMAGING AND PW

PW SPECTRAL DOPPLER

PW SPECTRAL DOPPLER NORMAL SAMPLE VOLUME WITH NO SPECTRAL BROADENING LARGER THAN NORMAL SAMPLE VOLUME WITH SPECTRAL BROADENING

PW - ALIASING WRAP-AROUND INDICATES ALIASING

PW - ALIASING Example: The PRF is 4 khz, the Nyquist Limit is 2 khz. The Doppler shift exceeds the Nyquist Limit. POSITIVE DOPPLER SHIFT WITH THE NYQUIST LIMIT (N.L) EXCEEDED AS A RESULT OF HIGH VELOCITY FLOW

PW - ALIASING Example: The PRF is 8 khz, the Nyquist Limit is 4 khz. The Doppler shift does not exceed the Nyquist Limit. ALIASING: NYQUIST LIMIT EXCEEDED SAME DOPPLER SHIFT BUT ALIASING ELIMINATED SCALE ADJUSTED TO INCREASE THE PULSE DOPPLER PRF AND RAISE THE NYQUIST LIMIT

PW - ALIASING Example: The PRF is 8 khz, the Nyquist Limit is 4 khz. The Doppler shift does not exceed the Nyquist Limit. ALIASING: NYQUIST LIMIT EXCEEDED SAME DOPPLER SHIFT BUT ALIASING ELIMINATED BASE LINE LOWERED TO INCREASE THE PULSE DOPPLER PRF AND RAISE THE NYQUIST LIMIT

PW - ALIASING Example: The PRF is still 4 khz, the Nyquist Limit is still 2 khz. The cursor was adjusted to increase the Doppler angle, which reduced the Doppler shift to a value below the Nyquist Limit. ALIASING: NYQUIST LIMIT EXCEEDED ALIASING ELIMINATED DOPPLER ANGLE INCREASED SCALE, BASELINE, AND PRF UNCHANGED

PW - ALIASING Example: The PRF is still 4 khz, the Nyquist Limit is still 2 khz. The transducer frequency was changed from 10 MHz to 5 MHz, which reduced the Doppler shift to a value below the Nyquist Limit. ALIASING: NYQUIST LIMIT EXCEEDED ALIASING ELIMINATED TRANSDUCER FREQUENCY DECREASED SCALE, BASELINE, AND PRF UNCHANGED

PW - ALIASING Example: The PRF is 5 khz, the Nyquist Limit is 2.5 khz. The Doppler shift exceeds the Nyquist Limit. NO WRAP-AROUND BUT ALIASING STILL PRESENT THE BASE LINE WAS MOST LIKELY LOWERED TO ELIMINATE WRAP- AROUND BUT THE DOPPLER SHIFT STILL EXCEEDS THE NYQUIST LIMIT

NYQUIST LIMIT THE NYQUIST LIMIT IS EQUAL TO THE DOPPLER PRF DIVIDED BY 2

NYQUIST LIMIT NYQUIST LIMITS (PRF 2) PRF N.L. 1 khz (1000 Hz) 500 Hz 2 khz (2000 Hz) 1000 Hz 3 khz (3000 Hz) 1500 Hz 4 khz (4000 Hz) 2000 Hz 5 khz (5000 Hz) 2500 Hz 6 khz (6000 Hz) 3000 Hz

CW NO ALIASING CW - NO ALIASING:

ANGLE-CORRECT PW - VELOCITY CORRECT: PROPER ANGLE-CORRECT VELOCITY SCALES PW - VELOCITY INCORRECT: IMPROPER ANGLE-CORRECT

WALL FILTERS WALL FILTER SETTING NORMAL WALL FILTER SETTING TOO HIGH

DOPPLER GAIN DOPPLER GAIN SETTING NORMAL DOPPLER GAIN SETTING TOO HIGH

TRANSCRANIAL DOPPLER NON-IMAGING TCD STUDY WITH A SINGLE-ELEMENT PW TRANSDUCER

TRANSCRANIAL DOPPLER PW TRANSDUCERS USED FOR TRANSCRANIAL DOPPLER

ANALOG DOPPLER Non-spectral

ANALOG DOPPLER

PULSATILITY INDEX (PI) PI = (peak systolic velocity end diastolic velocity) mean velocity

RESISTIVITY INDEX (RI) RI = (peak systolic velocity end diastolic velocity) peak systolic velocity

COLOR-FLOW IMAGING

COLOR-FLOW IMAGING STANDARD COLOR MAP IN THIS SECTOR SCAN, SAMPLES ARE OBTAINED FROM MANY DIFFERENT ANGLES-TO-FLOW. THE RED HUES REPRESENT POSITIVE DOPPLER SHIFTS. THE BLUE HUES REPRESENT NEGATIVE DOPPLER SHIFTS. THE DIRECTION OF FLOW IS FROM THE LEFT (L) OF THE IMAGE TO THE RIGHT (R) OF THE IMAGE. THE BLACK AREA IN THE CENTER OF THE VESSEL IS THE RESULT OF A 90º DOPPLER ANGLE.

COLOR-FLOW IMAGING ENHANCED COLOR MAP IN THIS LINEAR SCAN, ALL SAMPLES ARE OBTAINED FROM THE SAME ANGLE-TO-FLOW. WHEN THE BOX-CURSOR FORMS A PARALLELOGRAM WITH THE TOP SKEWED TO THE RIGHT WITH THE BOTTOM SKEWED TO THE LEFT: THE BLUE HUES (UPPER COLOR SCALE) REPRESENT POSITIVE DOPPLER SHIFTS. THE REDDISH HUES (LOWER COLOR SCALE) REPRESENT NEGATIVE DOPPLER SHIFTS. BASED ON THE ENHANCED MAP USED FOR THIS COLOR BAR SCALE, THE YELLOWISH HUE (IN THE CENTER OF THE VESSEL) REPRESENTS INCREASED VELOCITY. THE REGION OF TURBULENCE REPRESENTS REVERSE FLOW.

COLOR-FLOW IMAGING STANDARD COLOR MAP IN THIS LINEAR SCAN, ALL SAMPLES ARE OBTAINED FROM THE SAME ANGLE-TO-FLOW. THE BLACK AREA IN THE CENTER OF THE VESSEL IS THE RESULT OF A 90º DOPPLER ANGLE.

COLOR VARIANCE MAP COLOR-FLOW IMAGING

COLOR-FLOW IMAGING CAROTID

COLOR-FLOW IMAGING STANDARD COLOR MAP COLOR DOPPLER SAMPLE ANGLES 2-D, SPECTRAL DOPPLER, & COLOR-FLOW DOPPLER ECHOCARDIOGRAPHIC STUDY (Triplex)

DOPPLER TISSUE IMAGING PARASTERNAL LONG AXIS VIEW, 2-D ECHOCARDIOGRAPHY & DTI

DOPPLER TISSUE IMAGING MITRAL VALVE PROLAPSE, COLOR M-MODE USING DTI

COLOR-FLOW & POWER DOPPLER IMAGING COLOR-FLOW DOPPLER POWER DOPPLER

POWER DOPPLER & SPECTRAL DOPPLER

POWER DOPPLER

Answers to the following TWENTY FOUR practice questions were derived from material in the textbook:

Question 1 What describes the Doppler shift from moving reflectors? low when the Doppler angle is close to zero the sum of the transmitted and received frequencies high if the Doppler angle is 90 degrees the difference between the transmitted and received frequencies Page 59

The drawings represent reflectors that are moving at the same speed. The arrows indicate the direction of movement relative to the respective transducer. Which reflector causes the LOWEST returning frequency? A B C D E Question 2 Pages 59 and 61

Question 3 What does a Doppler system measure? frequency shift while calculating blood velocity frequency shift while calculating sound velocity frequency shift while calculating attenuation blood velocity while calculating frequency shift Page 60

Question 4 Which one of the following factors does not affect the frequency of the Doppler shift? size of the Doppler probe angle at which the probe is pointed at the vessel velocity of blood in the vessel transmitted frequency Page 60

Question 5 What is an advantage of continuous wave Doppler over pulsed Doppler? a lower Nyquist limit spectral analysis is not required a wider range of shift frequencies without aliasing depth selectivity is possible Page 63

Question 6 When will aliasing begin to occur? when the Doppler shift is one-half the Nyquist limit when the Doppler shift exceeds one-fourth the PRF when the Doppler shift exceeds the Nyquist limit when the Doppler shift is 50% of the Nyquist limit Pages 66 through 68

Question 7 Which one of the following uses a method other than just measuring frequency shift to detect movement? CW Doppler Power Doppler PW Doppler color-flow Doppler Page 80

Question 8 What causes the problem in this PW spectral display? transducer frequency too low aliasing spectral broadening excessive output power Pages 66 through 68

Question 9 What can be done to correct the problem in the spectral display? use a higher frequency transducer decrease the output power increase the Doppler angle decrease the PRF Pages 66 through 68

Question 10 What is the result of the gate settings in this image? aliasing and an accurate velocity calculation spectral broadening and an accurate velocity calculation a thin spectral envelope and an accurate velocity measurement spectral broadening and an inaccurate velocity calculation Pages 65 and 70

Question 11 What is an ultrasound scanner that uses a single probe to display a real time image along with spectral information? a duplex system an annular array a triplex system a CW Doppler system Page 65

Question 12 What does the letter A represent in the spectral display? aliasing the peak Doppler shift the mean Doppler shift the negative Nyquist Limit Page 62

Question 14 What does the letter C represent in the spectral display? a large window the peak Doppler shift PW Doppler shifts from a very small sample volume spectral broadening Page 62

Question 13 What does the letter B represent in the spectral display? the zero baseline the positive velocity scale the peak Doppler shift the positive frequency shift scale Page 62

Question 14 What does the letter C represent in the spectral display? a large window the peak Doppler shift PW Doppler shifts from a very small sample volume spectral broadening Page 62

Question 15 What does the letter D represent in the spectral display? the spectral baseline the Nyquist Limit the peak Doppler shift the positive velocity scale Page 62

Question 16 What does the letter E represent in the spectral display? the negative PW frequency shift scale the negative CW frequency shift scale the peak Doppler shift the negative velocity scale Page 62

Question 17 Which of the following is a limitation of CW Doppler? frequent aliasing depth selectivity is not possible inability to detect peak velocities a low Nyquist Limit Page 63

Question 18 What is the process used for color-flow Doppler to automatically assess the data from multiple sampling sites to produce a display representing mean Doppler shift frequencies? autocorrelation quadrature phase detection FFT analysis zero crossing detection Page 77

Question 19 When will aliasing begin to occur when using a 5 MHz Doppler system with a PW PRF of 15 khz? when the Doppler shift exceeds 5 khz when the Doppler shift exceeds 7.5 khz when the Doppler shift exceeds 15 khz when the Doppler shift exceeds 30 khz Pages 66 through 68

Question 20 Which Doppler waveform produces the highest pulsatility index? biphasic monophasic triphasic post-stenotic Page 73

Question 21 Where is aliasing displayed in the color-flow Doppler image? A B C D Page 77

Question 22 Why is a black area present in the vessel on the colorflow Doppler image? Doppler angle of 90 degrees reversal of blood flow within the vessel aliasing plaque Page 75

Question 23 The direction of flow in the color-flow Doppler image is red to blue right (R) to left (L) left (L) to right (R) red to black Page 75

Question 24 Which letter in the color-flow Doppler image represents the greatest Doppler shift? A B C D E Pages 59, 75, and 80

END OF LESSON 12 For information on the accompanying textbook, visit the Website: www.sonicorinc.com