What are the two major functions of the ultrasound system?
- Preparation and transmission of electrical signals to the transducer, which creates a sound beam
- Reception of electrical signals from the transducer
What happens during the transmission portion of the system?
during transmission the transducer transforms electrical energy into acoustic energy
What happens during the reception portion of the system?
electrical signals are received from the transducer, processed and turned into clinically meaningful images and sounds
What is the function of the pulser?
the pulser determines the amplitude, pulse repetition period, and pulse repetition frequency
What is the function of the beam former?
beam former determines the firing delay patterns for phased array systems
What is the function of the receiver?
the receiver transforms the electrical signals from the transducer into a form suitable for display
What is the function of the storage?
storage archives the ultrasound studies. Using via computer hard drives, CD, DVD, videotape, etc.
When does the pulser functions?
during transmission
How does increasing pulser voltage affect the ultrasound beam?
It increases the strength of the transmitted pulse, causing stronger echoes and a brighter image.
How does low voltage affect an ultrasound beam?
A low voltage creates a low vibration which creates a weak sound beam and that creates a darker image.
What is the best way to improve signal-to-noise ratio?
Increase pulser voltage (output power)
What does Thermal Index (TI) and Mechanical Index (MI) measure?
The estimate thermal or mechanical bio-effects caused by output power
Does output power brighten the entire image or just part of it?
It brightens (or darkens) the entire image evenly, (not at specific depths)
What is considered noise in an ultrasound image?
Unwanted low level information (contamination)
Why cant output power make the image evenly bright from top to bottom
Because deep pulses naturally weaken due to attenuation and shallow pulses have less attenuation and output power changes all echoes equally
What is considered signal in an ultrasound image?
Meaningful information returning from the tissue
What happens to Signal:Noise ratio when output power is increased?
The Signal to noise ratio increases, Signal increases while noise stays the same
What happens when the output power is too low?
Noise becomes noticeable and the image quality is decreased
What does the beam former do during transmission?
It distributes the pulser’s electrical spike to multiple crystals with precise time delays for electrical steering and focusing
What process does the beam former use to reduce lobe artifacts?
Apodization (adjusts electrical spike voltages)
What does the beam former do during reception?
Applies dynamic receive focusing and dynamic aperture to optimize beam shape and resolution
What probes use beam formers?
Phased, linear, annular, and convex array probes (All array transducers)
What is the modern beam former called?
Digital beam former
