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Assessment of Sensitivity to Deformation Changes of Ventilation and Strain for Lung Functional Mapping Using Hyperpolarized Gas Tagging MRI Data

I Duarte1*, T Cui2 , W Miller3 , F Yin1 , J Cai1,4 , (1) Duke University Medical Center, Durham, NC, (2) Cleveland Clinic, Cleveland, OH, (3) University of Virginia, Charlottesville, Virginia, (4) The Hong Kong Polytechnic University, Kowloon, Yau Tsim Mong


(Sunday, 7/29/2018) 5:05 PM - 6:00 PM

Room: Karl Dean Ballroom C

Purpose: Lung ventilation has been investigated as a metric for functional avoidance treatment planning and treatment response assessment. This study aims to also investigate lung strain as an additional metric to assess respiratory mechanics, and compare both metrics’ sensitivity to changes in displacement vector fields using Hyperpolarized He-3 tagging Magnetic Resonance Imaging (MRI) data.

Methods: Lung images for three healthy subjects were acquired using a tagging Hyperpolarized Helium-3 MRI technique at both end-of-inhalation (EOI) and end-of-exhalation (EOE) phases. The center of mass of the tagged grids were tracked to obtain a sparse physiologically-based displacement vector field (DVF) between EOI and EOE phases. The DVF for the whole lung area was estimated through a cubic interpolation method of the sparse tagging DVF. Ventilation maps for all three subjects were generated through the Jacobian of the interpolated DVF. The principal strain maps were also computed at each voxel. Uniform and randomly distributed modifications were made to each subject’s DVFs and the modified strain and ventilation maps were compared to those generated from the original DVFs to assess their response and sensitivity to these changes.

Results: For uniform changes in DVF magnitude, the mean of the absolute percent differences within the lungs between original vs. modified ventilation maps ranged from 49.5-257.1% on average for all 3 subjects compared to 30.6-125.8% for the principal strain maps; average standard deviations were in the ranges of 21.3-135.0%, 3.6-9.7% respectively. For randomly distributed modifications to the DVF, the mean of absolute percent differences between ventilation maps were in the range of 712.0-2743.7% and 115.2-299.0% for principal strain, with standard deviations ranging from 235.9-1517.8% and 35.6-368.6% respectively.

Conclusion: Preliminary results suggest that ventilation might be a more sensitive metric to deformation changes compared to strain, showing larger mean absolute percent differences and standard deviations among all three subjects.

Funding Support, Disclosures, and Conflict of Interest: NIH grant: R21CA195317


Ventilation/perfusion, MRI, Deformation


IM/TH- MRI in Radiation Therapy: Development (new technology and techniques)

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