SPI Exam Questions pool ( Answered) rated A+. Concentration of

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SPI Exam Questions pool ( Answered) rated A+. Concentration of force in an area. Units are: (Pa) or Pascals. - ✔✔Pressure What are the units for density? - ✔✔kg/cm3 What are the seven aco ... ustic parameters and what are they determined by? - ✔✔-Period determined by SOURCE -Frequency determined by SOURCE -Amplitude determined by SOURCE -Power determined by SOURCE -Intensity determined by SOURCE -Wavelength determined by both SOURCE & MEDIUM -Propagation Speed determined by MEDIUM What is the frequency of audible sound? - ✔✔20Hz to 20 kHz The frequency of Ultrasound is greater than? - ✔✔20kHz What is the speed of sound in soft tissue? List the propagation speed of different media from slowest to fastest. *As a general rule sound travels fastest in solids, slower in liquids, and slowest in gases. - ✔✔Air>Fat>Soft Tissue (1,540 m/s)>Blood>Muscle>Bone 10^-6 is the exponent what is the prefix? What is the exponent and prefix that corresponds on the opposite side of the metric system? - ✔✔The prefix is MICRO often meaning millionth. 10^6, the prefix is MEGA often meaning million. 10^-9 is the exponent what is the prefix? - ✔✔The prefix is NANO often meaning billionth. *smallest 10^-3 is the exponent what is the prefix?What is the exponent and prefix that corresponds on the opposite side of the metric system? - ✔✔The prefix is milli often meaning thousandth. 10^3, the pefix is KILO often meaning thousand. Peak to Peak Amplitude - ✔✔It is the difference between maximum and minimum values of an acoustic variable. Therefore, peak-to-peak amplitude is twice the value of the amplitude. Amplitude is the the "bigness" of the wave. It is also the difference between the maximum value and the average or undisturbed value of an acoustic variable. What are the units? - ✔✔Pressure --Pa Density -- g/cm^3 Particle motion --cm, in, any distance Amplitude is the the "bigness" of the wave. It is also the difference between the maximum value and the average or undisturbed value of an acoustic variable. What are the units? - ✔✔Watts/ cm2 What are the units for Power? - ✔✔WATTS Is Power adjustable? - ✔✔Yes, there is a control on the ultrasound system that allows the sonographer to alter the initial power. How are Power and Amplitude related? - ✔✔Both amplitude and power are parameters that describe the size, or magnitude, of a wave. When power increases so does amplitude. power is proportional to the wave's amplitude squared. A sonographer has increased the amplitude of a wave by 4. How has the power changed? - ✔✔4x4=8 or 4^2=8 The power has increased 8 fold. A sonographer has increased the amplitude of a wave by 4. How has the power changed? - ✔✔4x4=16 or 4^2=16 The power has increased 8 fold. What is the relationship between intensity and amplitude? - ✔✔If a wave's amplitude is doubled, the intensity is increased to four times its original value. What are Power and Intensity both related to? - ✔✔AMPLITUDE^2 Two characteristics that affect the speed of sound - ✔✔Stiffness and Density Stiffness and its relationship to Speed - ✔✔Stiffness and Speed are directly related. Density and its relationship to Speed - ✔✔Density and Speed are inversely related. *Materials that are not stiff and very dense will have the slowest speed. Ex: Air has an exceedingly low stiffness. Therefore sound travels slowly in air. Can wavelength and propagation speed be adjusted by the sonographer? - ✔✔No *Speed changes only when the wave travels from one medium to a different medium. What is a hydrophone (microprobe)? - ✔✔It is a small hypodermic needle with a tiny piece of piezoelectric material attached to its end. A wire connects the PZT crystal to an oscilloscope. *It measures the characteristics of a sound beam. What parameters does the Hydrophone determine? - ✔✔PERIOD, PRF, AND PD are determined by the hydrophone signal. Radiation Force - ✔✔A transducer's sound beam creates a very small, but measurable force on any target that it strikes. When the sound beam is entirely absorbed or reflected by the target , the target acts as an extremely sensitive miniature postal scale. Acousto-Optics (Schlieren) - ✔✔Based on the interaction of sound and light. A shadowing system, allows us to view the shape of a sound beam in a medium. 3 devices measure the output of ultrasound transducers by absorption, the conversion of sound energy into heat - ✔✔Calorimeter- Measures total power in a sound beam Thermos bottle filled with absorption sound beam is directed into the bottle and is calculated by the rise in temp and time of heating Thermocouple - A tiny electronic thermometer. measure a sounds beams power at a particular location in the beam Liquid crystals- Change color based on their temp. MOOD RING Two techniques to study Bioeffects - ✔✔Mechanistic approach searches for a relationship between cause and effect Empirical Approach searches for a relationship between exposure and response What are the two important bioeffects of mechanisms? - ✔✔Thermal- proposes bioeffects from tissue temperature Cavitation- The interaction of sound waves with microscopic, stabilized, gas bubbles in the tissues. Thermal Index - ✔✔TI is a useful predictor of maximum temperature increase under most clinically relevant conditions. 3 forms of Thermal Index - ✔✔TIS- soft tissue thermal index, assumes sound is traveling in soft tissue TIB- bone thermal index, assumes that bone is at or near the focus of the sound beam TIC- cranial bone thermal index assumes that cranial bone is in the sound beams near field Two forms of Cavitation - ✔✔Stable- at lower MI levels, stable cavitation occurs. Gaseous Nuclei tend to oscillate or expand and contract. Bubbles a few millimeters in size double in size but DO NOT BURST. Transient- At higher MI levels transient cavitation occurs. BUBBLES BURST. *produces highly localized, violent effects, including: Colossal temps & Shock waves What is the highest of the Intensity measurements? - ✔✔Spatial Peak Temporal Peak What is the lowest of the intensity measurements? - ✔✔Spatial Average Temporal Average Which intensity measurement is the most important in regards to tissue heating? - ✔✔Spatial Peak Temporal Average What are the range in intensities from largest to smallest? - ✔✔SPTP>Im>SPPA>SPTA>SATA What is the log of 10,000 - ✔✔4 Signals that are decreasing in strength - ✔✔Negative decibels These two factors, PATH LENGTH and FREQUENCY OF SOUND determines - ✔✔Attenuation Three processes that contribute to Attenuation - ✔✔Reflection Scattering Absorption When the dimension of the boundary is large , that is, more than a few wavelengths of the sound - ✔✔Reflection When the boundary is smooth the sound is reflected in only one direction in an organized manner - ✔✔Specular Reflection Do specular reflections at an angle return back to the transducer? - ✔✔No When a wave reflects off an irregular surface, it radiates in more than one direction. Some of the sound returns back to the transducer but the signals are often weak. - ✔✔Diffuse Reflection (Backscatter) When a tissue interface is small; that is equal to or less than the wavelength of the incident sound beam - ✔✔Scattering What is the relationship between high frequencies and scattering - ✔✔Directly Related Higher frequency sound waves produce shorter pulses that create accurate images. What is the disadvantage? - ✔✔More Attenuation Less capable of traveling to substantial depths The number of decibels of attenuation that occurs when sound travels one centimeter - ✔✔Attenuation Coefficient db/cm What is the formula for TOTAL ATTENUATION? - ✔✔atten. coefficient(dB/cm)x distance (cm) The relationship between attenuation coefficient and frequency - ✔✔The attenuation coefficient is 1/2 of the frequency. What is the formula for attenuation coefficient in soft tissue? - ✔✔atten. coef. (dB/cm)= freq(MHz)/2 What is the Attenuation of Ultrasound in Media from lowest to greatest? - ✔✔Water>Blood>Fat>Soft Tissue> Muscle> Bone> Air [Show More]

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