Pass Ultrasound Physics Exam Study Guide Review

By Mansoor Khan

Pass Ultrasound Physics Exam Questions and Answers Study Guide Review: Test Prep Questions and Answers Study Guide Review is designed to help Ultrasound Program Students and Sonographers to prepare for ARDMS Ultrasound Physics Exam and provide sound foundation to pass the ARDMS SPI board exam.

• Language: English
• Publisher: BookBaby
• Release date: Nov 13, 2014
• ISBN: 9781483567686

Book preview

Intensity

Pulse Echo Instrumentation

Q1.   Name the components of an ultrasound system?

Answer:

The components of an ultrasound system are transducer, pulsar, receiver, scan converter, display, and master synchronizer.

Q2.   What is the Master Synchronizer?

Answer: Master Synchronizer is a component of ultrasound machine which maintains and organizes the proper timing and interaction of all components of the ultrasound machine so that ultrasound system can operate as a single integrated system.

Q3.   What is an ultrasound transducer?

Answer:

The ultrasound transducer is a part of ultrasound machine. It contains a piezoelectric material which converts electrical energy into acoustic energy during the transmission phase, and converts acoustic energy into electrical energy when the echoes return to the transducer after traveling in the body during reception phase.

Q4.   What is Channel?

Answer:

A channel in ultrasound system consists of a single crystal, the beam former, pulsar electronics, and the wire connecting them.

Q5.   What is a receive channel?

Answer:

Each active element in an ultrasound transducer is connected to an amplifier and processing chain. The amplifier and processing chain are collectively known as the receive channel. There are 256-512 active receive channels present in ultrasound systems. The benefits of more receive channels in ultrasound systems is greater processing flexibility.

Q6.   What is Switch?

Answer:

Switch in ultrasound system protects the delicate receiver components from the high voltage signals created during pulse creation. It directs low voltage signals from the transducer to the appropriate processing components within the system.

Q7.   What is interpolation?

Answer:

Fill in Interpolation is a technique in which made up pixels are used to fill the areas between the scan lines where there is no information available.

Q8.   What is frequency compounding?

Answer:

Frequency compounding is the technique of imaging with multiple frequencies and averaging them out. Frequency Compounding improves contrast resolution and reduces speckle which improves the image quality.

Q9.   What is Dynamic Frequency Tuning?

Answer:

Dynamic frequency tuning is a technique in which high frequency portion of the ultrasound pulse is used to create images from the shallow depths, and the low frequency portion of the ultrasound pulse is used to create the images from the greater depths.

Q10.   All of the following are components of an ultrasound system except?

a.  transducer

b.  pulsar

c.  alternator

d.  synchronizer

e.  display

f.  receiver

Answer: c. alternator

Alternator is not the component of the ultrasound machine.

Output Power

Q11.   What does the output power control?

Answer:

Output power is the amount of voltage applied to the piezoelectric element to produce an ultrasound pulse. Output power controls the amplitude of the voltage that excites the piezoelectric crystals.

Q12.   What is the relationship between pulsar voltage and the returning echo strength and increasing pulsar voltage will have what effect on the image?

Answer:

There is a direct relationship between pulsar voltage and the returning echo strength. By increasing the pulsar voltage increases the strength of the returning echo signal and increases the brightness of the image.

Q13.   What is the range of pulsar output voltage which excites a piezoelectric crystal in the ultrasound transducer?

Answer:

The strength of pulsar output voltage that excites the piezoelectric crystals ranges from 1-300 volts and lasts less than 1 microsecond.

Q14.   What is the range of input voltage signal to the receiver of an ultrasound system?

Answer:

The signal produced by the transducer upon receiving the returned echoes and sent to the receiver of the ultrasound system is extremely small and is in the micro volt to milli volt range.

Q15.   What determines the strength or intensity of the ultrasound wave?

Answer: The output power generated by pulsar determines the strength or intensity of the ultrasound wave produced by the transducer. The greater the strength of electrical signal from the pulsar that excites the piezoelectric crystal, the greater the intensity of the ultrasound wave produced.

Q16.   Can sonographer change the output power?

Answer:

The sonographer can increase or decrease the strength of output power from the pulsar. The different names used for output power control are output gain; transmit output, acoustic power, pulsar power, and energy output.

Q17.   What two measurements are used to standardize the output gain?

Answer:

Thermal index and mechanical index are the two measurements used to standardize the output gain.

Q18.   What does ALARA principle mean?

Answer:

The ALARA stands for As Low As Reasonably Achievable and is related to the output power.

During the exam, the sonographer should use minimum possible output power to obtain the images. Sonographer should choose settings that will maximize image quality while minimizing patient exposure to high ultrasound intensity.

Q19.   Following ALARA principle, what is the first thing to do if the image is too dark?

Answer: Try increasing receiver gain first

If the image is too dark, first try to increase the receiver gain. In most of the cases, the image will become bright and will be able to see structures.

Q20.   Following the ALARA principle, what is the first thing to do if the image is too bright?

Answer: Try decreasing output gain

If image is too bright, first try to decrease the output gain. Decreasing the output gain will decrease the risk of possible bioeffects.

Q21.   What is the difference between Output Gain and Receiver Gain?

Answer:

Output Gain is the amount of voltage applied to the piezoelectric crystal to produce an ultrasound pulse. The strength of the ultrasound wave produced depends upon the strength of the voltage applied to excite the crystal. The stronger the voltage applied the stronger will be the ultrasound wave produced. Output gain improves the signal to noise ratio. Increasing the output gain increases the risk of potential bioeffects.

Receiver Gain increases the strength of the small electric voltages received from the transducer to a level suitable for further processing. In amplification process all electrical signals are amplified equally, that’s why amplification or receiver gain increases the brightness of the entire image. There is no risk of bioeffects by increasing the receiver gain.

Q22.   What happens by changing the output power gain?

Answer:

Changing output power gain does the following:

    changes brightness of entire image

    alters signal-to-noise ratio

    has bioeffect concerns

Q23.   What happens by changing the receiver gain?

Answer:

Changing receiver gain does the following:

    changes brightness of entire image

    does not affect signal-to-noise ratio

    no bioeffect concerns

Pulsar

Q24.   What is a Pulsar?

Answer: Pulsar is a component of ultrasound machine which determines amplitude, pulse repetition period and pulse repetition frequency of ultrasound waves. The pulsar functions during transmission.

Q25.   What are the functions performed by the pulsar?

Answer:

The following are the functions performed by the Pulsar:

    generates the electrical signals which are applied to the piezoelectric elements

    controls the timing of electrical signals

    controls the strength and amplitude of the electrical signal

    determines the pulse repetition period

    determines the pulse repetition frequency

Q26.   What control does a sonographer use to modify pulsar voltage?

Answer:

The sonographer uses output gain control to change pulsar voltage. The output gain control is also known as power, output, transmitter output, acoustic power, pulsar power, and energy output.

Q27.   What is the relationship between pulsar voltage and the returning echo strength?

Answer:

There is a direct relationship between pulsar voltage and the returning echo strength.

Increasing the pulsar voltage, increases the strength of the returning echo signals and increases the brightness of the image.

Decreasing the pulsar voltage, decreases the strength of the returning echo signal and decreases the brightness of the image.

Q28.   How the pulsar determines the pulse repetition period?

Answer:

The pulsar determines the time between one voltage spike and the next which is called pulse repetition period.

Q29.   What type of pulsar generates a constant electrical signal in the form of a sine wave?

Answer:

In continuous wave transducer, the pulsar generates electrical signals continuously and produces continuous sound waves.

Q30.   What type of pulsar generates a single electrical spike, which creates a single sound pulse?

Answer:

In pulsed wave transducers, the pulsar generates a single electrical spike, which creates a single sound pulse.

Q31.   What type of pulsar generates numerous electrical spikes, which create a single sound pulse?

Answer:

In phased array transducers, the pulsar generates numerous electrical spikes, which create a single sound pulse.

Beam Former

Q32.   What is Beam Former?

Answer:

Beam Former is a component of ultrasound machine. Beam Former receives the electrical voltages from the pulsar during transmission and distributes it to the active elements of a phased array transducer.

Q33.   What are two important functions of the beam former?

Answer:

Beam former creates the appropriate phase delays and pulse sequencing to create the transmit beam and also creates the appropriate phase delays and pulse sequencing to create the receive beam.

Beam former also determines the firing delay patterns in phased array transducers for steering and focusing of the ultrasound beam.

Q34.   How the beam former works during transmission?

Answer:

During transmission, beam former receives the electrical voltage from the pulsar and distributes it to the active elements of a phased array transducer.

During transmission, the beam former also adjusts electrical voltages to different PZT crystals to prevent side lobes and grating lobes. It is also called apodization.

Q35.   How the beam former works during reception?

Answer:

During reception, the beam former creates time delays for dynamic receive focusing. It also varies the number of crystals used and controls dynamic aperture.

Q36.   What are the advantages of digital beam formers?

Answer:

The advantages of digital beam former are:

    no mechanical parts needed

    it is software programming and can be updated easily

    it can be used with wide range of frequencies

Q37.   What is Dynamic Aperture?

Answer:

The beam former varies the number of crystals used in order to control Dynamic Aperture during reception.

Q38.   What is Apodization?

Answer:

During transmission the beam former adjusts electrical voltages in phased array transducers to prevent grating lobes and side lobes. This process is called Apodization.

Noise

Q39.   What is Noise?

Answer:

Noise is low level signals that degrade the image. Noise is random and persistent disturbance that obscures or reduces the clarity of a signal.

Q40.   What is the most common method of overcoming noise?

Answer:

The noise can be reduced by increasing the output power. The signal to noise ratio increases by increasing the output power. Increasing the output power also increases the risk of exposure to possible bioeffects.

Q41.   What is Signal to Noise Ratio?

Answer:

A ratio between original signal and the degraded signal is called signal to noise ratio.

Signal to Noise Ratio is a comparison between the amount of meaningful information and contamination in an image.

It is amplitude of the signal divided by the amplitude of the noise.

Q42.   To improve image quality, what type of signal-to-noise ratio is desired?

Answer:

To improve image quality, high Signal-to-Noise Ratio is desired.

Q43.   How signal to noise ratio can be improved?

Answer:

The signal to noise ratio can be improved by:

    using a lower frequency transducer

    moving transmit focus deeper

    using a larger aperture transducer

    using a different imaging plane

    maneuvering to remove attenuators such as lungs and gas

    using an endocavity probe

Q44.   What is the relationship between output power gain and signal to noise ratio?

Answer:

There is a direct relationship between output power gain and signal to noise ratio. Increasing the output power increases the signal to noise ratio and is a common method of overcoming noise. High