Noninvasive Assessment of Oxygen Extraction Fraction in Chronic Ischemia Using Quantitative Susceptibility Mapping at 7 Tesla

Ikuko Uwano; Kohsuke Kudo; Ryota Sato; Kuniaki Ogasawara; Hiroyuki Kameda; Jun-Ichi Nomura; Futoshi Mori; Fumio Yamashita; Kenji Ito; Kunihiro Yoshioka; Makoto Sasaki

doi:10.1161/STROKEAHA.117.017166

Noninvasive Assessment of Oxygen Extraction Fraction in Chronic Ischemia Using Quantitative Susceptibility Mapping at 7 Tesla

Stroke. 2017 Aug;48(8):2136-2141. doi: 10.1161/STROKEAHA.117.017166. Epub 2017 Jun 29.

Authors

Affiliations

¹ From the Division of Ultrahigh Field MRI, Institute for Biomedical Sciences (I.U., K.K., H.K., F.M., F.Y., K.I., M.S.), Department of Neurosurgery (K.O., J.N.), and Department of Radiology (K.Y.), Iwate Medical University, Japan; Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Japan (K.K., H.K.); and Research and Development Group, Hitachi Ltd, Tokyo, Japan (R.S.). uwano@iwate-med.ac.jp.
² From the Division of Ultrahigh Field MRI, Institute for Biomedical Sciences (I.U., K.K., H.K., F.M., F.Y., K.I., M.S.), Department of Neurosurgery (K.O., J.N.), and Department of Radiology (K.Y.), Iwate Medical University, Japan; Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Japan (K.K., H.K.); and Research and Development Group, Hitachi Ltd, Tokyo, Japan (R.S.).

PMID: 28663515
DOI: 10.1161/STROKEAHA.117.017166

Abstract

Background and purpose: The oxygen extraction fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET.

Methods: Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template.

Results: The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps (r=0.69; P<0.001), especially in patients with a substantial increase in the PET-OEF ratio of 1.09 (r=0.79; P=0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF.

Conclusions: OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.

Keywords: carotid artery, internal; cerebrovascular disorders; magnetic resonance imaging; middle cerebral artery; positron-emission tomography.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Aged
Aged, 80 and over
Angiography, Digital Subtraction / methods*
Brain Ischemia / diagnostic imaging*
Brain Ischemia / metabolism
Brain Mapping / methods*
Cohort Studies
Female
Humans
Magnetic Resonance Angiography / methods*
Male
Middle Aged
Oxygen Consumption / physiology*
Oxygen Radioisotopes* / metabolism
Positron Emission Tomography Computed Tomography / methods*
Prospective Studies

Substances

Oxygen Radioisotopes