____ imaging invovles a rotating x ray beam
rate of attenuation with a CT varies by
Beam attenuates (ie weakens) as it passes through brain tissue
what is detected with a CT?
used to reconstruct 3d image
advantages to CT
disadvantages to CT
1. ionizing radiation
2. not as good for soft tissue
3. lower spatial resolution
with MRI, Rapid repetitions of ___ enhance gray-white contrast
with MRI, Infrequent RF pulses enhance___
advantages to MRI
1. high spatial resolution
2. no radiation
3. excellent contrast
4. functional/chemical imaing avail.
disadvantages to MRI
1. long study duration
2. no ferromagnetic or electronic devices
3. small as hell -- claustrophobia
with Magnetic resosnance spectroscopy you look at the
chemical structure of the brain
on MRS choline indicates
on MRS, creatine indciates
on MRS, lactate indicates
on MRS, NAA indicates
____ involves measuring water diffusion
DTI: Diffusion Tensor Imaging
DTI: Diffusion Tensor Imaging invovles measuring water diffusion along different orientatations within ___
fMRI in vivo measures
BOLD, blood-oxygen-level dependent, signals at baseline vs.
! experimental conditions
limitations of FMRI includes
spatial and temporal resolution
what does PET involves?
PET: radioactive tracer incorporated into a biologically active molecule (ex. Glucose, oxygen, dopamine transporters)
disadvantages of PET?
1. need a cyclotron to make radioisotope
2. radiation exposure
what are 5 applications of imaging mdoalities?
1. map nml brain development
2. alzheimers disease
3. image guieded neurosurgery
5. pain )in high vs. low sensitvity pts)
advantages of pet?
physiological variables can be determined
to study brain structure what could you use
CT or MRI
what to use when looking at vascualture?
what to use when looking at fiber tracts?
what to use when looking at brain perfusion?
what to use when looking at NT integrity?
what to use when looking at metabolism?
what to use when looking at chemical structure?
elements of ___ atomic numbers show up better on CT
high (ca iron barium lead)
on ct, hyodense areas can indicate
edema and infarction
hyperdense structures on ct can indicate
calcifications and hemorrhage and bone trauma
SPATIAL RESOLUTION OF ____ MILLIMETERS IN CT SCAN
SPATIAL RESOLUTION IS ___ MILLIMETER IN MRI
with mri, ___ is used isntead of xrays
when the rf pulse is turned off protons ___ with the external magnetic field
when RF pulse turns off
the energy from each spinning proton absorbed from the RF ___
as energy decays, an ___ is emitted which is picked up by an antennae
each pixel of an image on an mri is encoded with a nubmerical index that represents the
relaive strength of the RF signal in the area of the brain
each numerical index (which represents an RF signal) corresponds to a
gray scale level
how can a dr adjust an MRI to look at tissue he or she is most interested in?
varying the timing of the rf pulse
diag. applications of mri includr
inflammatory disease, neoplastic disease, epilepsy, stroke
MRS can derive __ and __
concentrations and ratios of chemicals
a ___ is applied with MRS
with MRS what represents the concentration of each chemical component of interest
the size of peak
on MRS ___ is raised in tumor tissue
The difference between T1 and T2 weighted MRI images is due to ____
density of fluids.
when a person is performing a task in the MRI scanner that results in increased neural activity, resulting changes in the concentration of _____ is represented by small changes in intensity values on the MR images.
in control condition of fmri the task is comprised of
all features of experimental task except the specific cognitive variable of interest
what imaging modalities have fairly poor spatial resolution
on an FMRI ___ was active during all emotions
FMRI studies have shown ___ regions important for memory formation have prolonged maturational trajectory
____ has been used in the management of AD, since hypometabolism in various brain regions have been associated with severity of clinical symptoms
what is APOE-4 allele related to?
genetic risk for alzheimers
APOE-4 allele carriers had inc brain activation during __ tasks
after 4 years the degree of brain activity correlated with memory decline
which studies use ionizing radiation
ct and pet
with studies can provide functional imaging
pet and mri
disorders to study with ct
hemorrhages, generalized atrophy
disorders to study with mri
disorders to study with pet