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Section 2 Exam Prep
Physics
| Question | Answer |
|---|---|
| Why must the electrical signals originating from the returning echoes be focused? | Sound wave divergence |
| A decrease in transducer element thickness will result in an ? in the operating frequency. | Increase |
| Which component in a modern scanning system changes the timing of the transmit and receive electrical signals in order to improve beam focusing? | Delay lines (time delays) |
| What determines the resonance frequency of an element? | Thickness |
| Axial Resolution Parameter | Spatial Pulse Length |
| Lateral Resolution Parameter | Beam Width |
| Elevational Resolution Parameter | Beam Slice Thickness |
| What type of mechanical transducer uses different sizes of circular elements to acquire ultrasonic images? | Annular |
| What is the axial resolution for pulses traveling through soft tissue in which the frequency is 3 MHz with four cycles per pulse? | 1.0mm |
| What portion of the transducer serves to reduce reflections due to impedance differeances from the crystal to the skin surface? | Matching Layer |
| What happens to the near field length (near field depth) for a single element, non-focused transducer if the diameter of the crystal is doubled? | Quadrupled |
| What is the name of the process where small amounts of electricity are generated by applying pressure to certain types of crystals? | Piezoelectric |
| Doubling the frequency causes axial resolution to be? | Improved by a factor of 2 |
| Ultrasound transducers convert ? energy into ? energy and vice versa. | Electric, ultrasound |
| When discussing constructive and destructive sound wave interference, which factor determines the "phase relationship" between two sound waves? | Time |
| Which transducer frequency would have the thinnest elements? | The highest frequency (ex. 10 MHz) |
| What type of early ultrasonic imaging transducer uses an electric motor to sweep (steer) the transducer elements past an acoustic window in the transducer housing? | Mechanical |
| For the same size non-focused, single element transducer, what happens to the near-field length when the frequency is increased? Decreased? | Lengthens, shortens |
| Which "principle" is used to shape, focus, and steer the sound beams produced by modern phased array transducers? | Huygen's |
| What type of array is the combination of linear and phased array operations? | Vector |
| What is the most likely effect on a scanning operation if the sonographer selects too many focal zones? | Degraded frame rate |
| How is destructive sound wave interference within the crystal, which negatively affects a transducer's performance, eliminated? | Using a crystal whose thickness is 1/2 the transmitted wavelength |
| What may happen to a transducer that is sterilized by steam (autoclaved) after an invase procedure has been performed? | Depolarization of the crystals |
| Where is the best lateral resolution located for a focused, single-element transducer? | Focal Zone |
| Axial resolution is determined by? | Spatial Pulse Length |
| Section thickness focusing requires multiple rows of? | Elements |
| What is the most common ceramic element used in modern diagnostic ultrasound transducers? | PZT |
| Electronic control of focusing is achieved by? | Phasing |
| Increasing frequency decreases penetration due to increased? | Attenuation |
| Linear array element groups are scanned by? | Sequencing |
| Which transducer element has the longest near zone? | 8 mm, 7 MHz (The larger the diameter and higher frequency, the longest near field) |
| What is an array transducer's aperture? | The active group of elements producing or receiving sound waves |
Created by:
marissagirl