Robin Kämpe1, Emelie Lind1, Freddy Ståhlberg1,2, Danielle van Westen2,3, Linda Knutsson1, Ronnie Wirestam1. 1. Department of Medical Radiation Physics, Lund University, Lund, Sweden. 2. Diagnostic Radiology, Department of Clinical Sciences Lund, Lund University, Lund, Sweden. 3. Imaging and Function, Skåne University Health Care, Lund, Sweden.
Abstract
INTRODUCTION: Global oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) were quantified in a test-retest study. Cerebral blood flow (CBF) data, required for CMRO2 estimation, were obtained using dynamic susceptibility contrast MRI (DSC-MRI). OEF and CMRO2 were quantified using two separate data sets, that is, conventional high-resolution (HR) gradient echo (GRE) phase maps as well as echo planar imaging (EPI) phase maps taken from the baseline (precontrast) part of the DSC-MRI time series. The EPI phase data were included to elucidate whether an extra HR-GRE scan is needed to obtain information about OEF and CMRO2 , or if this information can be extracted from the DSC-MRI experiment only. METHODS: Twenty healthy volunteers were scanned using 3 T MRI on two occasions. Oxygen saturation levels were obtained from phase data measured in the great cerebral vein of Galen, based on HR-GRE as well as EPI phase maps. In combination with DSC-MRI CBF, this allowed for calculation of OEF and CMRO2 . RESULTS: High-resolution-gradient echo- and EPI-based phase images resulted in similar OEF spread and repeatability, with coefficients of variation/intraclass correlation coefficients of 0·26/0·95 and 0·23/0·81, respectively. Absolute OEF values (HR-GRE: 0·40 ± 0·11, EPI: 0·35 ± 0·08) were consistent with literature data. CMRO2 showed similar repeatability, somewhat increased spread and reasonable absolute values (HR-GRE: 3·23 ± 1·26 ml O2 /100 g min-1 , EPI: 2·79 ± 0·89 ml O2 /100 g min-1 ). DISCUSSION: In general, the results obtained by HR-GRE and EPI showed comparable characteristics. The EPI methodology could potentially be improved using a slightly modified DSC-MRI protocol (e.g. with regard to spatial resolution and slice gap).
INTRODUCTION: Global oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) were quantified in a test-retest study. Cerebral blood flow (CBF) data, required for CMRO2 estimation, were obtained using dynamic susceptibility contrast MRI (DSC-MRI). OEF and CMRO2 were quantified using two separate data sets, that is, conventional high-resolution (HR) gradient echo (GRE) phase maps as well as echo planar imaging (EPI) phase maps taken from the baseline (precontrast) part of the DSC-MRI time series. The EPI phase data were included to elucidate whether an extra HR-GRE scan is needed to obtain information about OEF and CMRO2 , or if this information can be extracted from the DSC-MRI experiment only. METHODS: Twenty healthy volunteers were scanned using 3 T MRI on two occasions. Oxygen saturation levels were obtained from phase data measured in the great cerebral vein of Galen, based on HR-GRE as well as EPI phase maps. In combination with DSC-MRI CBF, this allowed for calculation of OEF and CMRO2 . RESULTS: High-resolution-gradient echo- and EPI-based phase images resulted in similar OEF spread and repeatability, with coefficients of variation/intraclass correlation coefficients of 0·26/0·95 and 0·23/0·81, respectively. Absolute OEF values (HR-GRE: 0·40 ± 0·11, EPI: 0·35 ± 0·08) were consistent with literature data. CMRO2 showed similar repeatability, somewhat increased spread and reasonable absolute values (HR-GRE: 3·23 ± 1·26 ml O2 /100 g min-1 , EPI: 2·79 ± 0·89 ml O2 /100 g min-1 ). DISCUSSION: In general, the results obtained by HR-GRE and EPI showed comparable characteristics. The EPI methodology could potentially be improved using a slightly modified DSC-MRI protocol (e.g. with regard to spatial resolution and slice gap).