Chapter 10 Flashcards
What is the ability to accurately distinguish two structures lying close together called?
Resolution
The ability to distinguish two structures lying close together front-to-back or parallel to the sound beam is called _____
Longitudinal, axial, range, radical, or depth resolution
Axial resolution is measured with units of _______
Distance, such as mm
If there are more cycles in a pulse, the numerical value of range resolution is ______
Greater
If a new pulsed transducer has many more cycles in its pulse, the image accuracy ______
Degrades
_____ frequency transducers generally have the best range resolution.
High
Which of the following transducers has the poorest axial resolution?
- 7 MHz and 4 cycles/pulse
- 6 MHz and 3 cycles/pulse
- 7 MHz and 5 cycles/pulse
- 6 MHz and 2 cycles/pulse
1.7 MHz and 5 cycles/pulse
In soft tissue, a 3 cycle, 1 MHz pulse has a pulse length equal to 4.5 mm. What is the axial resolution?
- 25 mm
4. 5 mm / 2= 2.25 mm
Which of the following transducers has the best axial resolution?
- 7 MHz and 4 cycles/pulse
- 6 MHz and 3 cycles/pulse
- 7 MHz and 5 cycles/pulse
- 6 MHz and 2 cycles/pulse
2.6 MHz and 2 cycles/pulse
Two different transducers create sound pulses. One transducer is labeled 5 MHz and the other, 3 MHz. Which transducer is more likely to create a more accurate image with respect to axial resolution? Which transducer probably has a lower numerical value of axial resolution?
The 5 MHz transducer is more likely to create an image with better axial resolution.
The higher frequency transducer creates a shorter pulse and thus has a lower numerical value of axial resolution. Lower numbers mean improved image quality.
Two different transducers create pulses. Both transducers create sound with a frequency of 4 MHz. One transducer creates a pulse that comprises 6 cycles and the other, 3 cycles. Which transducer is more likely to create a more accurate image with respect to axial resolution? Which transducer has a lower numerical value of axial resolution?
The 3 cycle pulse transducer is more likely to create an image with better axial resolution. Less ringing, or fewer cycles in a pulse, generally implies shorter pulses and improved axial resolution.
The 3 cycle pulse has a lower numerical value of axial resolution. Lower numbers mean improved image accuracy.
Two different transducers create pulses. One transducer is albeled 5 MHz and the other, 3 MHz. The 3 MHz transducer creates a more acurate image with respect to axial resolution. Explain.
Axial resolution is determined by pulse length. Shorter pulses have better axial resolution. In this question, the 3 MHz transducer has the best axial resolution, which means the 3 MHz pulse must be shorter than the 5 MHz pulse.
Since 3 MHz sound has a longer wavelength than 5 MHz sound, the only way that the 3 MHz transducer rings less. Thus, the 3 MHz pulse has fewer cycles than the 5 Mhz pulse.
What is the lateral resolution at a depth of 8 cm?
4.5 mm
At the end of the near zone, the beam diameter is one half the transducer diameter.
What is the lateral resolution at a depth of 16 cm?
9 mm
At a depth of twice the near zone, the beam is as wide as the transducer.
What is the best estimate for the resolution at 7 cm? 1 cm 9 mm 5 mm 14 mm
5 mm
