Submitted on October 30, 2008
Revised on January 20, 2009
Accepted on February 11, 2009
Probing Airway Conditions Governing Ventilation Defects in Asthma via Hyperpolarized MRI Image Functional Modeling
Lisa Marie Campana1*, Jennifer Kenyon1, Sanaz Zhalehdoust-Sani1, Yang-Sheng Tzeng1, Yanping Sun2, Mitchell S. Albert3, and Kenneth R. Lutchen1
1 Boston University
2 University of Massachusetts Medical School
3 University of Massachusetts Medical School, Worcester, MA 01655
* To whom correspondence should be addressed. E-mail: lcampana{at}bu.edu.
Image functional modeling (IFM) has been introduced as a method to simultaneously synthesize imaging and mechanical data with computational models in order to determine the degree and location of airway constriction in asthma. Using lung imaging provided by Hyperpolarized 3Helium MRI, we advanced our IFM method to require matching not only to ventilation defect location but to specific ventilation throughout the lung. Imaging and mechanical data were acquired for 4 healthy and 4 asthmatic subjects pre and post bronchial challenge. After provocation we first identify maximum sized airways leading exclusively to ventilation defects and highly constrict them. Constriction patterns are then found for the remaining airways so as to match mechanical data. Ventilation images were predicted for each pattern and visual and statistical comparisons were done with measured data. Results show that matching of ventilation defects requires severe constriction of small airways. The mean constriction of such airways leading to the ventilation defects need be 70-80% rather then fully closed. Also, central airway constriction alone cannot account for dysfunction seen in asthma, small airways must be involved.
