Emphysema quantification in inflation-fixed lungs using low-dose computed tomography and ³he magnetic resonance imaging

Objective: To evaluate the use of inflation-fixed lung tissue for emphysema quantification with computed tomography (CT) and 3He magnetic resonance (MR) diffusion imaging. Methods: Fourteen subjects representing a range of chronic obstructive pulmonary disease severity who underwent complete or lobar lung resection were studied. Computed tomographic measurements of lung attenuation and MR measurements of the hyperpolarized 3He apparent diffusion coefficient (ADC) in resected specimens fixed in inflation with heated formalin vapor were compared with measurements obtained before fixation. Results: The mean (SD) CT emphysema indices were 56% (17%) before and 58% (19%) after fixation (P = 0.77; R = 0.76). Index differences correlated with differences in lung volume (R ² = 0.47). The mean (SD) ³He ADCs were 0.40 (0.15) cm ²/s before and 0.39 (0.14) cm²/s after fixation (P = 0.03, R = 0.98). The CT emphysema index and the 3He ADC were correlated before (R = 0.89) and after fixation (R = 0.79). Conclusions: Concordance of CTand ³He MR imaging measurements in unfixed and inflation-fixed lungs supports the use of inflation-fixed lungs for quantitative imaging studies in emphysema.