title: Measurements of regional alveolar oxygen pressure using hyperpolarized 3He MRI.
abstract: OBJECTIVE
  The aim of this work is to review hyperpolarized (HP) helium-3 (3He) magnetic resonance imaging (MRI) methods to measure regional alveolar oxygen partial pressure (P(A)O2) and oxygen depletion rate (R) in the lung. We point out limitations of the methods and suggest improvements to increase their accuracy.
  
  
  METHODS
  P(A)O2 and R can be extracted from series of HP gas images acquired during breath hold by making use of the depolarizing effect of oxygen on HP gas. To separate oxygen-induced depolarization from other depolarizing effects, several techniques can be used. We review currently used techniques and point out their advantages and limitations.
  
  
  RESULTS
  We show that the precision of oxygen measurements depends on a variety of parameters and can vary within the measurement volume. Accuracy of the measurement also can be influenced by diffusion of oxygen and polarized 3He and generally is different for single-slice and multislice measurements. We present numerical simulations, phantom data, and in vivo data for illustration.
  
  
  CONCLUSIONS
  HP 3He MRI is a noninvasive, nonionizing, and repeatable imaging method that allows for quantitative analysis of lung function. The current techniques for measuring P(A)O2 have the potential to deliver clinically relevant functional images.
authors.affiliation: Department of Radiology, University of Pennsylvania School of Medicine, B1, Stellar-Chance Labs, Philadelphia, PA19104-6100, USA.
authors.forename: Martin C
authors.initials: MC
authors.lastname: Fischer
authors.forename: Stephen
authors.initials: S
authors.lastname: Kadlecek
authors.forename: Jiangsheng
authors.initials: J
authors.lastname: Yu
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
authors.forename: Kiarash
authors.initials: K
authors.lastname: Emami
authors.forename: Vahid
authors.initials: V
authors.lastname: Vahdat
authors.forename: David A
authors.initials: DA
authors.lastname: Lipson
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D000818:Animals; D003198:Computer Simulation; D006371:Helium; D007554:Isotopes; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000378:metabolism*; D011653:Pulmonary Diffusing Capacity; D011817:Rabbits
chemical_list: D007554:Isotopes; D006371:Helium; D010100:Oxygen