Three‐dimensional assessment of lung tissue density using a clinical ultrashort echo time at 3 tesla: A feasibility study in healthy subjects

PURPOSE: To implement and assess the performance of three-dimensional (3D) ultra-short echo (UTE) time for evaluating lung tissue density changes induced by gravity dependence and lung inflation. MATERIALS AND METHODS: Twelve healthy volunteers were imaged by 3D UTE at 3 Tesla, during free-breathing and breathholding of the subjects. MR signal intensities were measured in lung tissue and muscle regions. The variations of MR lung signal intensity and lung water content were evaluated as a function of lung inflation and anterior/posterior position. RESULTS: SNR in lung tissue ranged between 35 for free-breathing acquisitions and 7 for breathhold acquisitions at functional residual capacity. Lung-to-muscle signal ratios decreased from 0.58 in posterior areas to 0.34 in anterior areas. The average water content measured in lungs was equal to 34% and 58% in gravitationally nondependent and dependent regions of interest. CONCLUSION: The 3D UTE lung MRI provides signal within lung parenchyma and can be used to assess lung tissue density.