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Evaluating the Fractal Nature of 129Xe MRI Ventilation Heterogeneity

Rachel L Eddy^1,2, Alexander M Matheson^3,4, Marrissa J McIntosh^3,4, and Grace Parraga^3,4
¹St. Paul's Hospital, UBC Centre for Heart Lung Innovation, Vancouver, BC, Canada, ²Division of Respiratory Medicine, Department of Medicine, University of British Columbia, Vancouver, BC, Canada, ³Robarts Research Institute, London, ON, Canada, ⁴Department of Medical Biophysics, Western University, London, ON, Canada

We showed that ¹²⁹Xe MRI ventilation follows a fractal pattern and measured the fractal dimension. Fractal analysis can provide a new tool to measure MRI ventilation heterogeneity and investigate structure-function relationships in patients with lung disease.

Figure 1. ¹²⁹Xe MRI fractal analysis outline.

¹²⁹Xe MRI static ventilation was segmented into 5 clusters of signal intensity ranging from signal void or ventilation defects to hyperintense signal (Cluster5) (A) and the box-counting method was used to calculate fractal dimension (B). Fractal dimension was calculated for each MRI signal intensity cluster (C).

Figure 2. ¹²⁹Xe MRI fractal dimension measurements.

(A) Fractal dimension (D), R² and root-mean-squared error (RMSE) for all MRI signal clusters. (B) ¹²⁹Xe MRI ventilation (cyan) co-registered to anatomical ¹H (grey-scale) for representative participants with asthma with associated fractal dimensions. (C) Log-log plots showing fractal dimensions for defect regions (Cluster1), Cluster2 and Cluster4 for representative participants.