Determination of regional pulmonary parenchymal strain during normal respiration using spin inversion tagged magnetization MRI

In clinical practice, the assessment of lung mechanics is limited to a glob al physiological evaluation, which measures, in the aggregate, the contribu tions of the pulmonary parenchyma, pleura, and chest wall. In this study, w e used an MR imaging methodology which applies two-dimensional bands of inv erted magnetization directly onto the pulmonary parenchyma, thus allowing f or the quantification of local pulmonary tissue deformation, or strain, thr oughout inhalation. Our results showed that the magnitude of strain was max imal at the base and apex of the lung, but was curtailed at the hilum, the anatomical site of the poorly mobile bronchial and vascular insertions. Inp lane shear strain mapping showed mostly positive shear strain, predominant at the apex throughout inhalation, and increasing with expanding lung volum e. Anisotropy mapping showed that superior-inferior axial strain was greate r than medial-lateral axial strain at the apex and base, while the opposite was true for the middle lung field. This study demonstrates that localized pulmonary deformation can be measured in vivo with tagging AM, and quantif ied by applying finite strain definitions from continuum mechanics. (C) 200 1 Wiley-Liss, Inc.