Ultrasound Modes
Christopher R. Tainter
Michael Self
Cameron Smyres
A. B-mode
B. Color Doppler
C. Pulsed-wave Doppler
D. All of the above
View Answer
1. Correct Answer: D. All of the above
Rationale: Figure 5.1 shows a B-mode (brightness mode, or 2-D) background, with overlying color flow Doppler. Color flow Doppler applies a color scale to pulsed-wave Doppler signals, thus it is a type of pulsed-wave Doppler; therefore all three imaging modes are used to create Figure 5.1.
Selected Reference
1. Soni NJ, Arntfield R, Kory P. Point of Care Ultrasound. Elsevier; 2019.
2. A 38-year-old woman with a history of heavy vaginal bleeding and recent hysterectomy presents with tachycardia, hypotension, and respiratory distress. While performing a point-of-care cardiac ultrasound, you notice she has significant right ventricular dilatation. To evaluate her right ventricular function you assess her “tricuspid annular plane systolic excursion” (TAPSE). What ultrasound mode is the most accurate in measuring the change in distance of the tricuspid annulus along a single ultrasound crystal?
A. B-mode
B. M-mode
C. A-mode
D. C-mode
View Answer
2. Correct Answer: B. M-mode
Rationale: “M-mode,” which stands for motion mode, assesses images within a 2-D mode. After applying a cursor along a single line within the 2-D image, the movement of tissues along that single line is analyzed over time. Any movement of structures, including the changes in cavity sizes and movements of structures along that line, can be analyzed with improved temporal resolution. Common clinical applications include changes in the size of cardiac chambers, movement of cardiac valve leaflets throughout the cardiac cycle, changes in the diameter of the inferior vena cava during respiration, and the presence or absence of pleural sliding in assessing for possible pneumothorax.
Selected Reference
1. Ng A, Justiaan S. Resolution in ultrasound imaging. Contin Educ Anaesth Crit Care Pain. 2011 Oct;11(5):186-192. doi: 10.1093/bjaceaccp/mkr030.
3. A 67-year-old man presents after a syncopal episode while walking. On examination, a systolic murmur is noted, with a prominent S4. You use ultrasound to assess the flow across the aortic valve, and the pressure gradient between the left ventricle and the aorta to determine the severity of the abnormality. Which imaging mode is the most appropriate for this scenario?
A. Color flow Doppler
B. Color power Doppler
C. Continuous-wave Doppler
D. Pulsed-wave Doppler
View Answer
3. Correct Answer: C. Continuous-wave Doppler
Rationale: In continuous-wave Doppler mode, sound waves are emitted and received simultaneously and continuously along the entire path of the ultrasound beam. As there is no pulsed cycle, it avoids the aliasing effect of pulsed-wave Doppler imaging and can accurately measure high-velocity blood flow without a Nyquist limit. Both pulsed-wave Doppler and color-flow Doppler are limited by this aliasing effect, making them less effective for high-flow states, like evaluating stenotic or regurgitant valvular flow. Color power Doppler is more sensitive to low velocity than color Doppler, but is limited in that it analyzes only the amplitude of returning sound waves and does not provide any information regarding the direction of flow.
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