title: Intrapulmonary 3He gas distribution depending on bolus size and temporal bolus placement.
abstract: OBJECTIVE
  Dynamic ventilation (3)He-MRI is a new method to assess pulmonary gas inflow. As differing airway diameters throughout the ventilatory cycle can influence gas inflow this study intends to investigate the influence of volume and timing of a He gas bolus with respect to the beginning of the tidal volume on inspiratory gas distribution.
  
  
  METHODS
  An ultrafast 2-dimensional spoiled gradient echo sequence (temporal resolution 100 milliseconds) was used for dynamic ventilation (3)He-MRI of 11 anesthetized and mechanically ventilated pigs. The applied (3)He gas bolus was varied in volume between 100 and 200 mL. A 150-mL bolus was varied in its application time after the beginning of the tidal volume between 0 and 1200 milliseconds. Signal kinetics were evaluated using an in-house developed software after definition of parameters for the quantitative description of (3)He gas inflow.
  
  
  RESULTS
  The signal rise time (time interval between signal in the parenchyma reaches 10% and 90% of its maximum) was prolonged with increasing bolus volume. The parameter was shortened with increasing delay of (3)He application after the beginning of the tidal volume. Timing variation as well as volume variation showed no clear interrelation to the signal delay time 10 (time interval between signal in the trachea reaches 50% of its maximum and signal in the parenchyma reaches 10% of its maximum).
  
  
  CONCLUSIONS
  Dynamic ventilation (3)He-MRI is able to detect differences in bolus geometry performed by volume variation. Pulmonary gas inflow as investigated by dynamic ventilation (3)He-MRI tends to be accelerated by an increasing application delay of a (3)He gas bolus after the beginning of the tidal volume.
authors.affiliation: Klinik für Diagnostische und Interventionelle Radiologie der Johannes Gutenberg-Universität Mainz, Mainz, Germany. kgast@radiologie.klinik.uni-mainz.de
authors.forename: Klaus Kurt
authors.initials: KK
authors.lastname: Gast
authors.forename: Kristin
authors.initials: K
authors.lastname: Hawig
authors.forename: Michael
authors.initials: M
authors.lastname: Windirsch
authors.forename: Klaus
authors.initials: K
authors.lastname: Markstaller
authors.forename: Wolfgang Günter
authors.initials: WG
authors.lastname: Schreiber
authors.forename: Jörg
authors.initials: J
authors.lastname: Schmiedeskamp
authors.forename: Christoph
authors.initials: C
authors.lastname: Düber
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Claus Peter
authors.initials: CP
authors.lastname: Heussel
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D006371:Helium / Q000493:pharmacokinetics*; D007554:Isotopes; D008168:Lung / Q000378:metabolism / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D012984:Software; D013552:Swine
chemical_list: D007554:Isotopes; D006371:Helium