Ultrasound Physics, Terminology, and Knobology Flashcards
What does POCUS stand for and what specific questions does it answer?
POCUS = Point Of Care Ultrasound
To answers questions like
is there pericardial effusion
is there intraperiotneal fluid
are there glasstones
is there hydronephrosis
Advantages of POCUS (ultrasound)
- no ionizing radiation
- noninvasive
- portable
- easy to use - FAST
- inexpensive
- easily repeated at bedside, thereby enhancing clinicians’ ability to perform serial reassessments of pts
Disadvantages of POCUS (ultrasound)
- operator dependent
- limitations = poor image quality with fat and air
Physics: wavelength and frequency relationship and effect on tissue penetration
Wavelength is INVERSELY related to frequency
HIGHER frequency = SHORTER wavelength = don’t penetrate deeply into tissue
lower frequency = longer wavelength = CAN penetrate deeply into tissue
Low frequency vs high frequency probes -what can be viewed, what are disadvantages
LOW frequency probes:
- good for DEEP structure imaging ( long wavelengths)
- penetrate deeply but POOR RESOLUTION
- for ABDOMINAL structures = aorta, kidney, gallbladder
HIGH frequency probes:
- good for SUPERFICIAL structure imaging (short wavelength)
- poor penetration but GOOD RESOLUTION
- for SUPERFICIAL structures = blood vessels, breast tissue, thyroid tissue
Compare the different types of probes
- LINEAR (aka “vascular”) probe
- higher frequencies and resolution
- for superficial scanning and procedural guidance
- preserved lateral resolution - Sector/phased array (aka “cardiac”) probe
- lower frequencies
- small footprint for intercostal scanning
- high frame rates - Curvilinear (aka “curved array” or “abdominal”) probe
- ever lower frequencies
- large field view
- large footprint
What is FAST scan and what is it used to detect?
FAST = Focused Assessment with Sonography for Trauma
It’s a standard set of ultrasound examinations for the evaluation of injured patients
Purpose: detect free intraperitoneal fluid, pericardial fluid, pleural fluid, hemothorax/ pneumothroax in trauma pts
*not a definitive test = can NOT rule out intraabdominal injury
What structures are shown in the image; what area would you scan to see this?
Liver top, Kidney bottom, separated by morrison’s pouch (white line); diaphragm very top of image (white lines)
Scan RUQ at edge of lower lateral thoracic cage
Define echogenicity and list the three types w/description
Echogenicity = ability of structure to reflect sound waves or echoes
- Anechoic - complete absence of returning sound waves; looks black; ex. fluid
- Hypoechoic - structures that have few echoes and appear darker than surrounding tissue
- Hyperechoic - echogenic structures, appear brighter than surrounding tissue
What is the image and viewing what structure causes this?
ACOUSTIC SHADOWING!
- common artifact; occurs when sound waves encounter reflective surface
- hyperechoic or anechoic area appears deep to structure
- occurs b/c few sound waves can get behind or around structure ex. gallstones
What is the image, you see it with viewing what structure
POSTERIOR ACOUSTIC ENHANCEMENT
- common artifact; deep to an anechoic structure
- inc in echogenicity posterior to an anechoic structure b/c sound waves lose very little energy traveling through a fluid filled structure
- ex. bladder
What is the image, you see it with viewing what structure
EDGE ARTIFACT
- sound bent by structure in parallel with ultrasound beam and does not return to probe, resulting in appearance of shadow behind the surface
- arrowheads show edge artifact from wall of gallbladder
- seen w/imaging fluid-filled structures (ex. gallbladder)
What is the image
MIRROR ARTIFACT
- you see the “mirror image” of structure you’re imaging; distal in relation to the probe
- usually seen at the bottom or periphery of the scree
What is the image
REVERBERATION ARTIFACT
- seen w/ line placement
- multiple intermittent line “echoes” running parallel to actual needle
Describe movements of the probe
Sliding: moving along skin w/o changing angles
Rocking/ “heel toe”: tilt probe along axis of indicator (indicator is the notch the prob)
Fanning/sweeping : title problem perpendicular to axis of indicator
Rotating/twisting: rotate probe about axis of the cord w/o tilting
