Flashcards in MRI Deck (49)
Why do patients and physicians favor MRI?
T/F: MRI is considered a true multiplanar imaging
With soft tissue imaging, what is preferred, MRI or CT?
What is the first responder to bone pathology ?
Bone marrow activity is important for bone pathology, what imaging system is used to see bone marrow?
What percentage of sensitivity to change in the bone can MRI detect?
1% but is only regional
What two things interact with MRI processing?
Hydrogen protons (has magnetic charge)
External Magnetic field
Atomic nuclei have to have what characteristics to be manipulated by MRI?
Odd number of proton and neutrons
In which plane or direction of magnetic fields can hydrogen ions align?
Parallel or Anti-parallel
MRI magnets range of strength ?
.2-1.5 to 3 Tesla
MAgnetic field of earth
At what frequency and angle does the radio frequency have to be in order misalign the hydrogen to 90 or 180 degrees on its axis
Lamor-Frequency (42.58 MHz/T)
In which tissue do the proton orient the fastest in order?
3. Bone barely has H-looks black
Time between each RF pulse varying from 500-4000msec
Time from RF to listening for signal generated by patient varying from <40 to 100msec or >
Determining factor of type of image created
TR + TE
Weighted image w/ short TR and short TE
T1/ fat image
Appearance of water and fat with T1
Weighted image w/ long TR and Long TE
How does fat and water appear on T2
Why do the hydrogen’s align quicker in fat?
Hydrogen is less tightly bound to fat than it is to water substances
Image type is determined by TR and TE and what else?
Angle flip: Angle of deflection /flip of hydrogen proton
90 degree flip angle
<90 degrees flip angle
MRI Image Type:
Fat image-structures containing fat appear brighter/whiter (bone marrow,
Water-containing structures (edema, neoplasm, inflammation, CSF,
large amounts of Fe) appear dark
long TR, short TE
Spin Echo T1
MRI image Type:
Good anatomical detail, has properties of both T1 and T2
Spin T2 first Echo
MRI Image type:
Loosely bound water (neoplasms, edema,
CSF) appear bright/white
Tightly bound or low water content (ligaments, sclerosis, cortical bone) or
large amounts of Fe appear dark/black
Spin T2 second echo
MRI Image Types:
Faster exam time
Very sensitive to edema
90-180 degree flip angle
Fast Spin Echo