Cerebral MR oximetry during acetazolamide augmentation: Beyond cerebrovascular reactivity in hemodynamic failure
Background Oxygen extraction fraction (OEF) elevation predicts increased ischemic stroke incidence among patients with carotid steno‐occlusive disease, and can be estimated from quantitative susceptibility mapping (QSM) MRI. Purpose To explore QSM oximetry during acetazolamide (ACZ) challenge, hypot...
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Veröffentlicht in: | Journal of magnetic resonance imaging 2019-07, Vol.50 (1), p.175-182 |
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Zusammenfassung: | Background
Oxygen extraction fraction (OEF) elevation predicts increased ischemic stroke incidence among patients with carotid steno‐occlusive disease, and can be estimated from quantitative susceptibility mapping (QSM) MRI.
Purpose
To explore QSM oximetry during acetazolamide (ACZ) challenge, hypothesizing that detectable OEF alterations will reflect hemodynamic compromise in unilateral cerebrovascular disease (CVD) patients.
Study Type
Retrospective.
Subjects
Fourteen unilateral CVD patients, and 24 healthy controls (HC).
Field Strength/Sequence
Multiecho gradient echo (GRE) and T1‐weighted images at 3T.
Assessment
We constructed QSM images and R2* maps from multiecho GRE images. QSM‐OEF maps were generated from the susceptibility difference between venous blood and background brain tissue. Intrasubject diseased/contralateral hemisphere OEF ratios in the middle cerebral artery (MCA) territories were calculated. Intravascular susceptibility in the straight sinus (SS) and MCA was also measured.
Statistical Tests
The result significance was determined using t‐tests and Pearson's correlation.
Results
Mean and standard deviation for the patient diseased/contralateral OEF ratios were 1.15 ± 0.14 at baseline and 1.23 ± 0.17 post‐ACZ. Disease group R2* ratios were 0.95 ± 0.05 at baseline and 1.03 ± 0.08 post‐ACZ. Left/right OEF and R2* ratios for the HC group were 0.98 ± 0.06 and 0.99 ± 0.038, respectively. Susceptibility (ppb) in the SS and MCA in patients was 162.63 ± 35.4 and –22.33 ± 13.70, respectively, at baseline, 124.56 ± 37.43 and –19.27 ± 23.14 post‐ACZ. The HC group SS and MCA susceptibility was 146.10 ± 24.79 and –19.59 ± 12.37, respectively. Patient group OEF ratios were greater than 1.0 before and after ACZ challenge (P < 0.01 and < 0.001, respectively, one‐sample t‐test), and were greater than HC ratios (P < 0.001 unpaired t‐test). OEF and R2* ratios increased from baseline to post‐ACZ (P = 0.024, 0.004, respectively, paired t‐test). Detectable blood oxygenation change was confirmed by finding SS susceptibility decreased from baseline to post‐ACZ (P < 0.001, paired t‐test), while MCA susceptibility did not change significantly (P = 0.67, paired t‐test).
Data Conclusion
These results suggest QSM is sensitive to dynamic OEF modulation during hemodynamic augmentation.
Level of Evidence: 3
Technical Efficacy: Stage 3
J. Magn. Reson. Imaging 2019;50:175–182. |
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ISSN: | 1053-1807 1522-2586 |
DOI: | 10.1002/jmri.26546 |