Echocardiography Board Review, 2nd Edition 500 Multiple Choice Questions with Discussion Ramdas G. Pai, MD, Professor of Medicine, Loma LindaUniversity, CA, USA Padmini Varadarajan, MD, Associate Professor of Medicine,Loma Linda University, CA, USA Echocardiography is an essential tool for the modern-daycardiologist and routinely used in the diagnosis, management andfollow-up of patients with suspected or known heart diseases. This best-selling book now returns in a fully revised newedition, once again providing cardiologists andcardiology/echocardiography trainees with a rapid reference,self-assessment question and answer guide to all aspects ofechocardiography. Packed with full-color images and written by experiencedechocardiographers, the book covers: * applied ultrasound physics * practical hydrodynamics * valvular heart disease * myocardial diseases * congenital heart disease * non-invasive hemodynamics * surgical echocardiography Containing 500 case-based questions, including clearexplanations and discussions for every question,Echocardiography Board Review, 2nd Edition, isthe perfect preparation guide for all those about to take theNational Board of Echocardiography's Board exam, includingcardiology and echocardiography trainees and specialist physicianspreparing for re-certification. Sonographers planning to takeRDCS or RDMS certification examinations should find this book veryhelpful as well. Of related interestPractical Manual of Echocardiography in the Urgent Setting Fridman, ISBN 978-0-470-65997-7 Successful Accreditation in Echocardiography: A Self-AssessmentGuide Banypersad, ISBN 978-0-470-65692-1 Website www.wiley.com/go/cardiology
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Table of Contents
Ramdas G. Pai MD, FACC, FRCP (Edin)
Professor of MedicineLoma Linda University Medical CenterLoma Linda, CA, USA
Padmini Varadarajan MD, FACC
Associate Professor of MedicineLoma Linda University Medical CenterLoma Linda, CA, USA
This edition first published 2014 © 2014 by John Wiley & Sons, Ltd.
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Library of Congress Cataloging-in-Publication Data
Pai, Ramdas G., author.
Echocardiography board review : 500 multiple choice questions with discussion / Ramdas G. Pai,
Padmini Varadarajan.— Second edition.
p. ; cm.
ISBN 978-1-118-51560-0 (paper)
I. Varadarajan, Padmini, author. II. Title.
[DNLM: 1. Echocardiography— Examination Questions. WG 18.2]
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Cover image: Courtesy of the authors (thumbnails); iStock #10066374/© elly99 (background)
Cover design by Modern Alchemy LLC.
The Echocardiography Board Review is written for the primary purpose of helping candidates prepare for the National Board of Echocardiography and should be helpful to both cardiologists and anesthesiologists preparing for this certification process. At the time of its writing, there were no other published works available that comprehensively dealt with the material covered in these examinations in a question, answer, and discussion format. This second edition is thoroughly revised and 100 questions have been added. The authors have used this format in teaching echocardiography to cardiology fellows in training. One of the main impetuses for initiating this work was the request by many of the trainees and prospective echocardiography examination candidates to write such material. Similar requests have also come from echocardiography technicians preparing for their certification examination. There are 500 well-thought-out questions in this review book. The questions address practically all areas of echocardiography including applied ultrasound physics, practical hydrodynamics, imaging techniques, valvular heart disease, myocardial diseases, congenital heart disease, noninvasive hemodynamics, surgical echocardiography, etc. Each question is followed by several answers to choose from. The discussion addresses not only the rationale behind picking the right choice but also fills in information around the topic under discussion such that important key concepts are clearly driven. This would not only help in the preparation for the examinations but also give a clear understanding of various echocardiographic techniques, applications, and the disease processes they address.
This review would be helpful not only to the prospective examinees in echocardiography but also to all students of echocardiography in training, not only in cardiology and anesthesia training programs in this country but also internationally as well. This does not take the place of a standard textbook of echocardiography but complements the textbook reading by bringing out the salient concepts in a clear fashion. The questions on applied physics, quantitative Doppler, and images are of particular value. There are over 300 still images representing most of the key areas and these will improve the diagnostic abilities of the reviewer.
We feel this book will meet the need felt by students of echocardiography in not only preparing for examinations but also clearly enhancing the understanding of the subject in an easy-to-read manner. The authors are grateful to many of the trainees who expressed the need for such work and pressured us to write one.
1. The speed of sound in tissues is:
A. Roughly 1540 m/s
B. Roughly 1540 km/s
C. Roughly 1540 cm/s
D. Roughly 1540 m/min
2. The relationship between propagation speed, frequency, and wavelength is given by the formula:
A. Propagation speed = frequency × wavelength
B. Propagation speed = wavelength/frequency
C. Propagation speed = frequency/wavelength
D. Propagation speed = wavelength × period
3. The frame rate increases with:
A. Increasing the depth
B. Reducing sector angle
C. Increasing line density
D. Adding color Doppler to B-mode imaging
4. Period is a measure of:
A. Duration of one wavelength
B. Duration of half a wavelength
C. Amplitude of the wave
5. Determination of regurgitant orifice area by the proximal isovelocity surface area (PISA) method is based on:
A. Law of conservation of mass
B. Law of conservation of energy
C. Law of conservation of momentum
D. Jet momentum analysis
6. In which situation can you not use the simplified Bernoulli equation to derive the pressure gradient?
A. Peak instantaneous gradient across a nonobstructed mitral valve
B. Peak gradient across a severely stenotic aortic valve
C. Mean gradient across a severely stenotic aortic valve
D. Mean gradient across a stenotic tricuspid valve
7. Which of the following resolutions change with increasing field depth?
A. Axial resolution
B. Lateral resolution
8. With a fixed-focus transducer with crystal diameter 20 mm and wavelength 2.5 mm, what is the depth of the focus?
A. 40 m
B. 30 mm
C. 40 mm
D. 4 m
9. A sonographer adjusts the ultrasound machine to double the depth of view from 5 to 10 cm. If sector angle is reduced to keep the frame rate constant, which of the following has changed?
A. Axial resolution
B. Temporal resolution
C. Lateral resolution
D. The wavelength
10. Which of the following properties of a reflected wave is most important in the genesis of a two-dimensional image?
C. Pulse repetition period
D. Pulse duration
11. Increasing depth will change all of the following except:
A. Pulse duration
B. Pulse repetition period
C. Pulse repetition frequency
D. Duty factor
12. The two-dimensional images are produced because of this phenomenon when the ultrasound reaches the tissue:
C. Specular reflection
13. Attenuation of ultrasound as it travels through tissue is higher at:
A. Greater depth
B. Lower transducer frequency
C. Blood rather than soft tissue like muscle
D. Bone more than air
14. The half-intensity depth is a measure of:
A. Ultrasound attenuation in tissue
B. Half the wall thickness in mm
C. Coating on the surface of the transducer
D. Half the ultrasound beam width
15. What is the highest pulse repetition frequency (PRF) of a 3 MHz pulsed wave transducer imaging at a depth of 7 cm?
A. 21 000 Hz
B. 2 333 Hz
C. 11 000 Hz
D. 2.1 million Hz
16. Examples of continuous wave imaging include:
A. Two-dimensional image
B. Volumetric scanner-acquired LV image
C. Color flow imaging
D. Nonimaging Doppler probe (Pedoff)
17. Which of the following manipulations will increase the frame rate?
A. Increase depth
B. Increase transmit frequency
C. Decrease sector angle
D. Increase transmit power
18. The lateral resolution increases with:
A. Decreasing transducer diameter
B. Reducing power
C. Beam focusing
D. Reducing transmit frequency
19. Axial resolution can be improved by which of the following manipulations?
A. Reduce beam diameter
B. Beam focusing
C. Reduce gain
D. Increase transmit frequency
20. Type of sound used in medical imaging is:
C. Audible sound
Speed of sound in tissue is 1540 m/s. Hence, travel time to a depth of 15 cm is roughly 0.1 ms one way (1540 m/s = 154 000 cm/s or 154 cm/ms or 15 cm per 0.1 ms) or 0.2 ms for to and fro travel. This is independent of transducer frequency and depends only on the medium of transmission.
Wavelength depends on frequency and propagation speed. It is given by the following relationship: wavelength (mm) = propagation speed (mm/µs)/frequency (MHZ). Hence, propagation speed = frequency × wavelength.
Reducing the sector angle will reduce the time required to complete a frame by reducing the number of scan lines. This increases the temporal resolution. Decreasing the depth will increase the frame rate as well by reducing the transit time for ultrasound. Adding color Doppler will reduce the frame rate as more data need to be processed.
Period is the time taken for one cycle or one wavelength to occur. The common unit for period is µs. Period decreases as frequency increases. The relationship is given by the equation: period = 1/frequency. For a 5-MHZ ultrasound the period is 0.2 µs (1/5 million cycles) = 0.2 µs.
The law of conservation of mass is the basis of the continuity equation. As the flow rate at the PISA surface and the regurgitant orifice is the same, dividing the flow rate (cm3/s) by the velocity (cm/s) at the regurgitant orifice obtained by continuous wave Doppler gives the effective regurgitant area in cm2 (regurgitant flow rate in cm3/s divided by flow velocity in cm/s equals effective regurgitant area in cm2).
In a non-obstructed mitral valve flow velocities are low. Significant energy is expended in accelerating the flow (flow acceleration). As the flow velocity is low, energy associated with convective acceleration is low. As viscous losses in this situation are minimal, the other two components (flow acceleration and convective acceleration) of the Bernoulli equation have to be taken into account. In the simplified Bernoulli equation, the flow acceleration component is ignored. Put simply, when you deal with low-velocity signals in pulsatile system, the simplified Bernoulli equation does not describe the pressure flow relationship accurately.
Lateral resolution depends on beam width, which increases at increasing depths. Axial resolution depends on spatial pulse length, which is a function of transducer frequency, pulse duration, and propagation velocity in the medium.
Depth of focus equals squared crystal diameter divided by wavelength multiplied by 4. In this situation, (20 mm)2/(2.5 mm × 4) = 400/10 = 40 mm.
Lateral resolution diminishes at increasing depths owing to beam divergence. Frame rate determines the temporal resolution as temporal resolution is the reciprocal of frame rate. For example, frame rate of 50 fps gives a temporal resolution of 1/50 = 0.02 s or 20 m. Wavelength is a function of the transducer frequency and is independent of depth and frame rate adjustments.
Amplitude or strength of the reflected beam, and its temporal registration, which determines depth registration.
Pulse duration is the characteristic of the pulse and does not change with depth. Increase in depth will increase the pulse repetition period, and hence reduce frequency and the duty factor.
Backscatter or diffuse reflection produces most of the clinical images. Specular reflection reaches the transducer only when the incident angle is 90° to the surface, which is not the case in most of the images produced. Refracted and transmitted ultrasounds do not come back to the transducer.
Attenuation is the loss of ultrasound energy as it travels through the tissue and is caused by absorption and random scatter. It is greater with longer travel path length as it has to go through more tissue. Attenuation is greater at higher frequencies due to shorter wavelength. Attenuation is greatest for air followed by bone, soft tissue, and water or blood.
It is a measure of attenuation and reflects the depth at which the ultrasound energy is reduced by half. It is given by the formula: 6 cm/frequency in MHz For example, for an ultrasound frequency of 3 MHz the half-intensity depth is 2 cm, and for 6 MHz it is 1 cm.
The PRF is independent of transducer frequency and only determined by time of flight, which is the total time taken by ultrasound in the body in both directions. Ultrasound can travel 154 000 cm in a second at a travel speed of 1540 m/s. In other words, at 1 cm depth (2 cm travel distance) the technical limit to the number of pulses that can be sent is 154 000 cm/2 cm = 77 000 s−1 (Hz). Hence, the PRF equals 77 000/depth in cm. For 7 cm depth, the total distance is 14 cm. PRF = 154 000 (cm/s)/14 cm = 11 000 s−1.
Pedoff is a continuous wave Doppler modality for velocity recording. All other modalities utilize the pulsed wave technique, in which each of the crystals performs both transmit and receive functions.
Increase in the frame rate occurs by reducing the sector angle and reducing the depth, the former by reducing scan lines and the latter by reducing the ultrasound transit time. It is independent of transmit frequency and power.
Focusing increases lateral resolution. Increase in transducer diameter and frequency also increases lateral resolution.
Increasing the transmit frequency will reduce the wavelength and hence the spatial pulse length. This will increase the PRF and the axial resolution. Beam diameter and focusing have no effect on axial resolution.
Ultrasound is used in medical imaging. Typical frequency is 2–30 MHz: 2–7 MHz for cardiac imaging, 10 MHz for intracardiac echocardiography, and 20–30 MHz for intravascular imaging. Ultrasound in the 100–400 MHz range is used for acoustic microscopy. Frequency > 20 000 Hz is ultrasound. Audible range is 20–20 000 Hz and frequency < 20 Hz is called infrasound.
21. Doppler shift is typically in:
A. Ultrasound range
B. Infrasound range
C. Audible range
22. Duty factor refers to:
A. Power the transducer can generate
B. Range of frequencies the transducer is capable of
C. Physical properties of the damping material
D. Fraction of time the transducer is emitting ultrasound
23. Duty factor increases with:
A. Increasing gain
B. Increasing pulse duration
C. Decreasing pulse repetition frequency (PRF)
D. Decreasing dynamic range
24. Which of the following will increase the PRF?
A. Reducing depth
B. Decreasing transducer frequency
C. Reducing sector angle
D. Reducing filter
25. Persistence will have this effect on the image:
A. Smoothening of a two-dimensional image
B. Better resolution
C. Eliminating artifacts
D. Spuriously reducing wall thickness
26. Aliasing occurs in this type of imaging:
A. Pulsed wave Doppler
B. Continuous wave Doppler
C. None of the above
D. All of the above
27. The Nyquist limit at a PRF of 1000 Hz is:
A. 500 Hz
B. 1000 Hz
C. 2000 Hz
D. Cannot calculate
28. The Nyquist limit can be increased by:
A. Increasing the PRF
B. Reducing the PRF
29. The Nyquist limit can also be increased by:
A. Increasing transducer frequency
B. Reducing transducer frequency
C. Reducing filter
D. None of the above
30. Aliasing can be reduced by:
A. Decreasing the depth
B. Increasing the PRF
C. Reducing the transducer frequency
D. Changing to continuous wave Doppler
E. All of the above
31. What is the purpose of the depth or time gain compensation process adjusted by the echo cardiographer and performed in an ultrasound's receiver?
A. Corrects for depth attenuation and makes the image uniformly bright
B. Eliminates image artifacts
C. Eliminates aliasing
D. None of the above
32. Which of the following increases the Nyquist limit?
A. Increasing the depth
B. Reducing the sample volume depth
C. Increasing the transducer frequency
D. None of the above
33. The maximum Doppler shift that can be displayed without aliasing with a PRF of 10 kHz is:
A. 5 kHz
B. 10 kHz
C. Depends on depth
D. Cannot be determined
34. The PRF is influenced by:
A. Transducer frequency
B. Depth of imaging
35. Two identical structures appear on an ultrasound scan. One is real and the other is an artifact, the artifact being deeper than the real structure. What is this artifact called?
C. Speed error artifact
D. Mirror image
36. What is influenced by the medium through which sound travels?
A. Wavelength alone
B. Speed alone
C. Both wavelength and speed
D. None of the above
37. Image quality on an ultrasound scan is dark throughout? What is the first best step to take?
A. Increase output power
B. Increase receiver gain
C. Change to a higher frequency transducer
D. Decrease receiver gain
38. All of the following will improve temporal resolution except:
A. Decreasing line density
B. Decreasing sector angle
C. Increasing frame rate
39. Sound travels faster in a medium with which of the following characteristics?
A. High density, low stiffness
B. Low density, high stiffness
C. High density, high stiffness
D. Low density, low stiffness
40. Which of the following is associated with continuous wave Doppler compared to pulsed wave Doppler?
B. Range specificity
C. Ability to record higher velocities
D. All of the above
Doppler shift resulting from moving blood is generally audible as it is the difference between the transmitted and returned ultrasound frequency. One can hear them during Doppler examination. Audible frequency is 20–20 000 Hz.
It is pulse duration divided by pulse repetition period. Typical value for two-dimensional imaging is 0.1–1% and for Doppler it is 0.5–5%. Example for a 2 MHz transducer: Period = 1 s/frequency = 1/2 000 000 or 0.0005 ms. The wavelength in tissue is 0.75 mm (period = 0.0005 ms or 0.5 µs); if two periods are in a pulse then pulse duration is 1 µs or 0.001 ms and if PRF is 1000 Hz (pulse repetition period will be 1 ms or 1000 µs) then the duty factor is 1µs/1000 µs = 0.001 = 0.1%.
Proportional to pulse duration if the PRP is constant. If pulse duration is constant, decreasing the PRF will reduce the duty factor by increasing pulse repetition period. Please see explanation for question 22. Gain and dynamic range have no effect on duty factor.
Reducing depth reduces time of flight of ultrasound in the body and hence will increase the PRF. Transducer frequency, sector angle, and filter have no effect on PRF.
Persistence is the process of keeping the prior frames on the display console, and this will smoothen the image. This reduces random noise and strengthens the signal. However, fast-moving structures can produce artifacts and make the structures look thicker than they are. Some of the other smoothing algorithms include interdigitation and blooming to reduce the spoking appearance produced by the scan lines. Persistence does not affect resolution. It is a post-processing tool.
Aliasing or wrap-around occurs when the Nyquist limit or upper limit of measurable velocity is reached. The Nyquist limit is determined by the PRF. Spectral pulsed wave Doppler and color flow imaging are pulsed wave modalities.
Nyquist limit = PRF/2.
Nyquist limit = PRF/2. Hence increasing PRF will increase the Nyquist limit.
Reducing transducer frequency will increase aliasing velocity and reduces range ambiguity. For a given detected Doppler shift, the lower the transducer frequency, the higher is the measured velocity. V in cm/s = (77 Fd in kHz)/Fo in MHz for an incident angle of zero, where Fd is the Doppler shift and Fo is the transmitting frequency.
All of the above. Reducing depth reduces transit time and allows higher PRF. Also see explanation for questions 28 and 29. In continuous wave Doppler, there are separate crystals to transmit and receive crystals and hence no aliasing, thus allowing higher velocities to be measured.
It is post processing, which adjusts for loss of ultrasound that occurs at increasing depths.
The Nyquist limit is determined by the PRF and PRF = 77 000/depth in cm. Hence decreasing the sample volume depth will increase the PRF, which in turn will increase the Nyquist limit.
The Nyquist limit is PRF/2. Hence, a Doppler shift of >5 kHz in this case will cause aliasing. Depth influences the PRF.
The PRF is influenced by pulse duration and time needed for ultrasound to travel in tissue. Increasing depth will increase the time spent in the body. Transducer frequency does not influence PRF but can affect Doppler shift.
Mirror image artifact is a type of artifact where the artifact is always deeper than the real structure and occurs because of the structure or the surface between the two functioning as a mirror. Shape and size of the mirror image depend on shape of the reflecting surface (plane, convex, or concave).
Speed is determined only by the medium through which sound is traveling. For a given frequency, speed will determine the wavelength: the greater the speed, the shorter the wavelength. Period is the time taken for one cycle and is determined by frequency. Medium does not affect the period. Velocity = frequency × wavelength and period = 1/wavelength.
The first best action to take is to increase output power. This will brighten the overall image. If the image is still dark, then the receiver gain should be increased.
Multifocusing will decrease temporal resolution by decreasing the frame rate, whereas all the others will improve temporal resolution by facilitating an increase in the frame rate.
Sound travels faster in a medium with low density and high stiffness.
Aliasing and range specificity are properties of pulsed wave Doppler. Continuous wave Doppler is not associated with range ambiguity. Continuous wave Doppler will also permit recording of higher velocities than pulsed wave Doppler as it is not limited by the PRF as transmitted ultrasound is continuous.
41. As transducer frequency increases, backscatter strength:
C. Does not change
42. If an echo arrives 39 µs after a pulse has been emitted, at what depth should the reflecting object be on the scan line?
A. 3 cm
B. 6 cm
C. 1 cm
D. None of the above
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