Imaging the lungs in asthmatic patients by using hyperpolarized helium-3 magnetic resonance: assessment of response to methacholine and exercise challenge.
BACKGROUND
Imaging of gas distribution in the lungs of patients with asthma has been restricted because of the lack of a suitable gaseous contrast agent. Hyperpolarized helium-3 (HHe3) provides a new technique for magnetic resonance imaging of lung diseases.


OBJECTIVE
We sought to investigate the use of HHe3 gas to image the lungs of patients with moderate or severe asthma and to assess changes in gas distribution after methacholine and exercise challenge.


METHODS
Magnetic resonance imaging was performed in asthmatic patients immediately after inhalation of HHe3 gas. In addition, images were obtained before and after methacholine challenge and a standard exercise test.


RESULTS
Areas of the lung with no signal or sharply reduced HHe3 signal (ventilation defects) are common in patients with asthma, and the number of defects was inversely related to the percent predicted FEV(1) (r = 0.71, P <.002). After methacholine challenge (n = 3), the number of defects increased. Similarly, imaging of the lungs after exercise (n = 6) showed increased ventilation defects in parallel with decreases in FEV(1). The increase in defects after challenge in these 9 asthmatic patients was significant both for the number (P <.02) and extent (P <.02) of the defects. The variability and speed of changes in ventilation and the complete lack of signal in many areas is in keeping with a model in which the defects result from airway closure.


CONCLUSIONS
HHe3 magnetic resonance provides a new technique for imaging the distribution of inhaled air in the lungs. The technique is suitable for following responses to treatment of asthma and changes after methacholine or exercise challenge.
Samee
Saba
S
Department of Internal Medicine, Division of Asthma, Allergy, and Immunology, University of Virginia, Charlottesville, VA 22908-1355, USA.
Altes
Talissa
T
Powers
Patrick
P
de Lange
Eduard E
EE
Knight-Scott
Jack
J
Rakes
Gary
G
Mugler
John P
JP
Ciambotti
Jonathan M
JM
Alford
Bennet A
BA
Brookeman
James R
JR
Platts-Mills
Thomas A E
TA
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis*; D016085:Bronchoconstrictor Agents; D005080:Exercise Test; D006371:Helium; D006801:Humans; D008168:Lung / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D016210:Methacholine Chloride
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D006371:Helium