ARDMS SPI STUDY GUIDE QUESTIONS AND ANSWERS ALREADY PASSED

ARDMS SPI STUDY GUIDE QUESTIONS AND ANSWERS ALREADY PASSED In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... ✔✔Remain the Same because stiffness and density affect Propagation ...

ARDMS SPI STUDY GUIDE QUESTIONS AND ANSWERS ALREADY PASSED In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... ✔✔Remain the Same because stiffness and density affect Propagation Speed. What is the audible range? ✔✔20-20,000Hz >20,000Hz=Ultrasound Frequency is measured in ✔✔Hertz (Hz) is Cycles per Second Not affected by sonographer Increase Frequency; Decrease Depth A period is the length of time it takes for ✔✔one complete wavelength to pass a fixed point PRP is determined by ✔✔Transmit time and receive time. Period is measured in ✔✔Time (μs) When the sonographer changes the imaging depth what parameters are changed? ✔✔PRP, PRF, Duty Factor What is duty factor? ✔✔The percentage or fraction of time that the system is transmitting a pulse (Time Sound is ON or ON-Time). Propagation Speed in SOFT TISSUE ✔✔1.54 mm/μs (1540 m/sec) Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period ✔✔Time, (μs) Pulse duration is determined by ✔✔Sound Source Only Pulse Duration is controlled by ✔✔the ultrasound system and transducer Pulse Duration Formula ✔✔pulse duration (μs) = # cycles in pulse/frequency(MHz) PD= Number of cycles in Pulse/ Frequency(Hz) Spatial Pulse Length (SPL) (measurement) ✔✔The distance that a pulse occupies in space from the start to the end of a pulse. (mm) Typical values for spatial pulse length in soft tissue. ✔✔0.1 to 1.0 mm Spatial pulse length is determined by ✔✔sound source and medium Spatial Pulse Length is directly proportional to ✔✔the Number of Cycles in the Pulse and the Wavelength (Directly Proportional means that increased SPL will increase both the number of cycles in the pulse and the wavelength if increased). Spatial pulse length is inversely proportional to ✔✔Frequency (MHz) (Inversely Proportional means that increased SPL will lower frequency. This is because axial resolution is better with lower frequency) Pulse Duration (PD) ✔✔The actual time from the start of a pulse to the end of that pulse; a single transmit, talking, or "on" time. Time the pulse is on typically measured in (ms). Pulse Length ✔✔The distance of the pulse start to end or the duration or length of a single pulse Pulse Length is typically measured in (mm). the ability of an object to resist compression and relates to the hardness of a medium? ✔✔Stiffness. Think: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed An increase in pulse repetition frequency would lead to: ✔✔Increasing pulse repetition frequency, increases duty factor. ↑ PRF ↑ Duty Factor Which of the following would have the highest propagation speed? ✔✔Bone has the highest propagation speed, at 2000-4000 m/s. What has the lowest propagation speed? ✔✔air technically has the lowest propagation speed at 300 m/s Which has the Slowest Propagation Speed? Water Soft Tissue Bone Lung tissue ✔✔Lung Tissue As imaging depth increases, the pulse repetition frequency (PRF) must: ✔✔Decrease As imaging depth increase, pulse repeition freqency (PRF) decreases. ↑ Imaging Depth ↓ PRF What describes the amount of refraction that occurs at an interface? ✔✔Snell's law Refraction: the redirection of the transmitted sound beam Snell's law describes the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media. Pressure is typically expressed in: ✔✔Pascals (Pa) The typical range of frequency for diagnostic ultrasound imaging is ✔✔1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging. The attentuation coefficient in soft tissue is equal to: ✔✔Attentuation Coeffcient = 1/2 (one half of the frequency in soft tissue) The attentuation coeffcient (in dB/cm) is the rate at which sound is attentuated per unit depth. Micro is denoted as: ✔✔Micro is denoted as millionth (µ) What is described as the distance over which one cycle occurs? ✔✔Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle. Remember, it asks for distance over which one cycle occurs. Stiffness and propagation speed are ✔✔Directly Related Also remember: ↑ Stiffness ↑ Speed ↓ Density ↑ Speed Areas of high pressure and density are referred to as: ✔✔Compressions What type of wave is sound? ✔✔Mechanical and Longitudinal Wave The frequency ranges for ultrasound are: ✔✔Ultrasound frequency is 20 to 20,000 Hz The speed of sound in soft tissue is ✔✔Speed of sound in soft tissue is 1540 m/s Which transducer fires the elements in groups? ✔✔Linear sequenced array fires the elements in groups The units for wavelength is ✔✔Wavelength units are (Millimeters) Enhancement is caused by ✔✔Weakly attenuating structures The wavelength in a material having a propagation speed of 1.5 mm/µs employing a transudcer frequency of 5.0 MHz is: ✔✔0.3 mm wavelength = c/f 1.5 mm/µs / 5 MHz = 0.3 mm An ultrasound transducer converts ✔✔Electrical energy into Mechanical energy and vice versa Lowest attenuation to highest ✔✔bone, muscle, fat, air If frequency doubles, what happens to the wavelength? ✔✔Wavelength is decreased by 1/2 Frequency and Wavelength are: ✔✔Inversely related What happens to intensity if the amplitude of a signal is halved? ✔✔Amplitude halved will result in intensity quartered amplitude = intensity2 Ultrasound pulses contain a range of frequencies called ✔✔bandwidth How is time related to frequency ✔✔inversely What describes the percentage of time that sound is on? ✔✔Duty factor is the percentage of time the sound is being transmitted A 3 dB gain would indicate an increase in intensity by: ✔✔Two Times 3 dB results in doubling of intensity (or power) The intensity of the ultraosund beam is usually greater at the focal zone because of ✔✔the smaller beam diameter Attenuation denotes ✔✔Progressive weakening of the sound beam as it travels Which of the following has the lowest intensity ✔✔SATA is the lowest of the intensities What is the definition of the beam uniformity ratio? ✔✔Beam Uniformity Ratio = Spatial peak / Spatial average Continuous wave Doppler has a duty factor of ✔✔100% CW Doppler is always transmitting sound making it's duty factor 100% The spatial pulse length is defined as: ✔✔the product of the wavelength and the number of cycles in a pulse? SPL = wavelength x cycles What term and philosophy relates the amount of exposure time for the sonographer and patient during a diagnostic ultrasound examination? ✔✔ALARA - As Low As Reasonably Achievable What term is defined as the body's pathologic response to illness, trauma or severe physiologic or emotional stress? ✔✔Shock The inertia of the medium describes its: ✔✔Density. Inertia is described by Newton's principle - an object at rest will stay at rest. An object in motion stays in motion, unless acted on by an outside force. Greatest attenuation would occur at: ✔✔long distance with high frequency A 3MHz sound beam travels through two media. It attenuates 5 dB in medium A and 6 dB in medium B. ✔✔Total attentuation is 11 dB Attenuation simply adds up as sound travels. What would you do to create a wave with the highest possible intensity? ✔✔Highest intensity would occur with a short distance and low frequency. Lowest Attenuation is found at ✔✔lowest frequency, with the shortest path length. What results in the most attenuation? ✔✔most attenuation occurs at the high frequency and long distance. Which media has the greatest attenuation and the slowest speed? ✔✔Air Air > Bone & Lung > Soft Tissue > Water What type of wave is sound? ✔✔Mechanical and Longitudinal wave The speed of sound in soft tissue: ✔✔1540 m/s The unit for wavelength: ✔✔Distance (mm) Enhancement is caused by: ✔✔weakly attenuating structures Lowest attenuating to highest attenuation ✔✔Fat-Muscle-Bone-Air List propagation speed from lowest to highest ✔✔Air-Fat-Muscle-Bone Which of these media has the lowest attenuation and the greatest speed? bone tendon lung fat air ✔✔Bone Air > Bone & Lung > Soft Tissue > Water Bone is more stiff than air (remember ↑ stiffness, ↑ speed) What describes the physics of refraction mathematically? ✔✔Snell's Law What is a reflection arising from a rough boundary? ✔✔Non-specular Specular reflection is from a smooth reflector (like mirrors). They return in one direction. Whereas, non-specular is diffuse or scatter, reflection from a rough boundary. When time-of-flight is measured, we can determine the ________? ✔✔Reflector Depth A sound pulse travels from the transducer to location A, reflects off of it, and returns to the transducer in 130 μs. How deep is location A? ✔✔Location A is 10 cm from the transducer Total travel distance would be 20 cm Which of the following would be considered the narrowest part of a sound beam? ✔✔The focus is the narrowest part of the beam Which of the following is the part of the transducer that stops the ringing of the element? ✔✔The damping material helps stop the ringing of the transducer Along with image depth, which of the following also determines the frame rate? ✔✔Image depth and the number of lines per frame determines the frame rate. Which type of resolution is an accurate representation of moving structures? ✔✔Temporal resolution, also known as frame rate, is the ability to display moving structures in real time. What type of transducer that utilizes elements arranged in a concentric pattern? ✔✔The annular array transducer ultilizes elements arranged in concentric rings What transducer would be considered an advantage of linear array over a phased array transducer? ✔✔The linear array has a wider near field of view compared to a phased array transducer Mechanical Transducers: ✔✔Have moving parts Uses a motor to steer the beam Most transducers are no longer mechanical May be focused with a lens or phased focuses Along with crystal diameter, the divergence in the far field is also determined by... ✔✔Frequency and crystal diameter determines the divergence in the far field What would cause an increase in frame rate? ✔✔Decreasing the imaging depthwould increase the frame rate When you decrease the imaging depth it can work faster (increase frame rate) because it doesn't have to go as deep. The diameter of the beam in the Fresnel zone/near zone does what? ✔✔Decreases Which resolution is best in the clinical imaging? ✔✔Axial resolution is best in imaging will increase the near zone length? ✔✔A large crystal diameter with high frequency would increase the near zone length What will decrease beam divergence in the far field? ✔✔A large crystal diameter and high frequency would decrease the beam divergence in the far field Imaging transducers have ✔✔Imaging transducers have low quality factors and wide bandwidiths. What is the speed of a wave with a wavelength of 3 m and a frequency of .1 Hz? ✔✔0.3 m/s wave speed= frequency x wavelength Wavelength and Frequency are ✔✔inversely proportional to each other How do you calculate the speed of a wave given the wavelength and frequency? ✔✔Frequency (Hz) x wavelength (distance)= Wave Speed What is the speed of a wave with a frequency of 2 Hz and a wavelength of 87 m? ✔✔174 m/s 2Hz x 87m= 174m/s speed of a wave: frequency x wavelength The ____ of a wave is the number of wavelengths that pass a fixed point in a second. ✔✔frequency Frequency is the number of wavelengths that pass a fixed point in a second A sound wave is traveling in the body and propagates from muscle to air. What percentage of the sound wave is most likely reflected at the muscle-air boundary? ✔✔75% Which of the following lists is in decreasing order? ✔✔Mega, kilo, deca, milli, nano The conversion of sound energy to heat ✔✔Absorption Acoustic Speckle ✔✔the interference pattern caused by scatterers that produces the granular appearance of tissue on a sonographic image Acoustic Variables ✔✔changes that occur within a medium as a result of sound traveling through that medium Amplitude ✔✔The maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector Attenuation ✔✔A decrease in the amplitude and intensity of the sound beam as sound travels through tissue. Attenuation Coefficient ✔✔The rate at which sound is attenuated per unit depth Axial Resolution ✔✔The ability to accurately identify reflectors that are arranged parallel to the ultrasound beam Backscatter ✔✔Scattered sound waves that make their way back to the transducer and produce an image on the display Beam Uniformity Ratio ✔✔The ratio of the center intensity to the average spatial intensity; also referred to as the SP/SA factor or beam uniformity coefficient Capacitive Micromachined Ultrasound Transducers ✔✔Technology used to create comparable transducer technology to piezoelectric materials Compression ✔✔An area in the sound wave of high pressure and density Continuous Wave ✔✔Sound that is continuously transmitted Damping ✔✔The process of reducing the number of cycles of each pulse in order to improve axial resolution Decibels ✔✔A unit that establishes a relationship or comparison between two values of power, intensity, or amplitude Density ✔✔Mass per unit volume Directly Related ✔✔Relationship that implies that if one variable decreases, the other also decreases or if one variable increases, the other also increases; also referred to as Directly Proportional Distance ✔✔How far apart objects are AKA vibration or displacement Duty Factor ✔✔The percentage of time that sound is actually being produced Elasticity ✔✔The ability of a material to bounce back after being disturbed Frequency (Hz) ✔✔The number of cycles per second Half-Intensity Depth ✔✔the depth at which sound has lost half of its intensity Half Intensity Depth is also called ✔✔Half-Value Layer Thickness Hertz (Hz) ✔✔A unit of frequency Hydrophone ✔✔a device used to measure the output intensity of the transducer Impedence ✔✔the resistance to the propagation of sound through a medium. Inertia ✔✔Newton's principle that states that an object at rest stays at rest and an object in motion stays in motion, unless acted on by an outside force. Intensity ✔✔the power of a wave divided by the area over which it is spread; the energy per unit area Intensity Reflection Coefficient (IRC) ✔✔The percentage of sound reflected at an interface. The percentage of the sounds intensity that is reflected when sound hits a boundary or tissue Interface is the dividing line between 2 different media. Intensity Transmission Coefficient (ITC) ✔✔The percentage of sound transmitted at an interface -orThe percentage of intensity that continues forward after beam strikes an interface Interface ✔✔The dividing line between two different media Inversely Related ✔✔Relationship that implies that if one variable decreases, the other increases or if one variable increases, the other decreases; also referred to as inversely proportional Longitudinal Wave ✔✔Waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling. Medium ✔✔Any form of matter; Solid, Liquid, or Gas Non-specular Reflectors ✔✔Reflectors that are smaller than the wavelength of the incident beam Which gain will increase the risk of bioeffects? ✔✔Transmit What is considered the memory of an ultrasound instrument? ✔✔Digital Scan Converter Spectral Broadening Suggests ✔✔Turbulent Flow What happens to axial resolution with Pulse Wave Doppler ✔✔Axial Resolution Degrades when using Pulse Wave Doppler What color is usually used in Color Flow Doppler variance map to indicate turbulent flow? ✔✔Green A Doppler (high pass filter) eliminates? ✔✔high amplitude signals, low velocity flow The Doppler wall filter is considered a: ✔✔High Pass Filter The Nyquist Limit is equal to: ✔✔PRF/2 Pulse Repetition Frequency divided by two Multiple echoes, equally spaced originating from a gas bubble is called ✔✔Ring Down An increase in red blood cell velocity will____________Doppler Shift: ✔✔Increase increase in rbc velocity increases Doppler shift The primary advantage of CW Doppler is: ✔✔Absence of Sampling Rate The range for ultrasound begins: ✔✔at 20,000Hz or 20KHz (Useful Frequency Range for Clinical Imaging is 2MHz-10MHz) Which instrument control affects the amplitude (db) of the outgoing signal? ✔✔Transmit Gain; Amplitude can be affected by the sonographer What is used to convert Doppler shift information into color? ✔✔Autocorrelation What is used to process conventional Doppler shift information but is too slow of a method for Color Doppler? ✔✔Fast Fourier transform Pulse Repetition Frequency ✔✔The number of pulses that an ultrasound system transmits into the body each second. Unit: Hz. Typically 4-15 KHz. PRF and Depth of View are inversely related. When the system is imaging deeper, the pulse repetition frequency is lower, as well as, the number of pulses created each second. What is the best way to increase the near field length of an ultrasound beam? ✔✔Increase Transducer Diameter What is the range of frequencies produced by a dampened PZT element? ✔✔bandwidth What is bandwidth? ✔✔range of frequencies in a pulse The percentage of time that the ultrasound instrument is emitting ultrasound is called? ✔✔Duty Factor The maximum value is 1, the minimum is 0 What is the unit of Duty Factor? ✔✔Duty Factor is Unit-less If the ultrasound is produced as a continuous wave (CW), the duty factor will have a value of 1. With Pulsed Wave the whole value of On-Time is fractioned. What is Q-factor or Quality Factor? ✔✔The "Q factor" describes the bandwidth of the sound emanating from a transducer Transducer Q Factor (Q = Quality) is associated with two characteristics of the crystal • purity of their sound and • length of time the sound persists (Unitless measurement) Fundamental Frequency(Hz)/Bandwidth(range of frequency in the pulse) The unit of duty factor is: ✔✔Unitless Clinical imaging transducers are: ✔✔Wide bandwidth; Low Q factor Wide range of frequencies in the pulse and short period of time that the sound is emitted (pulsed wave) Power/Area= ✔✔Intensity Increasing wavelength will_______frequency? ✔✔Decrease Beam Properties ✔✔The ultrasound beam propagates as a longitudinal wave from the transducer surface into the propagation medium, and exhibits two distinct beam patterns: - a slightly converging beam out to a distance specified by the geometry and frequency of the transducer (the near field), and - a diverging beam beyond that point (the far field). Does Beam Width directly affect frame rate? ✔✔No: The following directly affect frame rate: Depth of Penetration Field of View Number of Focuses and Line Density What affects frame rate? ✔✔Depth of Penetration, Field of View, Number of Focuses, and Line Density. Frame Rate= Number of Frames/Second When will a reflection occur at the boundary of two media? ✔✔If the acoustic impedances of the tow media are different. Snell's Law ✔✔Describes the relationship between the angles and the velocities of the waves. When an ultrasonic wave passes through an interface between two materials at an oblique angle, and the materials have different indices of refraction, both reflected and refracted waves are produced In ultrasound, Snell's Law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for a given frequency. The Angle of Incidence ✔✔Refers to the angle of deviation from a perpendicular line to the surface of the tissue Therefore, the desired orthogonal(perpendicular) incident wave in ultrasound should be considered to have an angle of incidence of zero. When the angle of incidence is greater, fewer sound waves are reflected back to the transducer resulting in a more hypoechoic (darker) image with less clarity. The optimal reflection with the most sound waves occurs when the angle of incidence approaches zero and is virtually perpendicular (orthogonal) to the tissue of interest. Law of Reflection ✔✔the angle of incidence is equal to the angle of reflection Mechanical Transducers utilize what kind of focusing? ✔✔Fixed Focusing: Sonographers cannot determine the location of # of foci. Mechanical Transducers use Cross-Sectional imaging, rotating wheel, wobbler, and oscillating mirror. The transducer frequency is primarily determined by the transducer element's what? ✔✔Thickness For pulsed transducers..the main or center frequency of the transducer is determined by the thickness and the propagation speed of the piezoelectric material. PZT is also called ✔✔Ceramic, Active Element, or Crystal A strongly focused transducer implies a: ✔✔Short focal length and Increased Beam Divergence B-mode displays reflector: ✔✔Amplitude and Distance An increase in the number of pixels on the display will improve: ✔✔Detail Resolution Propagation speed is determined by ✔✔Medium only - density and stiffness of media Bulk Modulus describes the change in the material's volume under external stress. Increasing transmit gain increases everything except: ✔✔Frequency Gain is a receiving function •Does not impact how much energy is transmitted to patient (i.e. power) The correct depth placement of reflectors depends primarily upon: ✔✔Propagation Speed What will increase the color flow jet area displayed? ✔✔Increasing Color Gain Increasing Propagation Speed ✔✔air: 330 m/sec fat: 1450 m/sec water: 1480 m/sec soft tissue: 1540 m/sec liver: 1550 m/sec kidney: 1560 m/sec blood: 1570 m/sec muscle: 1580 m/sec bone: 4080 m/sec The most common type of transducer used in echo is: ✔✔Sector Phased Array What are the four acoustic variables? ✔✔1. Temperature 2. Density 3. Particle Motion 4. Pressure The Doppler effect is presented as a ___________________ when the source and the receiver are in motion relative to each other. ✔✔Frequency Shift + or - Doppler Shift ✔✔receiver toward the transducer= + shift receiver away from transducer = - shift + toward (above baseline) - away (below baseline) ✔✔