title: Improved technique for measurement of regional fractional ventilation by hyperpolarized 3He MRI.
abstract: Quantitative measurement of regional lung ventilation is of great significance in assessment of lung function in many obstructive and restrictive pulmonary diseases. A new technique for regional measurement of fractional ventilation using hyperpolarized 3He MRI is proposed, addressing the shortcomings of an earlier approach that limited its use to small animals. The new approach allows for the acquisition of similar quantitative maps over a shortened period and requires substantially less 3He gas. This technique is therefore a better platform for implementation in large species, including humans. The measurements using the two approaches were comparable to a great degree, as verified in a healthy rat lung, and are very reproducible. Preliminary validation is performed in a lung phantom system. Volume dependency of measurements was assessed both in vivo and in vitro. A scheme for selecting an optimum flip angle is proposed. In addition, a dead space modeling approach is proposed to yield more accurate measurements of regional fractional ventilation using either method. Finally, sensitivity of the new technique to model parameters, noise, and number of included images were assessed numerically. As a prelude to application in humans, the technique was implemented in a large animal study successfully.
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6100, USA. kiarash.emami@uphs.upenn.edu
authors.forename: Kiarash
authors.initials: K
authors.lastname: Emami
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kadlecek
authors.forename: John M
authors.initials: JM
authors.lastname: Woodburn
authors.forename: Jianliang
authors.initials: J
authors.lastname: Zhu
authors.forename: Jiangsheng
authors.initials: J
authors.lastname: Yu
authors.forename: Vahid
authors.initials: V
authors.lastname: Vahdat
authors.forename: Stephen
authors.initials: S
authors.lastname: Pickup
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D000465:Algorithms; D000818:Animals; D006371:Helium; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes; D008168:Lung / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium; D010100:Oxygen