High Yield PTEeXAM Review Part 6-8 Flashcards
What is a normal DF range?
- 2 - 0.5%
i. e. Listening 99.8% of time
What is duty factor determined by?
Sound source only
What is duty factor inversely related to?
Depth
What is the Duty Factor % equation?
Pulse Duration* / *Pulse Repetition Period
How does the Pulse repetition frequency change with shallow vs. deep images?
Shallow = Higher PRF
Deep = Lower PRF
How does duty factor change with depth?
Shallow = Higher DF Deeper = Lower DF
What is the typical value of a pulse duration?
0.5 - 3.0 microseconds
What is the typical pulse repetition period?
0.1 - 1.0 ms
What is the typical pulse repetition frequency?
1 - 10 kHz
What is the typical spatial pulse length?
0.1 - 1.0 mm
During PWD echo, the frequency of the emitted beam is determined by what two things?
- Thickness of piezoelectric crystals
- Speed of propagation of sound in the crystals
What is the equation for resonant frequency?
Velocity of sound in crystal* / [*2 * thickness of the crystal]
Which ASD is more common:
Superior* sinus venosus VSD or an *inferior sinus venousus VSD?
superior = More common
What is a superior sinus venousus ASD associated with?
Anomalous Venous Drainage of the RUPV
What is a inferior sinus venousus ASD associated with?
Anomalous pulmonary venous drainage of a scimitar vein
Scimitar syndrome
Drains from hypoplastic RLL of the lung
Aortopulmonary collaterals
What 3 things does Scimitar syndrome have?
- Inferior Sinus venous ASD
- RLL hypoplastic lung with scimitar vein draining into the IVC
- Aortopulmonary collaterals going to RLL of the lung
What is ostium primum ASD associataed with?
Trisomy 21
Near AV valves (Cleft leaflets)
- Septal TV
- Anterior MV
What is a partial AV canal?
Primum ASD with No VSD
What is a transitional AV canal?
Primum ASD with restrictive inlet VSD
What is a complete AV canal?
Primum ASD + Non-restrictive inlet VSD
An ostium secundum ASD is a defect in what structure?
Defect in septum primum (Area of fossa ovalis)
What is ostium secundum ASD associated with?
Mitral valve prolapse
Transmitral Flow Propagation Velocity:
load dependent or load independent?
Load dependent
What does the backing material of the echo probe function to do?
Shortens the pulse duration
The matching layer is how thick in comparison to the wavelength?
About 1/4 length of the wavelength
The piezoelectric crystals are how thick compared to the wavelength?
About 1/2 the wavelength
What is the benefit of a short pulse duration?
Improved axial resolution
Why? Axial resolution = 1/2 * Spatial Pulse Length
How does backing material affect bandwidth?
Increases bandwidth
How does increased bandwidth affect Q factor?
Q = RF / Bandwidth
How does frequency affect penetration?
Increased frequency = Increased penetration (More attenuation)
How does a decreased frequency affect axial resolution?
Worsens it
Why? worsen frequency = Longer spataial pulse length)
What does decreased frequency do to the focal length?
Shorter focal length
NL (Near field length) = r2 / Wavelengths
What is the doppler velocity index for the aortic valve?
V LVOT / V Aortic Valve
What are the values for dimensionless index for:
No Aortic Stenosis
V LVOT / V Aortic Valve
Normal 1.0 or above
What are the values for dimensionless index for:
Mild Aortic Stenosis
>0.5
V LVOT / V Aortic Valve
What are the values for dimensionless index for:
Moderate Aortic Stenosis
0.25 - 0.5
V LVOT / V Aortic Valve
What are the values for dimensionless index for:
Severe Aortic Stenosis
<0.25
V LVOT / V Aortic Valve
What is acceleration time for prosthetic acceleration?
What is normal vs. stenotic?
AT >100 ms = Stenotic
AT <100ms = Normal
How would acceleration time and ejection time affect your determination of stenosis aortic valve prosthesis?
Acceleration Time / Ejection time >0.4 = Stenosis
What peak velocity is associated with prosthetic valve aortic stenosis?
> 4 m/s
What mean gradient is associated with prosthetic valve aortic stenosis?
> 35 mmHg
What effective orifice area is associated with prosthetic valve aortic stenosis?
< 0.8 cm2
List 8 risk factors (measurements) for SAM after MVR?
1. End diastolic diameter < 45 mm
2. C-sept distance >2.5 cm (Distance from coaptation point to closest part of the ventricular septum)
3. Narrow LVOT (< 20 mm)
4. Mitral-Aortic angle <120 degrees (Angle formed by intersection of MV annulus and AV annulus
- AL / PL < 1.3 (anterior mitral leaftlet to posterior leaflet ratio = anterior annulus to coaptation point / posterior annulus to coaptation point)
- Basal septal hypertrophy > 15 mm
- Anterior mitral leaflet length > 20 mm (End-diastole from ME 5 chamber view)
- Posterior mitral length > 15 mm (End - diastole from ME 5 chamber a long posterior leaflet “pushes” the coaptation point towards LVOT)
How does a decrease in beam width affect lateral resolution?
Decrease in beam width = Improved lateral resolution
What resolution types is most important to least important?
Hint: Include the mneumonic
ALE = Mneumonic (Like the beer)
Axial > Lateral > Elevational
What is the definition of wavelength?
Distance / Length of a single cycle
What is the spatial pulse length?
Length of the entire pulse
What is period?
TIme it takes to complete a single cycle
What is frequency on a wavelength?
inverse of period
(# of cycles / second)
What is pulse duration?
Time it takes to complete a single pulse
Analogous to the spatlal pulse length (Distance)
What is the pulse repetition period?
TIme for one pulse to send and then listen
What is the pulse repetition frequency?
Inverse of the pulse repetition period
of pulses per second
What is the nyquist limit equation?
1/2 of the Pulse Repetition Frequency
What resolution is important for the pulse repetition frequency?
Temporal Resolution
What is power?
Rate of energy transfer
AKA
Rate at which work is performed
What is intensity?
Power / Area
During CWD, the frequency of the U/S beam is determined by:
Frequency of the electrical current applied to the crystal
What are the indications for surgery or alcohol ablation therapy for HOCM?
- LVOT obstruction with resting peak instantaneous gradient > 30 mmHg
- SAD (Syncope, Angina, Dyspneaa) symptoms impairing life
- Persistent symptoms despite medical therapy
What wall thickness on echo would warrant alcohol ablation or septal myectomy with HOCM?
> 30 mm
What global strain would warrant intervention with HOCM?
> -18 (More negative than -18
What E / Vp ratio predicts PCWP >15 mmHg in patients with decreased LVEF?
> 2.5
The Annular focusing technique refers to?
Focusing in all directions
What occurs when the wavelength is much larger than the reflector?
Raleigh Scattering
What is attenution?
Decrease in intensity / power / amplitude
How does attenuation relate to frequency?
Higher frequency = Increased attenuation
What is specular reflection?
Reflection off of a smooth surface-only in one direction
What is diffucse reflection?
Reflection off an irregulra surface (More than one direction)
- Interfaces at suboptimla angles to the sound beaama can still produce reflections
What tissue has the most diffuse reflection?
Lung
- Sound wave is bigger than the tissue
If the image is too dark, what do you increase?
Gain
If the image is too bright, what do you decrease?
Decrease Power First
What does an increased power do to lateral resolution?
Degradation of lateral resolution
Formation of Grating Lobes leads to….
deterioration of lateral resolution
A reduction in spataion pulse length will do what to axial resolution?
Improve it
Formula: 1/2 SPL = Axial resolution
How would a decreased beam height affect elevational resolution?
Decreased beam height = Improved elevational resolution
What body tissue has the highest propagation velocity for ultrasound?
Bone
How do low frequency transducers affect:
Attenuation?
Penetration?
Low freq
- Decreased attenuataion
- Increased depth of penetration
