Question

Regarding MRI risks and safety: 

a. The most often encountered adverse incidents in patients undergoing MR scanning in England are burns 

b. The main risk of the static magnetic field is its potential to cause a biological effect 

c. At field strengths of 3 T and higher, there is a potential risk for the function of artificial heart valves to be impaired due to the Lenz effect 

d. Peripheral nerve stimulation can occur in response to the radio frequency fields 

e. The maximum allowed rise in total body temperature in the normal scanning mode is 0.5°C

Answer 1

a. True. This is due to eddy currents arising in conducting loops. Burns can also occur where the arms and legs are touching, forming a conducting loop pathway. 

b. False. The main risk is that of a ferromagnetic object entering the inner MR controlled area becoming a projectile. 

c. True. The Lenz effect is an induction of a magnetic field in a moving conductor that opposes the external magnetic field. It is of low significance at a 1.5 T field, but is a potential hazard at higher field strengths. 

d. False. This is caused by magnetic field gradients. 

e. True. In the first-level controlled mode with appropriate monitoring, the allowable temperature rise is 1°C.