MRI Flashcards
Why do patients and physicians favor MRI?
Noninvasive
Non-ionizing
T/F: MRI is considered a true multiplanar imaging
True
With soft tissue imaging, what is preferred, MRI or CT?
MRI
What is the first responder to bone pathology ?
Bone Marrow
Bone marrow activity is important for bone pathology, what imaging system is used to see bone marrow?
MRI
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
.25G(equator)
.6G(poles)
G=Gauss
10,000G= ___Tesla
1 Tesla
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)
90 degrees
In which tissue do the proton orient the fastest in order?
- Fat
- Water
- Bone barely has H-looks black
Pulse Sequence:
Time between each RF pulse varying from 500-4000msec
Time Repitition
Pulse sequence:
Time from RF to listening for signal generated by patient varying from <40 to 100msec or >
Time echo
Pulse sequence:
Determining factor of type of image created
TR + TE
Pulse sequence:
Weighted image w/ short TR and short TE
T1/ fat image
Pulse sequence:
Appearance of water and fat with T1
Fat=bright
Water=dark
Pulse sequence:
Weighted image w/ long TR and Long TE
T2- waterimage
Pulse sequence:
How does fat and water appear on T2
Water=bright
Pulse sequence:
Why do the hydrogen’s align quicker in fat?
Hydrogen is less tightly bound to fat than it is to water substances
Pulse sequence:
Image type is determined by TR and TE and what else?
Angle flip: Angle of deflection /flip of hydrogen proton
Pulse sequence:
Spin echo
90 degree flip angle
Pulse sequence:
Gradient echo
<90 degrees flip angle
MRI Image Type:
Fat image-structures containing fat appear brighter/whiter (bone marrow,
subcutaneous fat)
Water-containing structures (edema, neoplasm, inflammation, CSF,
large amounts of Fe) appear dark
long TR, short TE
Spin Echo T1
standard
MRI image Type:
Proton density
Good anatomical detail, has properties of both T1 and T2
Spin T2 first Echo
MRI Image type:
Water image
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
Classic/Standard
MRI Image Types:
Multiple echoes/TR
Faster exam time
Very sensitive to edema
90-180 degree flip angle
Fast Spin Echo
MRI IMAGE type:
Fast MRI using short TR and TE w/ flip angle < 90degrees,
Provides a T2 image in less time but does sacrifice some signal
Gradient Echo
GRE, GRASS, FLASH, FISP, MPGR, SPGR
MRI image type:
Technique that suppresses signal from fat, making small areas of
pathology (often appearing bright because of edema) more evident and increasing the
overall sensitivity of the exam, usually accomplished (STIR)
More sensitive to H20 and edema
Fat Supression (STIR)
Image type that displays functional joint movement.
kMRI
Image type that is used to image vascular flow?
MRA
Image type that reveal distribution of fluid restriction as seen in stroke?
Diffusion MRI
Image type that displays concentration of biochemical metabolites?
MR spectroscopy
Image type that displays changes in oxygen concentration associated with neural activation and provides high resolution imaging of the brain
Functional MRI
Image weight bearing image (kMRI) that can reveal pathologies that may be missed such as canal stenosis, transitional motion and disc lesion
Upright MRI
Indication for MRI
Suspicion of Cervical, thoracic, lumbar disc disease
Suspicion of central canal/ foramina or lateral recess stenosis
Suspicion of spinal cord pathology
Congenital disorders
Marrow infiltration
Bone neoplasm
Failed back syndrome
Failure to improve w/ tx
Active vs. inactive spndylolithesis(STIR preferred)
Painful scoliosis
Contraindications to MRI
1st trimester
Ferromagnetic artifacts e.g., Aneurysm Clips
Intraocular foreign bodies (welders)permanent eyeliner
Subcutaneous Metal shards
& some Shrapnel
Cardiac pacemekers/defibrillators/implanted neurotranmitters (TENS units)
Cochlear Implants, some prosthetic heart valves
Calustrophobia – ~5% rejection rate
Individual patient rejection criteria have been established by each MRI facility should
be stringently enforced
1971 in MRI history
Damadian discovered Nuclear Magnetic resonance ability to differentiate cancerous from healing tissue
1976 in MRI history
Damadian et al. First NMR image of mouse and later human thorax
What is MR Imaging looking for?
Water/edema
DiscHErniation without surrounding osteophytosis, can be acute, subacute of chronic. Seen on MRI
Soft herniation
These symptoms describe:
Saddle paresthesia or anesthesia
Bowel or bladder disturbances
Lower extremity mote weakness and sensory deficits
Reduced or absent lower external reflexes
LBP
Uni/bilateral sciatic
CaudaEquina Syndrome
Cyst that can have no symptoms, no way to be seen on plain films (on MRI) and is due to complication of facet DJD
Synovial cyst
Modic Endplate:
Represents changes that demonstrate disruption and fissuring of the endplate by vascularized fibrous tissues that invade the adjacent marrow
Appears dark on T1 and bright on T2
Can convert to a type II
Type one Modic
Represents marrow edema
ModicEnplate Changes:
Demonstrate endplate disruption with fatty marrow replacement in the adjacent vertebral body.
Bright on T1&2
Modic Type II
fat degeneration of subchondral marrow
ModicEndplate change:
Reflects the relative absence of marrow in areas of fibrous or compact bone deposition.
Correlate with bone sclerosis on plain film
Dark T1&T2
Modic Type III
Cyst found on MRI typically in sacrum
Perineural- fluid filled meninges dilation of nerve root sheath
Asymptomatic, 20% symptomatic
May need drainage
Tarlov’s cyst
