Analysis of intrapulmonary O(2) concentration by MR imaging of inhaled hyperpolarized helium-3.
Inhalation of hyperpolarized (3)He allows magnetic resonance imaging (MRI) of ventilated airspaces. (3)He hyperpolarization decays more rapidly when interacting with paramagnetic O(2). We describe a method for in vivo determination of intrapulmonary O(2) concentrations ([O(2)]) based on MRI analysis of the fate of measured amounts of inhaled hyperpolarized (3)He in imaged regions of the lung. Anesthetized pigs underwent controlled normoventilation in a 1.5-T MRI unit. The inspired O(2) fraction was varied to achieve different end-tidal [O(2)] fractions (FET(O(2))). With the use of a specifically designed applicator, (3)He (100 ml, 35-45% polarized) was administered at a predefined time within single tidal volumes. During subsequent inspiratory apnea, serial two-dimensional images of airways and lungs were acquired. At least once in each animal studied, the radio-frequency excitation used for imaging was doubled at constant FET(O(2)). Signal intensity measurements in regions of interest of the animals' lungs (volume range, 54-294 cm(3)), taken at two different radio-frequency excitations, permitted calculation of [O(2)] in these regions of interest. The [O(2)] fractions in the regions of interest correlated closely with FET(O(2)) (R = 0.879; P < 0.0001). O(2)-sensitive (3)He-MRI may allow noninvasive study of regional distribution of ventilation and alveolar PO(2) in the lung.
Eberle
B
B
Department of Anesthesiology, Johannes Gutenberg University, D-55131 Mainz, Germany. eberle@anaesthesie.klinik.uni-mainz.de
Weiler
N
N
Markstaller
K
K
Kauczor
H
H
Deninger
A
A
Ebert
M
M
Grossmann
T
T
Heil
W
W
Lauer
L O
LO
Roberts
T P
TP
Schreiber
W G
WG
Surkau
R
R
Dick
W F
WF
Otten
E W
EW
Thelen
M
M
D000280:Administration, Inhalation; D000818:Animals; D005240:Feasibility Studies; D006371:Helium / Q000008:administration & dosage; D007554:Isotopes; D008168:Lung / Q000033:anatomy & histology* / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D009994:Osmolar Concentration; D010100:Oxygen; D012119:Respiration; D013552:Swine; D013990:Tidal Volume
D007554:Isotopes; D006371:Helium; D010100:Oxygen