SPI Exam Review. Predictor Questions and answers. Questions pool. Rated A

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SPI Exam Review. Predictor Questions and answers. Questions pool. Rated A What is a hydrophone? What does it measure? - ✔✔A small needle with piezoelectric crystal at the end. It measures pres... sure in a sound beam. What is a schlieren? - ✔✔A machine that uses acousti-optics to measure sound and light in beam profiles. What is a calorimeter? - ✔✔A machine that can calculate total power of the beam measuring heat gain and the time itakes to obtain the heat. What is the AIUM and FDA bioeffects intensity limit? - ✔✔SPTA 100mW/cm2 (unfocused) 1 W/cm2 or 1,000mW/cm2 (focused) Highest and lowest output intensity - ✔✔Highest- Pulsed doppler Lowest- gray scale imaging Are the strongest conclusions made when mechanistic and empiracle approaches agree? - ✔✔Yes Mechanistic- "Cause-effect" Empiraical- "Exposure- Response" Where is temperature elevation at a tissue-bone interference most likely? - ✔✔Bone since bone is a sound absorber. Which intensity is related to heating of tissue? - ✔✔SPTA *exams that cause temps over 41*C is considered harmful to a fetus. Name the three thermal indices - ✔✔TIS-Thermal index in soft tissue TIB- Thermal index in bone TIC- Thermal index at cranial bone or near skin surface TI of 3 means that a temperature elevation of 3*C may occur. Intensity of focused and unfocused beams - ✔✔Unfocused- 100mW/cm2 Focused- 1,000mW/cm2 or 1 W/cm2 Mechanical index equation - ✔✔MI= Peak-Pressure / square root of frequency Mechanical index is higher (more likely to produce cavitation) with: - ✔✔Higher pressure, lower frequency Stable cavitation - ✔✔Bubbles do not burst Transient Cavitation - ✔✔Bubbles burst *also called normal or inertial cavitation. In Vitro - ✔✔"Outside of body" Epidemiological studies - ✔✔A large number of patients is required. Limitations of epidemiologic studies - ✔✔often retrospective amiguities other risk factors Which beam is more dangerous, focused or unfocused? - ✔✔Unfocused What is the importance of quality assurance? - ✔✔Routinely evaluate the ultrasound system to obtain optimal images. Is a phantom an objective or subjective standard? - ✔✔Objective AIUM 100mm Test Object - ✔✔Propagation speed of 1,540m/s but does not have attenuation properties of soft tissue and cannot evaluate gray scale. Tissue Equivalent Phantom - ✔✔Sound has a velosity of 1,540m/s. Attenuates like soft tissue so it can evaluate gray scale. Doppler phantom - ✔✔pump forces echogenic fluid through the vessels at known velocities. Used to assess accuracy of CW doppler. What is ultrasound's gold standard? - ✔✔angiography Hyperechoic - ✔✔Portions of an image that are brighter than surrounding tissues Hypoechoic - ✔✔Portions of an image that are not as bright as surrounding tissues, or tissues that appear less bright than normal Isoechoic - ✔✔Structures with equal echo brightness Homogeneous - ✔✔A protion of tissue or a structure that has similar echo characteristics throughout. Heterogeneous - ✔✔Displaying a variety of different echo characteristics within the tissue. Six basic assumptions of imaging systems - ✔✔1. Sound travels in a straight line 2. Sound travels directly to a reflector and back 3. Sound travels exactly 1,540m/s 4. reflections arise from structures positioned along the beam's main axis. 5. intensity of the of the reflections is related to the scattering characteristics of the tissue. 6. The imaging plane is extremely thin. Reverberations - ✔✔Multiple echoes appearing on the display as a result of US "pin-ponging" between two reflectors. Looks like a ladde [Show More]

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