Ultrasound Bioeffects and Safety Flashcards
7 cards from real ARDMS SPI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ultrasound Bioeffects and Safety flashcards as text
The FDA regulatory limit for spatial-peak temporal-average intensity (ISPTA.3) for fetal/obstetric ultrasound is:
Answer: 72 mW/cm²
The FDA limits ISPTA.3 to 72 mW/cm² for fetal and neonatal cephalic applications to protect the developing fetus.
When scanning directly over fetal bone in the third trimester, which Thermal Index should be displayed?
Answer: TIB (Bone Thermal Index)
TIB (Bone Thermal Index) is used when the beam is focused at or near fetal bone, which absorbs more ultrasound energy and can heat adjacent tissue significantly.
Which operator action would most effectively reduce thermal bioeffect risk without eliminating diagnostic utility?
Answer: Reducing output power and using gain controls to compensate image brightness
Reducing output power lowers acoustic energy deposition, while compensating with receive gain maintains image quality without additional thermal risk.
Non-thermal mechanical bioeffects of ultrasound include all of the following EXCEPT:
Answer: Protein denaturation from elevated tissue temperature
Protein denaturation is a thermal effect caused by temperature rise, not a non-thermal mechanical effect; cavitation, streaming, and microstreaming are all mechanical in nature.
The Output Display Standard (ODS) requires that real-time MI and TI values be displayed on the monitor when they exceed:
Answer: MI > 0.5 or TI > 0.5
The ODS mandates display of MI and TI when either exceeds 0.5, alerting operators that exposure is approaching levels warranting attention.
A sonographer performing an extended neonatal brain exam should be MOST concerned about which type of Thermal Index?
Answer: TIC — because the cranial bone is in the near field of the beam
TIC (Cranial Bone Thermal Index) applies when the beam passes through the skull in the near field, as the bone absorbs energy and heats the adjacent brain tissue.
Which statement correctly describes the relationship between ultrasound frequency and cavitation threshold?
Answer: Lower frequency lowers the cavitation threshold, making cavitation more likely
Lower frequencies produce longer rarefaction half-cycles that allow bubbles more time to grow, thereby lowering the pressure threshold required to initiate cavitation.