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
What is the best estimate for the resolution at 4 cm? 1 cm 9 mm 5 mm 14 mm
5 mm
What is the best estimate for the resolution at 21 cm? 1 cm 9 mm 5 mm 14 mm
14 mm
The ability to distinguish two structures lying close together is called _________
Resolution
The ability to distinguish two structures lying close together front to back is called _________
Axial Longitudinal Range Radial Depth Resolution
The ability to distinguish two structures lying close together side by side is called _________
Lateral Angular Transverse Azimuthal Resolution
Axial resolution and lateral resolution are both measured with units of ______
Distance, such as mm
When the number of cycles in a pulse increases while the frequency remains the same, the numerical value of the range resolution ________
Increases
When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the image quality ________
Degrades
______ frequency transducers have the best range resolution.
High frequency
Name the 4 synonyms for axial resolution.
Longitudinal Axial Range Radial Depth
Name the 3 synonyms for lateral resolution.
Lateral
Angular
Transverse
Azimuthal
The length of a pulse is 8 mm. What is the minimum distance between two reflectors, positioned one in front of the other, that still produces two echoes on our image?
4mm
The value is one half the pulse length
