Biomedical Engineering Reference
In-Depth Information
ASL data and due to the powerful noise reduction achieved by
the fitting and filtering algorithms. Furthermore, DASL achieves
unparalleled temporal resolution when compared to other ASL
techniques, a fundamental feature to enable its application to the
measurement of the hemodynamic response to functional brain
stimulation and to the measurement of vascular transit times.
Recently, there has been renewed effort to map the perfu-
sion territories of major cerebral arteries
(71)
. While other ASL
methods have been developed to measure arterial territories in the
brain, none of the proposed techniques to date have enough tem-
poral resolution to allow detailed characterization of the changes
in vascular perfusion patterns associated with cerebrovascular dis-
eases such as focal ischemia or hemorrhage. DASL is likely to be
particularly suited for these applications where the changes in vas-
cular territories are accompanied by changes in transit-times due
to alteration in the perfusion patterns.
In conclusion, DASL is destined to constitute a versatile
experimental platform for studying the spatial and temporal char-
acteristics of functional cerebral hemodynamics. Further opti-
mization of the technique will allow analysis of the vascular nature
of the BOLD and the CBF responses, as well as the changes in vas-
cular transit-times and perfusion territories associated with func-
tional hyperemia.
Acknowledgment
This research was supported by the Intramural Research Program
of the NIH, National Institute for Neurological Disorders and
Stroke.
References
1. Rakic,P. (2002) Evolving concepts of cortical
radial and areal specification.
Prog Brain Res
,
136
, 265-280.
2. Ogawa,S., Tank,D.W., Menon,R., Eller-
mann,J.M., Kim,S.G., Merkle,H., Ugurbil,K.
(1992) Intrinsic signal changes accompanying
sensory stimulation: Functional brain mapping
with magnetic resonance imaging.
Proc Natl
Acad Sci U S A
,
89
, 5951-5955.
3. Phelps,M.E., Mazziotta,J.C., Huang,S.C.
(1982) Study of cerebral function with
positron computed tomography.
J Cereb Blood
Flow Metab
,
2
, 113-162.
4. Lieke,E.E., Frostig,R.D., Arieli,A., Ts'o,D.Y.,
Hildesheim,R.,
high
resolution
imaging
based
on
slow
intrinsic-signals.
Annu
Rev
Physiol
,
51
,
543-559.
5. Villringer,A., Dirnagl,U. (1995) Coupling of
brain activity and cerebral blood flow: Basis
of functional neuroimaging.
Cerebrovasc Brain
Metab Rev
,
7
, 240-276.
6. Lauritzen,M. (2001) Relationship of spikes,
synaptic activity, and local changes of cerebral
blood flow.
J. Cereb. Blood Flow Metab
,
21
,
1367-1383.
7. Attwell,D.,
Iadecola,C.
(2002)
The
neural
basis
of
functional
brain
imaging
signals.
Trends Neurosci
,
25
, 621-625.
8. Iadecola,C. (2004) Neurovascular regulation
in the normal brain and in Alzheimer's disease.
Nat. Rev. Neurosci
.,
5
, 347-360.
Grinvald,A.
(1989)
Opti-
cal
imaging
of
cortical
activity:
Real-time
imaging
using
extrinsic
dye-signals
and
