Related Experiment Video
Updated: May 16, 2026

Tumor Hypoxia Assessment: In Vivo 3D Oxygen Imaging Through Electron Paramagnetic Resonance
Published on: February 14, 2025
Hematocrit and oxygenation dependence of blood (1)H(2)O T(1) at 7 Tesla
Ksenija Grgac1, Peter C M van Zijl, Qin Qin
1The 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.
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.
Related Concept Videos
Oxygen Transport in the Blood
Hypoxia
Types of Hypoxia
There are four primary types of hypoxia, each resulting from a different cause:
1. Anemic hypoxia: This type occurs due to insufficient oxygen delivery caused by a lack of red blood cells (RBCs) or RBCs with abnormal or...
Hemoglobin
When all four heme groups are bound to oxygen, the resulting molecule is called oxyhemoglobin. As a result, arterial blood...
Respiration and Gaseous Exchange
Respiration involves the exchange of gases, especially oxygen (O2) and carbon dioxide (CO2), between the alveoli and body cells, a process facilitated by blood circulation. As a result, the cardiovascular system, which involves the...
Magnetic Resonance Imaging
Special considerations while measuring oxygen saturation
Ensuring accuracy in vital sign recordings while prioritizing patient comfort and minimizing anxiety is important.

