Commentary on "The influence of lung airways branching structure and diffusion time on measurements and models of short-range 3He gas MR diffusion"

Abstract

In a recently published paper by Parra-Robles and Wild, the authors challenge the in vivo lung morphometry technique (based on hyperpolarized gas diffusion MRI) developed by our Washington University research group. In this Commentary we demonstrate that the main conclusion of Parra-Robles and Wild, that our MRI-based lung morphometry technique "produces inaccurate estimates of the airway dimensions", does not have any scientific basis and is not in agreement with the considerable body of peer-reviewed scientific reports as well as with Parra-Robles and Wild's own data. On the contrary, our technique has a strong theoretical background, is validated, and provides accurate 3D tomographic information on lung microstructural parameters previously available only from invasive biopsy specimens. This technique has already produced a number of results related to lung morphology and function that were not previously available. In our Commentary we also discuss a number of other incorrect statements in and shortcomings of Parra-Robles and Wild's paper.

Keywords: Diffusion; Hyperpolarized gas; Lung morphometry; MRI.

Figure 1

(Adopted from (4)). Plot of mean linear intercept (Lm) obtained by means of lung morphometry with hyperpolarized ³He diffusion MRI vs. direct measurement under the microscope. Each point represents an average across one explanted lung (two points on the left correspond to normal lungs, two points in the middle – lungs with moderate emphysema, and two points on the right – lungs with severe emphysema). The dashed line represents equality of the two measures of Lm.