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Quiet (good for acoustic stimulation); fMRI may have
noise >90 dB
Less sensitive to movement artifact
Allows metabolic and receptor mapping
Allows imaging of brain regions that are typically
difficult to image with fMRI because of the presence of a susceptibility
artifact (orbitofrontal cortex, inferior temporal lobe) that causes
both distortion and loss of signal
Allows the use of standard measurement devices (physiological,
behavioral) inside the scanner (i.e., avoids the complication for the
need of specially designed MRI-compatible hardware)
(In the MRI
environment, the presence of a very strong static magnetic field
commands the use of diamagnetic components; moreover, every electric
device in the scanner room needs to be carefully shielded to prevent
interference problems to and from the scanner. Scanning is not used
in patients who have pacemakers or ferromagnetic metal parts in
Injection of a radioactive isotope precludes the use
of PET for longitudinal studies in which the same subjects are scanned
repeatedly over an extended period of time.
PET provides an integral measure (over time) of brain
activity (for activation techniques), with a temporal resolution
on the order of minutes because of the lifetime of the isotope.
By comparison, fMRI has a temporal resolution on the order of seconds.
This prevents the use of sophisticated, event-related designs with
PET. Also, the number of images typically collected with PET on
a single subject rarely exceeds a dozen, thereby limiting the statistical
treatment in the analysis of the data.
Spatial resolution is more limited with PET than with
Cyclotron must be located nearby.
PET is more expensive than fMRI (utilization costs
per hour: fMRI, ~$500; PET, ~$2,000).
The acquisition procedure is time-consuming and requires
more resources. (One scan typically lasts ~3 hours [fMRI
typically lasts <1 hour].
In comparison, the MRI experimental setup is easier to perform and
can be operated by just one person.)