Imaging the brain Flashcards
Brain image technique that images of the soft tissues, Clear image, standard for complex neuro ds
MRI
Indications for brain MRI
- Vascular (Ischemic and hemorrhagic stroke, AVM-arteriole venous malformation, aneurysm, Venous thrombosis)
- Infection (abscess, cerebritis, encephalitis, meningitis)
- Inflammatory/Demyelinating Lesions (multiple sclerosis, sarcoidosis, etc.)
- Tumor (primary CNS and metastatic)- appear early on MRI- helps w/ treatment of cancer
- Trauma (epidural hematoma, subdural hematoma, contusion)
- Hydrocephalus- fluid balance in brain
Contraindications of MRI
- Implanted devices and other metallic devices- bc MRI is a magnet no metal even in the room not being scanned
- Pacemakers and other implanted electronic devices
- Aneurysm clips and other magnetizable materials
- Cochlear implants
- Some artificial heart valves
- Intraocular metallic foreign bodies
- Screening CT of the orbits if history suggests possible metallic foreign body in the eye.
- welder: parts of metal in eye they are unaware of
- Unstable patients (most resuscitation equipment cannot be brought into the scanning room)- people who have metal ports
- Other relative contraindication – severe agitation or claustrophobia (may require anxiety medication or anesthesia assistance)
- Children, developmental disabilities- can be hard for people to stay still, takes long time (longer than CT)
Limitations of MRI
- Subject to motion artifact- stay still for 30-40 min, very small head movements will mess up data
- CT is faster
- nferior to CT in detecting acute hemorrhage
- CT is better at detection of burst and contusion to bone- with bone
- Inferior to CT in detection of bony injury
- Requires prolonged acquisition time for many images
- CT is cheaper and takes less time to be passed by insurance
- MRI is for measuring people chronically over time
Advantages of MRI of brain: (compared to CT scan of brain)
- High quality soft tissue delineation
- Better views of posterior fossa and temporal lobes
- No ionizing radiation
- Non-invasive
- Can detect old hemorrhage and inflammatory lesions better than CT
- Can detect acute infarct within 30 mins
- Can directly scan any plane, e.g. Coronal, Sagittal, Axial, Oblique.
- CT only gets 1 plane of image- can be sliced but only 1 angle
Disadvantages of MRI of brain:
- can not see as thin images with MRI as CT
- Bone imaging limited
- Claustrophobia and time
- Cannot use with pacemaker or ferromagnetic implant, caution with stents, tattoos, welders, any implanted metal
Pituitary gland- common in tumors- can see better on MRI or CT?
MRI - it is soft tissue
MRI has a lot of detail of soft tissue
value of sagittal images in MRI
- can see lobes
- corpus callosum
- cranio cervical junction
- evaluation of venous sinuses
- pituitary gland
value of coronal images in MRI
- pituitary gland, chiasm, hypothalamus
- hippocampal region
- skull base and posetior fossa
- trigeminal nerve
- vascular anatomy
What type of MRI scan is best for detecting: Subacute Hemorrhage, Fat-containing structures, Anatomical Details
T1 W Images
T2 W Images
FLAIR Images
T1 W Images
What type of MRI scan is best for detecting:
Edema, Demyelination, Infarction,
Chronic Hemorrhage
T2 W Images
What type of MRI scan is best for detecting: Edema, Demyelination,
**Infarction esp. in Periventricular location
FLAIR Images
CT or MRI is often used to evaluate damage during stroke recovery?
MRI
Subdural Hematomas (bleeding under dura- contusion- acutely looks more hyperdense and as time goes on is becomes less dense)
are typically crescent shaped as they expand to fill space
Acute hematomas appear hyperdense (white) on CT scan)
Chronic hematomas appear hypodense (gray or black; darker than brain tissue) as the tissue is compressed
