12/10/2014 introduction to ultrasound pfn: somusl01slides.jsomtc.org/somusl01/somusl01.pdf ·...
TRANSCRIPT
12/10/2014
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Slide 1JSOMTC, SWMG(A)
Introduction to UltrasoundPFN: SOMUSL01
Hours: 1.5
Instructor:
Slide 2JSOMTC, SWMG(A)
Terminal Learning Objective
Action: Communicate knowledge of ultrasound
Condition: Given a lecture in a classroom environment
Standard: Received a minimum score of 75% on the written exam IAW course standards
Slide 3JSOMTC, SWMG(A)
Reason
As a SOF medic you will often find yourself in an austere environment with limited resources available to aid in diagnosis and treatment of your patients. Ultrasound is becoming more readily available on the battlefield and is a tool that can enhance your diagnostic and treatment capabilities.
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Slide 4JSOMTC, SWMG(A)
Agenda
Identify ultrasound applications
Identify the basic principles and physics of ultrasound
Identify ultrasound transducer function, characteristics, use and types
Define ultrasound terminology
Identify operating controls of the M‐Turbo and Nanomax
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Ultrasound Applications
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Scope of PracticeE‐FAST in trauma
AbdomenChest
Musculoskeletal/soft tissueFracture/dislocations
VascularAccessBlood flow/DVT
OcularFB/retinal detachmentRetrobulbar hemorrhage
GenitourinaryBladderEctopic pregnancyScrotal pain & swelling
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Basic Principles and Physics of Ultrasound
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Basic Principles
Ultrasound machine probes create sound waves
Generate waves of vibration from the probe that travel through the tissue of the patient and return to the probe
Received by the machine and interpreted to provide images on screen
Different tissue densities affect the ultrasound beam
Slide 9JSOMTC, SWMG(A)
Basic Principles
The intensity of the returning echo determines the brightness of the image on the screen
Strong signals
White (hyperechoic) images
Weak signals or lack of signal all together
Black (hypoechoic) images
Tissue densities determine the many shades of gray in between
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Grayscale Concept
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Physics
Diagnostic ultrasound uses sound waves in the frequency range 2‐20 MHz
Key properties of sound waves:
Frequency
Wavelength
Amplitude
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Physics ‐ Parallel Concepts
Conceptually, ultrasound is similar to a laser range finder
Sound waves sent from the transducer bounce off the object and return
The ultrasound machine calculates distance to the object from the round‐trip time, and creates a grey scale image on the screen
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What Does it Mean to Me?
Lower frequencies image deep structures, but sacrifice resolution
Higher frequencies provide better resolution, but sacrifice depth
HIGHER FREQUENCYShorter wavelength
LOWER FREQUENCYLonger wavelength
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Ultrasound Transducer Function, Characteristics, Use and Types
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Transducer Function
Footprint of transducer
Electrically excitable crystals
Beam is ~ 1mm
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Transducer Characteristics
The workhorse of the US machine
Sends out sound waves 1% of the time
Listens for echoes 99% of the time
Frequencies are fixed or adjustable
“Footprint” is what touches the patient
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Transducer Use
Hold the probe lightly in your hand
Like a pencil
Small movements equal big changes
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Transducer Use
Probe marker facing the patient’s right or head
Exceptions
Cardiac and procedures
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Probe Indicator ‐ Leading Edge
Generally to the patient’s head or right side
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Transducer Choices
Curvilinear Array (Curved Probe)
Freq range (2‐5 MHz), 30cm depth
Abdomen, FAST, AAA
Linear Sequential Array (Linear Probe)
Freq range (5‐10 MHz), 9cm depth
Vascular access, pneumothorax, regional anesthesia
Phased Array (Sector or Cardiac Probe)
Freq range (1‐5MHz), 35cm depth
Cardiac, E‐FAST, AAA
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Rotating
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Rocking/Fanning
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Sliding
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Ultrasound Terminology
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Screen Orientation
Far Field
Near Field
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Image Quality ‐ The 4 P’s
Use Plenty of gel
Perpendicular to structure
Pressure (right amount)
Scan in multiple Planes
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Gel and Water Stand‐offs
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Ocular Stand‐off
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Ultrasound Transmission Gel
Use lots of it!
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Scanning Planes
Sagittal Axial
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Coronal Plane
Divides body or organ into anterior and posterior axis
Used in cardiac and OB/GYN applications
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Image Quality ‐Machine
Depth: Place the object of interest in the center of the screen
Machine will autofocus to the center of the screen giving it the best resolution
Right side markings show depth in cm
Gain: brightness of the image
Can be adjusted for each scan
Be careful not to use too much or too little gain
Autogain
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Depth
Too Little Too Much
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Depth ‐ Just Right!
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Gain
Too Little Too Much
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Gain ‐ Just Right!
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Image Resolution
Spatial resolution
The ability to distinguish two separate objects close together
Temporal resolution
The ability to accurately locate structures or events at a specific point in time
Can be improved by decreasing depth & narrowing the sector angle
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Scanning Modes
B‐mode:
Brightness mode
Nearly all of your scans will begin and stay in this mode
Organs appear differently based on their tissue densities
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Scanning Modes
M‐mode:
Motion mode provides a reference line on screen
Shows motion towards and away from probe at any depth along that line
Used for detecting fetal heartbeats and pneumothoracies
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Slide 40JSOMTC, SWMG(A)
B‐Mode/M‐Mode of Heart
M-modeB-mode
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Scanning Modes
Spectral doppler
Color flow doppler
Blue ‐ away
Red ‐ towards
Power doppler
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Attenuation
As the ultrasound beam travels through the body, it looses strength & returns less signal
Certain tissue densities cause this effect:
Slow: bone, diaphragm, pericardium and air = bright (hyperechoic) images
Moderate: muscle, liver and kidney = gray (isoechoic) images
Faster: blood, ascites and urine = darker (hypoechoic) images
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Artifacts
Posterior enhancement
Reverberation
Edge artifact
Shadowing
Mirror image
Comet tail
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Posterior Enhancement
Hyperechoic streaking distal to interface of anechoic structure
Not a true artifact
Allows visualization of structures located distal to hypoechoicstructure which is called an acoustic window
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Reverberation
Bouncing of signal from two reflective surfaces close together
Very useful artifact
Presence indicative of normal lung motion
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Comet Tail
Primary use for detecting normal pleural motion, foreign body, needle location
ABSENCE of this artifact is present in PTX secondary to wide apposition of parietal and visceral pleura
Long axis (LA) slide of the chest wall
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US Images of FB Left and Right
Thorn
Comet Tail
BB
Thorn Projectile
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Edge Artifact
A distal shadow from the edge of spherical fluid filled structures
Not a form of “shadowing”
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Shadowing
Anechoic streaking distal to surface with high reflectivity (blocks the US beam transmission)
Anything that blocks the beam
Air
Stones
Bones
Foreign body
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Mirror Image
Appearance of same image on both sides of highly reflective surface such as the diaphragm with liver seen on both sides (normal)
Misinterpretation by machine of signal timing puts image where it thinks it should be
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Operating Controls of the M‐Turbo and Nanomax
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M‐Turbo Keyboard
ABCDEFG
HIJK
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Main ScreenPt. Info
Resolutionsetting
Orientationmarker
On screen options
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Nanomax Main Screen
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Questions?
Slide 56JSOMTC, SWMG(A)
Terminal Learning Objective
Action: Communicate knowledge of ultrasound
Condition: Given a lecture in a classroom environment
Standard: Received a minimum score of 75% on the written exam IAW course standards
Slide 57JSOMTC, SWMG(A)
Agenda
Identify ultrasound applications
Identify the basic principles and physics of ultrasound
Identify ultrasound transducer function, characteristics, use and types
Define ultrasound terminology
Identify operating controls of the M‐Turbo and Nanomax
12/10/2014
20
Slide 58JSOMTC, SWMG(A)
Reason
As a SOF medic you will often find yourself in an austere environment with limited resources available to aid in diagnosis and treatment of your patients. Ultrasound is becoming more readily available on the battlefield and is a tool that can enhance your diagnostic and treatment capabilities.