Blood oxygen level-dependent MRI of cerebral CO2 reactivity in severe carotid stenosis and occlusion.
OBJECTIVE
Impaired cerebrovascular reserve capacity (CVC) is a risk factor for ischemic events in patients with high-grade carotid stenosis and occlusion. In this study, the CVC in response to a CO2 challenge was evaluated with blood oxygen level-dependent (BOLD) MRI and the results compared with those of a transcranial Doppler CO2 tests.


METHODS
A T2*-weighted single-shot multigradient echo-planar imaging sequence was used to determine cerebral CO2 reactivity. T2* values were calculated for each pixel at rest and during a challenge with 7% CO2, and a reference function was fitted to the T2* time courses. Whole-brain color-coded DeltaT2* parameter maps were calculated and visually evaluated for regional differences. Additionally, a region-of-interest analysis was undertaken. Average values for DeltaT2* normalized to changes in end-tidal PCO2 were calculated.


RESULTS
Color parameter maps showed areas of decreased BOLD effect within the internal carotid artery territory in 12 of 13 hemispheres with impaired CVC in transcranial Doppler CO2 test. Regional normalized DeltaT2* was highly correlated with changes of middle cerebral artery blood flow velocity in transcranial Doppler CO2 test. Normalized DeltaT2* was significantly reduced in hemispheres with impaired CVC in transcranial Doppler (P<0.0001).


CONCLUSIONS
BOLD MRI can easily be included in routine MRI exams. The technique is robust and yields diagnostic information concerning the cerebrovascular reserve.
Ziyeh
Sargon
S
Section of Neuroradiology, University Hospital of Freiburg D-79106 Freiburg, Germany. ziyeh@nz.ukl.uni-freiburg.de
Rick
Jochen
J
Reinhard
Matthias
M
Hetzel
Andreas
A
Mader
Irina
I
Speck
Oliver
O
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001769:Blood / Q000378:metabolism*; D001921:Brain / Q000473:pathology; D002245:Carbon Dioxide / Q000737:chemistry* / Q000378:metabolism; D002340:Carotid Artery Diseases / Q000473:pathology*; D002343:Carotid Artery, Internal / Q000473:pathology; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D013223:Statistics as Topic; D013997:Time Factors; D018608:Ultrasonography, Doppler
D002245:Carbon Dioxide; D010100:Oxygen