104 Final Exam Review Flashcards
What are the functions of an ultrasound system?
Preparation, Transmission, and Reception
What is the job of a transducer?
Transforming electrical energy into sound and vice versa
What does a pulser do? How does this affect the image?
Creates a signal to excite the PZT. This change in voltage modifies the brightness of the entire image.
How does the pulser affect PRP?
The pulser determines the time between voltage spikes, which is PRP.
What does it mean when the SNR is high?
The signal is stronger than the noise
What are the 4 functions of the beam former?
- It receives the pulser’s spike and distributes it to PZT. 2. It adjusts voltage for apodization. 3. establishes time delays for dynamic receive focusing. 4. It varies the number of PZT used.
What is the switch used for?
It protects the sensitive electrical components from the strong voltage of creating a pulse. It also directs the signals from the transducer to the components.
What is a channel made of?
PZT, the electrical components, and the wire.
What does a receiver do? What are the components?
It prepares information to be displayed. Amplification, Compensation, Compression, Demodulation, Reject
What is amplification. Since it is adjustable, what button is it?
It makes a pulse bigger. The gain of the overall image.
What is Compensation. Since it is adjustable, what button is it?
Compensation combats attenuation. It is the Time-Gain-Compensation button
What is Compression. Since it is adjustable, what button is it?
It keeps the electrical signal and grey scale within the accurate and visible limits. It is the dynamic range button.
What is demodulation. Is it adjustable?
Converts the negative voltages to positive and smooths out the “bumps” It is not adjustable.
What is reject. Is it adjustable?
Eliminates the low-level echoes to sharpen the image. It is adjustable.
How does Dynamic Frequency Tuning relate to frequency?
The higher frequency creates superior parts of the image because it attenuates faster, lower frequency must be used to create the deeper parts. DRT selectively chooses which frequency to use to optimize image quality.
What does the synchronizer do?
maintains and organizes the system’s components
Why do ultrasound machines need to send multiple pulses?
- because sound travels in a straight line but we want the whole picture and 2. beams have to be narrow for lateral resolution.
How many crystals are in a mechanical, linear or annular phased, linear sequential, convex/curvilinear, and vector probes?
mechanical has 1, linear phased has 100-300, sequential, convex, and vector have 120-250
What is frame rate determined by
depth, speed of sound, pulses per frame
Is high frame rate linked to a good or bad temporal resolution? Is it linked to high or low T(frame)
Good temporal resolution, low T(frame)
What is T(frame)
the time for a single frame.
What is the equation for T(frame)
T(frame) = PRP x number of pulses
What is temporal resolution?
The ability to display real-time changes.
How is line density related to Temporal resolution?
High line density = high pulses per image = Lower frame rate and also lower temporal resolution
