Davies Ultrasound Physics Review| 717 questions| verified answers| 84 pages

1. What action would be most in keeping w the ALARA principle while performing a diagnostic ultrasound exam? CORRECT ANSWERS: Complete the diagnostic scan in a timely fashion at the lowest output power that achieves a quality image Advocating use of the ALARA principle (as low as reasonably achievable) prudently minimizes the risk of bio effects (even tho epidemiological studies have revealed no known risk associated with the use of diagnostic ultrasound). 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? CORRECT ANSWERS: Increase transmit power. The transmit power is the only control listed that will affect 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. Increasing frequency will not increase exposure. 3. To minimize the risk of biologic effects of ultrasound to the fetus, which imaging mode tradeoff would be most applicable? CORRECT ANSWERS: Use M-mode instead of pulsed-wave Doppler to measure the fetal heart rate. Pulsed wave Doppler increases the time average intensity compared to M-mode. 4. What potential bioeffect occurs through absorption of sound energy by tissue? CORRECT ANSWERS: Heating Sound attenuation in tissue is primarily due to absorption (conversion of ultrasound to heat). 5. When practicing universal precautions, you should do all the following EXCEPT: CORRECT ANSWERS: Wash gloves between exams for reuse from one patient to another. (It is recommended that gloves be worn during every ultrasound examination. They should be discarded after use). -wear gloves when there is a potential for contract with patient body fluid -change gloves when moving from one patient to another -Wash hands immediately after gloves are removed - Wear face masks or eye protection whenever there is a possibility of blood splashing in your face 6. A nosocomial infection is defined as one that: CORRECT ANSWERS: Is hospital-acquired 7. Thermally induced biologic effects should be preventable by avoiding a local tissue temperature increase exceeding: CORRECT ANSWERS: 1°C