Term
|
Definition
| Includes that portion of the sound spectrum having a frequency greater than 20,000 cycles per second (KHz), which is considerably above the audible range. |
|
|
Term
| Identify the differences between specular, and scattered echoes |
|
Definition
Specular: produced by reflectors that are large relative to ultrasound wavelength (i.e. endocardial surface of the left ventricle). Such targets reflect a relatively greater proportion of the ultrasound energy in an angle dependent fashion. Spatial orientation and shape of the reflector determine the angles of specular echoes.
Examples:endocardial, epicardial surfaces, valves, and pericardium
Scattered: targets that are small relative to the wavelength of the transmitted ultrasound, sometimes referred to as Rayleigh scatters. The resultant echoes are diffracted or bent and scattered in all directions. Because the percentage of energy returning to the transducer from scattered echoes is considerably less then that resulting from specular interactions, the amplitude of the signals produced by scattered echoes is very low. Scattered echoes contribute to the visualization of surfaces that are parallel to the ultrasonic beam and also provide the substrate for visualizing the texture of gray scale images. |
|
|
Term
| Discuss the difference between phased-array and linear-array transducers |
|
Definition
Phased-array - consist of a series of small piezoelectric elements interconnected electronically. In such transducers, the wave front of the beam consists of the sum of the individual wavelets produced by each element. By manipulating the timing of excitation of individual elements, both focusing and steering are possible. If all elements are excited simultaneously, each one will produce a circular wavelet that combines to generate a longitudinal wave front that is parallel to the face of the transducer and propagates in a direction perpendicular to that face. Electronic transmit focusing of the beam is also possible.-Transducers that employ anular phased-array technology have the capacity to focus in both dimensions, resulting in a compact, high-intensity beam profile.
Linear array - Such transducers have a rectangular face with crystals aligned parallel to one another along the length of the transducer face. Unlike phased-array transducers, the elements are excited simultaneously so the individual scan lines are directed perpendicular to the face and remain parallel to each other. This results in a rectangle-shaped beam that is unfocused. Linear-array technology is often used for abdominal, vascular, or obstetric applications. |
|
|
Term
| List the variables involved in real-time sector scanning |
|
Definition
-Depth of examination
-Frame rate
-PRF
-Angle of sweep
-Line density |
|
|
Term
| Identify the components of resolution |
|
Definition
Spatial resolution (p. 19): the smallest distance that two targets can be separated for the system to distinguish between them.
a. Axial resolution: refers to the ability to differentiate two structures lying along the axis of the ultrasound beam (i.e one behind the other)
b. Lateral resolution: refers to the ability to distinguish to reflectors that lie side by side relative to the beam.
Contrast Resolution (p. 20): the ability to distinguish and to display different shades of gray within the image. This is important both for the accurate identification of borders and for the ability to display texture or detail with in the tissues.
Temporal resolution (p. 20):or frame rate, refers to the ability of the system to accurately track moving targets over time. It is dependent on the amount of time required to complete a scan, which in turn is related to the speed of ultrasound and the depth of the image as well as the number of lines of information within the image. (the greater the number if frames per unit of time the smoother the real time image) Main reason M-Mode is still useful. |
|
|
Term
| List the different echocardiographic controls and define what each one does |
|
Definition
Time Gain Compensation (TGC)(p. 27 HF, pg. 35 WB): (Depth gain compensation) Allows returning signals from different depths to be selectively suppressed or amplified to provide relatively uniform signal strength. The purpose of this device is to compensate for the loss of ultrasonic energy (i.e., attenuation) as the beam propagates through the body. The primary purpose is to enhance the far echoes and suppress near echoes, without creating distortion or artifact.
Reject Control (p. 27 HF, p. 35 WB): eliminates noise and undesired weak echoes. Control that eliminates low amplitude pulses produced by weaker echoes that return from grating lobes or multiple scattering from within the tissue. This scattering is called “acoustic noise.”
Compression (p. 36 WB)(p. 27 HF): The process of decreasing differences between the smallest and largest echovoltage amplitudes. Done by logarithmic amplifiers that amplify weak inputs more than strong ones. (Changes the sharpness of the image)Through the technique of nonlinear compression, a wide dynamic range can be handled for processing by the scan converter. |
|
|
Term
| Discuss the factors that influence the components of spatial resolution |
|
Definition
Frequency or wavelength (p. 19)- The primary determinants of axial resolution are the frequency of the transmitted wave, and more importantly, its effect on pulse length. Higher frequency is associated with shorter wavelength, and the size of the wave relative to the size of the object determines resolution. In addition to frequency, pulse length or duration also affects axial resolution. The shorter the train of cycles is, the greater the likelihood that two closely positioned targets can be resolved. Because a higher frequency and/ or broad bandwidth transducer delivers a shorter pulse, it is also associated with higher resolution.
Width of the beam (p. 20)- Lateral resolution is affected by many factors: The width or thickness of the interrogating beam, at a given depth, is the most important determinant. Ideally, the ultrasonic beam should be very narrow to provide a thin “slice” of the heart. Lateral resolution diminishes as beam width (and depth)increases.
Gain (p. 20)- the amplitude, the degree of amplification, of the received signal. When the gain is low, weaker echoes from the edge of the beam may not be recorded and the beam appears narrow. If system gain is increased weaker and more peripheral targets are recorded and beam width appears greater. Thus, to enhance lateral resolution, a minimal amount of system gain should be employed. |
|
|
Term
| Discuss the relationships between frequency, wavelength, penetration and resolution |
|
Definition
Increase Frequency/ Decrease wavelength; therefore, you decrease penetration but increase resolution.
Decrease frequency/ increase wavelength; therefore, you increase penetration but decrease resolution. |
|
|
Term
| Describe the potential artifacts found in echocardiography to include: side lobes, reverberations, shadowing and near field clutter |
|
Definition
Side Lobes (p. 29): occur because not all the energy produced by the transducer remains within the single, central beam. Instead, a portion of the energy will concentrate off to the side of the central beam and propagate radially, a phenomenon known as edge effect. A side lobe may form where the propagation distance of waves generated from opposite sides of a crystal differs by exactly one wavelength. Side lobes are three dimensional artifacts, and their intensity diminishes with increasing angle. The artifact created by side lobes occurs because all returning signals are interpreted as if they originated from the main beam.(examples AV groove and the fibrous skeleton of the heart)
Reverberations (p.30): As the reflected ultrasound returns to the transducer, it is likely that a portion of the returning signal undergoes a second reflection. This portion of the acoustic energy again reflects off the far wall and is finally returned to the transducer. With each step, the signal becomes weaker but may still be within the range of detection by the transducer. Typically, a reverberation artifact that originates from a fixed reflector will not move with the motion of the heart. It appears as one or more echo targets directly behind the reflector, often at distances that represent multiples of the true distance. In some cases, the source of reverberations is not apparent.
Shadowing (p.30): opposite of reverberations. Results in the absence of echoes directly behind the target. Occurs when one attempts to visualize structures beyond a region of unusually high attenuation, such as a strong reflector. Acoustic shadow is created when no reflections are produced. (i.e. valves)
Near field clutter (p. 32): ringdown artifact. Arises from high –amplitude oscillations of the piezoelectric elements. This only involves the near field and has been greatly reduced in modern-day systems. Is troublesome when trying to identify structures that are particularly close to the transducer. (IE RV free wall, or LV Apex) |
|
|
Term
| Discuss the Doppler principle "Alignment" |
|
Definition
| Whereas echocardiography functions optimally when the beam and the target are at right angles, doppler equations rely on a more parallel alignment between the beam and the flow of blood |
|
|
Term
| What are the principles of Doppler echocardiography |
|
Definition
-Alignment
-Pitch and motion
-Frequency
-Doppler shift |
|
|
Term
| Discuss the Doppler principle "Pitch and motion" |
|
Definition
-If the source of sound is stationary, then the pitch or frequency of that sound was constant,
-Sound moved toward the listener, the frequency increased and the pitch appeared to rise.
-If the sound source was moving away from the listener; the frequency of the sound decreased relative to the listener and the pitch appeared lower. |
|
|
Term
| Discuss the Doppler principle "Frequency" |
|
Definition
-If the target is stationary, the frequency and wavelength of the emitted and reflected ultrasound are identical.
-If the target is moving toward the transducer, the reflected frequency is shifted upward proportional to the velocity of the target relative to the transducer.
-Movement of the target away from the transducer results in reflected ultrasound having a lower frequency than the emitted ultrasound, a downward shift in frequency.
-The increase or the decrease in frequency due to relative motion between the transducer and the target is referred as Doppler shift |
|
|
Term
| Discuss the Doppler principle "Doppler shift" |
|
Definition
-Depends on the transmitted frequency of the ultrasound, the speed of sound, the intercept angle between the interrogating beam and the flow, and, finally, the velocity of the target.
-The angle of incidence ()- only becomes significant beyond approximately 20 degrees.
-Doppler imaging is the opposite of echocardiographic imaging, because in echo a higher transducer frequency is desirable because it is associated with higher resolution. With Doppler imaging, a lower frequency is advantageous because it allows high flow velocity to be recorded.
-The primary job of the Doppler instrument is to measure the Doppler shift, and from this measurement, velocity can be calculated.
-The Doppler shift is defined as the difference in frequency between the transmitted and received or backscattered signal. |
|
|
Term
| Define pulsed and continuous wave Doppler and distinguish the advantages and disadvantages of each |
|
Definition
Pulsed wave (p. 34): short intermittent bursts of ultrasound that are transmitted through the body. Only “listens” at a fixed and very brief time interval after transmission of the pulse.
-Limitation- is the maximal velocity that can be accurately resolved. This occurs because of aliasing.
-Advantage- Interrogates the distribution of blood flow values within a relatively limited region.
Continuous wave (p. 36-37):simultaneously transmits and receives ultrasound signals continuously. One type of transducer employs two distinct elements: one to transmit and the other to receive. Alternatively with phased array technology, one crystal within the array is dedicated to transmitting while another is simultaneously receiving. Signal is not pulsed, range resolution is impossible and the reflected signals all along the ultrasound beam are sampled simultaneously.
-Disadvantage- It is impossible to know where along the sample beam that any recorded velocity signal arises.
-Advantage- Aliasing does not occur and very high velocities can be accurately resolved |
|
|
Term
| List the five basic types of Doppler techniques |
|
Definition
1. Continuous wave Doppler
2. Pulsed wave Doppler
3. Color flow imaging
4. Tissue Doppler
5. Duplex scanning |
|
|
Term
|
Definition
Spectral: (p.38) By digitizing a snapshot of Doppler shift information and then applying a complex mathematical technique called fast Fourier transform, thin instantaneous flow velocity spectrum can be displayed. At each instant, the range of velocities determines the width of the Doppler signal and the frequency distribution of each individual velocity is represented by the gray scale.
-(p. 38) Laminar flow has a narrow envelope of velocities, indicating that most of the blood cells travel over a narrow range of velocity.
-(p.38) Turbulence- both the direction and range of velocities increase, and this leads to a widening of the spectral pattern.
-(p.38) Distinction between laminar and turbulent flow can only be made in PW b/c in CW a narrow spectral envelope almost never occurs.
-(p. 37) Provides information of direction and velocity of flow, it is useful to display this information graphically by plotting instantaneous flow velocity against time.
-(p.37) Velocity is displayed on the vertical axis with flow toward the transducer above the baseline and flow away from the transducer below the baseline.
-(p. 47)The first Doppler format to be clinically used was a spectral display of the returning frequency shifts, which as noted previously, is converted to velocity on all modern clinical scanners. This is typically displayed with reference to a zero crossing line. Any signal above that line represents motion toward the transducer, and any signal below the line represents motion away from the transducer. The magnitude of the frequency shift is directly related to velocity by the Doppler equation.
-(p.47)Acquired through two different methods, continuous and pulsed wave. |
|
|
Term
| Discuss the principles of color flow imagine Doppler to include the presentation of laminar and turbulent flow |
|
Definition
(p. 38-39)
-Form of pulsed wave Doppler
-Uses multiple sample volumes along multiple raster lines to record the Doppler shift.
-Laminar- red (towards) the transducer, blue ( away from the transducer.
-The brightness of these primary colors encodes the magnitude of the the mean velocity.
-High variance (turbulence)
*coded green/ mosaic appearance
-By using a color reject threshold, only flow above a given velocity level is displayed as color. This limits the potential for “information overload”.
(p. 51)
-Color flow imaging is a variation of pulsed Doppler imaging and shares all its limitations.
-Evaluation of regurgitant valvular lesions and detection of intracardiac shunts
-Low Nyquist limit and lower frame rate
-The frequency shift at each site is converted into a color and then the pixel at the interrogation site encoded with that color.
-Traditional color flow maps encode negative velocities in varying shades of blue and flow toward the transducer in barying shades or red.
-Either the intensity or the hue of the individual color is then directly related to the magnitude of the Doppler shift, indicating velocity.
-Because of a relatively low Nyquist limit even normal physiologic flow velocities frequently exceed the Nyquist limit and aliasing occurs in which flow may be encoded in the opposite color. |
|
|
Term
| Discuss what information is needed to accurately quantify blood flow and to measure pressure gradients in echocardiography |
|
Definition
Quantifying blood flow: (p.216-217) -Time Velocity Integral: Individual velocities during the ejection phase must be sampled and then integrated to measure flow volume *Angle 0 will have a predictable effect on measured velocities. Aligning the ultrasound beam as close as possible to the direction of flow is critical if true velocity is to be measured. Misalignment between the ultrasound beam and flow can only result in underestimation of velocity, never overestimation *Pattern of blood flow where velocity is being measured will affect the accuracy of the Doppler equation. If a sample volume is placed within laminar flow the Doppler will record a clean signal or uniform velocity. Flow becomes increasingly disturbed or turbulent (i.e. less laminar) as the velocity increases or the cross-sectional area changes. The highest velocities and most laminar flow generally occur at the center of the profile. Fortunately, flow passing through a normal heart valve or the proximal great vessels tends to be laminar with a flat profile and is therefore suitable for quantitative analysis.
-Cross-sectional Area- measured at the same point, such as through one of the 4 cardiac valves. -Can be measured using M-mode or 2D -Largest dimension should be used because it most likely corresponds to the true diameter.
-Pressure gradients: (p.223-227)The flow velocity through a valve must increase as the valve area decreases. -Bernoulli Equation: P = 4v2
-Velocity proximal and distal to the stenosis -When the incident angle increases beyond 20 degrees, a significant error is introduced into the Doppler equation that results in underestimation of true velocity. To avoid this problem color doppler imaging can be used to visualize the blood flow, thereby facilitating proper alignment. -It should be emphasized that the maximal velocity should always be sought out and used for the calculation of gradient. |
|
|
Term
| Discuss the significance of contrast echocardiography and list some of the common agents |
|
Definition
-Contrast Echo (p.76): microbubbles, either purposely injected into the circulation or as a side-effect of an intravenous injection. (p.78-79)
Detection of right-to-left shunts by detection of contrast targets in the left heart remains a primary use of contrast echocardiography.
Left-to-Right shunts also can be detected if a negative contrast effect is noted in the right heart. Standard for the diagnosis of a patent foramen ovale.
Perfluorocarbon- based contrast enhances visualization of the LV border and provides increased accuracy for border detection, chamber volume determination, evaluation of regional wall motion, and detection of mural thrombi. Additionally, new contrast agents are capable of opacification of the LV myocardium. When used for this purpose, the contrast agent parallels myocardial blood volume and can be used as a marker of normal and abnormal perfusion. Finally, contrast agents can be used to enhance Doppler signals.
Contrast agents(p.76): gases containing air, perflurocarbons, agitated saline, surfactant, indocyanine green dye have been used to reduce surface tension and create a population of smaller, more stable microbubbles. Albumin( patient’s blood), saccharide particles. |
|
|
Term
| List the biologic effects of ultrasound |
|
Definition
-Pose minimal risks to the patient
-Newer applications and instruments may involve higher levels of energy, so that the potential impact of such approaches should be examined.
-Biological effects depend on the total energy applied to the region.
-Intensity of the ultrasound beam and the duration of exposure are an important factor. Produces heat.
-Cavitation- refers to the formation and behavior of gas bubbles produced when ultrasound penetrates into the tissue.
-Oscillatory, sheer, radiation, pressure, microstreaming, suggestions of changes that might occur at chromosomal level with developing fetus. |
|
|
Term
| List the standard size transducers for children, adults, and neonates and understand why they are appropriate |
|
Definition
For large thick chested individuals : 2.0-2.5 MHz
Children /small adults: 3.5 or 5.0 MHz
Infants/children: 7.0- 7.5 MHz |
|
|
Term
| Discuss patient positioning and transducer placement used for echocardiographic examinations |
|
Definition
-The echo exam is performed with the patient supine and/or in the left lateral decubitus position which allows for better visualization of the heart when gravity pulls it down from behind the sternum.
-Transducer placement: The American Society of Echocardiography for transthoracic imaging in the adult include the left and right parasternal locations, the cardiac apex, the subcostal window, and the suprasternal notch. |
|
|
Term
| List the normal variants found on 2-D echo for RA |
|
Definition
-Chiari network
-Eustachian valve
-Crista terminalis
-Catheters/ Pacemaker leads
-Lipomatous hypertrophy of interatrial septum
-Pectinate muscles
-Fatty material (surrounding the tricuspid anulus) |
|
|
Term
| List the normal variants found on 2-D echo for LA |
|
Definition
-Suture line following transplant
-Fossa ovalis
-Calcified mitral anulus
-Coronary sinus
-Ridge between LUPV and LAA
-Lipomatous hypertrophy of interatrial septum
-Pectinate muscles
-Transverse sinus |
|
|
Term
| List the normal variants found on 2-D echo for RV |
|
Definition
-Moderator band
-Muscle bundles/trabeculations
-Catheters and pacemaker leads |
|
|
Term
| List the normal variants found on 2-D echo for LV |
|
Definition
-False cords
-Papillary muscles
-LV trabeculations |
|
|
Term
| List the normal variants found on 2-D echo for AO |
|
Definition
-Brachiocephalic vein
-Innominate vein
-Pleural effusion |
|
|
Term
| Discuss the difference between two-dimensional, and Doppler exams |
|
Definition
2-D:
Ultra sound target - Tissue
Goal of diagnosis - Anatomy
Type of information - Structural
Optimal alignment - Perpendicular
Between beam and target
Preferred transducer - High
frequency
Doppler:
Ultra sound target - Blood
Goal of diagnosis - Physiology
Type of information - Functional
Optimal alignment - Parallel
Between beam and target
Preferred transducer - Low frequency |
|
|
Term
| Discuss how echocardiography can be used to monitor a variety of invasive procedures |
|
Definition
-Pericardiocentesis(p.663)
-Procedures with high frequency intracardiac probes (p.664)
-Procedures that involve crossing the atrial septum (mitral valvuloplasty, percutaneous ASD closure and atrial septostomy for severe PHTN)(p.664)
-Assist in placement of catheters (i.e. retrograde cardioplegia catheter)(p.657)
-Placement of an IABP (p.657)
-Placement of an occlusive balloon or perfusion device in the AO (p. 657) |
|
|
Term
| Discuss the method in which linear measurements are made |
|
Definition
| M-Mode -leading edge to leading edge, boundary defined as the leading edge of the reflective echo. |
|
|
Term
| Identify and define the points of a mitral valve M-mode, to include the B-bump |
|
Definition
B- bump: particular motion of the mitral valve that occurs in late diastole as the valve drifts shut with increasing LV pressure (Page 214)
E-wave: height correlates with transmitral flow and, in absence of significant MR, with LV SV. (Maximal early opening)(p. 141)
D-point: Onset of diastole and leaflets begin to separate in response to passive filling.
F-point: Marks the end of rapid/ passive filling and the leaflets are drifting towards each other
A-point: Peak leaflet separation following atrial contraction.
C-point: Where the leaflets co-apt the move gradually anteriorly |
|
|
Term
| Given the appropriate measurements, calculate ejection fraction and fractional shortening from a M-mode |
|
Definition
Ejection fraction= (SV/LVIDd) x 100
Fractional shortening= (LVIDd - LVIDs / LVIDd) x 100
(x 100 to convert from 0.XX to a percentage) |
|
|
Term
| Identify normal and abnormal patterns of mitral valve inflow with relation to the E and A waves |
|
Definition
Normal (Pg. 172)-Mitral E-wave exceeds the later flow, which occurs with atrial systole both in velocity and volume (E wave > A wave)
Age (Pg. 172-173)With advancing age, there is natural stiffening of the ventricle, which results in delayed relaxation. A progressive decrease in E-wave velocity and an increase in A- wave velocity with age so that the anticipated E/A ratio in a disease-free individual older than age of 60 is often less than 1.0.
Delayed relaxation:(Page 173) reduced E/A ratio.
Ventricular noncompliance with elevated diastolic pressure: (Page 173) exaggeratted E/A ratio with a pathologically short deceleration time, the so-called restrictive physiology pattern. |
|
|
Term
| Discuss the limitations in examining the right ventricle in echo |
|
Definition
-unusual crescent shape
-irregular endocardial surface
-complex contraction mechanism
-factors coupled with the location of the RV almost directly behind the sternum |
|
|
Term
| List the echocardiographic findings with right ventricular overload |
|
Definition
- (Pg. 206) Hypertrophy of the free wall and IVS (associated with the increase in the trabeculations of the RV walls
- (Pg. 207-208) Distortion of the shape and motion of the IVS- Flattening= abnormal pressure gradient between the left and the right ventricles. When right ventricular pressure is increased, this normal septal curvature is altered and the septum appears flattened and displaced toward the left ventricle. Flattening occurs in pressure overload in systole and diastole, with volume overload septal flattening is predominantly during diastole. The degree of septal flattening during systole and diastole can be useful to distinguish volume from pressure overload.
- (Pg. 209) Dilation of the RV |
|
|
Term
| Identify the best transthoracic view for measuring the right atrium |
|
Definition
-Apical four Chamber
-Subcostal view |
|
|
Term
| Discuss why stress echocardiography is used in echocardiography |
|
Definition
| - Determine future events: (Pg. 507) Wall motion, left ventricular function and mass are well established determinants of the risk of future cardiovascular events. - Identify new CAD prior to known MI: (Pg. 507)- positive finding is the detection of a new wall motion abnormality remote from the site of previous infarction. (Predict the location and extent of CAD). - Myocardial Viability/Revascularization: (Pg. 511,513) Assessment of myocardial viability after revascularization. - Preoperative (Pg 512) - Women: (Pg 513)- due to false negative stress tests some doctors prefer to combine their test with a stress echo. - Valvular Heart Disease:(Page 517)Assessment of severity of valvular heart disease |
|
|
Term
| List the potential risks involved in performing a transesophageal echo |
|
Definition
Topical anesthesia
-Allergic reactions
-Toxic methemoglobinemia
Conscious sedation
-Respiratory compromise/hypoxia
-Hypotension
-Paradoxical hypertension
-Paradoxical agitation
-Idiosyncratic reactions
Probe insertion: immediate
-Oral trauma
-Dental trauma
-Esophageal perforation
-Vagal reaction
Probe insertion: delayed
-Aspiration
-Tachycardia( Paroxysmal SVT, VT) |
|
|
Term
| Discuss the contraindications of transesophageal echocardiography |
|
Definition
Absolute- a. Recent esophageal trauma/surgery b. Recent esophageal bleed
Relative - Poorly cooperative patient
Esophageal pathology
-Severe dysphagia
-Esophageal stricture
-Diverticula
-Bleeding variances
-Cancer
Cervical spine disorders
-Atlantoaxial joint disorder
-Orthopedic conditions that prevent neck flexion |
|
|
Term
| Given a definition for A-mode, B-mode, or M-mode, identify the correct term |
|
Definition
A-mode: amplitude mode, the height of the spike corresponds to the amplitude of the returning echo.
B-mode: brightness mode, the intensity of the signal corresponds to the brightness of the dot.
M-mode: Motion mode, s single dimension of anatomy to be graphed against time |
|
|
