Oxygen extraction fraction measurement using quantitative susceptibility mapping: Comparison with positron emission tomography

Abstract

The purposes of this study are to establish oxygen extraction fraction (OEF) measurements using quantitative susceptibility mapping (QSM) of magnetic resonance imaging (MRI), and to compare QSM-OEF data with the gold standard (15)O positron emission tomography (PET). Twenty-six patients with chronic unilateral internal carotid artery or middle cerebral artery stenosis or occlusion, and 15 normal subjects were included. MRI scans were conducted using a 3.0 Tesla scanner with a three-dimensional spoiled gradient recalled sequence. QSM images were created using the morphology-enabled dipole inversion method, and OEF maps were generated from QSM images using extraction of venous susceptibility induced by deoxygenated hemoglobin. Significant correlation of relative OEF ratio to contra-lateral hemisphere between QSM-OEF and PET-OEF was observed (r = 0.62, p < 0.001). The local (intra-section) correlation was also significant (r = 0.52, p < 0.001) in patients with increased PET-OEF. The sensitivity and specificity of OEF increase in QSM was 0.63 (5/8) and 0.89 (16/18), respectively, in comparison with PET. In conclusion, good correlation was achieved between QSM-OEF and PET-OEF in the identification of elevated OEF in affected hemispheres of patients with unilateral chronic steno-occlusive disease.

Preoperative Cerebral Oxygen Extraction Fraction Imaging Generated from 7T MR Quantitative Susceptibility Mapping Predicts Development of Cerebral Hyperperfusion following Carotid Endarterectomy

“…Against our expectations, however, a recent study has demonstrated that QSM-OEF at 7T MR imaging achieved only a slight improvement in the correlation coefficient, and the sensitivity/specificity of OEF obtained with 15 O-PET included substantial systematic biases in terms of the agreements compared with that at 3T MR imaging. 22,23 This issue can be mainly attributed to the relatively low spatial resolution of the source images at 7T MR imaging, which was comparable with that at 3T MR imaging. 22,23 Although the blood oxygen level-dependent effect is much stronger at 7T MR imaging than at 3T MR imaging, susceptibility information of minute venous structures at 7T MR imaging was presumably overlooked due to the low resolution of the images.…”

“…22,23 This issue can be mainly attributed to the relatively low spatial resolution of the source images at 7T MR imaging, which was comparable with that at 3T MR imaging. 22,23 Although the blood oxygen level-dependent effect is much stronger at 7T MR imaging than at 3T MR imaging, susceptibility information of minute venous structures at 7T MR imaging was presumably overlooked due to the low resolution of the images. 23 Thus, whereas the use of a 7T scanner in the present study is a significant limitation on the availability of QSM-OEF, the same results as in the present study could probably be obtained with QSM-OEF at 3T MR.…”

“…23 The OEF maps with voxels of interest of 25 mm 3 were generated from the processed QSM images according to a previous study. 22,23 In brief, the susceptibility difference between venous structures and surrounding brain tissues, ⌬, is expressed by the following equation:…”

“…[19][20][21] Quantitative susceptibility mapping (QSM) is a postprocessing technique for quantifying the magnetic susceptibility of venous structures and brain parenchyma from T2*-weighted magnitude/phase images, which can be easily obtained by commercial scanners. 22 Indeed, a recent study has introduced an OEF measurement method based on the QSM technique and has demonstrated that cerebral OEF images generated from QSM at 7T MR imaging correlate with OEF images on PET and provide high sensitivity and high specificity for detecting misery perfusion in the middle cerebral artery territory in patients with unilateral chronic ICA or MCA steno-occlusive disease. 23 The purpose of the present study was to determine whether preoperative OEF imaging generated from 7T MR QSM could identify patients at risk for cerebral hyperperfusion following CEA.…”

Susceptibility-Based Neuroimaging: Standard Methods, Clinical Applications, and Future Directions

“…[93, 94] Early quantitative studies to measure oxygen saturation typically modeled large draining veins[95] and cortical vessels[96] as long cylinders parallel to the main field. With this assumed geometry and orientation, a simple relation exists between the measured field shift ΔB vein-water and the oxygen extraction fraction (OEF): ΔB vein-water = 4π Δχ do0 Hct OEF, where Δχ do0 is the susceptibility shift between fully oxygenated and fully deoxygenated blood.…”