Radiology and Imaging Sciences, Emory University, Atlanta, Georgia, USA.
Department of Radiology, New York University, New York, New York, USA.
J Magn Reson Imaging. 2019 Jul;50(1):175-182. doi: 10.1002/jmri.26546. Epub 2018 Nov 3.
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.
To explore QSM oximetry during acetazolamide (ACZ) challenge, hypothesizing that detectable OEF alterations will reflect hemodynamic compromise in unilateral cerebrovascular disease (CVD) patients.
Retrospective.
Fourteen unilateral CVD patients, and 24 healthy controls (HC).
FIELD STRENGTH/SEQUENCE: Multiecho gradient echo (GRE) and T -weighted images at 3T.
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.
The result significance was determined using t-tests and Pearson's correlation.
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).
These results suggest QSM is sensitive to dynamic OEF modulation during hemodynamic augmentation.
3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:175-182.
氧提取分数（OEF）升高可预测颈动脉狭窄性疾病患者缺血性卒中发生率增加，可通过定量磁化率映射（QSM）MRI 进行评估。
探讨乙酰唑胺（ACZ）挑战期间的 QSM 血氧测定，假设可检测到的 OEF 变化将反映单侧脑血管疾病（CVD）患者的血液动力学损伤。
回顾性研究。
14 例单侧 CVD 患者和 24 例健康对照者（HC）。
磁场强度/序列：3T 多回波梯度回波（GRE）和 T1 加权图像。
我们从多回波 GRE 图像构建了 QSM 图像和 R2*图。QSM-OEF 图是根据静脉血和背景脑组织之间的磁化率差异生成的。计算大脑中动脉（MCA）区域中线粒体 OEF 比值。还测量了直窦（SS）和 MCA 中的血管内磁化率。
采用 t 检验和 Pearson 相关分析确定结果的显著性。
患者患病/对侧 OEF 比值的平均值和标准差在基线时为 1.15±0.14，ACZ 后为 1.23±0.17。疾病组的 R2比值在基线时为 0.95±0.05，ACZ 后为 1.03±0.08。HC 组的左/右侧 OEF 和 R2比值分别为 0.98±0.06 和 0.99±0.038。患者的 SS 和 MCA 中的磁化率在基线时分别为 162.63±35.4 和-22.33±13.70，ACZ 后分别为 124.56±37.43 和-19.27±23.14。HC 组的 SS 和 MCA 磁化率分别为 146.10±24.79 和-19.59±12.37。患者组的 OEF 比值在 ACZ 前后均大于 1.0（P＜0.01 和＜0.001，单样本 t 检验），且大于 HC 比值（P＜0.001，非配对 t 检验）。OEF 和 R2*比值从基线增加到 ACZ 后（P=0.024，0.004，配对 t 检验）。通过发现 SS 磁化率从基线到 ACZ 后降低（P＜0.001，配对 t 检验），确认了可检测到的血氧变化，而 MCA 磁化率无明显变化（P=0.67，配对 t 检验）。
这些结果表明 QSM 对血液动力学增强期间的动态 OEF 调制敏感。
3 级 技术功效：第 3 阶段 J. Magn. Reson. Imaging 2019;50:175-182.
