Davies Ch 10 Bioeffects

Which intensity parameter is not applicable for continuous- wave ultrasound?

(SATA,SPTA,SPPA,SAPA) ans = SPPA & SAPA

Which of the following would show the highest intensity value?

(SPTP, SATA, Im, SPPA,SATP) ans = SPTP

The risk of adverse effects is low when the mechanical index is less than:

1

According to the AlUM Statement on Mammalian In Vivo Biological Effects no independently confirmed significant biological effects have occurred with intensities below ____________ for mammalian tissues exposed in vivo. Assume unfocused ultrasound.

100 mW/cm^2

Avoiding a local temperature increase exceeding _________ should ensure that there are no thermally induced biological effects

1° C

In the AlUM statement, no known ill effects have been reported for TI values less than:

2

Which of the following parameters relates to tissue heating?

Absorption

The circulatory motion of fluid particles that is occasionally seen with ultrasound is termed:

Acoustic streaming

Using a hydrophone, you can measure:

Amplitude & duty factor

The ALARA principle stands for:

As low as reasonably achievable

You are performing an obstetrical ultrasound exam and notice that the thermal index (TI) is greater than 1. The increase in temperature will be greatest in:

Bone

Stable cavitation refers to:

Bubbles that oscillate in size with the variations in sound pressure

A study designed to determine if there is an association between an adverse eftect in a population and exposure to a particular agent is a(n):

Epidemiological study

The thermal index indicates:

Estimated maximum temperature increase in tissue

What should be limited when the thermal index exceeds 1:

Exposure time

The thermal index (TI) will be greatest with:

High frequency, high intensity

Cavitation in mammalian tissue is more likely to occur under which of the following conditions?

High pressure and low frequencies

If the mechanical index reading is too high during the exam, what adjustments can lower it?

Increase the transducer frequency. & Decrease acoustic power.

Increased tissue heating occurs with which of the following?

Increased focusing

Which of the following will increase the acoustic exposure to the patient?

Increased transmit power

The following advantage is associated with use of the MI and TI indices:

Information is available on the screen to help the sonographer implement the ALARA principle.

A mechanism by which biological effects are induced include all EXCEPT:

Ionization

You are performing a first trimester obstetrical examination and wish to determine the fetal heart rate. What is the most prudent method to obtain this measurement?

M-mode ultrasound

The units for peak negative pressure are:

Mega Pascal

Use of maximum system gain results in:

None of the above (Increased tissue heating, Increased risk of cavitation, Fluid particle streaming, Increased sound absorption)

What ultrasound application has the lowest FDA-approved PTA values?

Ophthalmic

Which of the following would most likely have the highest PTA value?

PW Doppler

Which operator control adjusts the intensity of the transmitted pulse?

Power (dB)

With Doppler, which control would affect acoustic exposure?

Pulse repetition frequency

Which intensity descriptor has the lowest numerical value for the characterization of a pulsed-wave ultrasonic field?

SATA

What intensity descriptor is used in the AlUM Statement on Mammalian In Vivo Biological Effects?

SPTA

You are performing a transcranial ultrasound examination. What output index is most pertinent to this study?

TIC

Which acoustic output label describes temperature increase in bone?

TIC & TIB

What does the mechanical index indicate on an ultrasound system?

The likelihood of cavitation during an ultrasound exam

You are performing a carotid ultrasound and notice that the TI reading is 1. What does this indicate?

The output level is high enough that temperature could increase as much as 1°C if the transducer were held stationary.

If you wish to practice the ALARA principle, which of the following techniques should you employ?

Use the lowest transmit power that allows adequate tissue visualization.