MRSO CHAPTER 12 EXAM QUESTIONS AND
ANSWERS
To generate enough electrical fields to create a pt burn, an implant or foreign body
must be larger than? - ANSWER: 2 cm in size
When implants or foreign bodies exceed 2cm in size, the danger of heating rises
until what? - ANSWER until the length or diameter of an implant is equal to half
the wavelength of the radiofrequency utilized; this is the point where the highest
heating temperatures are reached.
At 1.5 Tesla, the radiofrequency is roughly 63.9 MHZ, and the full wavelength is
around 500mm; therefore, what is the length or diameter of an implant? -
ANSWER 250mm or 25cm, the most substantial heating of the implant will occur.
At 3 Tesla, the resonant frequency is around 128MHz, and the complete
wavelength is approximately 240mm - ANSWER, so when the length of the
diameter of the implant is 12cm, the most significant heating of the implant will
occur.
How do you determine the energy distribution of an implant? - ANSWER
Maximum SAR, for example 2W/kg x.001 (the SAR from the implant's distance
from the isocenter) =.002 W/kg
What is the SAR limit for normal mode? - ANSWER: 2W/kg
The spine echo pulse sequence consists of a 90-degree radiofrequency pulse
followed by one or more 180-degree refocusing pulses; the quantity of heat
deposited by a 180-degree refocusing pulse is 10 times that of a 90-degree
radiofrequency pulse. - Answer four times the amount.
ANSWERS
To generate enough electrical fields to create a pt burn, an implant or foreign body
must be larger than? - ANSWER: 2 cm in size
When implants or foreign bodies exceed 2cm in size, the danger of heating rises
until what? - ANSWER until the length or diameter of an implant is equal to half
the wavelength of the radiofrequency utilized; this is the point where the highest
heating temperatures are reached.
At 1.5 Tesla, the radiofrequency is roughly 63.9 MHZ, and the full wavelength is
around 500mm; therefore, what is the length or diameter of an implant? -
ANSWER 250mm or 25cm, the most substantial heating of the implant will occur.
At 3 Tesla, the resonant frequency is around 128MHz, and the complete
wavelength is approximately 240mm - ANSWER, so when the length of the
diameter of the implant is 12cm, the most significant heating of the implant will
occur.
How do you determine the energy distribution of an implant? - ANSWER
Maximum SAR, for example 2W/kg x.001 (the SAR from the implant's distance
from the isocenter) =.002 W/kg
What is the SAR limit for normal mode? - ANSWER: 2W/kg
The spine echo pulse sequence consists of a 90-degree radiofrequency pulse
followed by one or more 180-degree refocusing pulses; the quantity of heat
deposited by a 180-degree refocusing pulse is 10 times that of a 90-degree
radiofrequency pulse. - Answer four times the amount.
