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Physics Module 5
Vocabulary
| Term | Definition |
|---|---|
| color flow doppler | multi-gated, pulsed doppler technique |
| autocorrelation | correlates each doppler shift received with the previous one to determine the direction of motion that occurred & the velocity change over time |
| color bar | key to the color map, calculates mean velocities and direction of flow with color |
| hue | the color perceived by the human eye |
| saturation | the degree to which the original color is diluted with white |
| brightness | the intensity of the color signal |
| color aliasing | occurs when the velocities breach the Nyquist limit; shown as a color reversal |
| color gain | amplifies all signals from moving structures within the color box or sector equally |
| color wall filter | prevents low velocity wall motion from being processed into color signals on the display |
| color persistence | a technique in which color frames are averaged over time |
| power doppler | identifies the presence of a Doppler shift but not velocity or direction flow |
| fluid dynamics | studies fluid flow through a system of tubes, like blood vessels, & the principles & equations that govern the ideal behavior of fluid flow |
| hemodynamics | study of blood flow & interrelationships of BP, blood flow, & physical properties of blood |
| potential energy | energy that is stored |
| kinetic energy | energy related to motion |
| hydrostatic pressure | form of potential energy determined by the weight of a column of fluid above a reference point, due to gravity |
| volumetric flow (Q) | the volume of blood which moves past a point per unit time |
| resistance | the force opposing blood flow; determined by length of a vessel, viscosity of fluid/blood, & radius of vessel; longer vessel = more resistance, higher viscosity = more resistance, smaller radius = more resistance |
| capacitance | the change in volume per change in time DV/Dt; vessels ability to distend |
| compliance | the change in volume per change in pressure V/P; ability to distend with pressure) |
| viscosity | the measure of the resistance of a fluid to flow due to the attraction of the molecules (stickiness) |
| Law of Conservation of Energy | energy is always conserved, never lost, only converted to another form |
| hematocrit | the fraction of blood volume which is red blood cells |
| Poiseuille's equation | states that for normal laminar flow, flow volume (Q) varies directly with the pressure gradient (P) and the radius of the vessel to the fourth (r) |
| Reynold's number | describes the tendency for turbulence to occur |
| Bernoulli's Principle | describes the relationship between pressure (potential energy) and velocity of blood flow (kinetic energy) |
| segmental pressures | an arterial US study done in the vascular lab; segmental pressures will show a drop of more than 20 mm Hg between segments if there is stenosis |
| Venturi effect | a jet effect (thumb on a garden hose) where the velocity of the fluid increases as the cross-sectional area decreases, while a pressure drop occurs |
| transmural pressure | pressure inside the vessel - pressure outside the vessel |
| calf muscle pump | aids in venous return from the lower extremities to the right atrium & consists of veins, venous valves, & contracting leg muscles |
| volumetric flow is AKA | cardiac output |
| cardiac output= | stroke volume x heart rate |
| stroke volume= | end diastolic volume - end systolic volume |
| velocity of flow (v) | the distance traveled by a fraction of blood over time (m/sec, cm/sec) |
| high capacitance | means a large change in volume occurs over a short time |
| high compliance | means a large increase in volume for a small increase in pressure |
| Ohm's Law | the flow of electricity through a wire and the flow of fluid through a tube and the flow of blood through a vessel are all similar; flows from a proximal area of higher pressure to a distal area of lower pressure |
| pressure gradient= | proximal pressure - distal pressure |
| if Reynolds number < 2000 | trend for laminar flow |
| if Reynolds number > 2000 | trend for turbulent flow |
| low transmural pressure = | veins have low volume with dumbbell shape |
| slightly higher transmural pressure = | veins have more volume with elliptical shape |
| high transmural pressure = | veins are round & overfilled |
| packet size | number of pulses sent per display line of color |
| high saturation/deeper hues represent | slower flow |
| low saturation/brighter hues represent | faster flow |
| color doppler angle of insonification < 90 degrees | colored red toward the transducer |
| color doppler angle of insonification > 90 degrees | colored blue away from the transducer |
| PISA | proximal isovelocity surface area |
| higher color persistence = | weak signal & color speckle |
| lower color persistence = | higher temporal resolution & used for flow that changes fast over a short time |
| What are the ways energy is converted in hemodynamics? | viscous loss, frictional loss, & inertial loss |
| pulsatile flow occurs in | arteries |
| phasic flow occurs in | veins |
| hydrostatic pressure value of heart | 0 mmHg |
| hydrostatic pressure value of head | -30 mmHg |
| hydrostatic pressure value of waist | +50 mmHg |
| hydrostatic pressure value of knee | +75 mmHg |
| hydrostatic pressure value of ankle | +100 mmHg |
| principle factor effecting resistance | radius of vessel |
| primary source of peripheral resistance | arterioles |
| mean velocity | average velocity |
| modal velocity | most commonly encountered velocity |
| max velocity | point of max velocity |
| packet | an ensemble of pulses traveling together |
| pourcelot/resistivity index | a measure of pulsatile blood flow that reflects the resistance to blood flow |
| Nyquist limit | causes aliasing; can be fixed by shifting baseline or changing scale |
| appearance of aliasing in CW doppler | no aliasing |
| appearance of aliasing in PW doppler | wrap around |
| appearance of aliasing in color doppler | color reversal |
| pulsatility/Gosling index | a measure of downstream resistance |
| Highest detectable Nyquist velocity away from the transducer | -63.6 cm/sec |
| Lowest detectable Nyquist velocity toward the transducer | +63.6 cm/sec |
| Velocity Mode | shows blue to red up & down |
| Variance Mode | shows color variation from side to side |
| blood pressure | the pressure exerted by a column of blood against the vessel wall |
| What can be calculated using the continuity equation? | stenotic orifice area |
Created by:
ginaliane
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