Computed DWI MRI Results in Superior Capability for N-Stage Assessment of Non-Small Cell Lung Cancer Than That of Actual DWI, STIR Imaging, and FDG-PET/CT

Background: Computed diffusion-weighted imaging (cDWI) is a mathematical computation technique that generates DWIs for any b-value by using actual DWI (aDWI) data with at least two different b-values and may improve differentiation of metastatic from nonmetastatic lymph nodes. Purpose: To determine the appropriate b-value for cDWI to achieve a better diagnostic capability for lymph node staging (N-staging) in non-small cell lung cancer (NSCLC) patients compared to aDWI, short inversion time (TI) inversion recovery (STIR) imaging, or positron emission tomography with 2-[fluorine-18] fluoro-2-deoxy-d-glucose combined with computed tomography (FDG-PET/CT). Study Type: Prospective. Subjects: A total of 245 (127 males and 118 females; mean age 72 years) consecutive histopathologically confirmed NSCLC patients. Field Strength/Sequence: A 3 T, half-Fourier single-shot turbo spin-echo sequence, electrocardiogram (ECG)-triggered STIR fast advanced spin-echo (FASE) sequence with black blood and STIR acquisition and DWI obtained by FASE with b-values of 0 and 1000 sec/mm². Assessment: From aDWIs with b-values of 0 and 1000 (aDWI₁₀₀₀) sec/mm², cDWI using 400 (cDWI₄₀₀), 600 (cDWI₆₀₀), 800 (cDWI₈₀₀), and 2000 (cDWI₂₀₀₀) sec/mm² were generated. Then, 114 metastatic and 114 nonmetastatic nodes (mediastinal and hilar lymph nodes) were selected and evaluated with a contrast ratio (CR) for each cDWI and aDWI, apparent diffusion coefficient (ADC), lymph node-to-muscle ratio (LMR) on STIR, and maximum standard uptake value (SUV_max). Statistical Tests: Receiver operating characteristic curve (ROC) analysis, Youden index, and McNemar's test. Results: Area under the curve (AUC) of CR₆₀₀ was significantly larger than the CR₄₀₀, CR₈₀₀, CR₂₀₀₀, aCR₁₀₀₀, and SUV_max. Comparison of N-staging accuracy showed that CR₆₀₀ was significantly higher than CR₄₀₀, CR₂₀₀₀, ADC, aCR₁₀₀₀, and SUV_max, although there were no significant differences with CR₈₀₀ (P = 0.99) and LMR (P = 0.99). Data Conclusion: cDWI with b-value at 600 sec/mm² may have potential to improve N-staging accuracy as compared with aDWI, STIR, and PET/CT. Evidence Level: 2. Technical Efficacy: Stage 2.