title: Amide proton transfer (APT) imaging of brain tumors at 7 T: The role of tissue water T1-Relaxation properties.
abstract: To provide insight into the effect of water T1relaxation (T1wat) on amide proton transfer (APT) contrast in tumors. Three different metrics of APT contrast-magnetization transfer ratio (MTRRex), relaxation-compensated MTRRex(AREX), and traditional asymmetry (MTRasym)-were compared in normal and tumor tissues in a variety of intracranial tumors at 7 Tesla (T).
  
  
  
  Six consented intracranial tumor patients were scanned using a low-power, three-dimensional (3D) APT imaging sequence. MTRRexand MTRasymwere calculated in the region of 3 to 4 ppm. AREX was calculated by T1watcorrection of MTRRex. Tumor tissue masks, which classify different tumor tissues, were drawn by an experienced neuroradiologist. ROI-averaged tumor tissue analysis was done for MTRRex, AREX, and MTRasym.
  
  
  
  MTRRexand MTRasymwere slightly elevated in tumor-associated structures. Both metrics were positively correlated to T1wat. The correlation coefficient (R) was determined to be 0.88 (P < 0.05) and 0.92 (P << 0.05) for MTRRexand MTRasym, respectively. After T1watcorrection (R = -0.21, P = 0.69), no difference between normal and tumor tissues was found for AREX.
  
  
  
  The strong correlation of MTRRexand MTRasymwith T1watand the absence thereof in AREX suggests that much of APT contrast in tumors for the low-power, 3D-acquisition scheme at 7 T originates from the inherent tissue water T1-relaxation properties. Magn Reson Med 77:1525-1532, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Khlebnikov
authors.affiliation: Philips Healthcare, Best, the Netherlands.
authors.forename: Daniel
authors.initials: D
authors.lastname: Polders
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Hendrikse
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Pierre A
authors.initials: PA
authors.lastname: Robe
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Eduard H
authors.initials: EH
authors.lastname: Voormolen
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Dennis W J
authors.initials: DW
authors.lastname: Klomp
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Hoogduin
mesh_terms: D000577:Amides / Q000378:metabolism*; D001834:Body Water / Q000000981:diagnostic imaging* / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000577:Amides; D011522:Protons
keywords: amide proton transfer (APT); brain tumor; magnetization transfer ratio (MTRRex); relaxation-compensated APT (AREX); traditional asymmetry (MTRasym) analysis; water T1-relaxation correction