US Physics 181-210
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You have been asked to perform an ultrasound study of a structure located about 3 cm below the skin surface. Which transducer frequency range would be most appropriate for this study?
Dynamic receive focusing uses:
Time delays before echo signals from array elements are combined
Varying the excitation voltage to each element in the group uses to form the ultrasound pulse is called:
Which of the following statements describes a phased array transducer?
Electronically focused along the length of the array, mechanically focused along the elevational dimension, and electronically steered
Resolution of two structures at different depths along the path of the sound beam is termed:
Which transducer has the same distance between the scan lines in both the near and far fields?
Which of the following minimizes the degree to which beam width varies with depth?
The sound beam can be focused by all of the following EXCEPT:
What type of focusing decreases the frames rate?
Multiple transmit focusing
For a single transducer to offer multiple frequency selections for scanning, it must have:
The ability to distinguish between adjacent structures that produce echoes of similar amplitude is termed:
When you increase the scan line density in the B-mode image, you improve:
The conversion of an incident pressure wave to an electrical signal is the:
Electronic focusing in the transmit mode is accomplished using:
Time delays to excite transducer elements
What is the purpose of subdicing?
To reduce grating lobes
What transducer component is designed to control ringing of the piezoelectric element?
The transducer you are using is an array assembly. What is an advantage of this type of transducer?
Transducer arrays enable electronic focusing and steering
What is an advantage of single-crystal or pure wave crystal transducers?
What type of transducer produced this image?
When increasing the number of transmit focal zones to improve spartial resolution, the tradeoff is:
Lateral resolution vs. temporal resolution
Which of the following is NOT associated with a low Q transducer?
Long pulse length
This image shows clear distinction between the gray scale of various structures in the fetal brain. The ability to distinguish similar structures with varying gray scale is termed:
If the number of cycles in the transmitted pulsed wave is increased:
Axial resolution is degraded
If the frame rate is too slow for adequate temporal resolution, what action could you take to improve frame rate?
Reduce the number of transmit focal zones
You have been requested to image a superficial mass and to adjust your equipment to optimize spartial resolution. Spartial resolution consists of:
Lateral and axial resolution
What is the purpose of the radiofrequency shield that is placed around the crystal and backing material of the ultrasound probe?
It reduces electromagnetic interface
The image on the left demonstrates poor lateral resolution compared to the image on the right. How were the system controls adjusted to optimize the image on the right?
Increased line density
What type of resolution is affected most by pulse duration?
With a standard one-dimensional linear array transducer, what type of resolution is affected most by electronic focusing and dynamic aperture?
What type of resolution is most affected by the mechanical focus on a linear array transducer?
US Physics 181-210