T. Krings et al., MR blood oxygenation level-dependent signal differences in parenchymal andlarge draining vessels: Implications for functional MR imaging, AM J NEUROR, 20(10), 1999, pp. 1907-1914
Citations number
36
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Neurosciences & Behavoir
BACKGROUND AND PURPOSE: One major limitation of current functional MR (fMR)
imaging is its inability to clarify the relationship between sites of cort
ical neuronal activation, small parenchymal venules that are in close proxi
mity to these sites, and large draining veins distant from the active paren
chyma, We propose to use gradient-echo blood oxygenation level-dependent (B
OLD) fMR time courses to differentiate large draining veins from parenchyma
l microvasculature.
METHODS: In eight research subjects, five of whom presented with space-occu
pying lesions near the central sulcus, gradient-echo fMR imaging was perfor
med during alternating periods of rest and motor activation, MR signal time
courses from parenchymal regions and draining veins of different diameters
, which were identified using contrast-enhanced T1-weighted scans, were eva
luated. Percent signal changes (Delta S) and the time to the onset of MR si
gnal rise (T-0) were calculated.
RESULTS: Mean Delta S for all subjects was 2.3% (SD +/-0.7%) for parenchyma
l activation, 4.3% (SD +/-1.0%) for sulcal macrovasculature, and 7.3 (SD +/
-1.1%) for large superficial bridging veins. The mean time to onset of MR s
ignal increase was 4.4 seconds for parenchymal task-related hemodynamic cha
nges and 6.6 seconds for venous hemodynamic changes, regardless of vessel s
ize. Both the differences in Delta S and T-0 were statistically significant
between venous and parenchymal activation (P < .0001).
CONCLUSION: Gradient-echo fMR imaging reveals hemodynamic task-related chan
ges regardless of vessel size and therefore might show macrovascular change
s distal to the site of neuronal activity, MR-signal time-course characteri
stics (Delta S and T-0) can be used to differentiate between small parenchy
mal and larger pial draining vessels, which is especially important in pres
urgical planning of neurosurgical procedures involving functionally importa
nt brain regions. The knowledge about the differences in Delta S and T-0 be
tween micro- and macrovasculature might lead to a more accurate description
of the spatial distribution of underlying neuronal activity.