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WINFOCUS’ BASIC ECHO (WBE)
Mark P. Hamlin, MD, MS
Associate Professor of Anesthesiology and Surgery University of Vermont College of Medicine
Co-Director of Surgical Critical Care Medical Director of Respiratory Care Services
Fletcher Allen Health Care Burlington, Vermont
Basic Ultrasound Physics and Knobology
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• A basic overview of sound
• Understanding types of transducers, and basic modes
• Understanding common controls across platforms
• Optimizing images
Outline
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• Transverse
• Longitudinal
Types of Waves
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Sound is a Longitudinal mechanical wave
Compressions an rarefac@ons of molecules in gas, liquid, or solid
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• Transverse
• Longitudinal
Types of Waves
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Sound is a Longitudinal mechanical wave
Compressions an rarefac@ons of molecules in gas, liquid, or solid
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• Audible sound 20 Hz to 20 KHz
• Ultrasound > 20 KHz
• Diagnostic Ultrasound 1 MHz to 20 MHz
Sound Waves
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• High Frequency (MHZ) gives better resolution, but limited tissue depth of view
• Low Frequency gives better tissue penetration
Frequency and Penetration
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Ultrasound Wave Interaction With Tissues
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Tissue 2
Attenuation
Refraction
Scattering
Tissue 1
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• Specular=mirror reflectors-‐ANGLE is CRITICAL FOR SPECULAR REFLECTORS
(Image demonstrates apparent gaps in vessel wall on sides due to lack of reflec@on)
• ScaOer=diffuse, irregulari@es in surface are larger than wavelength of wound wave
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Ultrasound Wave Interaction With Tissues
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Tissue 2
Attenuation
Refraction
Scattering
Tissue 1
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• Specular=mirror reflectors-‐ANGLE is CRITICAL FOR SPECULAR REFLECTORS
(Image demonstrates apparent gaps in vessel wall on sides due to lack of reflec@on)
• ScaOer=diffuse, irregulari@es in surface are larger than wavelength of wound wave
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• Period
• Frequency
• Wavelength
• Propagation speed
• 1540m/s in soft tissue, vs. 330 in air
Speed and Time
Characteristics of Sound Waves
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Period-‐Dura@on of one cycle 0.1-‐0.5 microsecs for US
Wavelength =Velocity (1540 m/s) X Frequency (in mHZ)
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• Amplitude
• Power
• Intensity
Bigness Characteristics of Sound
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• Power-Amount of energy transferred to tissues total
• Intensity-Concentration of energy
Power/Intensity
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Bioeffects on @ssues regulate limits of power output by medical US imaging devices.
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• Power-Amount of energy transferred to tissues total
• Intensity-Concentration of energy
Power/Intensity
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Bioeffects on @ssues regulate limits of power output by medical US imaging devices.
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Transducer Design
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Uncouples internal components from case
Piezoelectric crystal
Absorbs unnecessary sound
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• Piezo Electric crystals create sound when electricity applied!Energy created varies based on how fast and how strong electrical impulses are sent to crystals
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Transducer Types
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• Traditional-One sending/one receiving, or stepwise (L to R)
• Phased array-smaller footprint, but triangular image to see wide area
Non-phased array- shape of beam matches shape of probe end!Phased, by timing the energy releases the combined wavefronts can be shaped
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• Sound enters tissue
• Transducer sends sound and receives reflection, machine measures time, and since velocity known (1540) it plots distance
• Brightness=amount of reflection, acoustic characteristics of tissues
Creating an image
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Display Modes
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• A-mode
• (history)
• B-mode
• “2D”
• M-mode
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Knobology Rules
• “Platform vary, but basics don’t” • Button location will vary based on manufacturer design,
so don’t worry if you cannot find them right away
• More important to know basic approach
• “Continue to learn ‘knobs’ as you scan” • Understand basic knobology before scanning.
• Acceptable to review knobology as you are scanning
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Knobology Rules
•Platform manipulation and probe handling are key to:
•Achieving technical know-how
•Achieving interpretation expertise
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!device footprinting evolving...
so know ‘pros’ & ‘cons’
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!device footprinting evolving...
so know ‘pros’ & ‘cons’
Portability
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!device footprinting evolving...
so know ‘pros’ & ‘cons’
Portability
Power / Capability
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!Preparing to scan
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!Preparing to scan
Turn power on
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Ensure Proper Connections
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Ensure Proper Connections
Ensure properly connected probe adapter.
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Ensure Proper Connections
Connect ECG cable, either via patient monitor or applied 3-lead ECG.
Ensure properly connected probe adapter.
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!Select Your Transducer
Select ‘Cardiac’ transducer
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!Common Transducers
‘Cardiac’ ‘Deep penetration probe’
‘Linear’ ‘superficial penetration probe’
‘Curved’ ‘moderate penetration probe’
Different vendors have different probes. It is important to know your vendor’s probes, their usages, limitations, etc.
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Common Transducers‘Cardiac’ 5-1MHz, phased array 35cm scan depth
‘Linear’ 13-6MHz, 25-mm broadband 6cm scan depth
‘Small curved’ 8-5MHz, curved array 10cm scan depth
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Common Transducers‘Cardiac’ 5-1MHz, phased array 35cm scan depth
‘Linear’ 13-6MHz, 25-mm broadband 6cm scan depth
‘Small curved’ 8-5MHz, curved array 10cm scan depth
Remember: !• ↓ Frequency = ↑ penetration = ↓ resolution.!
• ↑ Frequency = ↓ penetration = ↑ resolution.
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Enter patient data
Pa#ent Preferable to enter pa@ent info before image storage.
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Patient data entry and storage
Create patient •Use keyboard •HT, WT, BP to
obtain indexed values.
Enter name, dob, etc.!Ht, weight to obtain indexed values. Such as cardiac index!Same page typically accessed to export images
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!Before you scan... review platform
keyboard
options
2D Doppler M-mode
gain
Image manipulation/ calculations
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!Before you scan... review platform
keyboard
options
gain
Image manipulation/calculations
2D Doppler M-mode
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!Be aware of options
Op@ons may change with mode selec@on.
options
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Adjust sweep speed
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Adjust sweep speed
AV interrogation via M-mode
S l o w e r
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Adjust sweep speed
AV interrogation via M-mode IVC collapsibility
FasterS l o w e r
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Gain
•This is a receiving function
•Does not impact how much energy is transmitted to patient (i.e. power)
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!Adjust gain & time gain compensation (TGC)
• Near field!
• Strong reflected signals
• Far field!
• Weak reflected signals
TGC allows compensation for Attenuation of signal due to absortion
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!Adjust gain & time gain compensation (TGC)
• Near field!
• Strong reflected signals
• Far field!
• Weak reflected signals
Time Gain Compensation (TGC)!
•Corrects varying depths of intensities in imaging field
•Adjust TGC to:
1.Decrease in the near field 2. Increase in the far field
TGC allows compensation for Attenuation of signal due to absortion
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!Adjust gain & time gain compensation (TGC)
• Near field!
• Strong reflected signals
• Far field!
• Weak reflected signals
Gain!• OVERALL amplification of returning ultrasound signal received from ALL depths
Time Gain Compensation (TGC)!
•Corrects varying depths of intensities in imaging field
•Adjust TGC to:
1.Decrease in the near field 2. Increase in the far field
TGC allows compensation for Attenuation of signal due to absortion
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!Extremes in tgc & gain
Too bright high amplitude
Too dark low amplitude
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!Extremes in tgc & gain
Too bright high amplitude
If gain too high, noise amplified, so differentiation lost
Too dark low amplitude
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graded tgc.....Gradual near-to-far field adjustment
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graded tgc.....Gradual near-to-far field adjustment
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gain affects image interpretation
Optimal gain
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gain affects image interpretation
Optimal gain
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gain affects image interpretation
↑ (‘over’) gain ↓ (‘under’) gain
Signal “blooming” vs. Signal “dropout”
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!gain affects image interpretation
↑ (‘over’) gain ↓ (‘under’) gain
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!gain affects image interpretation
Extent of left pleural effusion?
↑ (‘over’) gain ↓ (‘under’) gain
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start scanning
2D •Two-dimensional imaging •Most systems default to 2D at startup
Freeze •Regulates between active and still image
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2D-live vs. 2D-freeze
2D ‘live’ image
2D ‘frozen’ or ‘still’ image
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2D-live vs. 2D-freeze
2D ‘live’ image
2D ‘frozen’ or ‘still’ image
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M-mode
M-mode Temporal measurement of object(s) movement away and toward transducer
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IVC collapsibility via M-Mode
IVC via 2D time
Distance
M-mode
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IVC collapsibility via M-Mode
IVC via 2D time
Distance
M-mode
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!Doppler modes: pulse wave (PW),
color flow (CF), continuous wave (CW)
PW •transducer emits ultrasound in pulses
•Lower velocity •Velocity depth measurable
CW • transducer emits & receives
continuously • High velocity • Velocity depth indeterminate
CF (CFM) •Type of PW, transducer emits pulses
•Flow direction/ dynamics color coded
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CW • transducer emits & receives
continuously • High velocity • Velocity depth indeterminate
PW •transducer emits ultrasound in pulses
•Lower velocity •Velocity depth measurable
CF (CFM) •Type of PW, transducer emits pulses
•Flow direction/ dynamics color coded
Doppler modes: pulse wave (PW), color flow (CF), continuous wave (CW)
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Anatomy of Pulsed Ultrasound Beam
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Receive Time Listening
Time Off Time
Pulse repetition period Pulse repetition frequency
Duty Factor=Pulse repetition
period
Pulse Duration
Transmit Time
Talking Time On Time
Pulse Duration Pulse Length
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Pulse Wave Doppler
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Pulse Wave Doppler
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Pulse Wave DopplerPlace your ‘sample volume box’ over area of interest.
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Pulse Wave Doppler
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Pulse Wave DopplerTrace LVOT VTI + adjust HR using trackball.
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Color Flow Doppler
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow DopplerAdjust ‘Region of interest’ for color display
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
small region + shallow depth = ⬆temporal resolution
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
Adjust ‘Color gain’ amplifies signal
!By convention, Blue is Away from transducer-watch for “invert”
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Color Flow Doppler
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Color Flow Doppler
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Color Flow Doppler
Adjust ‘Color scale’: range of velocities displayed
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Color Flow Doppler
Detecting low velocities requires lower color scale
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!Continuous Wave Doppler
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!Continuous Wave Doppler
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!Continuous Wave Doppler
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!Continuous Wave Doppler
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!Continuous Wave Doppler
Move cursor using ‘trackball,’ mark with ‘Set’ button
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!Continuous Wave Doppler
V = 4.20m/s P =( 4v2) ~ 70.67mmHg
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Depth Controls the maximal imaging display distance.
Zoom Live image amplification of defined area.
Trackball & Set •Ball controls cursor movement, sector size, window rotation. •Set locks & unlocks.
Adjust depth, sector size, zoom...
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Effects of Imaging Depth
• Image size
• Depth change affects reduction/enlargement of displayed structures ➙ affects evaluation
•Frame rate
• Time per second an image is updated
• ↑ Depth of structure = ↑ US penetration needed = ↑wait-time between pulses = ↓ frame rate
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•Temporal resolution
•Ability to evaluate rapidly moving structures
•Directly related to frame rate
•For optimal temporal resolution keep imaging depth just beyond region of interest
•Lateral resolution •Ability to evaluate structures perpendicular
to US beam
•↑ Depth of structure = ↓ lateral resolution
Effects of Imaging Depth
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•Sector size • Usually starts with ‘wide & deep’ sector for broad
view
• Wide sector size = ↓ frame rate & ↓ temporal resolution
• If fast moving structure, narrow your sector or consider M-mode
•Zoom • Magnification without change in resolution
Effects of Imaging Depth
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Real-Time Imaging
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‣ Frame rate
‣ Temporal resolution - line density - sector size
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• Absolute amount of info returning slows procession
• Depth of viewing determines frame rate
• USE THE NARROWEST AND SHORTEST WINDOW YOU CAN
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!Sector Width
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!Sector Width
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!Sector Width
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Calculations
Worksheet •Compiles data & calculations. •May edit, delete, save.
Measure •Brings up cardiac calculations folders. •Some devices, use ‘trackball,’ ‘cursor,’ and ‘set’ to access.
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!Calculations & Measurements
Cardiac calculation •Open folder •Using ‘cursor,’ select specific measure or calculation.
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!Calculations & Measurements
Cardiac calculation •Open folder •Using ‘cursor,’ select specific measure or calculation.
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!LVOT Measurement
D = 1.43 cm
Measurements parallel to beam are most accurate, try to orient imaging to obtain this, example measure LVOT from PSLAX not Apical view.
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!LV 2D Measurements
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Options: image optimizing techniques
options
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•Frequency (freq)
•↑ freq = ↓ penetration = ↑ resolution of proximal structures
• If deep structures, will need ↓ freq.
• If superficial structures, will need ↑ freq.
•For example, obese patient may need ↓ freq.
Options: image optimizing techniques
Higher Frequency=greater attenuation in tissues
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!Frequency
↑ freq = ↓ penetration ↓ freq = ↑ penetration
Freq 3.6 MHz
Freq 1.5 MHz
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!Frequency
↑ freq = ↓ penetration ↓ freq = ↑ penetration
Freq 3.6 MHz
Freq 1.5 MHz
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B-color
Grey color scale
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B-color
Grey color scale
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B-color
Blue color scale Orange color scale
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!Summary
• Remember how to choose an appropriate ultrasound transducer
• Apply the basics of an ultrasound platform to any echocardiography device
• Practice basic image optimizing techniques
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• Ultrasound beam reflection is the basis for the image
• High frequency=high resolution but low penetration depth
• Image quality and temporal resolution are at odds
• Optimizing gain and imaging settings is essential for interpretation
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Take home messages!
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Questions?
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