Chapter 9 Flashcards
What is the best estimate of the diameter of width of the sound beam as it exits the transducer? 6 mm 9 mm 12 mm 8 mm
12 mm
At its beginning, the sound beam diameter its the same as the diameter of the active element
What is the diameter of the sound beam at a depth of 8 cm?
6 mm
At the end of the end of the near zone (8 cm), the beam diameter is one half the transducer diameter.
What is the diameter of the sound beam at a depth of 16 cm?
12 mm
At a depth equal to 2 near zone lengths, the beam diameter is the same as the diameter of the active element
At what depth is the focus?
8 cm
The focal depth is the same as the length of the near zone
What depth marks the beginning of the focal zone?
6 cm
The foal zone is the region around the focus. In this example, the focal zone begins at a depth 2 cm shallower that the focus.
What depth marks the end of the focal zone?
8 mm
The focal zone is the region around the focus. In this example, the focal zone ends at a depth 2 cm deeper than the focus.
At which of the following depths is the beam narrowing?
6 cm
The beam narrows within the near zone.
At which of the following depths is the depth widening? 2 cm 6cm 8cm 9.375
9.375
The beam only widens or diverges in the far zone. The only depth within the far zone is 9.375
At which of the following depths is the beam most likely to have the same diameter as it has at a depth of 11 cm? 1 cm 3cm 5cm 8 cm
5 cm
Think of the beam as being symmetrical around the focus. Thus, the beam diameter will be similar when it is 3 cm shallower and 3 cm deeper than the focus
Which of the following terms does not belong?
End of the Fraunhofer zone
The end of the Fraunhofer zone is the very end of the sound beam
A pair of 6 MHz probes are identical except for the active element diameter. The active element diameters are 6 mm and 10 mm, respectively. The sound beam of which probe will have a shallower focus?
The probe with a 6 mm active element has a shallower focus. Smaller diameter crystals produce beams with shallower foci.
A air of 9 mm diameter probes are identical except for frequency, which is 3 MHz and 6 MHz, respectively. Which beam will have a shallower focus?
The 3 MHz beam has a shallower focus. Focal depth increases with increasing frequency. The beam created by the 6 MHz probe has a deeper focus.
Which of the following probes creates a beam with the deepest focus? 4mm diameter, 4 MHz 6mm diameter, 8MHz 6mm diameter, 2 MHz 5mm diameter, 8 MHz
6mm diameter, 8 MHz
Longer focal lengths are associated with large diameter, high frequency probes.
Which of the following probes creates a beam with the shallowest focus? 4mm diameter, 4 MHz 6mm diameter, 8MHz 4mm diameter, 2 MHz 5mm diameter, 8 MHz
4mm diameter, 2 MHz
Shorter focal lengths are associated with small diameter, low frequency probes.
Which of the following probes creates a beam with the shallowest focus?
Small diameter, low frequency
Active element diameter and near zone length are ___________ related.
Directly
Transducer frequency and near zone length are _________ related
Directly
Wavelength and near zone are ________ related.
Inversely
A pair of 6 MHz probes are identical except for the active element diameters, which are 6 mm and 10 mm, respectively. Which beam will be more compact in the far field?
The probe with 10 mm active element has a less divergent beam. Larger diameter crystals product beams that diverge less in the far field.
A pair of 9 mm diameter probes are identical except for frequencies, which are 3 MHz and 6 MHz. Which sound beam will spread out more in the far field?
The 3 MHz beam
Which of the following probes creates a beam with the least divergence? 4 mm diameter, 4 MHz 6 mm diameter, 8 MHz 6 mm diameter, 2 MHz 5 mm diameter, 8 MHz
6 mm diameter, 8 MHz
Divergence is minimalized with large diameter, high frequency probes.
Which of the following probes creates a beam with the least divergence?
Small diameter, low frequency
Transducer frequency and beam divergence are __________ related.
Inversely
Active element diameter and beam divergence are __________ related.
Inversely
