Davies Ultrasound Physics Review Exam with
correct answers and rationale updated 2026
Section 1: Bioeffects and Safety
1. What action would be most in keeping with the ALARA principle while performing a diagnostic
ultrasound exam?
A. Allow multiple students to scan an obstetrical patient because the fetus is in a good position for
imaging.
B. Prolong the sonogram to make videos of the fetus for each family member.
C. Complete the diagnostic scan in a timely fashion at the lowest output power that achieves a
quality image.
D. Maximize the acoustic output to brighten the overall image.
Answer: C
Rationale: The ALARA (As Low As Reasonably Achievable) principle prudently minimizes the risk of
bioeffects by using the lowest output power that achieves a quality diagnostic image, while
completing the scan efficiently-1-4-5.
2. During performance of an obstetric ultrasound exam, you adjust the system parameters to
improve the image. Which of the following parameters would increase acoustic exposure?
A. Increase gain
B. Increase TGC
C. Increase transmit power
D. Increase frame averaging
Answer: C
Rationale: Transmit power is the only control listed that affects the exposure of the patient to
acoustic power. Gain, TGC, and frame averaging (persistence) do not affect sound transmission and
therefore do not affect exposure-1-5-11.
3. To minimize the risk of biologic effects of ultrasound to the fetus, which imaging mode tradeoff
would be most applicable?
A. Use M-mode instead of pulsed-wave Doppler to measure the fetal heart rate.
B. Use color Doppler instead of power Doppler to image the umbilical cord.
C. Use pulsed-wave Doppler instead of power Doppler to evaluate the fetal heart.
D. Use harmonics instead of fundamental to image the fetal spine.
Answer: A
Rationale: Pulsed-wave Doppler increases the time-average intensity compared to M-mode. Using
M-mode instead reduces acoustic exposure to the fetus-1-5-13.
,4. What potential bioeffect occurs through absorption of sound energy by tissue?
A. Cavitation
B. Heating
C. Attenuation
D. Reflection
E. Refraction
Answer: B
Rationale: Sound attenuation in tissue is primarily due to absorption, which is the conversion of
ultrasound energy to heat-1-4-13.
5. Thermally induced biologic effects should be preventable by avoiding a local tissue temperature
increase exceeding:
A. 1 degree C
B. 4 degrees C
C. 10 degrees C
D. 95 degrees F
Answer: A
Rationale: A local tissue temperature increase exceeding 1°C should be avoided to prevent thermally
induced biological effects-4-5-17.
6. What does the mechanical index indicate on an ultrasound system?
A. The maximum temperature increase in tissue
B. The minimum temperature increase in tissue
C. Acoustic power in milliwatts
D. The likelihood of cavitation during an ultrasound exam
Answer: D
Rationale: Mechanical index is derived from the peak rarefaction pressure and ultrasound
frequency, parameters shown to be associated with the onset of cavitation-1-5-13.
7. What should you limit when the thermal index exceeds 1?
A. Frequency
B. Exposure time
C. Gain
D. Frame rate
Answer: B
, Rationale: When the thermal index exceeds 1, exposure time should be limited to minimize
potential thermal bioeffects-1-5-11.
8. The thermal index indicates:
A. The likelihood of cavitation
B. Estimated temperature increase in tissue
C. The acoustic power in watts
D. The mechanical index value
Answer: B
Rationale: The thermal index indicates the estimated temperature increase in tissue. It is calculated
assuming certain values for absorption and thermal properties of tissues, taking into account beam
geometry, frequency, and power-5-11.
9. Increased tissue heating could occur when you:
A. Decrease frequency
B. Increase transmit power
C. Decrease exposure time
D. Decrease pulse repetition frequency
Answer: B
Rationale: Increasing transmit power increases acoustic output, which can lead to increased tissue
heating-4-11-13.
10. Which intensity descriptor has the lowest numerical value for the characterization of a pulsed-
wave ultrasonic field?
A. SPTA
B. SATA
C. SATP
D. SPTP
Answer: B
Rationale: SATA (spatial average, time average) has the lowest numerical value among the intensity
descriptors for pulsed-wave ultrasound-4-5-11.
11. Which intensity parameter is not applicable for continuous wave ultrasound?
A. SATA
B. SPTA
C. SPPA and SAPA
D. SPTP
correct answers and rationale updated 2026
Section 1: Bioeffects and Safety
1. What action would be most in keeping with the ALARA principle while performing a diagnostic
ultrasound exam?
A. Allow multiple students to scan an obstetrical patient because the fetus is in a good position for
imaging.
B. Prolong the sonogram to make videos of the fetus for each family member.
C. Complete the diagnostic scan in a timely fashion at the lowest output power that achieves a
quality image.
D. Maximize the acoustic output to brighten the overall image.
Answer: C
Rationale: The ALARA (As Low As Reasonably Achievable) principle prudently minimizes the risk of
bioeffects by using the lowest output power that achieves a quality diagnostic image, while
completing the scan efficiently-1-4-5.
2. During performance of an obstetric ultrasound exam, you adjust the system parameters to
improve the image. Which of the following parameters would increase acoustic exposure?
A. Increase gain
B. Increase TGC
C. Increase transmit power
D. Increase frame averaging
Answer: C
Rationale: Transmit power is the only control listed that affects the exposure of the patient to
acoustic power. Gain, TGC, and frame averaging (persistence) do not affect sound transmission and
therefore do not affect exposure-1-5-11.
3. To minimize the risk of biologic effects of ultrasound to the fetus, which imaging mode tradeoff
would be most applicable?
A. Use M-mode instead of pulsed-wave Doppler to measure the fetal heart rate.
B. Use color Doppler instead of power Doppler to image the umbilical cord.
C. Use pulsed-wave Doppler instead of power Doppler to evaluate the fetal heart.
D. Use harmonics instead of fundamental to image the fetal spine.
Answer: A
Rationale: Pulsed-wave Doppler increases the time-average intensity compared to M-mode. Using
M-mode instead reduces acoustic exposure to the fetus-1-5-13.
,4. What potential bioeffect occurs through absorption of sound energy by tissue?
A. Cavitation
B. Heating
C. Attenuation
D. Reflection
E. Refraction
Answer: B
Rationale: Sound attenuation in tissue is primarily due to absorption, which is the conversion of
ultrasound energy to heat-1-4-13.
5. Thermally induced biologic effects should be preventable by avoiding a local tissue temperature
increase exceeding:
A. 1 degree C
B. 4 degrees C
C. 10 degrees C
D. 95 degrees F
Answer: A
Rationale: A local tissue temperature increase exceeding 1°C should be avoided to prevent thermally
induced biological effects-4-5-17.
6. What does the mechanical index indicate on an ultrasound system?
A. The maximum temperature increase in tissue
B. The minimum temperature increase in tissue
C. Acoustic power in milliwatts
D. The likelihood of cavitation during an ultrasound exam
Answer: D
Rationale: Mechanical index is derived from the peak rarefaction pressure and ultrasound
frequency, parameters shown to be associated with the onset of cavitation-1-5-13.
7. What should you limit when the thermal index exceeds 1?
A. Frequency
B. Exposure time
C. Gain
D. Frame rate
Answer: B
, Rationale: When the thermal index exceeds 1, exposure time should be limited to minimize
potential thermal bioeffects-1-5-11.
8. The thermal index indicates:
A. The likelihood of cavitation
B. Estimated temperature increase in tissue
C. The acoustic power in watts
D. The mechanical index value
Answer: B
Rationale: The thermal index indicates the estimated temperature increase in tissue. It is calculated
assuming certain values for absorption and thermal properties of tissues, taking into account beam
geometry, frequency, and power-5-11.
9. Increased tissue heating could occur when you:
A. Decrease frequency
B. Increase transmit power
C. Decrease exposure time
D. Decrease pulse repetition frequency
Answer: B
Rationale: Increasing transmit power increases acoustic output, which can lead to increased tissue
heating-4-11-13.
10. Which intensity descriptor has the lowest numerical value for the characterization of a pulsed-
wave ultrasonic field?
A. SPTA
B. SATA
C. SATP
D. SPTP
Answer: B
Rationale: SATA (spatial average, time average) has the lowest numerical value among the intensity
descriptors for pulsed-wave ultrasound-4-5-11.
11. Which intensity parameter is not applicable for continuous wave ultrasound?
A. SATA
B. SPTA
C. SPPA and SAPA
D. SPTP
