Respuesta :
Answer:
Option C
Explanation:
Given:
- Depth of tissue d = 12 cm
- frequency of ultrasound f = 1 MHz
- Input Intensity I_i = 1000 W/m^2
- attenuation coefficient soft tissue a = 0.54
Find:
- Out-put intensity at the required depth
Solution
- The amount of attenuation in (dB) with the progression of depth is given by:
Attenuation = a*f*d
Attenuation = 0.54*12*1
Attenuation = 6.48 dB
- The relation with attenuation and ratio of input and output intensity is given by:
Attenuation = 10*log_10 (I_i / I_o)
6.48 dB = 10*log_10 (I_i / I_o)
I_i / I_o = 10^(0.648)
I_o = 1000 / 10^(0.648)
I_o = 225 W/m^2
- Hence the answer is option C: I_o = 250 W/m^2
