Program Information

Evaluation of Lung Deformation Using Three Dimensional Strain Maps

T Cui

T Cui¹*, Q Huang² , W Miller³ , X Zhong⁴ , F Yin⁵ , J Cai⁶ , (1) Duke University, Durham, NC, (2) Duke Unversity, Durham, NC, (3) University of Virginia, Charlottesville, VA, (4) Siemens Healthcare, Atlanta, GA, (5) Duke University Medical Center, Durham, NC, (6) Duke University Medical Center, Durham, NC

Presentations

MO-C-17A-8 Monday 10:15AM - 12:15PM Room: 17A

Purpose:
To develop a systematic approach to generate three dimensional (3D) strain maps of lung using the displacement vector field (DVF) during the respiratory deformation, and to demonstrate its application in evaluating deformable image registration (DIR).

Methods:
A DVF based strain tensor at each voxel of interest (VOI) was calculated from the relative displacements between the VOI and each of the six nearest neighbors. The maximum and minimum stretches of a VOI can be determined by the principal strains (E₁, E₂ and E₃), which are the eigenvalues and the corresponding strain tensors. Two healthy volunteers enrolled in this study under IRB-approved protocol, each was scanned using 3D Hyperpolarized He-3 tagging-MRI and 3D proton-MRI with TrueFISP sequence at the end-of-inhalation (EOI) and the end-of-exhalation (EOE) phases. 3D DVFs of tagging- and proton-MRI were obtained by the direct measurements of the tagging grid trajectory and by the DIR method implemented in commercial software.

Results:
3D strain maps were successfully generated for all DVFs. The principal strain E1s were calculated as 0.43±0.05 and 0.17±0.25 for tagging-MRI and proton-MRI, respectively. The large values of E₁ indicate the predominant lung motion in the superior-inferior (SI) direction. Given that the DVFs from the tagging images are considered as the ground truth, the discrepancies in the DIR-based strain maps suggest the inaccuracy of the DIR algorithm. In the E₁ maps of tagging-MRI for subject 1, the fissures were distinguishable by the larger values (0.49±0.02) from the adjacent tissues (0.41±0.03) due to the larger relative displacement between the lung lobes.

Conclusion:
We have successfully developed a methodology to generate DVF-based 3D strain maps of lung. It can potentially enable us to better understand the pulmonary biomechanics and to evaluate and improve the DIR algorithms for the lung deformation. We are currently studying more subjects to evaluate this tool.


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