214 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 210-215
SciRes Copyright © 2009 JBiSE
were quite reasonable, and in accordance with previ-
ously published PET results from normal subjects. For
example, Kaneko et al. [20] observed MTT values of 6.1
s in grey matter and 8.1 s in white matter, and the large
study by Leenders et al. [21] showed CBV-to-CBF ratios
of 5.7 s in insular grey matter and 7.3 s in white matter.
Application of the calibration factor to the present data
resulted in a corrected whole-brain average CBF of ap-
proximately 42 ml/(min100g). Literature values of nor-
mal global CBF in humans at rest vary over a consider-
able range [22,23], but are typically between 40 and
50ml/(min100g) for the adult population. For example,
Knutsson et al. [9] obtained a whole-brain average CBF
of 40ml/(min100g) (in elderly normal subjects) by
Xe-133 SPECT, Slosman et al. [24] observed a global
CBF of 43ml/(min100g) in male volunteers (age interval
29-38 years), also by use of Xe-133 SPECT, Dörfler et
al. [22] reported a global CBF estimate of 48ml/
(min100g) based on extracranial sonography and Mat-
thew et al. [25] observed 40 ml/(min100g) using H2
15O
PET. Finally, Yonas et al. [26] employed stable xenon
computed tomography (Xe-CT) and extracted regional
CBF values of 92ml/(min100g) in the highest-flow
compartments, 54ml/(min 100g) in mixed-cortical re-
gions (calculated from linear-regression equations and
corresponding to the age of 33 years) and an age-inde-
pendent white-matter regional CBF of 20ml/(min100g).
In conclusion, DSC-MRI showed promising results in
the detection of controlled perfusion changes, induced
by spontaneous hyperventilation, in individual subjects.
In accordance with previously reported DSC-MRI ex-
periments, uncorrected absolute CBF values appeared to
be overestimated.
5. ACKNOWLEDGEMENTS
This study was supported by the Swedish Research Council (project no.
13514), the Swedish Cancer Society and the Crafoord Foundation,
Lund.
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