Central Nervous System GW Flashcards
BBB imaging is most useful for these suspected pathologies
- Primary or metastatic disease (glioma, meningioma
- Intracranial inflammatory disease (abscess, encephalitis)
- Cerebrovascular disease (hemorrhage, occlusion, hemangioma)
- Head trauma complications (subdural hematoma, brain death)
BBB imaging RPs
Tc99m Pertechnetate
Tc99m pentetate DTPA
15-30 mCi
What is the least desired RP for BBB imaging and why
Tc99m pertechnetate because it uptakes in choroid plexus and you have to use a blocking agent of potassium perchlorate
Which RP for BBB imaging is most desired and why
Tc99m DTPA because it is rapidly cleared by kidneys - lower exposure to patient
can image sooner
no blocking agent required
How much potassium perchlorate must be administered for imaging BBB with pertechnetate
0.2-1 g oral
How is BBB imaging typically acquired
Planar, 3 phase, LEAP/converging collimator
How is pt positioned for BBB imaging
Flow - upright with head and nose touching collimator
Blood pool and delays - ANT, POST, LATs with lead on face, and vertex with lead on shoulders
Normal BBB imaging findings
In 6 secs you’ll see right and left carotid arteries, and anterior cerebral artery
SSS showing means arterial blood is entering venous system
Abnormal findings BBB imaging
Disruption of BBB will show increased localization of RP in the area of pathology
Brain death flow will show tracer in carotids but a complete absence in middle and anterior cerebral arteries due to increased intra cranial pressure
What is brain perfusion imaging used for
Functional abnormalities
1. Cerebrovascular disease (stroke, TIAs)
2. Dementia
3. Psychiatric disorders
4. Seizure disorders
5. Head trauma (cerebral brain death)
How is brain perfusion imaging performed
SPECT, except brain death is planar
How is brain death imaging performed
Planar
Brain perfusion RPs
99mTc exametazime HMPAO
99mTc bicisate ECD
10-20 mCi
Pt prep for brain perfusion imaging
Quiet, dimly lit room, unstimulated
Which RPs cross the BBB
Tc99m exametazime HMPAO
Tc99m bicisate ECD
And then becomes fixed in the brain cells - can image up to 6 hours
What RP must you use a fresh generator eluate <2 hours old
99mTc exametazime HMPAO
Maximum imaging time for brain perfusion agents
Can image up to 6 hours after injection because HMPAO and ECD become fixed in brain cell
Normal tracer distribution in brain perfusion imaging
Symmetric in both hemispheres. Grey matter will show more than white matter (more blood flow). White matter may have no uptake
Abnormal distribution in brain perfusion imaging
Acute cerebral infarct - cold spot.
Alzheimer’s - decreased perfusion in parietal, temporal, and frontal lobes.
Multifarct dementia - multiple areas of decreased uptake.
Schizophrenia - decreased perfusion to frontal lobes.
Depression - decreased uptake over entire cerebral cortex.
Manic - greatly increased perfusion overall.
Active seizure - intense focal uptake.
Interventional drug for brain perfusion
Acetazolamode “diamox” (1g) - induces cerebral vasodilation
RP is injected 25 mins later
BBB imaging/brain perfusion is also called
Cerebral angiography
Planar brain death RP
Tc99m exametazime HMPAO usually
- can obtain images 1-3 hours later
-or can take flow study
Tc99m ECD
Can use 99mTc DTPA - less desirable
Where is CSF produced
Choroid plexus
What does CSF do
Shock absorber for the CNS
Cisternography indications
Diagnosis of normal pressure hydrocephalus, CSF leaks, ventricular shunt patency
Cisternography RP
In111 pentetate DTPA
0.5 mCi
T 1/2 2.8 days
Excreted renally
Where is cisternography RP injected
Intrathecally in subarachnoid space, between 3rd and 4th lumbar vertebrae
Normal cisternography didtribution
4-6 hrs: Activity seen in spinal cord ascending to basal cisterns
24 hrs: tracer clearance from the basal cisterns, activity seen in subarachnoid space surrounding cerebral hemispheres, interhemispheric cisterns, and SSS
Abnormal cisternography
NPH: visualization of lateral ventricles at any point and delay of activity in SSS
CSF leak: leak activity and activity on swabs
Ventricular shunt patency imaging RP and route
99mTc pertechnetate - not approved for intrathecal use, we can use it here bc it’s going into shunt
In111 pentetate - less desired
Directly into shunt reservoir
Dopamine transporter imaging RP
I123 ioflupane
3-5mCi
Dopamine transporter imagine indications
Detects degeneration of the dopaminergic nigrotriatal pathway
- differentiated pts with essential tremor from Parkinsonism syndromes
Drug contraindications for DatScan
Cocaine, -phetamines, stimulants, ephedrine, bupropion, fentanyl, anesthetics (ketamine), SSRIs
*Antiparkinsonian drugs do not interfere
Acquisition type for datscan
SPECT
3-6 hrs after injection
Normal datscan findings
Comma sign
- the head of the caudate nucleus and putamen
Abnormal datscan findings
Period sign (incomplete comma)
Another name for normal pressure hydrocephalus
Communicating hydrocephalus
