Intrapulmonary 3He gas distribution depending on bolus size and temporal bolus placement.
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.
Gast
Klaus Kurt
KK
Klinik für Diagnostische und Interventionelle Radiologie der Johannes Gutenberg-Universität Mainz, Mainz, Germany. kgast@radiologie.klinik.uni-mainz.de
Hawig
Kristin
K
Windirsch
Michael
M
Markstaller
Klaus
K
Schreiber
Wolfgang Günter
WG
Schmiedeskamp
Jörg
J
Düber
Christoph
C
Kauczor
Hans-Ulrich
HU
Heussel
Claus Peter
CP
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
D007554:Isotopes; D006371:Helium