title: Assessment of regional ventilation and deformation using 4D-CT imaging for healthy human lungs during tidal breathing.
abstract: This study aims to assess regional ventilation, nonlinearity, and hysteresis of human lungs during dynamic breathing via image registration of four-dimensional computed tomography (4D-CT) scans. Six healthy adult humans were studied by spiral multidetector-row CT during controlled tidal breathing as well as during total lung capacity and functional residual capacity breath holds. Static images were utilized to contrast static vs. dynamic (deep vs. tidal) breathing. A rolling-seal piston system was employed to maintain consistent tidal breathing during 4D-CT spiral image acquisition, providing required between-breath consistency for physiologically meaningful reconstructed respiratory motion. Registration-derived variables including local air volume and anisotropic deformation index (ADI, an indicator of preferential deformation in response to local force) were employed to assess regional ventilation and lung deformation. Lobar distributions of air volume change during tidal breathing were correlated with those of deep breathing (R(2) ≈ 0.84). Small discrepancies between tidal and deep breathing were shown to be likely due to different distributions of air volume change in the left and the right lungs. We also demonstrated an asymmetric characteristic of flow rate between inhalation and exhalation. With ADI, we were able to quantify nonlinearity and hysteresis of lung deformation that can only be captured in dynamic images. Nonlinearity quantified by ADI is greater during inhalation, and it is stronger in the lower lobes (P < 0.05). Lung hysteresis estimated by the difference of ADI between inhalation and exhalation is more significant in the right lungs than that in the left lungs.
authors: Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa; IIHR-Hydroscience and Engineering, The University of Iowa, Iowa City, Iowa;
authors: Nariman
authors: N
authors: Jahani
authors: Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa; IIHR-Hydroscience and Engineering, The University of Iowa, Iowa City, Iowa;
authors: Sanghun
authors: http://orcid.org/0000-0001-5030-0296
authors: S
authors: Choi
authors: Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa; IIHR-Hydroscience and Engineering, The University of Iowa, Iowa City, Iowa;
authors: Jiwoong
authors: J
authors: Choi
authors: Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa;
authors: Krishna
authors: K
authors: Iyer
authors: Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa; Department of Internal Medicine, The University of Iowa, Iowa City, Iowa; Department of Radiology, The University of Iowa, Iowa City, Iowa.
authors: Eric A
authors: EA
authors: Hoffman
authors: Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa; IIHR-Hydroscience and Engineering, The University of Iowa, Iowa City, Iowa; ching-long-lin@uiowa.edu.
authors: Ching-Long
authors: CL
authors: Lin
mesh_terms: D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D005652:Functional Residual Capacity / Q000502:physiology; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012119:Respiration / Q000276:immunology*; D013990:Tidal Volume / Q000502:physiology
keywords: four-dimensional computed tomography; hysteresis; image registration; regional ventilation; tidal volume