Adv Ultrasound Physics - Pulsed Echo Instrumentalization

what are the two major functions of the ultrasound system?

preparation/transmission & reception

what does preparation/transmission do?

It generates and sends ultrasonic pulses into the body, converting electrical energy into sound waves.

what does reception do for ultrasound

It receives the reflected ultrasonic waves and converts them back into electrical signals for image processing.

what does the beam former consist of?

master synchronizer, pulser, pulse delay, T/R Switch, amplifier

what does the beam former do?

firing patterns for phased array systems. switches the element between transmit and receive functions

what is a phased array system?

A type of ultrasound system that uses multiple small transducer elements to electronically steer and focus the ultrasound beam, allowing for improved image quality and flexibility in scanning.

what is the beam former responsible for?

phasing voltages for electronic steering/focusing, dynamic recieve focusing, apodization, and dynamic apature

does the beam former function during transmission or reception?

both

what does the master synchronizer do?

Coordinates the timing and operation of all components in the ultrasound system, ensuring proper sequencing of pulses and data acquisition.

what is the function of the pulser?

Produces electrical voltages that are sent to the transducer elements to activate the PZT. Determines the amplitude, PRF, PRP, and Code Excitation. Adjustable

What happens to the pulser if it increases or decreases

it changes the entire brightness of the image. lower pulses are desired

How does having a lower voltage affect an image?

gentle vibrations, weak sound beam/reflection, dark image

describe signal to noise ratio

a comparison of meaning information to the amount of contamination

what is the noise in SNR

persistent disturbance that obscures a signal’s clarity

What is the difference between having a high or low SNR

If SNR is high, the image is clearer and more detailed; if low, the image is grainy and less distinguishable.

what is the most common way to improve the SNR

increasing the output power or coded excitation

What is the purpose of the Transmit/Receive Switch

Provides protection for the receiver from the high voltages produced by the pulser

What is another name for the Receiver

signal processor

What are the five functions of the signal processor

amplification, compensation, compression, demodulation, rejection

What are synonyms for amplification

overall gain, receiver gain

What is the purpose of adjusting the amplification

increases or decreases the strength of all of the returning echos equally. higher = brighter and lower = darker

Is amplification brightness uniform or concentrated

uniform

what are amplification measured in

decibels dB

what is the purpose of compensation

part of the receiver that corrects for attenuation, makes image uniformly bright

explain near gain in TGC Curve Anatomy

at superficial depths, reflections undergo a small, constant amount of compensation

explain delay in TGC Curve Anatomy

depth where variable compensation begins

explain slope in TGC Curve Anatomy

compensation corrects for the effects of increasing attenuation

explain knee in TGC Curve Anatomy

depth where reflections are maximally compensated

explain far gain in TGC Curve Anatomy

maximum amount of compensation the receiver can provide

explain lateral gain compensation

addresses differences in echo signals

where is lateral gain compensation used

echocardiography

what is lateral gain compensation determined by

series of sliding controls

what are synonyms for compression

dynamic range, log compression, gray maps

what is the purpose compression

reduces number of grey scales on display, decreases the difference between the largest and smallest amplitudes within the signal

what is the relation between compression and dynamic range

inverse related, adjustable

what happens if compression images are preformed twice

first keeps electrical signals w/in the accuracy range of the system’s electronics and keeps the gray scale range w/in the range of detection of the human eye

What is another name for demodulation

detection

what is the purpose of demodulation

changes the form of the electrical signals within the receiver so that it is more suitable for display on the monitor

What is the only non adjustable reciever

demodulation/dectection

what are the two steps of demodulation

rectification and smoothing (eneveloping)

What is rectification

conversion of all negative voltages into positive voltages. makes it easier for the machine to handle

what is smoothing (enveloping)

where there is placement of smooth lines around the “bumps” and evens out. changes the radio frequency signal into the video signal

What are synonyms for rejection

threshold, suppression

what is the purpose of rejection

allows the machine to ignore low level echoes. does not affect bright echos.

What is differences between output power and reciever gain

OP improves SNR and increases patient exposure

what are the similarities between the output power and receiver gain

affect of overall brightness dark image increases receiver gain and bright image decreases output power

What is a phased array

direct sound waves move in a specific direction

What are the two key words for a pulser

output and power

What is another word for brightness

brilliance

What happens if there is an extreme output power

it increases bioeffects

What does the phrase ALARA mean

as low as reasonably achievable

the transmit/receive switch is part of which ultrasound compartment

beam former

What are the key words for compensation

attenuation, TGC

What are the key words for demodulation

smoothing, positive/negative, non adjustable

What are the key words for low level echos

rejection

What are the key words for amplification

gain

output power is controlled by which of the following

pulser

describe a function of the pulser

max depth penetration

what is the purpose of the T/R switch

it ensures that the pulser voltages go to the transducer and the receiver voltages from the transducers go to the signal processer

which part of the ultrasound system is responsible for coded excitation

the pulser

compression and dynamic range have what kind of relationship

inverse relationship

What is the order of the ultrasound machine

pulser, beam former, transducer, T/R switch, receiver, scan converter, display and storage

what part of the ultrasound system is responsible for switching the element function from transmit to recieve

beam former

which of the following components of the beam former protects sensitive receiver components from high voltages of a pulse

T/R switch

T/F the lower the frequency of the ultrasound beam, the shallower is the delay of the TGC curve

false

describe the demodulation process

changing the form of a sound pulse

the process of demodulation incorporates what kind of task?

rectification and smoothing

what is a task that is NOT performed by the receiver of an ultrasound system

degaussing

how would an ultrasound image appear with a wide dynamic range

low contrast with many shades of gray

T/F reciever gain is another way to describe pulse

false

you have increased the transmit power while performing a pelvic ultrasound examination. name actions that may increase

voltage application, acoustic power, penetration, image brightness

what is a typical pulse output voltage that excited a piezoelectric crystal

40 volts

T/F the sonographer can make an image of uniform brightness by adjusting both output power and receiver gain

false

T/F the SNR ratio remains unchanged when a sonographer adjusts receiver gain

false

at which imaging depth is the slope of the TGC curve most effective

the focal zone

T/F attenuation is a receiver function

false

the amount of amplification occurring in the receiver is determined by what

receiver gain

which action would improves the signal to noise ratio

increasing output power

what best describes the region of the minimum amplification on a standard TGC curve

focal zone

which receiver function creates an image of comparable brightness from top to bottom

swept gain compensation

which transducer system is most likely to have the longest delay in its TGC curve

2.5 MHz annular array

T/F the process of elimination low amplitude signals from furthering processing is called subordination

false

what does the far gain of a depth gain compensation curve represent

maximum amplification related to compensation

what is the process of adjusting for path length related attenuation called

time gain compensation

the output of an ultrasound pulser determines the ______ of the acoustic pulse

intensity

the knee of a TGC curve represents the

area of maximum amplification

which component is affected when the sonographer adjusts the output power

pulser

T/F the primary purpose of demodulation is the preparation of the electrical signal for display on a television monitor

true

a sonographer wants to adjust the dynamic range of displayed echoes. which control should be modified

compression

at which depth is the slope of the TGC curve most effective

the focal zone

which of the following function of the receiver is used to suppress or eliminate low frequency signals, reduce acoustic noise, and does not affect intense echoes

rejection

what is the order in which the signal travels in the ultrasound system

pulser, beam former, transducers, receiver, memory, display