Obtaining Good Echo

8/6/2019 Obtaining Good Echo

http://slidepdf.com/reader/full/obtaining-good-echo 1/6

Oh-Echo ch01.tex V1 - July 20, 2006 6:14 P.M. Page 1

1How to Obtain a Good

Echocardiography

Examination: UltrasoundPhysics, Technique,

and Medical Knowledge

The burgeoning technologic revolution of the past two

decades hasproduced a continuousevolutionin thedefini-

tion of a complete and comprehensive echocardiographic

evaluation (Fig. 1-1). Echocardiography is now a fully FIG1.1

grown tree. It has numerous clinical applications, with var-

iousforms of ultrasoundtechnologybeing usedthroughout

the entire field of cardiovascular medicine. This mature ul-

trasound tree has grown from a seed planted more than

50 years ago. Since then, the tree has been trimmed and

nourished carefully by many pioneers to serve the needs of

patients and clinicians.

In 1954, Edler and Hertz (1) of Sweden were the first

to record movements of cardiac structures, in particular,

the mitral valve, with ultrasound. In the early 1960s in

the United States, Joyner and Reid (2) at the University of

Pennsylvania were the first to use ultrasound to examine

the heart. Shortly afterward, in 1965, Feigenbaum and

colleagues (3) at Indiana University reported the first

detection of pericardial effusion with ultrasound and

were responsible for introducing echocardiography into

the clinical practice of cardiology. However, M-mode

echocardiography produced only an ‘‘ice pick’’ view of the

heart;two-dimensional (2D) sector scanning, developed in

the mid-1970s, allowed real-time tomographic images of

cardiacmorphologyand function(4). Thefirstphased array

2Dsector scan atMayo Clinicwasmade onMarch17, 1977.

Although the development of Doppler echocardiography

paralleled that of M-mode and 2D echocardiography from

the early 1950s, it was not used clinically until the late

1970s. Pressure gradients across a fixed orifice could

be obtained reliably with blood-flow velocities recorded

by Doppler echocardiography. Two groups, Holen and

colleagues (5) and Hatle and colleagues (6), should be

credited for introducing Doppler echocardiography into

clinical practice.

Numerous validation studies subsequently confirmed

the accuracy of Doppler echocardiography in the assess-

mentof cardiac pressures.Therefore, theDoppler technique

made echocardiography not only an imaging but also a

hemodynamictechnique. On thebasisof theDoppler con-

cept,colorflowimaging wasdeveloped inthe early1980sso

that blood flow could also be visualized noninvasively (7).




2 Chapter 1

Figure 1-1 Echocardiography has become a mature tree thathas numerous branches and is still growing. CFI, color flowimaging; ICUS , intracardiac ultrasonography; I-Op, intraoperativeechocardiography, IVUS , intravascular ultrasonography;TEE , trans-esophagealechocardiography;3D/4D, three- and four-dimensionalechocardiography.

Another ingenious modification of Doppler echocardio-

graphy was tissue Doppler imaging (TDI), which allows

echocardiographers to record myocardial tissue velocity

and to measure the extent of myocardial deformation as

strain(8,9). Thesemeasurements providea sensitive assess-

ment of systolic and diastolic function and are becoming a

standard componentof a comprehensive echocardiography

examination. Widespread clinical use of transesophageal

echocardiography (TEE) began in 1987 (10), and the

subsequent development of intravascular and intracardiac high-frequency transducers has permitted extraordinarily

detailed imaging and hemodynamic assessment of the car-

diovascular system. Most recently, three-dimensional (3D)

echocardiography has become a reality. It provides a more

realistic depiction of cardiovascular structures and more

accurate volumetric quantitation (11,12).

With these technologic advances, the application of

echocardiography has been spreading into numerous clin-

ical areas, including the evaluation of diastolic function,

stress echocardiography, intraoperative echocardiography,

fetal echocardiography, contrast echocardiography, intrac-

ardiac imaging, and vascular imaging. The size of the

ultrasound unit is becoming smaller, and some units

can be hand-carried to the patient’s bedside (13,14). We

are fortunate to have this versatile diagnostic modality to

provide reliable structural, functional, and hemodynamic

information about the cardiovascular system of our pa-tients.

ULTRASOUND AND TRANSDUCER

Echocardiography uses ultrasound to create real-time

images of the cardiovascular system in action. Ultrasound

represents sound waves with a frequency of 20,000 Hz or

A Time

Period

Figure 1-2 Diagram of a sound wave. A, amplitude.

more. All sound waves (Fig. 1-2) are characterized by the FIG1.2

following seven variables (15): frequency ( f ), wavelength

(λ), period (p), speed (s), amplitude (A), power, and

intensity.

f = the number of cycles per second; 1 cps is 1 Hz.

λ = the length of one complete cycle of the sound; its

usual unit of measure is millimeters (mm).

s = the speed or velocity of sound waves through a

medium is equal to the product of f and λ (s = f • λ)

and is determined by the characteristics of the

medium. Speed is not affected by the frequency of

sound. The average speed of sound in soft tissue is

1,540 m/s.

p = the time duration of 1 cycle; hence, 1 s/ f = p or

f • p = 1.

A = the magnitude of a sound wave, the maximum

change from the baseline.

Power is the rate at which energy is transferred from a

sound beam, in watts (W), and is proportional to the

amplitude squared (15).

Intensityis theconcentration of energyin a sound beam

and equals power divided by its cross-sectional area.

Sound waves canbe combined to createone wave. Thus,twoin-phase (orsuperimposed) waves createa wavewith a

larger amplitude, and two out-of-phase (or mirror-image)

waves create a wave with a smaller amplitude or the two

waves cancel each other if they have the same amplitude.

This phenomenon is called interference (15). It is used

in pulse-inversion and pulse-modulation techniques for

harmonic imaging and contrast echocardiography.

At the start of an echocardiography examination, the

appropriate transducer is selected according to the type of

examinationand patient’s bodyhabitus. A higherfrequency

transducerprovidesbetter resolution, butit hasa shallower

depth of penetration. For the pediatric population, the

transducer frequency is usually 5 to 7.5 MHz (1 MHz =

1million cps), but for adults the transducer frequency at

the start of an examination is usually 2 to 2.5 MHz and

occasionally 5 MHz for patients with a thin chest wall.

The transducer consists of piezoelectric elements that convert electrical energy to ultrasound and vice versa.

Electrical energy is applied to the transducer in pulses

with a defined pulse repetition frequency (PRF in kilohertz

[kHz]), producing ultrasound waves at defined, regular

intervals of pulsed repetition period. The wavelength of

the ultrasound generated is related to the thickness of

the piezoelectric elements. The thinner the elements, the

shorter the wavelength. Because the product of wavelength




How to Obtain a Good Echocardiography Examination: Ultrasound Physics, Technique, and Medical Knowledge 3

(λ) and sound frequency ( f ) is the speed of the sound in

the tissue (λ • f = 1, 540 m/s), sound frequency is related

inversely to the thickness of the piezoelectric elements.

These transducer elements need to move to generate

multidirectional ultrasound beams. This movement can

be achieved mechanically or electronically. Although a

mechanical transducer can produce multiple imaging lines

from a small transducerarea,the ultrasoundbeam diverges

more the deeper it penetrates tissue. In an electronic

transducer, multiple piezoelectric elements are arranged

in a straight line and sound beams are steered and

focused electronically. Most of the current ultrasound units

have electronic steering, with phased stimulation of the

piezoelectric elements. Because image resolution is better with shorter wavelengths, a higher frequency transducer

produces an image with better resolution but shallower

penetration. Technology has advanced to the point that a

transducer contains 3,000 piezoelectric elements to create

a matrix transducer, which allows real-time 3D imaging.

In fundamental imaging, echocardiographic images are

created when the transducer receives reflected beams of the

same frequency as the transmitted beam, but the interface

between tissue and blood can be delineated better with

the reception of harmonic frequencies. Harmonic imaging

has developed directly from arduous attempts to improve

the ultrasound imaging of contrast microbubbles. When

contrast microbubbles are imaged, the bubbles resonate

and produce harmonic frequencies(i.e.,equivalent to mul-

tiple of thetransmittedfrequency).When theonly reflected

frequency received to create the ultrasound image is equal

to a multiple (2 f , 3 f , . . .) of the transmitted frequency,

images of contrast microbubbles are preferentially pro-duced (contrast harmonic imaging). Like microbubbles,

myocardial tissues are able to generate harmonic frequen-

cies, and harmonic imaging improves the delineation of

the endocardial border (tissue harmonic imaging). As a

result, harmonic imaging is usually the imaging modality

of choice not only for contrast echocardiography but also

for a standard echocardiography examination. Additional

modificationsof harmonic imaginginclude pulseinversion

and power modulation imaging, which improved resolu-

tion in contrast imaging.A limitation of harmonic imaging

in routine 2D echocardiography is the increased sparkling

qualityto theultrasound image andthe increasedthickness

of the endocardial border. If the image quality is not opti-

mal in spite of all measures, including harmonic imaging,

then a contrast agent should be injected intravenously to

improve the definition of the endocardial border. Because

intravenous accessis required,a qualified memberof an in-travenous team should be available to start an intravenous

line as soon as contrast echocardiography is needed.

SCREEN DISPLAY AND KNOB SETTINGS

How best to display echocardiographic images on the

screen is a personal choice and should be choreographed

Figure 1-3 Still frame of a typical echocardiography monitorscreen. It is essential for the screen to display the patient’sidentification, blood pressure (BP ), and cardiac rhythm. The typeof transducer, field depth, color map, and other machine settingsare also displayed. In the example here, the BP was 120/52 mmHg, with a wide pulse pressure. Aortic valve shows doming (arrow )during systole (a break in the ECG at the bottom indicates thetiming of the image on the screen), with moderately severe aorticregurgitation that explains the wide pulse pressure. ‘‘H3.5 MHz’’indicates harmonic imaging with a 3.5-MHz transducer. Field depthis 160 mm (this information is important in stress echocardiographyand other quantitative studies for which the same depth isdesired for all images). ‘‘MI’’ indicates mechanical index, whichis an essential function in contrast echocardiography. ‘‘Store inprogress’’ indicates that the echocardiographic images are storeddigitally while the phrase is shown on the screen; thus, desiredimages need to be maintained during this period. HR , heart rate.

according to the clinical objectives of the examiner.

The following should be shown on the screen: the

patient’s identification, blood pressure at the time of theexamination, and a sharp electrocardiographic tracing with

prominent R and A waves (Fig. 1-3 and 1-4). Depth, size,

FIG1.3

FIG1.4

and gain settings of the ultrasound images need to be

adjusted frequently during the examination. To develop

an initial impression of the overall cardiac structure and

Figure 1-4 Initial parasternal long-axis view with an imagingdepth of 24 cm (240 mm on screen) demonstrating a large pleuraleffusion (PL) andpericardialeffusion(PE ). Lesionsin thedescendingaorta (*) can also be appreciated with a long imaging depth. LA,left atrium; LV , left ventricle; RV , right ventricle.




4 Chapter 1

function, theexaminationof an adultpatient usuallybegins

with a depth of 20 to 25cm and a widesector (90 degrees).

This also gives an idea about any unusual extracardiac

structures (Fig. 1-4). After the initial view, adjust the field

depth to use the entire screen to demonstrate the intended

cardiovascular images. A zoom or regional expansion

selection (RES) function should be used frequently to

visualize a region of interest in more detail. The zoomed

image is also betterfor making quantitative measurements,

with less intraobserver and interobserver variability. When

quantitative measurements are made, review the acquired

image in a cine loop format to identify a frame at a specific

timing of a cardiaccycle. Examples area mid-systolicframe

to measurethe diameter of theleftventricularoutflowtract,an end-systolic frame to measure the size of the left atrium,

and an end-diastolic frame to measure thewall thickness of

theleftventricle. Afteran overview,specificareasneedto be

imaged and it may be necessary to decrease the sector size,

which will improve temporal resolution by increasing the

frame rate. The gain of the image is controlled by overall

gainand regional gain(by time gaincompensation [TGC]).

As sound waves travel through a medium (e.g., tissue

or blood), the intensity weakens or attenuates. The degree

of attenuation is expressed in decibels (dB). Absorption

represents a conversion of sound energy to anotherform of

energy and is the major reason for attenuation. Therefore,

attenuation is determined by ultrasound frequency and

tissue depth. Attenuation is also greater for high-frequency

sounds, which result in higher absorption and more

scatter. Total attenuation is calculated by multiplying the

attenuation coefficient by the length of imaged tissue. TGC

allows amplification of ultrasound beams from deeper depths because different amplitudes of ultrasound signals

are produced when received from different depths. More

TGC is required for higher frequency transducers, which

create more attenuation. Compression also reduces the

differences between the smallest and largest amplitudes

of ultrasound images by reducing the total range without

altering the signal ratio.

Once 2D images are optimized, color flow imaging

is turned on to visualize the intracardiac blood flow

characteristics and to identify any turbulent flow within

the heart. Occasionally, color flow imaging demonstrates

hemodynamic or structural abnormalities that are not

readily apparent with 2D echocardiography alone. When

color flow imaging is used to show a regurgitant jet,

the color map aliasing velocity should be set as high

as possible (by moving the velocity scale up as far as

possible). The color gain should be increased to the point that it just begins to create background noise and then

decreased to the level that optimizes color flow imaging

of blood flow. The size of the color flow sector should be

optimized because the frame rate for color flow imaging

is inversely proportional to the area of imaging. The

location and size of color flow imaging can be adjusted

according to the objectives of the examination. If 2D

or color flow imaging (or both) identifies an area of

concern, a further quantitative assessment is made, such as

measuring the size of the lesion, calculating the area of the

stenotic or regurgitant orifice, or calculating the pressure

gradient. Even without the presence of obvious structural

or functional abnormalities, several areas of the heart need

to be interrogated to assess systolic and diastolic function.

Therefore, a pulsed wave Doppler examination follows

and complements color flow imaging. A pulsed wave

Doppler examination of the left ventricular outflow tract

andthe mitralleaflettipsis routinelyperformedto calculate

strokevolume and to assess diastolic function, respectively.

Other relatively routine pulsed Doppler examinations

includethe right ventricular outflow tract, pulmonary vein,

hepaticvein, upperdescending aorta,and abdominal aorta. A comprehensive echocardiography examination should

include a continuous wave Doppler examination of the

descending aorta to assess for the presence of coarctation,

especially in patients who have hypertension or a bicuspid

aortic valve. Another important area of a pulsed wave

Doppler examination is the mitral anulus, but the Doppler

mode needs to be changed to TDI.

Pulsed wave Doppler has been modified to record

velocityfrom thetissues which is lower in absolute velocity

but higher in amplitude. When TDI or myocardial imaging

is selected, higher tissue velocities are filtered out and

only lower tissue velocities, usually 5 to 20 cm/s, are

recorded. Because of the higher amplitude, the gain needs

to be decreased when the examination is switched from

regular pulsed wave Doppler imaging to TDI. TDI has

numerous applications (see Chapter 4). It is essential in

evaluating cardiac function (systolic and diastolic) and

the timing of cardiac events, and it is useful in assessing mechanical dyssynchrony among different regions of the

left ventricle (16,17). Myocardial strain and strain rate

can be derived from TDI (18). Tissue tracking and tissue

synchronization imaging (TSI) have been developed to

allow echocardiographers to assess the pattern and timing

of myocardial contraction readily with color imaging of

tissue Doppler velocities.

Duringa Doppler examination, therecording of velocity

is optimized by selecting or adjusting the velocity scale,

gain, baseline position, sweep speed, sample volume size,

and respiratory cycle. Recording space should be used fully

by selecting the highest velocity to be about 25% higher

than the obtained velocity. For example, if aortic stenosis

velocityis 4 m/s, it isbetter to havethehighestvelocity scale

setat 5 m/sinsteadof 7 m/s. Ifpulmonaryveinpeakvelocity

is 80 cm/s, it is better to have the Nyquist limit or aliasing

velocity at 120 cm/s instead of 200 cm/s. The baseline canbe shifted accordingly to demonstrate fully the obtained

or desired recorded velocity. Initial Doppler gain should

be increased to the point of background noise and then

decreased to produce optimal contrast with the recorded

signal.Colorization of the Doppler signalfrequentlymakes

the velocity sharper and is available on most machines by

pushing or selecting that option. The smallest possible

sample volume size (1–2 mm) usually is selected to record




How to Obtain a Good Echocardiography Examination: Ultrasound Physics, Technique, and Medical Knowledge 5

the pure velocity signal from the region of interest when

a slight variation in sample volume location can produce

different velocities, as in the left ventricular outflow tract

or mitral leaflet tips. However, a larger sample volume size

(3–5 mm)may benecessary toobtaina goodvelocity signal

from an area of interest that is small, as in a pulmonary

vein, or hepatic vein, or during tissue Doppler imaging of

the mitral anulus. Color flow imaging is helpful as a guide

for locating the ideal site for placing a sample volume.

When the region of interest moves with the cardiac cycle or

with respiration, a signal may be obtained by instructing

thepatient to hold hisor her breathor by slightly changing

the location of the sample volume during several attempts

to obtain the signal. The sweep speed is usually set at 50 mm/s for recording Doppler velocities, but when time

intervals are measured, it may be increased to 100 mm/s.

When multiple cardiaccycles need to be recorded together,

the sweep speed is reduced to 25 mm/s, especially when

the respiratory variation of Doppler velocity is assessed.

Because contrast can dramatically enhance weak Doppler

signals, it should be considered for improving the accuracy

of the examination of patients who have weak tricuspid

regurgitation or an aortic stenosis jet.

GOAL-DIRECTED AND COMPREHENSIVEEXAMINATION BY WELL-TRAINEDPERSONNEL

To perform a clinically pertinent echocardiography exam-

ination, it is important to have a strategy to determine

which of the numerous echocardiographic views and pa-

rameters will providethe optimalinformationfor assessing

the patient being examined. A strategy is best formulated

after the examiner (sonographer or physician) has a clear

understanding of the clinical problem or problems to

be evaluated. An echocardiography examination is highly

useful clinically and cost-effective when sound medical

knowledge is combined with sound technical skills, in-

cluding an understanding of ultrasound physics (15,19)

and the instrumentation, and interpretive skills. Some

start echocardiographic training by developing technical

expertise, and others approach this training after medical

school or residency. The miniaturization and portability

of echocardiographic machines may provide a strong

incentive for physicians to learn technical and interpre-

tive skills of ultrasonography during medical school (13)

or residency, akin to learning about heart sounds by us-

ing a stethoscope. Sonographers take a different road to

sonography, approaching echocardiography by learning

and perfecting technical skills. When a sonographer under-

stands which echocardiographic parameters are important

for a specific clinical diagnosis or for thepatient’ssymptoms

and why, he or sheis truly an accomplished echocardiogra-

pher. Therefore, the echocardiography examination shouldintegrate the medical and sonographic skills to produce

clinically relevant and visually attractive echocardiograms.

Physician training requirements for the performance

and interpretation of adult transthoracic echocardiography

examinations have been developed by the ACC/AHA Task

Force on competence in collaboration with the American

Society of Echocardiography, the Society of Cardiovascular

Anesthesiologists, and the Society of Pediatric Echocardio-

graphy (Table 1-1) (20). There are three levels of physician TAB1.1

training:

Level 1 training is defined as the minimal introduc-

tory training that must be achieved by all trainees

in adult cardiovascular medicine. This includes a ba-

sic understanding of the physics of ultrasound, the

fundamental technical aspects of the examination, car-

diovascular anatomy and physiology related to echocar-

diographic and Doppler imaging, and recognition of

simple and complex cardiac abnormalities and their

pathophysiology.

Level 2 training is the minimum recommended training

for a physician to perform echocardiography and to

interpret echocardiograms independently.

Level 3 training requires at least 12 months of training

that provides a level of expertise sufficient to enable a

physician to serve as director of an echocardiography

laboratory and to be directly responsible for quality

TABLE 1-1TRAINING REQUIREMENTS FOR THE PERFORMANCEAND INTERPRETATION OF ADULT TRANSTHORACIC

ECHOCARDIOGRAPHY EXAMINATIONS

Cumulative durationof training, mo

Minimum total numberof examinationsperformed

Minimum numberof examinationsinterpreted

Level 1 3 75 150

Level 2 6 150 (75 additional) 300 (150 additional)

Level 3 12 300 (150 additional) 750 (450 additional)




6 Chapter 1

control and for training sonographersand physicians in

echocardiography.

DIGITAL ECHOCARDIOGRAPHY

Digital echocardiography has profoundly changed and

improved the practice of echocardiography (21). It is

extremely convenient to acquire, transmit, and review

echocardiographic imagesdigitally. However, because only

a limited number of cardiac cycles usually are acquired, it

is essential for examiners to capture the most representa-

tive cardiac cycles. The number of cardiac cycles for image

acquisition can be adjusted. One cycle is most economicalfor storage space, but it may not be representative, espe-

cially if the underlying rhythm is not regular. Acquisition

of more cardiac cycles increases the time and storage space

of thestudy.If thepatient hasnormalsinusrhythm, a good

compromise is to capture two or three cardiac cycles. How-

ever, one cardiac cycle is better for stress echocardiography

because each view is compared with other images simul-

taneously side by side. If the patient has atrial fibrillation,

three to five cardiac cycles should be acquired.

Digitalimaging exposes theultrasoundsystem to therisk

of viruses, worms, and parasites of the electronic system.

To maintain the function of the machine and the security

of patient information, the ultrasound unit needs to be

protected against these electronic hazards.

ECHOCARDIOGRAPHY REPORT

Ideally, the echocardiographic reporting system should

be integrated with the digital imaging system. With this

integrated system, measured echocardiographic data are

transferred automatically to the echocardiographic report

and a still frame or even small clip of a real-time image can

be included.

The echocardiography report is the medium through

which an echocardiographer conveys not only the descrip-

tive findings of echocardiography but, more importantly,

the clinical implications and diagnostic considerations in

the context of the patient’s clinical presentation. A report

should do the following three things: 1) answer referral

questions; even if echocardiography does not demonstrate

any abnormality to explain the patient’s symptoms, the

absence of positive findings should be stated; 2) describe

unsuspected,but clinicallyimportant, findings; and 3) pro-

vide basic data for all patients. The basic data include thefollowing: left ventricular systolic and diastolic function,

left ventricular cavity size, wall thickness, right ventricular

size andfunction,valvular structureand function, left atrial

volume, anatomyof thegreatvessels, andpulmonaryartery

systolic pressure. Typical echocardiography reports from

the Mayo Clinic laboratory are shown in the Appendix.

REFERENCES1. Edler I, Hertz CH. The use of ultrasonic reflectoscope for the continuous

recording of the movements of heart walls. 1954. Clinical Physiology andFunctional Imaging, 2004;24:118–136.

2. Joyner CR Jr, Reid JM. Applications of ultrasound in cardiology and car-diovascular physiology. Progress in Cardiovascular Diseases, 1963;5:482–497.

3. Feigenbaum H, Waldhausen JA, Hyde LP. Ultrasound diagnosis of pericar-dialeffusion. JAMA: theJournalof theAmerican MedicalAssociation,1965;191:711–714.

4. Tajik AJ, Seward JB, Hagler DJ, et al. Two-dimensional real-time ultra-sonic imaging of the heart and great vessels: Technique, image orien-tation, structure identification, and validation. Mayo Clinic Proceedings,1978;53:271–303.

5. Holen J, Aaslid R, Landmark K, et al. Determination of pressure gradient in mitral stenosis with a non-invasive ultrasound Doppler technique. ActaMedica Scandinavica, 1976;199:455–460.

6. Hatle L, Brubakk A, Tromsdal A, et al. Noninvasive assessment of pressuredrop in mitral stenosis by Doppler ultrasound. British Heart Journal, 1978;40:131–140.

7. Omoto R, Kasai C. Physics and instrumentation of Doppler color flowmapping. Echocardiography, 1987;4:467–483.

8. McDicken WN, Sutherland GR, Moran CM, et al. Colour Doppler velocity imaging of the myocardium. Ultrasound in Medicine and Biology,1992;18:651–654.

9. Heimdal A, Stoylen A, Torp H, et al. Real-time strain rate imaging of the left ventricle by ultrasound. Journal of the American Society of Echocardiogra-phy, 1998;11:1013–1019.

10. Seward JB, Khandheria BK, Oh JK, et al. Transesophageal echocardio-graphy: Technique, anatomic correlations, implementation, and clinicalapplications. Mayo Clinic Proceedings, 1988;63:649–680.

11. Zamorano J, Cordeiro P, Sugeng L, et al. Real-time three-dimensionalechocardiography for rheumatic mitral valve stenosis evaluation: Anaccurateand novelapproach.Journalofthe American Collegeof Cardiology,2004;43:2091–2096.

12. Kuhl HP, Schreckenberg M, Rulands D, et al. High-resolution transthoracic real-time three-dimensional echocardiography: Quantitation of cardiac vol-umes and function using semi-automatic border detection and comparison with cardiac magnetic resonance imaging. Journal of the American Collegeof Cardiology, 2004;43:2083–2090.

13. Wittich CM, Montgomery SC, Neben MA, et al. Teaching cardiovascular

anatomy to medical students by using a handheld ultrasound device.JAMA: the Journal of the American Medical Association, 2002;288:1062–1063.

14. Seward JB, Douglas PS, Erbel R, et al. Hand-carried cardiac ultrasound(HCU) device: Recommendations regarding new technology: A report fromthe Echocardiography Task Force on New Technology of the Nomenclatureand Standards Committee of the American Society of Echocardiography.Journal of the American Society of Echocardiography, 2002;15:369–373.

15. Edelman SK, ed. Understanding Ultrasound Physics: Fundamentals andExam Review, 2nd ed. Woodlands, TX: ESP, 1994.

16. Ommen SR, Nishimura RA, Appleton CP, et al. Clinical utility of Doppler echocardiography and tissue Doppler imaging in the estimation of left ventricular filling pressures: A comparative simultaneous Doppler-catheterization study. Circulation, 2000;102:1788–1794.

17. Oh JK, Tajik J. The return of cardiac time intervals: The phoenix is rising.Journal of the American College of Cardiology, 2003;42:1471–1474.

18. UrheimS, EdvardsenT, TorpH, et al. Myocardialstrainby Doppler echocar-diography: Validation of a new method to quantify regional myocardialfunction. Circulation, 2000;102:1158–1164.

19. Kremkau FW, ed. Diagnostic Ultrasound: Principles and Instruments, 6thed. Philadelphia: W.B. Saunders, 2002.

20. Quinones MA, Douglas PS, Foster E, et al. American College of Cardiology, American Heart Association, American College of Physicians-AmericanSocietyof Internal Medicine,AmericanSocietyof Echocardiography,Society of Cardiovascular Anesthesiologists, Society of Pediatric Echocardiography. ACC/AHA clinical competence statement on echocardiography: A report of

the American College of Cardiology/American Heart Association/AmericanCollege of Physicians-American Society of Internal Medicine Task Forceon Clinical Competence. Journal of the American College of Cardiology,2003;41:687–708.

21. Hansen WH, Gilman G, Finnesgard SJ, et al. The transition from an analog to a digital echocardiography laboratory: The Mayo experience. Journal of the American Society of Echocardiography, 2004;17:1214–1224.

Documents

Obtaining Good Echo