title: T1 and T2 values of human neonatal blood at 3 Tesla: Dependence on hematocrit, oxygenation, and temperature.
abstract: OBJECTIVE
  Knowledge of blood T1 and T2 is of major importance in many applications of MRI in neonates. However, to date, there has not been a systematic study to examine neonatal blood T1/T2 relaxometry. This present study aims to investigate this topic.
  
  
  METHODS
  Using freshly collected blood samples from human umbilical cord, we performed in vitro experiments under controlled physiological conditions to measure blood T1 and T2 at 3 Tesla (T) and their dependence on several factors, including hematocrit (Hct), oxygenation (Y) and temperature.
  
  
  RESULTS
  The arterial T1 in neonates was 1825 ± 184 ms (Hct = 0.42 ± 0.08), longer than that of adult blood. Neonatal blood T1 was strongly dependent on Hct (P < 0.001) and Y (P = 0.005), and the dependence of T1 on Y was more prominent at higher Hct. The arterial T2 of neonatal blood was 191 ms at an Hct of 0.42, which was also longer than adult blood. Neonatal blood T2 was positively associated with blood oxygenation and negatively associated with hematocrit level, and can be characterized by an exchange model. Neonatal blood T1 was also positively associated with temperature (P < 0.001).
  
  
  CONCLUSIONS
  The values provided in this report may provide important reference and calibration information for sequence optimization and quantification of in vivo neonatal MRI studies.
authors.affiliation: Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Peiying
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Lina F
authors.initials: LF
authors.lastname: Chalak
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Krishnamurthy
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Imran
authors.initials: I
authors.lastname: Mir
authors.affiliation: Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Shin-lei
authors.initials: SL
authors.lastname: Peng
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Department of Radiology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.|Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Pennsylvania, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Hanzhang
authors.initials: H
authors.lastname: Lu
mesh_terms: D001831:Body Temperature; D005312:Fetal Blood / Q000502:physiology*; D006400:Hematocrit; D006801:Humans; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D012815:Signal Processing, Computer-Assisted
chemical_list: D010100:Oxygen
keywords: blood oxygenation; hematocrit; longitudinal relaxation time; neonate; transverse relaxation time; umbilical cord blood