Magnetization tagging decay to measure long-range 3He diffusion in healthy and emphysematous canine lungs
✍ Scribed by Jason C. Woods; Dmitriy A. Yablonskiy; Kimiaki Chino; Tariq S.K. Tanoli; Joel D. Cooper; Mark S. Conradi
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 340 KB
- Volume
- 51
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
Spatial modulation (tagging) of the longitudinal magnetization allows diffusive displacements to be measured over times approximately as long as T~1~ and over correspondingly long distances. Magnetization tagging is used here with hyperpolarized ^3^He gas in canine lungs with unilateral elastase‐induced emphysema. A new scheme for analyzing images subsequent to tagging determines the spatially‐resolved fractional modulation and its decay rate, using a sliding window. The diffusivity so determined over seconds and centimeter lengths, D~sec~, is smaller in all cases than the diffusivity measured over milliseconds and hundreds of microns, D~msec~ (in healthy lungs, this ratio is about 0.1). While D~msec~ is sensitive to lung microstructure on the alveolar level, D~sec~ reflects airway connectivity and provides new information on lung structure. The results show substantial increases in D~sec~ in the lungs of four dogs with clear evidence of emphysema. For these dogs, the fractional increase in long‐range diffusivity D~sec~ in the emphysematous lungs was greater than that in short‐range diffusivity D~msec~. Magn Reson Med 51:1002–1008, 2004. © 2004 Wiley‐Liss, Inc.