Ultrasound Robert L Metzger Ph D RAPHEX General

Ultrasound Robert L. Metzger, Ph. D.

RAPHEX General Question 2001 D 53: 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.

RAPHEX Answer to 2001 Question D 53 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.

RAPHEX General Question 2001 D 56: A 5 MHz ultrasound beam passes through 4 cm of soft tissue (absorption coefficient 1. 0 d. B/cm-MHz). The original intensity is reduced by a factor of: A. 20 B. 40 C. 100 D. 1000 E. 10, 000

RAPHEX Answer to General Question D 56 C. The attenuation in d. B is given by: Attenuation (d. B) = 1 d. B/MHz-cm x 5 MHz x 4 cm = 20 d. B. But: d. B = 10 log (Ii/Io) = 2 Ii/Io = 102

RAPHEX General Question 2002 D 59: The attenuation of ultrasound in soft tissue, in db/cm-MHz, is: A. 0. 1 B. 1. 0 C. 100 D. 1000

RAPHEX Answer to General Question D 59 B

RAPHEX General Question 2003 D 63: The wavelength of a 2 MHz ultrasound beam is _______ mm. A. B. C. D. E. 0. 02 0. 55 0. 77 2. 0 5. 0

RAPHEX Answer to General Question D 63 C. Wavelength = velocity v/frequency f. The average velocity in tissue is 1540 m/s. Frequency = 2 x 106 s-1.

RAPHEX General Question 2003 D 65: In ultrasound, the intensity of a reflected echo depends on all of the following except: A. B. C. D. Depth to interface. Transducer diameter. Transducer frequency. Difference in acoustical impedance

RAPHEX Answer to General Question D 65 B. Transducer diameter affects only lateral resolution.