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Chapter 12 MRSO Exam Questions With
Correct Revised Answers
In order to produce enough electrical fields to cause a pt burn, an implant or foreign body must
be greater than? - answer✔✔2cm in size
When implants or foreign bodies become greater that 2cm in size, the risk of heating increases
until what? - answer✔✔until the length or diameter of an implant is equal to half the wavelength
of the radiofrequencies used; this is the point where the highest temperatures of heating are
reached
at 1.5 Tesla the radiofrequency is approximately 63.9 MHZ and the Full wavelength is Approx
500mm, so what does that make the length or diameter of an implant? - answer✔✔250mm or
25cm, the most significant heating of the implant will take place
At 3 Tesla, the resonant freq is approx. 128MHz and the full wavelength is approx. 240mm -
answer✔✔so when the length of the diameter of the implant is 12cm, the most significant
heating of the implant will take place
How do you calculate energy disposition of an implant? - answer✔✔Max SAR for example:
2W/kg x .001 (this is the SAR from the distance of the implant from isocenter)= .002 W/kg
what is the SAR limit on normal mode? - answer✔✔2 W/kg
The spine echo pulse sequence utilizes a 90 degree radiofrequency pulse, followed by a one or
more 180 degree refocusing pulses; the amount of heat deposited from a 180 degree refocusing
pulse is __________times the amount as what is deposited by a 90 degree radiofrequency pulse.
- answer✔✔4 times the amount
Pulse Sequences RESTORE or DRIVE pulse sequences utilize a what degree pulse sequence? -
answer✔✔270 degree RF pulse prior to the following repetition time
The echo planar imaging sequence has a better chance of what than burning the pt? -
answer✔✔causing peripheral nerve damage
The time-varying gradient field poses the risk of induced current within the pt; This is known as
what? - answer✔✔peripheral nerve stimulation
Chapter 12 MRSO Exam Questions With
Correct Revised Answers
In order to produce enough electrical fields to cause a pt burn, an implant or foreign body must
be greater than? - answer✔✔2cm in size
When implants or foreign bodies become greater that 2cm in size, the risk of heating increases
until what? - answer✔✔until the length or diameter of an implant is equal to half the wavelength
of the radiofrequencies used; this is the point where the highest temperatures of heating are
reached
at 1.5 Tesla the radiofrequency is approximately 63.9 MHZ and the Full wavelength is Approx
500mm, so what does that make the length or diameter of an implant? - answer✔✔250mm or
25cm, the most significant heating of the implant will take place
At 3 Tesla, the resonant freq is approx. 128MHz and the full wavelength is approx. 240mm -
answer✔✔so when the length of the diameter of the implant is 12cm, the most significant
heating of the implant will take place
How do you calculate energy disposition of an implant? - answer✔✔Max SAR for example:
2W/kg x .001 (this is the SAR from the distance of the implant from isocenter)= .002 W/kg
what is the SAR limit on normal mode? - answer✔✔2 W/kg
The spine echo pulse sequence utilizes a 90 degree radiofrequency pulse, followed by a one or
more 180 degree refocusing pulses; the amount of heat deposited from a 180 degree refocusing
pulse is __________times the amount as what is deposited by a 90 degree radiofrequency pulse.
- answer✔✔4 times the amount
Pulse Sequences RESTORE or DRIVE pulse sequences utilize a what degree pulse sequence? -
answer✔✔270 degree RF pulse prior to the following repetition time
The echo planar imaging sequence has a better chance of what than burning the pt? -
answer✔✔causing peripheral nerve damage
The time-varying gradient field poses the risk of induced current within the pt; This is known as
what? - answer✔✔peripheral nerve stimulation
