Physics Ch 10, 11, 24 Flashcards
The ability to accurately distinguish two structures lying close together is called?
Resolution
T/F Axial and lateral resolution are both measured in units of time
False- Measured in distance
T/F Continuous wave frequency is determined by the beam width
False- Determined by frequency of electrical signal from ultrasound system
T/F The thickness of the ceramic and the speed of sound in the ceramic are determining factors for pulsed wave frequency
True
T/F Lateral resolution is equal to beam width
True
T/F Phased array transducers have the electronic focusing
True
T/F Phased array electronic focusing technique can always be used in single element transducers
False-used only on multi-element transducers, never on single crystal transducers
With which of the following operations can lateral resolution of a given depth be estimated
,
LATA
Lateral Angular Transverse Azimuthal
LARRD
Longitudinal Axial Range Radial Depth
The length of a pulse is 10 mm. What is the minimum distance between two reflectors, positioned one in front of the other, that still produces two echoes on our image?
5 mm
*Value is one-half the pulse length
Fixed focus transducers have what type of lateral resolution
poor lateral resolution
Lateral resolution
The ability to distinctly identify two structures that are very close together when they are side by side, or perpendicular, to the sound beam’s main axis
Lateral resolution is best at the focus where the beam is..
narrowest
The effects of focusing
- Beam diameter in near field and focal zone is reduced
- Focal depth is shallower
- Beam diameter in the far zone increases
- Focal zone is smaller
Three methods of focusing
- External focusing
- Internal focusing
- Phased array focusing
Better axial resolution is associated with ___ cycles per pulse and ___ numerical values
Fewer, Lower
What type of transducers have the poorest axial resolution?
Longest pulse, lowest frequency, and the most ringing (more 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
What happens to the numerical value of range resolution when the number of cycles changes but the frequency stays the same
,
What display mood provides information regarding reflector motion?
M-mode
X-axis, Y-axis, Z-axis
,
A-mode
,
B-mode
,
M-mode
,
