SPI Flashcards (definitions and formulas)

Pulsatile Flow - Answer- Flow that Accelerates and decelerates w/ each cardiac cycle Infrasound - Answer- Below the range of human hearing, less that 20 Hz Audible Sound - Answer- The range of human hearing 20-20,000Hz ALARA - Answer- (as low as reasonably achievable) provides the least amount of energy exposure possible to the patient Compression - Answer- Squeezing signal amplitudes into a narrower range Ultrasound - Answer- Above the range of human hearing, greater than 20,000 Hz B-Mode - Answer- Mode of operation in which the display presents a spot of appropriate brightness for each echo received by the transducer (Brightness mode) Wavelength - Answer- length of space over which a cycle occurs Wavelength formula - Answer- Wavelength = Propagation speed/frequency SATA - Answer- Spatial Average, temporal average *lowest intensity SPTP - Answer- Spatial peak, Temporal Peak *highest intensity Continuous wave (CW) - Answer- Ultrasound in which cycles repeat indefinitely; not pulse Rarefaction - Answer- Regions of low pressure and density in a compressional wave Pressure - Answer- concentration of force M-mode - Answer- Display mode that shows motion (depth on vertical axis and time on horizontal) Depth Gain Compensation - Answer- (TGC) time gain compensation Transducer - Answer- A device that converts one form of energy into another Intensity - Answer- Concentration of power in an area Intensity formula - Answer- Power/area Phantom - Answer- tissue equivalent device that has characteristics that are representative of tissues Test Object - Answer- A device without tissue-like properties that is designed to measure some characteristics of imaging system Aliasing - Answer- Improper Doppler-shift inför from a pulsed spectral dipper or color doppler instrument when the true doppler shift exceeds 1/2 PRF Anechoic - Answer- Black (echo free) Hypoechoic - Answer- Weak echoes Nyquist limit - Answer- Doppler shift frequency above which aliasing occurs; 1/2 the PRF Speckle - Answer- Granular appearance of images and soectral displays that is caused by the interference of echoes from the distribution of scatters in tissue Baseline shift - Answer- more baseline up or down on a spectral display (this can help with aliasing) Continuous wave Doppler - Answer- A doppler device or procedure that uses continuous wave ultrasound Disturbed flow - Answer- When parallel streamlines are altered from their straight form Frequency spectrum - Answer- The range of doppler shift frequencies present in a returning echo Doppler Spectrum - Answer- Range of frequencies present in doppler shifted echoes Fluid - Answer- Substances that flow and conform to the shape of their containers Flow - Answer- to move in a stream Parabolic flow - Answer- Max flow speed in the center of the lumen and min flow speed at the walls Laminar flow - Answer- Flow in which fluid layers slide over each other in a smooth, orderly manner, w/ no mixing between layers Hertz - Answer- Unit of frequency Medium - Answer- Material through which a wave travels Period - Answer- time it takes for one cycle to occur interference - Answer- combination of positive and or negative pressures turbulence - Answer- flow app tern that is random and chaotic, w/ particles moving in different speeds and directions stenosis - Answer- Narrowing of a vessel lumen Constructive interference - Answer- combination of positive or negative pressures Plug flow - Answer- Fluid speed in essentially constant across the tube Poise - Answer- Unit of viscosity Poiseuille Equation - Answer- predicts volume flow rate Priority - Answer- the gray scale echo strength below which color-doppler information is shown preferentially on a display Pulsed Doppler - Answer- A doppler device or procedure that uses pulsed wave ultrasound Range gating - Answer- PW Dopplers ability to select info from a particular depth along the beam Sample volume - Answer- Anatomic region from which pulsed doppler echoes are accepted Saturation - Answer- The amount of hue present in a mix w/white Spectral analysis - Answer- presentation of doppler spectrum Spectral broadening - Answer- Widening of the doppler shift spectrum; occurs for disturbed and turbulent flow Spectral Doppler display - Answer- Presentation of doppler info Phase quadrature - Answer- two signals differing by 1/4 of a cycle Hue - Answer- Color Inertia - Answer- Resistance to acceleration Luminance - Answer- Brightness of a presented color and saturation Wall filter - Answer- Allows elimination of clutter caused by tissue and wall motion Impedance - Answer- Resistance that sound encounters in traveling through a medium Megahertz - Answer- One million hertz Longitudinal wave - Answer- wave in which the particle motion in parallel to the direction of wave travel Kilohertz (kHz) - Answer- one thousand hertz Intensity Transmission Coefficient - Answer- Fraction of the incident intensity that is transmitted into the second medium Window - Answer- An anechoic region appearing beneath echo frequencies presented on a doppler spectral display Volumetric flow rate - Answer- Volume of fluid passing a point [er unit of time Viscosity - Answer- Resistance of fluid to flow Variance - Answer- a measure of spectral broadening Streamlines - Answer- a line representing the path of motion of a particle of fluid Spectral Analyzer - Answer- a device that derived a frequency spectrum from a complex signal Near zone - Answer- The region of the sound beam in which the beam diameter decreases as the distance increases from the transducer Digital to analog converter - Answer- device that converts a # to a proportional voltage amplitude Imaging Depth Forumla - Answer- Rate of speed x time of travel/2 A-mode - Answer- mode of operation in which the display presents echo amplitude versus depth Analog - Answer- Related to a procedure or system in which data are represented by proportional, continuously variable, physical quantities Image Processor - Answer- An electronic device that manipulates and prepares images for visual presentation Distance/Range equation - Answer- Distance = rate of speed x Time of travel ITC equation - Answer- 1-IRC Aperture - Answer- size of transducer element Axial - Answer- In the direction of the transducers axis Spatial Pulse Length (SPL) - Answer- Length of a pulse from front to the back Specular reflection - Answer- Reflection from a large, flat, smooth boundary Intensity Formula - Answer- power/area Power formula - Answer- amplitude^2 SPTA - Answer- Spatial peak, temporal average *bioeffect Impedance formula - Answer- Density x propagation speed Overall attenuation formula - Answer- Attenuation coefficient x pathlength Sound - Answer- Traveling wave of acoustic variables Scattering - Answer- diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface refraction - Answer- Change of sound direction when it crosses a boundary reflector - Answer- Media Boundary that produces a reflection Reflection - Answer- portion of sound returned from a media boundary; echo Rayls - Answer- Units for impedance Pulse repetion period - Answer- time from the beginning of one pulse to the start of the next Linear array - Answer- array made of rectangular elements arranged in a straight line Linear Phased Array - Answer- Linear array operated by applying voltage pulses to all elements but w/small time differences to direct US pulse out in various directions Linear sequenced array - Answer- Linear array operated by applying voltage pulses to groups of elements sequentially Image memory - Answer- The part of the image processor where echo info is stored in image format Axial resolution - Answer- The minimum reflector separation required along the sound travel to produce speared echoes Analog to digital converter - Answer- A device that converts voltage amplitude to a number Apodization - Answer- Non uniform driving of elements in an array to reduce grating lobes Digital - Answer- Related to a procedure or system in which data are represented by numeric digits Display - Answer- A device that presents a visual image derived from voltage received from an image processor Elastography - Answer- Imaging tissue stiffness by tracking movement under mechanical stress Frame - Answer- A single image produced by one complete scan of the sound beam Pulse duration - Answer- Time it take for one pulse to occur (beginning to end) Pulse repetition frequency - Answer- # of pulses that occur in one second Power - Answer- rate at which energy is transferred Pulse - Answer- Collection of ultrasound cycles Persistence - Answer- Averaging sequential frames together to provide a smoother image appearance and to reduce noise Attentuation coeficient formula - Answer- Frequency/2 Intensity equation - Answer- Power/area SPL equation - Answer- # of cycles in pulse x wavelength or # of cycles in pulse x prop speed/frequency Sector - Answer- Curved construction pulses travel out in different directions Side lobes - Answer- weaker beams of sound traveling out from a single element in directions different from those of the primary beam Source - Answer- Emitter of ultrasound:trasnducer Vector array - Answer- Linear sequenced array that emits pulses from different starting points and in different directions Q factor - Answer- a number that indicated to what extent the transducer can operate at the center of main frequency Amplification - Answer- The process by which small voltages are increased to larger ones Amplifier - Answer- A device that acomplishes amplification Compensation - Answer- Equalization of received echo amplitude differences caused by different attenuations for different reflector depths DF equation - Answer- PD/PRP Oblique incidence - Answer- Sound direction that is not perpendicular to media boundaries Imaging depth formula - Answer- Rate x time/2