title: Evaluation of a multiple spin- and gradient-echo (SAGE) EPI acquisition with SENSE acceleration: applications for perfusion imaging in and outside the brain.
abstract: Perfusion-based changes in MR signal intensity can occur in response to the introduction of exogenous contrast agents and endogenous tissue properties (e.g. blood oxygenation). MR measurements aimed at capturing these changes often implement single-shot echo planar imaging (ssEPI). In recent years ssEPI readouts have been combined with parallel imaging (PI) to allow fast dynamic multi-slice imaging as well as the incorporation of multiple echoes. A multiple spin- and gradient-echo (SAGE) EPI acquisition has recently been developed to allow measurement of transverse relaxation rate (R2 and R2(*)) changes in dynamic susceptibility contrast (DSC)-MRI experiments in the brain. With SAGE EPI, the use of PI can influence image quality, temporal resolution, and achievable echo times. The effect of PI on dynamic SAGE measurements, however, has not been evaluated. In this work, a SAGE EPI acquisition utilizing SENSE PI and partial Fourier (PF) acceleration was developed and evaluated. Voxel-wise measures of R2 and R2(*) in healthy brain were compared using SAGE EPI and conventional non-EPI multiple echo acquisitions with varying SENSE and PF acceleration. A conservative SENSE factor of 2 with PF factor of 0.73 was found to provide accurate measures of R2 and R2(*) in white (WM) (rR2=[0.55-0.79], rR2*=[0.47-0.71]) and gray (GM) matter (rR2=[0.26-0.59], rR2*=[0.39-0.74]) across subjects. The combined use of SENSE and PF allowed the first dynamic SAGE EPI measurements in muscle, with a SENSE factor of 3 and PF factor of 0.6 providing reliable relaxation rate estimates when compared to multi-echo methods. Application of the optimized SAGE protocol in DSC-MRI of high-grade glioma patients provided T1 leakage-corrected estimates of CBV and CBF as well as mean vessel diameter (mVD) and simultaneous measures of DCE-MRI parameters K(trans) and ve. Likewise, application of SAGE in a muscle reperfusion model allowed dynamic measures of R2', a parameter that has been shown to correlate with muscle oxy-hemoglobin saturation.
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Jack T
authors.initials: JT
authors.lastname: Skinner
authors.affiliation: Barrow Neurological Institute, St. Joseph's Hospital, Phoenix, AZ, USA.
authors.forename: Ryan K
authors.initials: RK
authors.lastname: Robison
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Elder
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA; Monroe Carol Children's Hospital, Vanderbilt University Medical Center, Nashville, TN, USA.
authors.forename: Allen T
authors.initials: AT
authors.lastname: Newton
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Phoenix, AZ, USA.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Damon
authors.affiliation: Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA. Electronic address: chad.quarles@vanderbilt.edu.
authors.forename: C Chad
authors.initials: CC
authors.lastname: Quarles
mesh_terms: D000054:Acceleration; D000328:Adult; D000465:Algorithms; D001921:Brain / Q000473:pathology* / Q000502:physiology; D001932:Brain Neoplasms / Q000473:pathology*; D003287:Contrast Media / Q000737:chemistry; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D005583:Fourier Analysis; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007866:Leg / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D009132:Muscles / Q000473:pathology; D010100:Oxygen / Q000737:chemistry; D055420:Perfusion Imaging; D015424:Reperfusion; D012984:Software
chemical_list: D003287:Contrast Media; D010100:Oxygen
keywords: Dynamic susceptibility contrast; MRI; Multi-echo; Muscle; Parallel imaging; Perfusion