Pulmonary MRI with ultra-short TE using single- and dual-echo methods: comparison of capability for quantitative differentiation of non- or minimally invasive adenocarcinomas from other lung cancers with that of standard-dose thin-section CT

Objective: The purpose of this study was thus to compare capabilities for quantitative differentiation of non- and minimally invasive adenocarcinomas from other of pulmonary MRIs with ultra-short TE (UTE) obtained with single- and dual-echo techniques (UTE-MRI_Single and UTE-MRI_Dual) and thin-section CT for stage IA lung cancer patients. Methods: Ninety pathologically diagnosed stage IA lung cancer patients who underwent thin-section standard-dose CT, UTE-MRI_Single, and UTE-MRI_Dual, surgical treatment and pathological examinations were included in this retrospective study. The largest dimension (D_long), solid portion (solid D_long), and consolidation/tumor (C/T) ratio of each nodule were assessed. Two-tailed Student’s t-tests were performed to compare all indexes obtained with each method between non- and minimally invasive adenocarcinomas and other lung cancers. Receiver operating characteristic (ROC)-based positive tests were performed to determine all feasible threshold values for distinguishing non- or minimally invasive adenocarcinoma (MIA) from other lung cancers. Sensitivity, specificity, and accuracy were then compared by means of McNemar’s test. Results: Each index showed significant differences between the two groups (p < 0.0001). Specificities and accuracies of solid D_long for UTE-MRI_{Dual2nd echo} and CT_Mediastinal were significantly higher than those of solid D_long for UTE-MRI_Single and UTE-MRI_{Dual1st echo} and all C/T ratios except CT_Mediastinal (p < 0.05). Moreover, the specificities and accuracies of solid D_long and C/T ratio were significantly higher than those of D_long for each method (p < 0.05). Conclusion: Pulmonary MRI with UTE is considered at least as valuable as thin-section CT for quantitative differentiation of non- and minimally invasive adenocarcinomas from other stage IA lung cancers. Clinical relevance statement: Pulmonary MRI with UTE’s capability for quantitative differentiation of non- and minimally invasive adenocarcinomas from other lung cancers in stage IA lung cancer patients is equal or superior to that of thin-section CT. Key Points: • Correlations were excellent for pathologically examined nodules with the largest dimensions (D_long) and a solid component (solid D_long) for all indexes (0.95 ≤ r ≤ 0.99, p < 0.0001). • Pathologically examined D_long and solid D_long obtained with all methods showed significant differences between non- and minimally invasive adenocarcinomas and other lung cancers (p < 0.0001). • Solid tumor components are most accurately measured by UTE-MRI_{Dual2nd echo} and CT_Mediastinal, whereas the ground-glass component is imaged by UTE-MRI_{Dual1st echo} and CT_lung with high accuracy. UTE-MRI_Dual predicts tumor invasiveness with 100% sensitivity and 87.5% specificity at a C/T threshold of 0.5.