Preparation and transmission of electrical signals to transducer

Reception of electrical signals from transducer + subsequent processing into clinically meaningful images and sounds

1. Transducer
2. Pulser and Beam Former
3. Receiver
4. Display
5. Storage
6. Master Synchronizer

Converts electrical energy into acoustic energy during transmission

Converts returning acoustic energy into electrical energy during reception

Controls electrical signals sent to transducer for sound pulse generation (transducer output)

Produces electrical voltage 10-500 volts to excite PZt during transmission

Determines PRF, pulse amplitude, PRP

Creates firing pattern for phased array systems = beam former

Processes electrical signal produced by transducer during reception

Can boost strength of signals via receiver gain

Produces picture on appropriate display

Controlled by the power knob

Alters image brightness by adjusting strength of the sound pulse sent into the body

Higher voltage magnitude -> higher transducer output -> brighter image + improves signal-to-noise ratio

With ALARA, always decrease power before overall gain if image is too bright

If image is too bright, lateral and longitudinal resolution degrade

Random disturbance that obscures or reduces clarity of a signal

May contaminate images with low level, undesirable signals

Continuous wave

Pulses wave and single crystal

Pulsed wave and arrays

Pulser mode that stimulates many elements to fire per pulse

One electrical spike per element fired 

aka Beam Former

Part of transmitter

Functions with array transducers

Responsible for apodization

Modern systems utilize digital beam former via software programming (stable and versatile)

Protects sensitive electrical components in the receiver from the high voltages created during transmission

Also directs electrical signals to appropriate processing component

Amplification

Compensation

Compression

Demodulation

Rejection

Amplification

aka Overall Gain aka Receiver Gain aka Gain

Increases strength of all electrical signals in the receiver prior to further processing

Can be adjusted by sonographer

Every signal treated identically to change brightness of entire image

Cannot create uniform brightness, signal-to-noise ratio unchanged

Used to create image of uniform brightness from top to bottom

Example: brightening echoes returning from greater depths

Adjusted by the sonographer

Related to transducer frequency: higher frequencies attenuate faster and generally need more TGC

Keeps signals within operating range of system's electronics and gray scale within range of what human eye can see

Does not alter relative relationship between voltages

Decreases with dynamic range of signals

Changes gray scale mapping

Changes signal's form to one more suitable for TV display

Not adjustable by sonographer; performed automatically by the system

Via rectification and smoothing/enveloping

Rejection

aka Suppression aka Threshold

Displays low level echoes only when clinically meaningful

Determines which super low level echoes are important enough to appear on an image

Affects all low level signals 

Adjustable by sonographer

Used by some ultrasound systems to utilize higher frequencies to create shallow parts of the image and lower frequencies to create deeper parts of the image

Takes advantage of range of frequencies present for optimal imaging