title: Contributors to contrast between glioma and brain tissue in chemical exchange saturation transfer sensitive imaging at 3 Tesla.
abstract: Off-resonance saturation transfer images have shown intriguing differences in intensity in glioma compared to normal brain tissues. Interpretation of these differences is complicated, however, by the presence of multiple sources of exchanging magnetization including amide, amine, and hydroxyl protons, asymmetric magnetization transfer contrast (MTC) from macromolecules, and various protons with resonances in the aliphatic spectral region. We report a study targeted at separating these components and identifying their relative contributions to contrast in glioma. Off-resonance z-spectra at several saturation powers and durations were obtained from 6 healthy controls and 8 patients with high grade glioma. Results indicate that broad macromolecular MTC in normal brain tissue is responsible for the majority of contrast with glioma. Amide exchange could be detected with lower saturation power than has previously been reported in glioma, but it was a weak signal source with no detectable contrast from normal brain tissue. At higher saturation powers, amine proton exchange was a major contributor to the observed signal but showed no significant difference from normal brain. Robust acquisition strategies that effectively isolate the contributions of broad macromolecular MTC asymmetry from amine exchange were demonstrated that may provide improved contrast between glioma and normal tissue.
authors.affiliation: Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Ave E25, Cambridge, MA 02139, USA; Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA. Electronic address: rscheide@alum.mit.edu.
authors.forename: Rachel
authors.initials: R
authors.lastname: Scheidegger
authors.affiliation: Brain Tumor Center and Neuro-Oncology Unit, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA; Neurology, Harvard Medical School, Boston, MA 02115, USA. Electronic address: ewong@bidmc.harvard.edu.
authors.forename: Eric T
authors.initials: ET
authors.lastname: Wong
authors.affiliation: Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA; Radiology, Harvard Medical School, Boston, MA 02115, USA. Electronic address: dalsop@bidmc.harvard.edu.
authors.forename: David C
authors.initials: DC
authors.lastname: Alsop
mesh_terms: D000328:Adult; D000465:Algorithms; D000577:Amides / Q000737:chemistry; D001921:Brain / Q000473:pathology*; D001932:Brain Neoplasms / Q000473:pathology*; D003198:Computer Simulation; D003952:Diagnostic Imaging; D005260:Female; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011522:Protons
chemical_list: D000577:Amides; D011522:Protons
keywords: APT — amide proton transfer imaging; Brain tumors; CEST — chemical exchange saturation transfer; Glioblastoma; Glioma; MT, MTC — magnetization transfer contrast; Magnetization transfer asymmetry; NOE — nuclear overhauser effect; SAFARI — saturation with alternating frequency RF irradiation; z-Spectroscopy