If a sample is placed in an applied magnetic field, the net magnetic moment of the sample will:
A. a) Be zero, due to the large number of spins and random orientation of vectors.
B. b) Align along the direction of the applied magnetic field.
C. c) Will have no preferred orientation.
查看答案
Why does clinical MRI detect the magnetic resonance signal of water protons in the body?
A. a) Because only water protons have spin.
B. b) Because water has an odd number of neutrons.
C. c) Because water protons are the most abundant spins in the body.
How much energy is converted into heat by an electron beam in an X-ray tube?
A. 1%
B. 10%
C. 99%
What minimizes the X-ray dose?
A. The faster the X film, the better
By collimating less exposed areas
C. Use lead to protect vulnerable areas
D. With low-energy X-rays
E. B and C
F. A and D
What are the advantages of using fluoroscopy to image swallowed barium meal?
A small movie and a high-resolution still photo are available.
B. The detection system is longer.
C. It is displayed vertically.
微信支付 
支付宝支付