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Physics Ch. 8
| Question | Answer |
|---|---|
| which component of an ultrasound system is made of lead zirconate titanate (PZT)? | transducer active element |
| the impedance of acoustic gel is greater than the impedance of the matching layer but less than the impedance of the piezoelectric element. T or F? | false |
| what is the thickness of the matching layer of a 2 MHz pulse wave transducer? | 1/4 wavelength |
| which is more important in the determination of the frequency of the sound? | propagation speed of active element |
| which action would cause a PZT crystal to lose its special properties? | exposing it to temperatures above curie point |
| increased thickness of the backing material decreases the quality factor. T or F? | true |
| which properties of the piezoelectric crystal results in the highest emitted acoustic wave frequency? | thin, high propagation speed |
| what is the region from the transducer to the smallest cross-sectional area of a sound beam? | near zone |
| the area that starts at the beam's smallest diameter and extends deeper is the | fraunhofer zone |
| what is the point or location where a beam reaches its smallest dimension | focus |
| if the narrowest diameter of a sound beam is 8cm, then the PZT crystal's diameter is 16 cm. T or F | true |
| the higher the frequency of the acoustic wave, the shorter the near zone length. T or F | false |
| the greater the diameter of the piezoelectric crystal or the aperature, the longer the near zone length. T or F | true |
| which design will create a beam with the shallowest focus? | small diameter, low frequency |
| which design will create a beam with the deepest focus? | large diameter, low frequency |
| which design will create a beam with the deepest focus that will allow for deep imaging? | large diameter, low frequency |
| as sound travels deeply into the far zone, the beam diverges. which will decrease degree of divergence in the far zone? | large diameter, high frequency |
| the lateral resolution of an ultrasound system is primarily determined by the___ | width of the sound pulse |
| the focus of an ultrasound beam is the location where the ____ | optimum transverse resolution occurs |
| in comparison to the near zone, focusing is generally ineffective in the far zone. T or F? | true |
| which focusing technique is different from the others: lens, curved crystal, fixed and phased | phased |
| with these transducers, the ultrasound beam is steered through the FOV by a motor | mechanical & annular phased array |
| these transducers typically produce an image that, throughout its entire depth, is approximately as wide as the ultrasound transducer footprint. | linear switched array |
| these transducer are not mechanically or electronically steered to create a 2D image. which 2 are sequenced | linear switched array & convex or curvilinear array |
| where does the image shape originate when using a linear phased array transducer | at the center of the array |
| these transducers steer the beam with a motor and focus the beam with an acoustic lens or a curved PZT element | mechanical transducer |
| what is the relative scan line density over an area at a depth of 10 cm when compared to the line density of 1 cm when using a linear phased array transducer? | lower density |
| the "curved pattern" of delays in the electrical spikes used in a linear phased array transducer focuses the beam during transmission. T or F | true |
| which focus is different than the others? lens, mirror, phased, dynamic receive | dynamic receive |
| which 2 of the following terms are associated with phased-array transducers? | multi-focus and adjustable |
| mechanical transducers direct the ultrasound beam in many different directions to create a frame through the FOV. T or F | true |
| a single element mechanical transducers is focused electronically. T or F? | false |
| how many transmit focal zones are possible for one transmit pulsed beam? | one |
| phased array technologies have the ability to variably focus an ultrasound beam to different depths. T or F | true |
| what is the advantage os dynamic receive focusing? | applied continuously to all depths along scan line to improve lateral resolution |
| what is the advantage of multiple transmit zones? | improves lateral resolution |
| what is the shape of the elements in an annular phased array transducer? | circles |
| what is the shape of the elements in a linear array transducer? | rectangles |
| for a linear array transducer, what is used to focus the beam in the elevational plane? | acoustic lens |
| annular phased array transducers focus sound beams in all planes and at all depths through a relatively "long" focal zone. T or F | true |
| what image is created with a 2D array transducer? | 3D image |
| grating lobes can be reduced by... | variable voltage with highest to center element |
| what is the typical frame rate when using a mechanical scanner? | 15-30 fps |
| what is the communication between each element with individual wiring and the beam former? | digital converter |
| which part of this image is obtained using electronic steering technique? | color box |
| grating lobes can be reduced by... | sub-dicing elements with spacing in between |
Created by:
dcontice