Show:
Sound Beam Divergence Relationships
Transducers & Divergence
Receiver Functions
Amplification & Compensation
Compression, Demodulation & Reject
100
What are the 2 factors that determine beam divergence?
Transducer diameter, frequency of the sound
100
True or false. Transducer frequency and beam divergence are inversely related.
True. Higher frequencies create less divergent beams.
100
What are the 5 receiver functions listed in order that they occur?
1. Amplification 2. Compensation 3. Compression 4. Demodulation 5. Reject
100
Amplification is also called ________
Receiver gain
100
_______ changes the gray scale characteristics of the image.
Compression
200
Crystal diameter and beam divergence are _______ related.
Inversely
200
True or false. Active element diameter and beam divergence are inversely related.
True. Crystals with larger diameters create less divergent beams.
200
All of the following are functions of the receiver except: A) Demodulation B) Suppression C) Amplification D) Attenuation
D) Attenuation
200
True or false. Amplification alone cannot make an image of uniform brightness from top to bottom.
True. Compensation creates an image that is uniformly bright from top to bottom.
200
The 2 processes that make up demodulation are: _______ and ______.
Rectification (converts all negative voltages into positive voltages), smoothing/enveloping (places a smooth line around the bumps and evens them out)
300
Larger diameter crystals improve _______ resolution in the _____ field.
Lateral, far
300
Which of the following probes creates a beam with the most divergence? A) small diameter, high frequency B) large diameter, high frequency C) small diameter, low frequency D) large diameter, low frequency
C. Divergence is pronounced with small diameter, low frequency probes.
300
Of the 5 functions of the receiver, which are adjustable by the sonographer?
Amplification, compensation, compression, reject.
300
Amplification is measured in _____.
Decibels (dB)
300
Reject is also called: _______ or ______.
Threshold, suppression
400
Frequency and beam divergence are ________ related.
Inversely
400
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 is more divergent. Beams are more compact as frequency increases.
400
What does the receiver do? (definition)
The receiver prepares the information contained in the tiny electrical signals generated by the PZT crystals for eventual display on the system's monitor.
400
Compensation is also known as: (3 answers)
Time gain compensation (TGC), depth gain compensation (DGC) and swept gain.
400
What effect does demodulation have on an ultrasound image?
None. Demodulation has no visible effect on an ultrasound image.
500
______ frequency improves _________ resolution in the far field.
Higher, lateral
500
Which of the following probes creates a beam with the least divergence? A) 4 mm diameter, 4 MHz B) 6 mm diameter, 8 MHz C) 6 mm diameter, 2 MHz D) 5 mm diameter, 8 MHz
B. Divergence is minimized with large diameter, high frequency probes.
500
______ is where all signals are treated identically whereas ______ is where the signals are treated differently based on reflector depth.
Amplification, compensation
500
3 identical masses are locate in the body at the depths of 2 cm, 4 cm and 6 cm. The echo will be strongest from the mass at ___ cm.
2 cm. Echoes arising from greater depths are weaker because sound beams attenuate the farther they travel.
500
What is rejects effect on an ultrasound image?
Rejection affects all low-level signals on the image, regardless of their location. Rejection does not affect bright echoes.