Magnetic Resonance Imaging Flashcards
How are coronal MRI images viewed?
from the front
How are axial MRI images viewed?
from below
How are sagittal MRI images viewed?
from left to right
Disease processes that give rise to low signal intensity on T1 imaging give rise to ___ signal intensity on T2
high
What gives rise to high signal intensity on a T1 image?
*light appearance
bone marrow
What gives rise to low signal intensity on a T1 image?
*dark appearance
IVDs
What gives rise to the lowest signal intensity on a T1 image?
*black appearance
CSF
What gives rise to high signal intensity on a T2 image?
*light appearance
CSF and IVDs
T1 images are made at ___ energy levels. Why?
High, so most of the energy from the radiofrequency remains in the tissues
T2 images are made at ___ energy levels.
low
Because T2 images are made at low energy levels, how does this effect the image?
They appear grainier and display less spatial resolution
What do T1 images measure energy from?
Structures such as fat, which give up energy rapidly
What do T2 images measure energy from?
Structures such as water, which does not readily give up energy
T1 imaging measures energy ___ in the process of longitudinal remagnetization
early
T2 imaging measures energy ___ in decay of transverse relaxation
late
T2 imaging is valuable in detecting what?
inflammation
In summary, ___ gives rise to high signal intensity on T1-weighted images and low to intermediate signal on T2
fat
In summary, ___ gives rise to high signal intensity on T2-weighted images and very low signal on T1
water
What structures show low signal intensity on all sequences?
Tendons, ligaments, menisci, and cortical bone
Does red or yellow marrow display a higher signal intensity on T1 images?
yellow
What type of signal intensity do muscles exhibit on T1 and T2 images?
intermediate signal intensity for both, although signal intensity slightly lower on T2
What also gives rise to intermediate signal intensity on T1 and T2 images?
cartilage
MRI is very sensitive for detecting changes and variations in bone marrow, which is important in the diagnosis of what?
- bone tumors
- stress fractures
- AVN
What is the best modality for differential diagnosis between disk herniations and other causes of nerve root impingement?
MRI
Is an MRI more sensitive than a bone scan for detecting bone metastases? Why or why not?
More, because it has the ability to stage neoplasms in bone and soft tissues along with extent of tissue invasion prior to surgery
What are the contraindications to MRI?
- ferrous metals
- pacemakers
- claustrophobia
