title: Measurement of pulmonary partial pressure of oxygen and oxygen depletion rate with hyperpolarized helium-3 MRI: a preliminary reproducibility study on pig model.
abstract: OBJECTIVE
  Pulmonary partial pressure of oxygen (pO(2)) and oxygen depletion rate (R) are two important parameters of lung function. The dependence of hyperpolarized (3)He (HP (3)He) T(1) on local oxygen concentration provides the basis for high-resolution mapping of the regional distributions of pO(2) and R in the lung. Although the oxygen-sensitive HP (3)He magnetic resonance imaging technique has been applied in human subjects and several animal species, reproducibility studies are rarely reported in the literature. This work presents a preliminary reproducibility study on a pig model. In this study, important scan parameters, such as measurement timing and flip angle, are optimized to minimize the noise-induced measurement uncertainty.
  
  
  METHODS
  In the in vivo study, five normal pigs and one diseased pig with simulated pulmonary emboli were scanned with a small flip angle gradient echo sequence. The pulmonary oxygen measurement was repeated two to four times in each pig. In each measurement, a series of six images were acquired with optimal timing and flip angle. The parametric maps were generated using a bin-based data processing procedure that applied the multiple regression fitting method to extract the pO(2) and R. Variations of global mean, percentiles, and regions of interest were calculated from the maps to analyze reproducibility.
  
  
  RESULTS
  The global statistical analyses show that average variation of global mean is 10.7% for pO(2) and 23.8% for R, and that the average variation of percentiles (10th, 25th, 50th, 75th, and 90th) and interquartile range is 14.8% for pO(2) and 30.4% for R. The region-of-interest analysis on the manually selected regions shows that the average variation of mean is 12.6% for pO(2) and 21.9% for R.
  
  
  CONCLUSIONS
  In this work, a preliminary study on the reproducibility of measuring pO(2) and R with HP (3)He magnetic resonance imaging on a pig model is presented.
authors.affiliation: Department of Radiology, University of Pennsylvania, MMRRCC, B1 Stellar-Chance Building, 422 Curie Boulevard, Philadelphia, PA 19104, USA.
authors.forename: Jiangsheng
authors.initials: J
authors.lastname: Yu
authors.forename: Sheeva
authors.initials: S
authors.lastname: Rajaei
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
authors.forename: Michelle
authors.initials: M
authors.lastname: Law
authors.forename: Kiarash
authors.initials: K
authors.lastname: Emami
authors.forename: John M
authors.initials: JM
authors.lastname: Woodburn
authors.forename: Stephen
authors.initials: S
authors.lastname: Kadlecek
authors.forename: Vahid
authors.initials: V
authors.lastname: Vahdat
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D000818:Animals; D006371:Helium; D007554:Isotopes; D008168:Lung / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D023421:Models, Animal; D010313:Partial Pressure; D012044:Regression Analysis; D015203:Reproducibility of Results; D013552:Swine
chemical_list: D007554:Isotopes; D006371:Helium