MRSO prep exam
IEC DB/DBA limits for MRI - ANS-140 DB 99 DBA
parameters to reduce noise in MRI - ANS--thicker slices
-larger FOV
-smaller matrix
-parallel imaging
-reducing bandwidth (increasing TE)
-active noise reduction
-Low SAR RF mode (increase in echo spacing)-thicker slices
MRI sequence that produces the most and least noise in MRI - ANS-Most noise
EPI/DWI
least noise spin echo sequence
an increase in slew rate and gradient amplitude causes an increase in - ANS-Peripheral
nerve stimulation
stimulation of the eyes in a patient causing an appearance of flashing lights -
ANS-magnetophosphenes
stimulation of the vestibular system causing a vestibular ocular reflex where the eyes
rapidly move side to side - ANS-nystagmus
what force causes the noise heard in MRI - ANS-lorentz forces
B1+rms - ANS-the amplitude of the B1 frequency over 10 seconds--the intensity of the
changing magnetic field in our patient will determine the amount of energy transferred to
our patient
SAR - ANS-energy per patient mass measured in J/Kg
SAR is measured per sequence
SAR limits: whole body--receive only coil & integrated Body coil - ANS-whole body
measured over 6 minutes
, first level operating mode 4 w/kg
normal operating mode 2 w/kg
SAR limit for head is 3.2 w/kg in both first level and normal operating mode
SAR limits local transmit/receive coil - ANS-local coil measured over 6 minutes
head--
normal operating mode 10 W/kg
first level operating mode 20 W/kg
trunk--
normal operating mode 10 w/kg
first level operating mode 20 w/kg
extremities--
normal operating mode 20 w/kg
first level operating mode 40 w/kg
relationship between SAR and flip angle & SAR and patient size - ANS-squared
relationship
doubled flip angle or patient size=4x increase in SAR
specific energy dose (SED) - ANS-total energy deposited in our patient for an entire
exam
measured in J/kg
limit for SED - ANS-14,400 J/kg
equivalent to 2 hours in normal operating mode
and 1 hour in first level operating mode
sequence to help decrease SAR - ANS-gradient echoes--gradients refocus hydrogen
opposed to RF pulses
IEC DB/DBA limits for MRI - ANS-140 DB 99 DBA
parameters to reduce noise in MRI - ANS--thicker slices
-larger FOV
-smaller matrix
-parallel imaging
-reducing bandwidth (increasing TE)
-active noise reduction
-Low SAR RF mode (increase in echo spacing)-thicker slices
MRI sequence that produces the most and least noise in MRI - ANS-Most noise
EPI/DWI
least noise spin echo sequence
an increase in slew rate and gradient amplitude causes an increase in - ANS-Peripheral
nerve stimulation
stimulation of the eyes in a patient causing an appearance of flashing lights -
ANS-magnetophosphenes
stimulation of the vestibular system causing a vestibular ocular reflex where the eyes
rapidly move side to side - ANS-nystagmus
what force causes the noise heard in MRI - ANS-lorentz forces
B1+rms - ANS-the amplitude of the B1 frequency over 10 seconds--the intensity of the
changing magnetic field in our patient will determine the amount of energy transferred to
our patient
SAR - ANS-energy per patient mass measured in J/Kg
SAR is measured per sequence
SAR limits: whole body--receive only coil & integrated Body coil - ANS-whole body
measured over 6 minutes
, first level operating mode 4 w/kg
normal operating mode 2 w/kg
SAR limit for head is 3.2 w/kg in both first level and normal operating mode
SAR limits local transmit/receive coil - ANS-local coil measured over 6 minutes
head--
normal operating mode 10 W/kg
first level operating mode 20 W/kg
trunk--
normal operating mode 10 w/kg
first level operating mode 20 w/kg
extremities--
normal operating mode 20 w/kg
first level operating mode 40 w/kg
relationship between SAR and flip angle & SAR and patient size - ANS-squared
relationship
doubled flip angle or patient size=4x increase in SAR
specific energy dose (SED) - ANS-total energy deposited in our patient for an entire
exam
measured in J/kg
limit for SED - ANS-14,400 J/kg
equivalent to 2 hours in normal operating mode
and 1 hour in first level operating mode
sequence to help decrease SAR - ANS-gradient echoes--gradients refocus hydrogen
opposed to RF pulses
