1) What does Flow indicate?
It indicate the volume of blood moving during a particular time
What does velocity indicate?
It indicates the speed or stiffness of a fluid moving from one location to another
What happens to venous flow in the leg during inspiration?
It decreases
In normal individuals, How does respiration affect venous flow?
-venous pressure is low pressure
-muscles responsible for respiration alter pressures in the thorax,
and the abdomen.
During the expiration the Thoracic Pressure________________.
Increases
During the expiration the venous return from the head, and arms to the
heart___________________
Decreases
What happens during inspiration?
Diaphragm moves downward toward the abdomen
Thoracic pressure decreases
Abdominal pressure increases
Venous return from upper body to the heart increases
Venous return from the legs decreases.
Inertial loss occurs during:
-Pulstalile flow
-Phasic flow
-velocity changes at a stenosis
Blood flow is lost in three ways:
-Viscous loss
-frictional loss
-inertial loss
What is hematocrit?
It is the percentage of blood made up of RBC's.
What are the characteristics of turbulent blood flow?
-It is characterized by chaotic flow patterns in many different directions and many speeds.
What is the single most important source of pressure in the human body?
HEART
Where does the Plug flow occur most frequently?
-AT THE AORTA OR BEGINNING OF THE GREAT VESSELS
-All of the layers blood cells travel at the same velocity.(Aorta)
which types of blood Flow are the most common found in normal physiologic state?
LAMINAR (PLUG AND PARABOLIC FLOW)
What is HYDROSTATIC PRESSURE?
IT IS THE PRESSURE RELATED TO THE WEIGHT OF BLOOD PASSING ON A VESSEL MEASURED AT A
HEIGHT ABOVE OR BELOW HEART LEVEL
What is the hydrostatic pressure at the top of the head in the supine patient and why?
- (Zero) because all the body parts are at the same level as the heart (al the vessels).
If the pressure increases the flow...
Increases
If the resistance decreases the blood flow
Increases
What does the Bernoulli's principle describes?
The relationship between the velocity and pressure in a moving fluid.
The velocity at the level of the stenosis
Is Highest within the stenosis
What type of blood flow is arterial Flow?
Pulsatile Flow
What type of blood flow does the vein system have?
Phasic (Steady) Flow
Poiseuille's equation explains the relationship between:
-It describes the relationship between the vol. of the blood and the resistance to flow
In a blood vessel.
-Q(volume flow rate) and Pressure gradient, Radius, Length of vessel, and Viscosity of fluid
According to Poiseuille's law, what happen if?
Pressure increases to the Volume flow ___INCREASES
Radius decrease to the Volume flow___DECREASES
Viscosity Increase to the Volume flow____DECREASE
The length of the vessel decrease to the volume_ INCREASE
What is Friction?
It is the resistance to motion because of two moving objects touching each other.
What effects does the stenosis cause to the blood flow?
Changes in flow direction
Increased velocity as vessel narrows (velocity is highest where the vessel is narrowest)
Turbulence downstream from the stenosis
Pressure Gradient across the stenosis(Pressure downstream from stenosis is lower than the
pressure u
What is the relationship between the pressure, blood flow and resistance?
If pressure increases the Blood flow will _increases
If pressure decreases the resistances will __decreases
If Flow increases the Resistance will _DECREASE
What is Doppler shift?
It is A CHANGE IN THE FREQUENCY OF SOUND, AS A RESULT OF MOTION BETWEEN THE SOURCE OF
SOUND OR THE REFLECTOR OF SOUND
DOPPLER SHIFT = REFLECTED FREQUENCY - INCIDENT FREQUENCY
What is the name of process that the transducer uses to extract the low Doppler frequency that
rides on the top of much higher transducer frequency?
DEMODULATION
What is the relationship between the velocity of blood and Doppler shift?
It is directly related
What is the relationship between the Doppler shift and transducer frequency?
It is direct related
What is the relationship between the Doppler shift and propagation speed?
It is indirect related
Sonographers can use spectral display to show Doppler information. What information is given
along the vertical axis (Y) and what information is given along the horizontal axis (X)?
Vertical axis (Y) velocity or Doppler shift
Horizontal (X) . Time
The higher the position on the color bar, will the velocity of the RBC's be slower or higher?
Higher(faster)
What ARE the methods that can be used to correct aliasing?
INCREASES OR RAISE THE NYQUIST LIMIT OR REDUCE THE DOPPLER SHIFT
CW has range ambiguity, unlimited maximum velocity and no aliasing
True
What 3 factors will produce resistance to blood flow?
Viscosity of the fluid
Vessel length
Vessel diameter
When the Nyquist limit is exceeded this will cause aliasing to occur.
TRUE
What is measure pressure?
IT IS THE SUM OF HYDROSTATIC PRESSURE AND CIRCULATORY PRESSURE
Measured pressure= Circulatory Pressure + Hydrostatic Pressure.
What is the Mathematical equation of PRESSURE GRADIENT
Flow (Q) x Resistance
What are the characteristic of the studies done with Pulse wave Doppler Transducer?
a) Low quality factor
b) Lower sensitivity
c) Wide bandwidth pulse
What is the primary disadvantage of pulse Doppler?
Aliasing
What are the five techniques the sonographer should do to avoid aliasing artifacts?
a) Adjust the scale to its maximum
b) Select the new ultrasound view with shallower sample volume
c) Use baseline shift
d) Use CW Doppler
If you eliminated the Aliasing you can improve ______________
d) The ability to measure of the maximum velocity with Doppler
With gray scale sonographer can identify anatomic structures, but Color Doppler provides
information
a) The location of flow
b) Regarding direction of flow
c) It is considered semi-quantitative method
Color Flow measures ________________________ and spectral Doppler (pulse and CW)
measures_______________________
Mean Velocity and Peak velocity
The color map uses a dictionary to convert measured velocities into Pulse wave that appear on the
image
b) False
What are the two more used Color Maps?
a) Velocity Mode
b) Variance Mode
In regarding to color map answer the following questions:
Red indicates flow ____________________________toward the transducer
Blue indicate flow ____________________________away from the transducer
Color at the Top of the map indicates __________________ Higher velocity flow toward the
transducer
Black region o
What kind the information does the Variance Mode provide?
Direction and speed of the blood flow
Difference between laminar flow and turbulent flow
The variance map also displays different colors side to side. The color in the right side of the map
indicate _______________flow
Turbulent
Large Doppler Packets or Ensemble packet has two advantages:
a) More accurate velocity measurement
b) Increased sensitivity to low flow
The disadvantages with large Doppler packets size are:
More time needed to acquire date. Reduced frame rate and decreased temporal resolution
What is Power Doppler?
It is a NON-Directional Color Doppler
(Only identifies the presence of a Doppler
shift. All vessels have the same color, regardless of the direction of blood flow. It is also called Energy
Mode or Color Angio)
What are the 3 advantages of Energy Mode or Power Doppler?
Increased sensitivity to low flow or velocity (venous flow or small vessels)
Unaffected by Doppler angles, unless the angles is exactly 90 degrees.
No Aliasing. (Velocity information is ignored)
What are the disadvantages of Power Doppler?
No measurement of velocity or direction
Lower frame rate/ poor temporal resolution
Susceptible to motion of the transducer, patient, or soft tissue.
(Flash artifacts)
What are the 2 most common Doppler artifacts?
Ghosting and Clutter
The Ghosting artifact is creating with;
Color Doppler
How can you eliminate clutter or ghosting Doppler artifacts?
Wall filter (High pass Filter) is used to eliminate low frequency.
What is Crosstalk Artifacts?
It is a special form of "mirror image" artifacts; arise only with Spectral Doppler
(They appears as an identical Doppler spectrum both above and below the baseline. The flow appears
bidirectional on the spectrum)
What are the causes of Crosstalk artifacts?
Doppler gain is set too high
The incident angle is near 90 degree
What are the methods used to analyze the spectral Doppler?
Fast Fourier Transform (FFT)
Autocorrelation
What is a Spectral Analysis?
It is a tool that break the complex signal into its basis "building Blocks' and identifies the individual
velocities that make up the reflected Doppler signal
What is the significance of displaying all components all component frequencies with Fast Fourier
Transform?
We can distinguish the laminar flow from the Turbulent flow
What does the pulse Doppler spectral window display with the turbulent flow?
SPECTRAL BROADENING
How do you call the anechoic region between the baseline and the spectrum waveform?
Spectral Window
What is Autocorrelation?
It is the digital technique uses to analyze COLOR FLOW DOPPLER
Which Doppler modalities have the greater sensitivity to show low velocity or small volume blood
flow?
Power Doppler
Which Doppler modalities have no aliasing artifacts?
CW Doppler /power Doppler
Doppler shift produce information about
Velocity
Is the angle between the direction of the flow and the direction of the sound beam is 90 degree,
what Doppler shift may you get?
No Doppler shift is created
If the vessel does not have color, the first thing you should do is
Check for the angle between flow and sound beam
For Color to appear in the vessel, the angle of the color box should be oriented other than
________________ degree
90 degree
What is the relationship between the Doppler shift and Frequency?
DIRECTLY RELATED
Reverberations appear on the display as _____________, __________________________ caused by
the bouncing of the sound wave between ________ ______________ _____________ positioned
_______________ to the ultrasound beam
MULTIPLES, EQUALLY SPACED ECHOES/ TWO STRONG REFLECTORS / PARALLEL
How does the sample volume depth affect the presence of aliasing?
Deeper sample creates more aliasing
When the color Gain is too high what artifacts will appear throughout the color box?
Color Confetti Artifacts.
When the color gain is set too low, what type of color Doppler will you get?
No Color, all color will disappear in the image
The wall filter removes the color from ______________reflectors such as blood cells and vibrating
tissues
Slowly moving
When using color map, if the colors that touch each other in the image map go through the map's
middle,
The flow reversal is present
The most effective way to eliminate Aliasing on a Color Doppler Flow is
Increasing the velocity scale (PRF)
Increasing the Color Doppler scale
Decreases the sensitivity to slow flows
What type of artifact will appear like a ladder - meaning parallel, equally spaced lines?
Reverberations
What are Comet Tail artifacts?
THEY ARE REVERBERATION WITH THE SPACES SQUEEZED OUT. IT APPEARS AS A SOLID
HYPERECHOIC LINE directed downward.
COMET TAIL IS AKA RING DOWN ARTIFACT
What is noise?
They are small amplitude echoes. They are the results of many sources.
Snow or vertical squiggly lines in the ultrasound image
When is mirror artifact created?
It is created when a sound reflects off a strong reflector and is redirected toward a second
structure
What are the characteristic of the Mirror artifacts?
A second copy of the true reflector
The artifact appears deeper that the true reflector
A bright reflector lies on a straight line between the artifact and the transducer
True reflector and artifact are equal distant from the mirror
Lobes are stronger than the primary beam and typically create reflections that appear on an image.
They improve lateral resolution and they appear as a second copy of the true reflector.
false
(lobes appears when the sound energy is transmitted in a direction other than
along the beam's main axis/ they are weaker than the primary beam /Don't created reflections that
appear on an image/degrades lateral resolution)
The ability to precisely locate a moving structures at all times and is improve with high frame rate is
called lateral resolution
false (Temporal resolution artifacts is best with high frames rates)
How does the system's display affect spatial resolution?
It is affected by the number of horizontal scan lines per frame. (It is related to overall detail in
an image. It is determined by line density/ axial resolution and lateral resolution)
what are the six assumptions of imaging systems?
1.- Sound travels in a straight lines
2.- Sound travels directly to a reflector and back
3.- sound travels in ST at 1,540 m/s(1.54 mm/micros)
4.- Reflections arise only from structures positioned in the beam's main axis.
5.- The imaging plane is very thin
what are the characteristic of speed error artifacts(Range error artifacts)?
a.- Correct number of reflectors
b.- improper depth
c.- appears as step-off
What are the characteristic of Enhancement?
Hyperechoic, the result of too little attenuation and located beneath a structure with normally low
attenuation. (It is the opposite of shadowing/ It may provide valuable diagnostic
information{cyst/GBladder/U.bladder} that helps to characterized tissue)
What are the characteristic of Focal enhancement?
A hyperechoic side-to-side region and results from increased intensity at the focus. (When a beam is
strongly focused, the intensity is the focal zone is increased. Reflections from the focal zone may be
abnormally strong)
Enhancement artifact is entirely _____________ _____ ______ _______ at which sound travels in a
medium.
UNRELATED TO THE SPEED/
An edge shadow artifacts is a special form of ___________________ that appears as ____________
region extending down from the edge of curved reflectors
SHADOWING/ HYPOECHOIC (Edge shadow artifacts prevents the display of true anatomic structures/
with edge shadow the sound beam refracts (bend) at the edge of the curved reflectors)
An edge shadow is also called ____________________ by _________________
SHADOWING BY REFRACTION
Shadow is entirely _______________ to the _________ of the sound in a ____________
UNRELATED/ SPEED /MEDIUM
Comet tail can also arise from the _________________, or _______________ of small structures
such as ______________________ after they have been bombarded by a _________ __________
RESONANCE/ VIBRATION/ gas bubbles/SOUND PULSE
Which artifacts is unrelated to the dimensions of an ultrasound pulse?
Refraction Artifacts
Which one artifacts does not result from multiple reflectors?
Enhancement
all of the following artifacts result in the placement of too many echoes on the image, EXCEPT;
Shadowing