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249 Cards in this Set
- Front
- Back
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*** True or False. Solids and liquids are material that flow.
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False. GASES and liquids are material that flow.
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*** True or False. Viscosity is the resistance of a fluid to flow.
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True.
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*** Fluid flows in a tube in response to a _________ __________ at the ends.
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pressure difference
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*** If pressure difference increases, volumetric flow rate....
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increases.
Q = ∆P / R Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² R = Resistance to flow. Units: poise |
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*** If flow resistance increases, volumetric flow rate....
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decreases.
Q = ∆P / R Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² R = Resistance to flow. Units: poise |
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*** If tube length increases, flow resistance...
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increases.
R = 8 * L * [ ŋ / ( π * r⁴ ) ] R = Flow resistance in long tube. Units: gm/cm⁴ -s L = Length. Units: cm ŋ = Viscosity. Units: poise r = Radius. Units: cm⁴ |
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*** If tube radius increases, flow resistance...
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decreases.
R = 8 * L * [ ŋ / ( π * r⁴ ) ] R = Flow resistance in long tube. Units: gm/cm⁴ -s L = Length. Units: cm ŋ = Viscosity. Units: poise r = Radius. Units: cm⁴ |
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*** If viscosity increases, flow resistance...
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increases.
R = 8 * L * [ ŋ / ( π * r⁴ ) ] R = Flow resistance in long tube. Units: gm/cm⁴ -s L = Length. Units: cm ŋ = Viscosity. Units: poise r = Radius. Units: cm⁴ |
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*** If pressure difference increases, flow rate...
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increases.
Q = [ ∆P * π * d⁴ ] / [ 128 * L * ŋ ] Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² d = Diameter. Units: cm⁴ L = Length. Units: cm ŋ = Viscosity. Units: poise |
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*** If diameter increases, flow rate...
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increases.
Q = [ ∆P * π * d⁴ ] / [ 128 * L * ŋ ] Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² d = Diameter. Units: cm⁴ L = Length. Units: cm ŋ = Viscosity. Units: poise |
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*** If length increases, flow rate...
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decreases.
Q = [ ∆P * π * d⁴ ] / [ 128 * L * ŋ ] Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² d = Diameter. Units: cm⁴ L = Length. Units: cm ŋ = Viscosity. Units: poise |
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*** If viscosity increases, flow rate...
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decreases.
Q = [ ∆P * π * d⁴ ] / [ 128 * L * ŋ ] Q = Volumetric flow rate. Units: mL/s ∆P = Change in pressure. Units: dyne/cm² d = Diameter. Units: cm⁴ L = Length. Units: cm ŋ = Viscosity. Units: poise |
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*** The volumetric flow rate in a tube depends on the ________ ________, the _________ and _________ of the tube, and the ________ of the fluid.
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pressure difference; length; diameter; viscosity
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*** True or False. Distorted flow is flow where layers of fluid slide over each other.
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False. LAMINAR flow is flow where layers of fluid slide over each other.
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*** True or False. Disturbed flow is a form of laminar flow in which streamlines are straight.
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False. Disturbed flow is a form of laminar flow in which streamlines are NOT straight.
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*** True or False. Turbulent flow is a laminar flow with random and chaotic speeds and directions.
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False. Turbulent flow is a NON laminar flow with random and chaotic speeds and directions.
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*** Pulsatile flow is non steady flow, with _______ and ______ over the cardiac cycle.
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acceleration; deceleration.
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*** True or False. Pulsatile flow in distensible vessels includes added forward flow without flow reversal over the cardiac cycle in some locations in circulation.
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False. Pulsatile flow in distensible vessels includes added forward flow AND/OR flow reversal over the cardiac cycle in some locations in circulation.
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*** True or False. Flow speed increases at stenosis, and turbulence can occur proximal to it.
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False. Flow speed increases at stenosis, and turbulence can occur DISTAL to it.
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*** True or False. If flow speed increases, the magnitude of the pressure drop increases.
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True.
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*** The Bernoulli effect is a ________ in pressure associated with _______ flow speed at stenosis.
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drop; high
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*** If scatter speed increases, the Doppler shift...
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increases.
fD = fR - fO = fO * [ 2 * v ] / c fD = Doppler shift. Units: kHz fR = Received frequency. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** If source frequency increases, the Doppler shift...
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increases.
fD = fR - fO = fO * [ 2 * v ] / c fD = Doppler shift. Units: kHz fR = Received frequency. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** The Doppler shift is the difference between the _________ _________ and the ________ _________ returning from moving scatterers.
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emitted frequency; echo frequency
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*** The Doppler shift frequency relates the Doppler shift to __________ __________ and __________.
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flow speed; frequency
fD = fR - fO = fO * [ 2 * v ] / c fD = Doppler shift. Units: kHz fR = Received frequency. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** The Doppler shift is proportional to.... ( 2 things)
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flow speed and operating frequency.
fD = fR - fO = fO * [ 2 * v ] / c fD = Doppler shift. Units: kHz fR = Received frequency. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** If the Doppler shift increases, the calculated scatterer speed...
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increases.
fD = [ fO * 2 * v * cos ϴ ] / c fD = Doppler shift. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** If the source frequency increases, the calculated scatterer speed...
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increases.
fD = [ fO * 2 * v * cos ϴ ] / c fD = Doppler shift. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** If the cosine increases, the calculated scatterer speed...
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decreases.
fD = [ fO * 2 * v * cos ϴ ] / c fD = Doppler shift. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** If the Doppler angle increases, the calculated scatterer speed...
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increases.
fD = [ fO * 2 * v * cos ϴ ] / c fD = Doppler shift. Units: kHz fO = Source frequency. Units: kHz v = Reflector speed. Units: cm/s c = Flow speed. Units: cm/s |
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*** Color-Doppler imaging is an extension of conventional ________ - ________ sonography and shows regions of blood flow or tissue motion in color.
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gray - scale
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*** Color Doppler uses conventional sonographic instruments that have the ability to detect ________ ________ and present them on the display in color.
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Doppler shifts
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*** What is the mathematical process commonly used to detect Doppler shifts in color Doppler instruments?
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Autocorrelation
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*** If ensemble length increases, frame rate...
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decreases.
FR = 77,000 / [ pen * L * n ] FR = Frame rate. Units: Hz 77, 000 Units: cm/s pen = Penetration. Units: cm LPF = Lines per frame n = Ensemble length |
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*** True or False. The color map, always shown on the display, is the key to understanding how image colors are related to Doppler characteristics.
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True.
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*** True or False. Changing Doppler angle in an image produces various colors in different locations.
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True.
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*** True or False. Proper understanding of the effects of _______ on the Doppler shift and of how _______ is related to the Doppler shift is necessary to interpret complex images properly.
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angle; color
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*** True or False. Doppler power displays color-encode Doppler color power values on the display.
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False. Doppler power displays color-encode Doppler SHIFT power values on the display.
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*** True or False. Doppler power displays do not have direction, speed, or flow of character information included but are sensitive to angle effects and aliasing.
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False. Doppler power displays do not have direction, speed, or flow of character information included and are INSENSITIVE to angle effects and aliasing.
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*** True or False. Doppler power displays are more sensitive than Doppler shift displays in that they can present slower flows as well as flows in deeper or tinier vessels.
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True.
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*** True or False. The Doppler detector detects Doppler shifts and determines their sign, positive or negative.
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True.
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*** True or False. The Doppler sample volume of a continuous-wave Doppler instrument is relatively small, being the overlapping region of the transmission and reception beams.
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False. The Doppler sample volume of a continuous-wave Doppler instrument is relatively LARGE, being the overlapping region of the transmission and reception beams.
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*** True or False. Wall filters remove clutter.
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True.
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*** True or False. Clutter is high-frequency Doppler shifts from moving tissues.
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False. Clutter is LOW-frequency Doppler shifts from moving tissues.
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*** What enables depth selectivity and a small Doppler sample volume?
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Range gating
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*** A pulsed wave Doppler system is a ________ system.
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sampling.
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*** _________ instruments enable intelligent use of the Doppler sample volume by showing its _________ in the gray-scale anatomic display.
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Duplex; location
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*** True or False. Spectral analysis presents Doppler shift frequencies in inverse numerical order.
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False. Spectral analysis presents Doppler shift frequencies in FREQUENCY order.
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*** True or False. Different flow conditions produce various spectral presentations.
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True.
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*** The _________ __________ __________ is used to generate Doppler shift spectral displays.
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fast Fourier Transform
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*** True or False. The spectral display is a presentation of Doppler shift versus depth.
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False. The spectral display is a presentation of Doppler SPECTRA versus TIME.
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*** What conditions produce spectral broadening?
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Disturbed or turbulent flow conditions.
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*** True or False. High and low impedance conditions upstream and downstream give rise to various spectral displays.
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True.
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True or False. Gas is a fluid.
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True.
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The units of viscosity are...
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Either poise or kilograms per meter-second: kg/m-s.
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The viscosity of blood plasma is what percentage greater than that of water?
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50%
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What is the viscosity of blood at 37 degrees C, in poise units? What is the normal range in blood?
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0.035 poise; ranges from 0.02 (anemia) - 0.10 (polycythemia)
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True or False. Blood viscosity varies with flow speed.
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True.
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What is the driving force behind fluid flow?
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Pressure. Force per unit area.
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True or False. Pressure is unequally distributed throughout a static fluid but exerts its force in all directions.
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False. Pressure is EQUALLY distributed throughout a static fluid AND exerts its force in all directions.
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What is another name for pressure difference?
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Pressure gradient.
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The strict definition of a pressure gradient is...
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The pressure difference divided by distance between the two pressure locations.
∆P / d |
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What is the word gradient refer to?
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Comes from Latin - gradus. Refers to the upward or downward sloping of something.
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As the pressure decreases from one end of a tube to the other, this decrease can be thought of as a...
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slope.
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The volumetric flow rate is sometimes simply called...
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flow.
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True or False. Volumetric flow rate (Q) is the volume of blood passing a point per unit of time.
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True.
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What is the total adult blood flow rate?
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5000 mL/min
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True or False. The total blood volume circulates in about 5 minutes.
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False. 1 min.
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The resistance of the arterioles accounts for what percent of the total resistance in systemic circulation?
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50%
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List the 5 types of flow.
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Plug
Laminar Parabolic Disturbed Turbulent |
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What is plug flow? Where is it mostly seen?
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Constant flow across a tube; Seen mostly at the entrance of a tube.
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What is laminar flow? Where is it mostly seen?
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Layers of straight and parallel fluid sliding over each other; Occurs further down the tube.
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At which part of a tube is flow speed at a maximum? A minimum?
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Max flow at center; Min flow at walls.
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What is a type of laminar flow with varying speeds across the tube in the shape of a parabola?
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Parabolic flow.
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In the case of parabolic flow, the average flow speed across the vessel is equal to what percentage of maximum flow speed?
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50%
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True or False. Parabolic flow is not commonly seen in blood circulation.
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True.
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True or False. The absence of non-parabolic flow is often an indicator of abnormal flow conditions.
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True.
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Disturbed flow occurs when the parallel streamlines describing the flow are _________ from their straight form.
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altered
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Where would disturbed flow occur? List 2
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Stenosis or bifurcation.
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True or False. In disturbed flow, particles of fluid no longer flow in the forward direction.
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False. In disturbed flow, particles of fluid STILL flow in the forward direction.
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Name two forms of laminar flow.
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Parabolic and disturbed.
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What are the circles called that appear in turbulent flow?
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Eddies.
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What causes turbulent flow to occur?
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An increase in flow speed.
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True or False. Turbulence can occur in the transition from high flow speed in a narrow channel to slow flow in a broad stream.
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True.
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With pulsatile flow, the relationship between the varying pressure and flow rate depends on...(three things)
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flow impedance, inertia, compliance
The INERTIA of the fluid as it accelerates and decelerates The COMPLIANCE (expansion and contraction) of nonrigid vessel walls. |
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The ________ _________ results in continued flow in the forward direction.
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Windkessel effect.
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Flow reversal is exactly what it sounds like. Where does it occur?
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Where there are no valves to prevent it. Like in distal circulation during diastole.
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So pulsatile flow includes both forward and reverse flow right?
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Right.
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What reveals much about the state of downstream arterioles where flow cannot be measured directly with ultrasound?
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Arterial diastolic flow.
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True or False. The average flow speed in a stenosis must be greater than the average flow speed proximal and distal to the stenosis so that the volumetric flow rate is constant throughout the vessel.
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True.
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True or False. Volumetric flow rate must be constant in two of the three regions: at the stenosis, distal to the stenosis and proximal to the stenosis.
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False. Volumetric flow rate must be constant in ALL THREE regions: at the stenosis, distal to the stenosis and proximal to the stenosis.
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True or False. The continuity rule says that volumetric flow rate is equal to constant flow speed across the vessel divided by the cross-sectional area of the vessel.
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False. The continuity rule says that volumetric flow rate is equal to AVERAGE flow speed across the vessel MULTIPLIED by the cross-sectional area of the vessel.
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If a stenosis has an area measuring one half the area of the proximal and distal vessel, the average flow speed within the stenosis is _________ the average flow speed proximal and distal to the stenosis.
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twice
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If a stenosis has a diameter that is one half the diameter of the adjacent area, the area at the stenosis is one fourth that of the adjacent area, so the average flow speed in the stenosis must __________.
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quadruple
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True or False. The diameter in Poiseuille's law refers to the diameter of the entire vessel but the diameter in the continuity rule refers to the diameter of a stenosis.
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True.
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Under Poiseuille's law, flow speed decreases with smaller diameters. Under the continuity rule, flow speed increases with smaller diameters.
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True.
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The maximum normal flow speed in circulation is about...
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100 cm/s
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The maximum normal flow speed in a stenosis is about...
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a few meters per second
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What are sounds produced by turbulence, which can be heard by stethoscope called?
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bruits
(brewey) |
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The ultimate stenosis is called an...
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occlusion
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According to the Bernoulli effect, the pressure at a stenosis is ________ ________ it is proximal and distal to the stenotic area.
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less than
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Pressure energy is converted to _________ _________ upon entry into a vessel.
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flow energy
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What is the formula for calculating a pressure drop across a stenotic valve (used in echo) ?
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∆P = 4 ( v₂ ) ²
∆P = Change in pressure v₂ = Flow speed in the jet |
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The Doppler effect/Doppler shift is...
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a change in frequency caused by a change in reflector motion.
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The Doppler equation can deal with any of three situations, what are they?
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1) Moving source
2) Receiver 3) Reflector * Reflector is the what we are concerned with in ultrasound. |
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A moving reflector is a combination of a ________ ________ and a ________.
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moving receiver; source
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True or False. For a moving reflector approaching a stationary source, more cycles of a wave are encountered in 1 second than would be if the reflector were stationary.
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True.
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True or False. The Doppler shift is equal to the source frequency minus the received frequency.
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False. The Doppler shift is equal to the RECEIVED frequency minus the SOURCE frequency.
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Physiologic flow speeds, even in highly stenotic jets, do not exceed...(what general speed ?)
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a few meters per second.
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The minimum detectable blood flow speed with Doppler ultrasound is...
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a few millimeters per second.
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The maximum detectable blood flow speed with Doppler is...
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determined by aliasing.
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Assuming the same blood vessel, a 4MHz transducer will have ________ the Doppler shift as a 2 MHz transducer.
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twice.
The Doppler shift is proportional to the operating frequency. |
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Doppler frequencies used in vascular studies are ________ than those used for anatomic imaging.
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less
Echoes from blood are weaker than those from soft tissues. |
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True or False. If the direction of sound propagation is exactly opposite the flow direction, the maximum negative Doppler shift is obtained.
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False. If the direction of sound propagation is exactly opposite the flow direction, the maximum POSITIVE Doppler shift is obtained.
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True or False. If the direction of sound propagation is the same as the flow direction, the maximum negative Doppler shift is obtained.
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True.
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True or False. The larger the Doppler angle, the less the Doppler shift.
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True.
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True or False. Estimation of the Doppler angle is a subjective operation subject to error.
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True.
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True or False. Error in estimation of the Doppler angle is more critical at smaller angles than at large ones.
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False. Error in estimation of the Doppler angle is more critical at LARGER angles than at small ones.
Because the cosine changes rapidly at large angles. |
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True or False. Doppler shift frequencies become very small at large angles, thereby reducing system sensitivity.
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True.
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At Doppler angles less than about ______ degrees, the sound no longer enters the blood at all but is reflected totally at the wall-blood boundary.
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30
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In Doppler echocardiography, angles of near ______ are useful.
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Zero
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List the 4 types of Doppler presentation.
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Audible sounds
Strip-chart recording Spectral display Color-Doppler display |
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Another name for Color-Doppler imaging is...
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color-flow imaging
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True or False. Echoes returning from stationary tissues are detected and presented in gray scale in appropriate locations along scan lines.
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True.
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Depth is determined by...
Brightness is determined by... |
echo arrival time
echo intensity |
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True or False. Doppler-shifted echoes can be recorded and presented in color at many locations along each scan line.
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True.
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One problem with using linear array presentation of color Doppler is that a 90 degree angle yields no Doppler shift. What is used to solve this problem?
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Phasing is used to steer the beam....results in a parallelogram.
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Doppler-shifted echoes are commonly detected in the signal processor using a mathematical technique called...
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autocorrelation
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True or False. Autocorrelation rapidly determines the mode and similarity of the Doppler shift signal at each location along the scan line.
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False. Autocorrelation rapidly determines the MEAN and VARIANCE of the Doppler shift signal at each location along the scan line.
Note: It also determines the sign ( + or -) of the signal. |
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How many Doppler samples (locations) per scan line are typically shown on a color Doppler display?
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100 - 400
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How many frames per second can be shown depending on the depth and width of a color Doppler display?
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5 - 50
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True. In color Doppler instruments multiple pulses are involved in all images because they are required in the autocorrelation process.
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True.
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True or False. Regarding color Doppler display, a four pulse minimum is required for one speed estimate.
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False. Regarding color Doppler display, a THREE pulse minimum is required for one speed estimate.
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True or False. Regarding color Doppler display, more pulses are required for improved accuracy of the estimates, for variance determinations and to improved detection of low frequency mean Doppler shifts.
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True.
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Steering angle control permits avoidance of ________ degree angles.
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90
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True or False. Color inversion alternates the color assignments on either side of the zero-Doppler-shift baseline on the color map.
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True.
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The wall filter eliminates ________ caused by tissue and wall motion.
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clutter.
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If the wall filter is set too high, _________ blood flow signals will be removed.
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slower
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True or False. The operator has control of PRF in gray-scale sonography but does not have control of PRF in Doppler.
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False. The operator has NO control of PRF in gray-scale sonography but DOES have control of PRF in Doppler.
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What controls the PRF in Doppler sonography?
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The scale control.
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Decreasing the scale control permits observation of ________ flows and increases the probability of _________.
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slower; aliasing
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Priority selects the gray-scale echo strength below which _______ will be shown at each ________ location.
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color; pixel
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Baseline control allows shifting the baseline up or down to correct _________.
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aliasing
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What is another name for smoothing?
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Persistence
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True or False. Smoothing provides frame to frame average to reduce clutter.
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False. Smoothing provides frame to frame average to reduce NOISE.
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True or False. The ensemble length is the number of pulses used for each color scan line.
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True.
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What is the minimum ensemble length? What is the common range?
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3; 10 - 20
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True or False. Greater ensemble lengths provide more accurate estimates of mean Doppler shift.
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True
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True or False. Greater ensemble lengths provide reduced detection of flows.
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False. Greater ensemble lengths provide IMPROVED detection of flows.
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True or False. Greater ensemble lengths provide lower frame rates.
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True.
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True or False. Greater ensemble lengths provide incomplete representation of flow within a vessel.
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False. Greater ensemble lengths provide COMPLETE representation of flow within a vessel.
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True or False. Wider color windows reduce frame rates because more scan lines are required for each frame.
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True.
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What are three limitations of color Doppler?
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Lower frame rate
Angle dependence Non-detailed spectral information |
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True or False. Spectral Doppler presents the entire range of Doppler shift frequencies received as they change over the cardiac cycle.
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True.
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True or False. Color Doppler displays present only a statistical representation of the complete spectrum at each pixel location on the display.
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True.
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The sign, mean value, and variance of the spectrum are color coded into combinations of ________, ________ and _______ that are presented at each displayed pixel location.
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hue; saturation; luminance
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True or False. Some Doppler displays have the capability of reading the quantitative digital values for mean Doppler shifts at chosen pixel locations.
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True.
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True or False. Mean values must be compared with the peak systolic values.
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True.
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True or False. Multiple foci are often used in color imaging.
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False. Multiple foci are NOT used in color imaging.
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Hue indicates the _______ of the Doppler shift.
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sign
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Changes in hue, saturation, and luminance up or down the map from the center indicate increasing Doppler shift ________.
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magnitude
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When selected, variance is shown as a change in _________ from left to right across the map.
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hue
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True or False. Doppler shift displays encode mean Doppler shifts in a 2D matrix according to the selected color map.
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True.
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True or False. Doppler power displays present 2D Doppler information by color-encoding the velocity of Doppler shifts.
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False. Doppler power displays present 2D Doppler information by color-encoding the STRENGTH of Doppler shifts.
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Power Doppler is free of ________ and ________ ________.
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aliasing; angle dependency
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Power Doppler is ________ sensitive to slow flow.
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more
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True or False. Power Doppler is effective at locating small or deep vessels.
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True.
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Doppler power displays have several alternative names. What are they? (list 4)
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Power Doppler
Ultrasound Angio Color Doppler Energy Color Power Angio |
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True or False. Doppler power display assigns various hue, saturation, and luminance values to Doppler shift power values.
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True.
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The power of Doppler shifts is determined by the ________ of moving scatterers producing Doppler shifts and is independent of Doppler shift frequency.
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concentration
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True or False. Magenta is used on some Doppler power maps.
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True.
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List three advantages and three disadvantages to Doppler Power Displays.
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Advantages:
More sensitive Angle independence No aliasing NOTE: The book groups angle independence and alias free into one bucket and calls them "uniform presentation". It then separates these two advantages in the box. The test bank might try to trick you here. Disadvantages: No direction No flow speed No flow character (laminar or turbulent) |
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The Doppler detector in color Doppler imaging instruments yields five things. What are they?
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Sign
Mean Variance Amplitude Power of the Doppler Spectrum P. 149 |
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True or False. Power Doppler integrates the area above the spectrum.
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False. Power Doppler integrates the area UNDER the spectrum.
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True or False. Power Doppler is essentially free of variations in flow speed.
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True.
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True or False. Power Doppler can be frame averaged to improve the signal to noise ratio and sensitivity.
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True.
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Lower ________ can be used to detect slow flows with Power Doppler.
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PRFs
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What are the two types of Spectral Doppler?
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Continuous Wave (CW) and Pulsed Wave (PW)
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CW operation detects Doppler-shifted echoes in the region of overlap between the beams of the ________ and ________ transducer elements.
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transmitting; receiving
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True or False. CW transducers are damped and have the same sending and receiving element.
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False. CW transducers are NOT damped and have DIFFERENT sending and receiving elements.
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PW ultrasound uses a ________ element transducer.
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single
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True or False. PW has longer pulses than other types of ultrasound.
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True.
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Through _______ _______, PW Doppler has the ability to select information from a particular depth along the beam.
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range gating
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True or False. To use PW effectively, it is often used with gray-scale.
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True.
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Instruments that combine both PW and gray-scale sonography are called...
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duplex scanners.
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PW and CW operations present Doppler shift information in both _______ form and as a visual display.
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audible
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If an instrument distinguishes between positive and negative Doppler shifts, it is called...
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bidirectional.
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CW Doppler instruments include a CW __________ and Doppler ________ that detects the changes in frequency.
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oscillator; detector
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The CW oscillator produces a continuously alternating voltage with a frequency range of...
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2 MHz to 10 MHz
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True or False. The ultrasound frequency is determined by the oscillator and is set to equal the operating frequency of the transducer.
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True.
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True or False. In the transducer assembly of a CW system, there is a separate receiving transducer element that produces voltages with frequencies less than the frequencies of the returning echoes.
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False. In the transducer assembly of a CW system, there is a separate receiving transducer element that produces voltages with frequencies EQUAL TO the frequencies of the returning echoes.
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Doppler shifts are typically what fraction of the operating frequency? This level puts them in the audible range.
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one thousandth of the operating frequency
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Regarding CW, Doppler shifts are commonly sent through a _________ __________ to a ________ ________ ________ for visual observation and evaluation.
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spectrum analyzer; spectral Doppler display.
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The CW detector ________ the echo voltages it receives from the receiving element, ________ the Doppler shift information in the returning echoes, and ________ the motion direction from the sign of the Doppler shift.
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amplifies; detects; determines
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True or False. Doppler shifts are determined by mixing the outgoing voltages with the CW voltage from the oscillator.
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False. Doppler shifts are determined by mixing the RETURNING voltages with the CW voltage from the oscillator.
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True or False. Mixing the returning voltages with the CW voltage produces both a difference and a sum. The sum is double the operating frequency and is filtered out.
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True.
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True or False. Mixing the returning voltages with the CW voltage produces both a difference and a sum. The difference is greater than zero for echoes returning from stationary structures and + or - for moving structures.
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False. The difference is ZERO for echoes returning from stationary structures and + or - for moving structures.
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Determining direction and separation of Doppler shift voltages is determined by the ________ ________ detector.
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phase quadrature
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True or False. The forward and reverse channel signals are sent to separate loud speakers so that forward and reverse Doppler shifts can be heard separately,
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True.
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The _________ represents zero Doppler shift.
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baseline
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The ________ ________ is placed in the overlapping region of the transmitting and receiving beams of a CW system.
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sample volume
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True or False. One problem with CW systems is that they can present confusing information if two or more blood vessels are being scanned.
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True.
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True or False. One advantage with PW systems is that they can present a relatively small sample volume at a selected depth.
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True.
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True or False. CW Displays for arterial circulation or the heart provide quantitative data.
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True.
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The term _________ _________ is used to describe the incorporation of the Doppler angle into the calculation process.
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angle correction or angle incorporation
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As the angle increases, the Doppler shift....
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decreases
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Another term for wall filter is...
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wall-thump filter
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True or False. The wall filter rejects weak echoes with high frequencies that overwhelm the weaker echoes from blood.
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False. The wall filter rejects STRONG echoes with LOW frequencies that overwhelm the weaker echoes from blood.
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The wall filter has a upper limit range of...
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25 to 3200 Hz
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True or False. A wall filter can erroneously alter diastolic flow and distal flow conclusions.
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True.
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Pulses in PW have lengths of...
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5 to 30 cycles long because it is a Doppler instrument.
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In PW, echo voltages from the transducer are processed in the...
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detector
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Regarding PW, in the detector, echo voltages are _________, their frequency is compared with the _________ frequency, and Doppler shifts are ________.
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amplified; pulser; determined
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Based on their arrival time, echoes coming from reflectors at a given depth may be selected by the amplifier ________.
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gate
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Motion information obtained from a specific depth is called...
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range gating.
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True or False. In PW, the operator controls the gate length and location.
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True.
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True or False. A PW Doppler instrument detects the complete Doppler shift.
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False. A PW Doppler instrument DOES NOT detect the complete Doppler shift.
Rather it obtains samples. |
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True of False. With PW, the mixer does not receive a continuous input echo voltage but rather a sampled one.
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True.
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True or False. PW echoes arrive from a sample volume depth in a pulsed form at a rate equal to the PRF.
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True.
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PW samples are connected and _________ to yield the sampled wave form.
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smoothed
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True or False. The range gate selects the sample volume location from which returning Doppler-shifted echoes are accepted.
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True.
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True or False. The width of the sample volume is equal to the beam depth at the sample volume depth.
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False. The width of the sample volume is equal to the beam WIDTH at the sample volume depth.
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True or False. Longer gate lengths are used when searching for the desired vessel and flow location, and shorter gate lengths are used for spectral analysis and evaluation.
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True.
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True or False. The Doppler sample volume is determined by beam width, gate length, and emitted pulse length.
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True.
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True or False. One fourth of the pulse length is added to gate length to yield effective sample volume length.
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False. One HALF of the pulse length is added to gate length to yield effective sample volume length.
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True or False. The pulse length must shorten as gate length is reduced.
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True.
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True or False. With duplex instruments, the imaging and Doppler flow measurements are done simultaneously.
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False. With duplex instruments, the imaging and Doppler flow measurements CANNOT be done simultaneously.
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True or False. With duplex instruments, electronic scanning with arrays permits rapid switching between imaging and Doppler functions.
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True.
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True or False. Imaging frame rates are slowed to allow for the acquisition of Doppler information between frames.
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True.
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True or False. A time-out from the spectral display is taken to present a sonographic frame.
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True.
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True or False. Regarding spectral analysis, the Doppler shift voltage form the detector goes directly to the display for presentation.
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False. Regarding spectral analysis, the Doppler shift voltage form the detector DOES NOT go directly to the display. It undergoes further processing.
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The presentation of spectral analysis is in the form of a Doppler ________ ________.
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frequency spectrum
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The term spectral means ...
The term analysis means... |
relating to a spectrum
to take apart |
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So...spectral analysis means breaking up frequency components of a wave and spreading them out in order of increasing frequency.
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Cool
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The variety of Doppler shifts received from vessels by the ultrasound system is called the...
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Doppler frequency spectrum.
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The mathematical technique the instrument uses to derive the Doppler spectrum from the returning echoes of various frequencies is called...
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fast Fourier Transform.
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Fast Fourier transform displays can show ________ ________ which is widening of the Doppler shift spectrum caused by a broader range of flow speeds.
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spectral broadening
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How many spectra can be generated per second in a spectral display?
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100 to 1000 spectra.
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True or False. Doppler signal power is proportional to blood cell concentration.
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True.
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True or False. A bright spot on a spectral display corresponds to a strong Doppler shift while a dark spot corresponds to a weak Doppler shift.
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True.
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True or False. A strong signal at a particular frequency and time on a spectral display means that many scattering blood cells are moving at speeds and directions corresponding to that Doppler shift.
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True.
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True or False. A weak frequency means that few blood cells are moving at speeds and directions corresponding to that Doppler shift.
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True.
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True or False. Spectral broadening is a ________ thickening of the spectral trace.
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vertical
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Spectral broadening can be produced artificially. The book names two situations. What are they?
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Excessive Doppler gain and beam spreading.
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Flow reversal in early diastole and lack of flow in late diastole indicate...
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high resistance to flow downstream (distal)
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Stenoses upstream (proximal) produce spectral displays that have the ________-_________ character.
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tardus-parvus
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Indicate whether color Doppler shift displays are quantitative, global or perfusion instruments.
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Quantitative: NO
Global: YES Perfusion: NO |
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Indicate whether color Doppler Power displays are quantitative, global or perfusion instruments.
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Quantitave: NO
Global: YES Perfusion: YES |
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Indicate whether Spectral displays are quantitative, global or perfusion instruments.
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Quantitave: YES
Global: NO Perfusion: NO |
