CNS Flashcards
(38 cards)
prior confirmation steps for brain death
EEG (rept)
bedside tests (doll eyes, pain sensation, resp test)
eval cortical activity/fx (CT scan prior)
nuc med
what mimics brain death
intoxication, DRUGS (OD), hypothermia
interpretation brain death
flow to carotid arteries is normal in all patients but hot nose is ONLY normal in brain dead patients bc blood go to nose instead of brain
tracers
30 mCi of TcO4, TcDTPA (20-30), Ceretec/ECD
remember upon injection (methods)
scalp tourniquet, good bolus bc we are looking at flow, rapid dynamic, post flows
what collimator do we prefer
LEAP
dynamic workflow
same for every tracer and brain death study-FIRST bc followin tracer
computer started b4 inj, prefer LEAP over HiRes bc more sensitive to cts dont care bout details of res, 2 sec/ frame for 90 frames
delay workflow
static immediately after dynamic= free tc and TcDTPA bc does not cross BBB
wait 20 min ECD/Ceretec to cross BBB
statics taken for 256 matrix, 500 k, position so cts are not picked up from rest of face (nose and up)
what are ECD/Ceretec used for
-cerebral perfusion imaging
-SPECT
properties needed to cross BBB
lipophillic, small molecule size, neutral charge, high extraction meaning it deposits in brain on first pass in high quanity, high affinity for brain cells (little to no redistribution)
Indications to use ECD/Ceretec
stroke, dementia, epilepsy, trauma, parkinsons, huntingtons, psych disorders, brain death
perk of no redistribution
can repeat scan if needed bc will stay in brain cells
Ceretec properties
-hexamethylpropylenamine oxime (HMPAO)
-first pass 80%
-peak activity is 1-2 min (how long tracer takes to get in brain/earliest u can image)
-3.5-7% retained in brain bc has to be lipophilic to crss BBB and converted by glutathione to hydrophilic compound so it does not come back out of brain
-unstable in vitro so we like ECD better
ECD properties
-Tc99m ethyl cysteinate dimer
-neurolite=brand name
-bicisate= common name
-first pass extraction= >70%
-peak activiy 1-2 min (how long to wait to get good target to bkg ratio)
-6-7% retained in brain
-less uptake in scalp and brain
-stable in vitro so we like better
ECD/Ceretec shared properties
flow depends on condition when injected»lights, noise, pain, position
dose=30 mCi
static delay= 30 min ECD and 2 hr Ceretec
(wait longer for ceretec for scalp and facial activity to go away so better target to bkg ratio)
ECD/Ceretec
scan
~36 min
-zoom
-circular
-matric =128
what changes are abnormal in ecd and ceretec
asymmetry between R and L, excess activity in concentrated area (pain stimulation or seizure, decrease activty in concentrated area (coma= pt not using brain, dementia)
ictal focus mean
during a seizure so more upatke happens during this, usually only on one side
interictal
in between seizures
pre and post ictal
b4 and after seizure respectively
post ictal=
decre uptake cuz no firing of signals anymore
diamox protocol
=sodium acetazolamide which evalutaes cerebral flow reserve; vasodilator— indicates angioplasty
dose= 1 gram in 50 cc dextrose IV
procedure= infuse over 10 min, wait 10 min to inject if using ECD
DaT scan not DiS scan
dose=3-5 mCi I 123 Ioflupane
-looks at dopamine transporters which are receptors for it so if it uptakes it then yay if not then boo
-parkinson vs essential tremors_> confusion between the two
indication for cisternogram
hydrocephalus or CSF leak
