title: Hematocrit and oxygenation dependence of blood (1)H(2)O T(1) at 7 Tesla.
abstract: Knowledge of blood (1)H2O T1 is critical for perfusion-based quantification experiments such as arterial spin labeling and cerebral blood volume-weighted MRI using vascular space occupancy. The dependence of blood (1)H2O T1 on hematocrit fraction (Hct) and oxygen saturation fraction (Y) was determined at 7 T using in vitro bovine blood in a circulating system under physiological conditions. Blood (1)H2O R1 values for different conditions could be readily fitted using a two-compartment (erythrocyte and plasma) model, which are described by a monoexponential longitudinal relaxation rate constant dependence. It was found that T1 = 2171 ± 39 ms for Y = 1 (arterial blood) and 2010 ± 41 ms for Y = 0.6 (venous blood), for a typical Hct of 0.42. The blood (1)H2O T1 values in the normal physiological range (Hct from 0.35 to 0.45, and Y from 0.6 to 1.0) were determined to range from 1900 to 2300 ms. The influence of oxygen partial pressure (pO2) and the effect of plasma osmolality for different anticoagulants were also investigated. It is discussed why blood (1)H2O T1 values measured in vivo for human blood may be about 10-20% larger than found in vitro for bovine blood at the same field strength.
authors.affiliation: The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Ksenija
authors.initials: K
authors.lastname: Grgac
authors.forename: Peter C M
authors.initials: PC
authors.lastname: van Zijl
authors.forename: Qin
authors.initials: Q
authors.lastname: Qin
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D003903:Deuterium / Q000493:pharmacokinetics*; D004912:Erythrocytes / Q000378:metabolism* / Q000473:pathology; D006400:Hematocrit / Q000379:methods*; D006454:Hemoglobins / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D006454:Hemoglobins; D003903:Deuterium; D010100:Oxygen