1. Ultrasound Robert L. Metzger, Ph. D.

2. RAPHEX General Question 2001 D53: In ultrasound, the largest reflections will occur between: A. Liver and muscle. B. Blood and water. C. Kidney and muscle. D. Blood and kidney. E. Fat and liver.

3. RAPHEX Answer to 2001 Question D53 E. The largest reflections (echoes) will occur when there is the greatest difference in acoustic impedance (Z) since R = (Z 2 – Z 1 ) 2 / (Z 2 + Z 1 ) 2.

4. RAPHEX General Question 2001 D56: A 5 MHz ultrasound beam passes through 4 cm of soft tissue (absorption coefficient 1.0 dB/cm- MHz). The original intensity is reduced by a factor of: A. 20 B. 40 C. 100 D. 1000 E. 10,000

5. RAPHEX Answer to General Question D56 C. The attenuation in dB is given by: Attenuation (dB) = 1 dB/MHz-cm x 5 MHz x 4 cm = 20 dB. But: dB = 10 log (I i /I o ) = 20 log (I i /I o ) = 2 I i /I o = 10 2

6. RAPHEX General Question 2002 D59: The attenuation of ultrasound in soft tissue, in db/cm-MHz, is: A. 0.1 B. 1.0 C. 100 D. 1000

7. RAPHEX Answer to General Question D59 B

8. RAPHEX General Question 2003 D63: The wavelength of a 2 MHz ultrasound beam is _______ mm. A. 0.02 B. 0.55 C. 0.77 D. 2.0 E. 5.0

9. RAPHEX Answer to General Question D63 C. Wavelength  = velocity v/frequency f. The average velocity in tissue is 1540 m/s. Frequency = 2 x 10 6 s -1.

10. RAPHEX General Question 2003 D65: In ultrasound, the intensity of a reflected echo depends on all of the following except: A. Depth to interface. B. Transducer diameter. C. Transducer frequency. D. Difference in acoustical impedance

11. RAPHEX Answer to General Question D65 B. Transducer diameter affects only lateral resolution.