Color Duplex Imaging Flashcards
Duplex imaging combines gray scale with Doppler and can appear as (A) M-mode and spectrum (B) B-mode and spectrum (C) color flow imaging and spectrum (D) all of the above
(D) All of the above. Color flow images can be used to position a single point, pulsed-Doppler, sample volume, as is the case with more conventional duplex imaging.
Doppler color flow imaging produces an image com-
posed of
(A) tissue echoes in gray scale and blood echoes in color
(B) moving soft-tissue echoes in gray scale and blood motion in color
(C) stationary tissues in gray scale and moving tissues in color
(D) stationary tissues in gray scale and stationary blood in color
(C) Stationary tissue in gray-scale and moving tissues in color. All moving tissues in a color flow imaging can produce color. Thus, stationary tissues are in gray scale, whereas moving tissues, including blood, are in color.
Color Doppler imaging is a term used to describe
(A) a form of color flow imaging
(B) a form of magnetic resonance imaging
(C) a new form of imaging relying on high-speed
propagation velocities in soft tissues
(D) a form of detecting flow with lasers
(A) A form of color flow imaging. Color flow imaging includes both Doppler and non-Doppler forms of imaging.
The Doppler effect occurs
(A) only to waves traveling more than 1,000 m/s
(B) only to ultrasound waves with intensities greater than 500 mW/cm2, SPTA
(C) to all waves coming from a moving wave source
(D) in ultrasound, but only when the targets are moving faster than 1.0 m/s
(C) To all waves coming from a moving wave source.
The Doppler effect happens to all waves coming from a moving source, regardless of propagating velocity or power levels.
The Doppler effect depends on
(A) the carrier frequency, the angle between echo source velocity and beam axis, and the reflectivity of blood
(B) the closing velocity between transducer and tissue, carrier frequency, and ultrasound propagation velocity
(C) the lowest Doppler-shift frequency detectable and the highest frequency without aliasing
(D) the largest change in acoustical impedance within the moving blood
(B) The closing velocity between transducer and tissue, carrier frequency, and ultrasound propagation velocity. The Doppler equation looks like the
following,
Df = 2(f/c) V cos 0
where F is the carrier frequency, c is the propaga-
tion velocity, and 0 is the Doppler angle. V cos 0 is the
closing velocity between the transducer and moving
tissue.
To calculate blood velocity using color flow imaging, a
sonographer must
(A) place a sample volume in the major streamline or jet within the vessel and set an angle correction parallel to the vessel wall
(B) assume that all flow is parallel to the vessel wall
(C) locate the major streamline and place the sampling angle at 60° to the vessel wall
(D) place a sample volume in the major streamline
or jet and set the angle correction parallel to the
streamline
(D) Place a sample volume in the major streamline or jet and set the angle correction parallel to the streamline. Because the color pattern shows the location of the major streamline or jet, calculating velocity requires correction relative to the flow geometry, not the vessel.
To preserve gray-scale texture, digital sampling for
gray-scale images must be at intervals of
(A) 0.6 mm
(B) one wavelength or less
(C) 1.0 mm
(D) 3 dB
(B) One wavelength or less. This is necessary for textural information to reach the display in a digital scan converter.
To preserve flow detail, digital Doppler sampling
intervals for a vascular color flow image must be at
intervals of
(A) 1-2 mm
(B) 1-2 cm
(C) one wavelength or more but less than 1 mm
(D) -6 dB
(C) One wavelength or more but less 1 mm. Digital
sampling for vascular flow information requires such
an interval because larger intervals cannot show the
flow patterns within the vessel.
Gray-scale tissue texture in a color flow imaging system depends on
(A) transmit focusing only
(B) receive focusing only
(C) the product of transmit and receive focusing
(D) the speed at which the ultrasound beam is moved by the scanhead
(C) The product of transmit and receive focusing. The effective beam width results from the mathematical product of both functions.
The shape of the sample volume in pulsed Doppler has
a major effect on the content of the Doppler signal.
(A) true
(B) false
(A) True. The sample volume and flow interact in a manner that depends on the geometry of the sample
volume.
To form the color patterns in a Doppler color flow
image, a color flow system samples down each Doppler
image line of sight for
(A) the amplitude of the Doppler signal
(B) the velocities of red blood cells
(C) the average Doppler shift frequency
(D) the velocity spread within the sample site
(C) The average Doppler shift frequency. At each sample site, the color flow system determines the average Doppler shift frequency.
The Doppler portion of a color flow image is a map of red-cell velocities.
(A) true
(B) false
(B) False. At each sample site, the system determines the average Doppler shift frequency. The display is then either these average frequencies or, in some cases, the calculated closing velocity. This velocity is the rate at which the flow is approaching or moving away from the transducer along the line of sight.
Separating moving soft tissue from moving blood in a
color flow image tests for
(A) Doppler signal amplitudes only
(B) tissue signal amplitudes only
(C) Doppler signal frequencies only
(D) the relationship between the amplitudes and frequencies ofthe Doppler signals
(D) The relationship between the amplitudes and frequencies of the Doppler signals. The system will then avoid coloring strong slow-moving echo sources (tissue) but still color moderately fast weak echo sources (blood).
A curving vessel within a color flow image shows color
in the vessel when the beam and vessel are parallel
but shows no color as the vessel turns perpendicular
to the beam. The loss of color means that
(A) the vessel is occluded
(B) the vessel is open, but the blood velocity is too
low to complete the image
(C) the dark region is diseased
(D) The Doppler effect works only when the vessel
is parallel to the ultrasound beam.
(B) The vessel is open, but the blood velocity is too low to complete the image. As the vessel curves away from the beam, the Doppler frequencies become too low to be portrayed. The completeness of a color flow image depends on the velocity of the blood flow and the Doppler angle.
The smallest vessels that appear in a color flow image
are about 1 mm in diameter. The smaller vessels are
absent because
(A) arterial blood velocities are too low in vessels
that are less than 1 mm in diameter
(B) the smaller vessels are shadowed by the
surrounding soft tissue
(C) soft tissue does not have many vessels that are
less than 1 mm in diameter
(D) the smaller vessels do not reflect ultrasound as
well as the larger vessels do
(D) The smaller vessels do not reflect ultrasound as
well as the larger vessels do. Every living cell in the
body is no more than two cell layers away from a red blood cell. The smaller vessels, however, are not sufficiently echogenic and vanish from the color display
first because of their small echo signals.
The color flow image provides information on (1) the
existence of flow, (2) the location of flow in the image,
(3) flow direction relative to transducer, (4) the maximum flow velocity
(A) all of the above
(B) 1, 3, and 4
(C) 3 and 4
(D) 1, 2, and 3
(D) 1, 2, and 3. Color provides information about the existence of flow, its location in the image, its location in the anatomy, the direction of the flow relative to the transducer, the direction of flow within the vessel, the flow pattern within the vessel, and the pulsatility of the flow. It does not indicate the velocity of the flow.
Detecting flow in a color flow imaging system depends
on the detection of
(A) changes in Doppler signal amplitude
(B) changes in Doppler signal frequency content
(C) changes in echo signal phase and frequency
content
(D) changes in echo signal phase
(D) Changes in echo signal phase. As with all directional Doppler systems, color flow systems detect the existence of motion with a change in echo signal phase. By measuring the direction of the phase change, the system shows whether the direction of motion is toward or away from the transducer.
One begins reading a color flow image by
(A) determining the maximum systolic frequency
(B) knowing the position ofthe scan plane on the patient’s body
(C) knowing the direction of flow relative to the
transducer
(D) determining the Doppler carrier frequency
(B) Knowing the position of the scan plane on the patient’s body. The expected flow pattern in any vessel comes from knowing how the scan plane is positioned on the patient. For example, the patient’s head is always placed on the image left in long axis scans, and the patient’s right side is on the image left in cross-sectional scans.
Changes in the Doppler shift frequencies within a color flow image sample site appear in the image as
(A) nothing; the image only shows changes in phase
(B) different colors (hues)
(C) different levels of color saturation (purity)
(D) different colors (hues) or different levels of saturation (purity)
(D) Different colors (hues) or different levels of saturation (purity). The average frequency within each Doppler sample site is portrayed as a change in either color saturation (purity or whiteness) or hue (color). The object is to use the color to show flow patterns within the vessel lumen or heart chambers.