EM: Block 1 Flashcards
What is the simple way to describe Dx US and what’s an example?
US signals assume a ? speed during travel through mediums
Pulse-echo principle- Sonar
Relative propagation
How is relative distance determined by US?
How are sound waves formed by the US?
Time elapsed for echo to return after hitting object
Electric current passes through transducer crystals
Define Piezoelectric effect
US calculations are made based on the assumption sound waves travels at the same speed through all tissues which is ? fast
Pressure-Electricity: generates constant high frequency, longitudinal, mechanical sound to be measured
1540m/s
Define Depth
How does this correlate to what is seen on the screen?
Time for returning echo relative to transducer distance
Louder echo= brighter pixels
Define Sound Waves
Define US
? units are used for Dx purposes
Repeated mechanical pressure wave through medium
Sound w/ frequency >20K Hz
2-15M cycles/sec (2-15MHz)
Define Amplitude
This unit is AKA ?
This unit correlates to ?
Peak wave pressure (height)
Loudness
Intensity of returning Echo
Loud= large amplitude
Soft= small amplitude
Define Period
Define Frequency
Time required for one complete cycle
Number of times wave is repeated per second
US spend 99% of their time conducting ? function
Define Pulse
Listening
1% of time generating waves
Period of wave generation
What is the relation to transducer frequency and image quality and when are they used
Higher= Inc resolution, dec tissue penetration
Linear: superficial structures/procedural guidance- vascular access, ocular US
Lower= dec resolution, inc penetration
Curved/Linear probe- bone Fxs
Define Velocity
What is the relation to this part of US and imaging
Speed of sound wave
Closer= better propagation
Travels faster in bone than soft tissue
Less dense molecules (gas) slows sound (vacuum)
Define Wavelength
What is the equation to determine this
Distance traveled/second
WL= propogation speed/frequency
When does attenuation begin/end
What factors can affect it
Pulse generation through round trip path until returns, recorded as echo
Lack of- fluid, bright
Wavelength Number of interfaces Degree of homo/heterogeneity Medium Tissue type/density
US travels best w/ the least ? such as through ?
This explains why ? procedure is done for OB
Attenuation
Homogenous fluid filled
Transabdominal US of uterus/ovaries w/ filled bladder, creates acoustic window to posterior anatomy
Attenuation occurs MC by ?
Reflection- wave redirected back to source; foundation of US
Scattering- beam hits interface smaller/irregular than bean
Absorption- acoustic to thermal energy (therapeutic US)
Refraction- redirection of sound wave when crossing medium boundaries
US should evaluate anatomy at _* to maximize structure reflection
Therapeutic US uses ? principle of US
90*
Absorption, not used for Dx US
What are the different modes on US and what are they used for
Curvilinear, LF probe:
B: brightness, converts amplitude of returning echo to 2D image
Used by most of EM
Phase Array probe-
M: motion, simultaneous B-mode and the waveform
What is used to view/assess fetal heart rate w/ US in the ER
Define Doppler
M-mode, less energy than Doppler
Interpretation of frequency shifts (train noises)
Towards= high frequency
Away from= low frequency
Doppler displays ? two pieces of info
What does Color Doppler use to produce images
Flow direction
Velocity
Pulse-Echo principle
Define Power Doppler
Define Echogenecity
Amplitude/strength of motion, better for slow flow/low volume states (torsion)
Amplitude of signal reflected from structure compared to amplitude reflected from surrounding structures
Define Hyperechoic
Define Hypoechoic
More echogenic/inc amplitude (brightness)
Less echogenic/less amplitude
What is the leading cause of MisDx w/ US
What can be the benefit of this cause of mis-Dx
Image artifacts
Some artifacts= pathology
What are 4 causes of artifacts
Define Shadowing
Attenuation/refraction
From w/in PT
Operator error
External sources
Sound hits highly reflective surface, returned w/ little energy w/out continuing to deeper structures
Clean Shadows can be caused by ?
Dirty Shadows can be caused by ?
Ribs Gallstones Calcified structures
Acoustic mismatch at tissue/air interface, normally bowel gas
What causes posterior acoustic enhancement
This phenomenon can be used to confirm presence of fluids where?
Sound waves passing through low attenuation, increased energy= inc echogenecity posterior w/ less attenuation
Joints
Tissue necrosis
Anesthetics after injection
The presence of ? is the enemy to US
Why?
Gas
Difference in density disperses sound waves
Define Reverberation artifacts
Why are these bad?
Sound bounces of two highly reflective objects causing brigh arcs in equidistant intervals
Obliterates B-mode image distally (lungs)
Define Mirror Artifacts
Why are these bad?
Objects appearing on both sides of a strong reflector; diaphragm during FAST
NO pathology
Duplication of structures leading to incorrect interpretation
Define Side Lobes
Acoustic power is AKA ? and relates to the ? produced by transducers
Lower intensity beams originating at angles to primary beam, results in false info (oblique line/acoustic echo)
TVUS
Output- amplitude produced by transducer
Wave amplitude- determine brightness/quality
Increasing acoustic power results in ?
Acoustic power is directly related to ?
Higher amplitude, stronger return echoes that increase contrast between light/dark areas
Intensity
Define ALARA
Define Gain
As Low As Reasonably Achievable
Control to adjust brightness w/ acoustic power
Difference between Power and Gain
P: changes brightness by changing strength of sound entering body
G: inc amplification of signals after echoes have returned to transducer
Define Time Gain Compensation
What is the most frequently used knob on US
Adjustment of brightness at different depths; near/far fields
Depth
What are the two reasons to adjust depth
When is the zoom function most useful
Greater depth= smaller structures, fit more on display
Inc depth= longer listening to collect data
Measuring small structures-
Need to magnify one section to focus on deeper structures, w/out changing number of pixels
Define Cine Loop
Define Footprint
Last several seconds of image saved for re-review
Area that sound waves leave and return to transducer; larger better for deeper
Low frequency curved transducers have a ? footprint and are used for ?
High frequency curved transducers are used for ?
Linear array transducers are used for ?
Large
Deep: thorax abdomen bladder
Endocavitary scans (vag/rectal)
Superficial structures w/ high frequency
What are phases array transducers used for?
What are the land marks for internal jugular access?
Echos, small footprint= easy intercostal imaging
SCM and Clavicular
What are the land marks for femoral access?
What are complications from US line placement
Inguinal ligament
Femoral artery
Arterial/vessel puncture
Bleeding
PTx
Hemothorax
What two vessels are preferred for peripheral access
What type of transducer is used?
Basilic/Cephalic
Linear
What is a screening test to eval abdominal trauma instead of an EFAST
What has a better specificity and thus, the DxTest of choice in trauma centers
Dx Peritoneal Lavage
CT
What are the disadvantages of doing a FAST
Operator dependent
Interpreting difficulties if obese/gaseous PT
Inability to differentiate hemorrhage from ascites
Can’t eval retroperitoneum as well as CT
What are the indications to do a FAST exam
FAST can identify what 3 parts about found fluids
Blunt/penetrating trauma Undifferentiated HTON Subacute torso trauma Trauma w/ pregnancy Pediatric trauma
Presence Amount Location
FAST exams are particularly helpful in what blunt trauma scenarios
Hemodynamically unstable
Unreliable PE due to intoxication, distracting injury, CNS injury
Unexplained HOTN and equivocal PE
When are FASTs conducted for penetrating trauma
What are the 5 eFAST windows
Uncertain immediate surgery
Multiple wounds
Uncertain trajectory into pericardium, lower chest or epigastrium
RUQ LUQ Cardiac Pelvis Chest
?mL of fluid in abdomen/chest is needed for visual identification w/ US
How much is needed in the for visualization on CXR?
250mL/20mL
50-100 in upright chest
175 in supine chest
What is the most beneficial assessment for a PTs w/ penetrating torso trauma and HOTN?
What are the classic PE findings for this exam?
Cardiac FAST
Distended neck veins
HOTN
Muffled heart tones
How is the pneumothorax exam conducted
What is the MC normal sign when looking for PTx?
High freq linear probe on 2nd intercostal space, MCL x 4-5 respiration cycles
Lung sliding- excludes PTx
When is the transducer dot NOT pointing to the L
Define Seashore Sign
Define Stratosphere Sign
Cardiac- to PTs head/L hip
Parasternal long axis
+ lung sliding
Barcode sign- no lung sliding
What is the alternating point between Seashore and Stratosphere sign
If clinician can see ? and ?, PTx can be confidently excluded
Lung point sign- when lung contacts parietal pleura w/ inspiration
Lung sliding
B lines
If clinician sees ?, suspicion of PTx exists and is increased if ? is seen
What does the lung points sign indicate
No lung sliding or B lines
A-lines
100% specific for PTX and correlates to radiographic size
RUQ view
LUQ view
Phased array, marker to head
Phased array, marker to head/knuckles to bed
Subxyphoid view
Alternate cardiac view
Phased array, marker to PTs right
Phased array, marker to PTs L hip
Bladder views
Lung views
Transverse: marker to R
Sagittal: marker to head
Linear probe, marker to head
What is the gold standard for Dx of cardiac abnormalities
What are the primary indications for conducting a focused cardiac US
Echocardiography
Cardiac arrest Massive PEs Volume statue/fluid response Pericardial effusion/tamponade LV structure/function Unexplained HOTN Guide emergency pacing
PTs presenting w/ ? get cardiac US
What views is the most useful for POC cardiac US and why?
Chest pain
Dyspnea
Trauma
Syncope
Subcostal 4 chamber view, No interference w/ thoracostomy, CPR, subclavian line insertions or intubations
What are four ways to increase poor quality images from subcostal 4 chamber views
US gel
Shallow angle to chest wall
Move transducer to R to use L liver lobe as a window
Move off xiphoid/over intercostal space to image PT w/ barrel chest/large AP diameter
When using sub-xiphoid view, where are the chambers being seen
What is on top of all of these landmarks
Top L: RV
Bottom L: RA
Top R: LV
Bottom L: LA
Liver
How is the parasternal long axis view obtained
If done correctly, what structures will be on the right side of the images?
Align US plane w/ long axis of LV
Transducer perpendicular to chest wall L to sternum w/ indicator to L hip
AV/MV
Proximal aorta/LA
How is the parasternal short view obtained
What are the 3 views obtained
Rotate transducer 90* clockwise from parasternal long view position
Aortic valve- mercedes sign
Mitral valve- fish mouth view
Papillary muscles
What are the 4 views obtained with the apical 4 chamber view
What type of view is the apical view?
When is this view preferred?
Base Mitral Apex Papillary
Coronal- 4 chambers on one plane
Assessing LV function and size
When using the IVC view, what finding is consistent w/ low right sided filling pressures
Where is the transducer indicator pointing during this view
Collapses >50%
PTs head
Screening PoC US are done on PTs >50y/o w/ pain or ? Sxs?
Elective Tx of AAAs is suggested when they’re what size
Groin Flank Abdomen Back
Dizziness/Syncope
Unexplained HOTN
Cardiac arrest
5.5cm or larger
What is the triad for ruptured AAA
Pain Palpable mass HOTN
Pain is most consistently found
Palpating mass- unreliable
HOTN- not always found in ruptures
Most AAAs rupture in ? direction causing ? effect
What is the max external diameter considered normal?
Retroperitoneum
Transient tamponade
<3cm
When the celiac artery branches off of the aorta, what is the sign
What is the sign called when passing the SMA
Seagull sign
Mantle sign
What probe is used when assessing for AAAs
What is the MC reason structures wouldn’t be seen
Curvilinear probe
Gas
How is an AAA scan conducted
What are the 3 measurements taken
Transverse view- from prox (Celiac/SMA) to distal (bifurcation)
Prox: level to Celiac/SMA
Mid: between xyphoid and bifurcation
Distal: umbilicus, above bifurcation
What is done during the sagittal view of the AAA exam
AAA US Summary
Video only, no measurements
Curvilinear- prox to dist
Transverse: marker to PT R, Measure 3- prox, mid, dist
Saggital: marker to PT head
When is an US of the eye warranted
What is the normal measurement of the optic nerve
HA/AMS
Acute vision changes
Trauma
Inc ICP
3mm
How do you differentiate retinal or vitreous detachment
Retinal- attached posterior, vertical flow
Vitreous- not attached at disc, horizontal flow
What causes a “comet-tail” artifact when doing an eye US?
Ocular Summary
Doppler w/ metal debris
LInear transducer w/ 2 orthogonal planes: Transverse- marker to PT R Sagittal: marker to PTs head Measure ONSD at 3mm from retina, N=<5mm >5mm= Inc ICP (+20mmHg)
Where are most DVTs Dx
What is the gold standard imaging test for Dx DVTs?
Proximal veins of LE
US of prox LE
Most algorithms for Dx DVTs use ? combos of info
Flow Chart
Clinical suspicion
D-dimer
Compression US
DCT Deck- Slide 7
Where do we start the US assessment for DVTs?
What structure is the compression assessed at?
Junction of great saphenous/ common femoral
Inguinal ligament
Where is the popliteal vein located?
Where does the popliteal vein trifurcate?
Adjacent/superficial to popliteal artery, mid fossa
Pop-on-top
Distal popliteal fossa
DVT summary
Linear transducer
Curvilinear if obese w/ marker to PT R
Supine, frog leg w/ 30* reverse trandelenberg
Scan prox femoral/popliteal veins, compress q1cm x 10cm
US are more sensitive than CXR for Dx of ? Fxs
How do foreign bodies that have been retained for >24hrs appear on US?
What can be done to improve ability to find/visualize foreign bodies
Rib
Halo from edema/pus
Local anesthetic adjacent to foreign body
If an abscess is seen on US but has color flow, what does that mean?
What appearance doe cellulitis have on US?
Necrotic lymph node
Cobblestoning
Define Anisotropy
What type of foot print is seen at the top of the screen for a HF transducer?
What type of foot print is seen if a LF probe is used?
Not 90* causing tendon to appear dark/torn when not
Flat across
Curved shape into screen
2D imaging can be AKA ? or ?
Where is Morrison’s pouch and what is it AKA?
What is the name of the fascia that surrounds the pouch?
B-mode
Gray Scale imagines
Between Liver/Kidney
Hepatorenal recess
Gerota’s fascia- anterior
(Zuckers on posterior)
The intensity of US beam, or the amount of energy, determines the ? of the US
How do images appear if the near or far fields are over/under gained?
Bioeffects
Near, top half is darker if under gained:
Far field, lower half is darker and under gained
Sector size of the linear transducer is identical to ?
Phased array transducer is sometimes AKA ?
Footprint of the transducer
Cardiac probe
When attempting peripheral IV access, normally ? vein is used
What does E-FAST stand for
Basilic vein
Extended Focused Assessment w/ Sonography in Trauma
If PT has Neg-FAST exam and are not stable, what is the next step?
It is important to capture the pole of ? on ? side
Repeat/continue assessment
R sided, inferior kidney pole
What structure makes visualization of fluids appear first on LUQ view
Where would this be seen
Splenocolic ligament
Sub-diaphragm
Free fluid in abdomen is usually going to pool on ? side
What valve leaflet is being assessed during the PSL view
L side
Anterior leaflet of Mitral valve
? bladder view is more sensitive
What probe is used for the abdominal and pneumothorax scans
Saggital
R/L/Pelvic- phased array
Pneumo- linear
What are the parts of a Sky Ocean Beach sign
What part is lost during a PTx
Sky- soft tissue
Ocean- hyper echoic pleura
Beach- motion artifacts
Beach
Subxyphoid view transducer and position
Phased array, PTs R
Alt: PSL, phased array, PTs L hip
Bladder view transducer and position
Phased array
Transverse: PTs R
Sagital: PTs head
Lung view transducer and position
Linear probe, PTs head
What is the best view to ID mod/large pericardial effusion
What is the best view to ID gross cardiac activity/stand still
Subcostal
Subcostal or Parasternal
What is the best view to assess heart chamber size
What view is best for assessing 2d EF
Apical 4 chamber
Subcostal PSL or Apical
What view is the best for measuring E-point septal separation to estimate EF
What view is best for evaluating gross valve motions
PSL
Parasternal long or short
What view is best for assessing volume status by IVC size/collapsability
Subcostal sagittal view
What is the name of the sign seen in the PSA view
Mercedes sign of aortic valve
Where is the indicator pointing during the apical 4 chamber view
Where is the proximal IVC located?
PT R hip
Subcostal midline saggital view: posterior to liver into RA
Where is the transducer pointing during the IVC view
All cardiac US views use ? probe
PTs head
Phased array
Sub-Xyphoid View
PTs R:
RV
RA LV
LA
PSL View
PTs L Hip:
RV
LV Ao
LA
PSS View
PTs R hip:
Mercedes Fish Papillary
4AC View
PTs R Hip at PMI:
RV LV
RA LA
What was the rule about seeing a vein that crosses over in the abdomen
One time AAA screenings are done for men between ? age that have tobacco Hx
Above SMA= splenic
Between SMA/Aorta= L renal going to IVC
65-75y/o
? is most mis-Dx as AAA
Type of artifact
Kidney stone
Shadow Edge Artifact Gas Reverberation Acoustic enhancement Mirroring Side lobes
Septal thickness measured w/
MSK probe
What is NOT seen on PSS view
PSL
Linear
???
How do you adjust for PAE
Sector size larger than transducer
Gain
Curvillinear
Plot end point separation
Parasternal separation
On abdominal exam, IVC takes on ? appearance
M mode
Tear dropped
Sagittal view of aorta, what is the sequence of structures branching off
How can you decrease optic echoes that are creating difficulty Dx borders of optic nerve sheath
Celiac artery
SMA
Dec gain due to PAE
How could a subtle lens dislocation be accentuated on US?
Consensual pupillary constriction
Well’s Score
S/Sxs of DCT- 3
PE most likely Dx- 3
Tachy- 1.5
Immobile/Post-op x 4wks- 1.5
Prior DVT/PE- 1.5
Hemoptysis- 1
Ca/Tx x 6mon- 1
Low <2 High>6
Unlikely 0-4
Likely 5 or +
How do you know if you’re looking at PTs R or L leg on US during DVT scan
R: GSV runs medial to CFV
Arteries to L side of screen
