Is it better to include necrosis in apparent diffusion coefficient (ADC) measurements? The necrosis/wall ADC ratio to differentiate malignant and benign necrotic lung lesions: Preliminary results

Purpose To determine whether the use of necrosis/wall apparent diffusion coefficient (ADC) ratios in the differentiation of necrotic lung lesions is more reliable than measuring the wall alone. Materials and Methods In this retrospective study, a total of 76 patients (54 males and 22 females, 71% vs. 29%, with a mean age of 53 ± 18 years, range, 18–84) were enrolled, 33 of whom had lung carcinoma and 43 had a benign necrotic lung lesion. A 3T scanner was used. The calculation of the necrosis/wall ADC ratio was based on ADC values measured from necrosis and the wall of the lesions by diffusion‐weighted imaging (DWI). Statistical analyses were performed with the independent samples t ‐test and receiver operating characteristic analysis. Intraobserver and interobserver reliability were calculated for ADC values of wall and necrosis. Results The mean necrosis/wall ADC ratio was 1.67 ± 0.23 for malignant lesions and 0.75 ± 0.19 for benign lung lesions ( P < 0.001). To estimate malignancy the area under the curve (AUC) values for necrosis ADC, wall ADC, and the necrosis/wall ADC ratio were 0.720, 0.073, and 0.997, respectively. A wall/necrosis ADC ratio cutoff value of 1.12 demonstrated a 100% sensitivity and 98% specificity in the estimation of malignancy. Positive predictive value was 100%, and negative predictive value 98% and diagnostic accuracy 99%. There was a good intraobserver and interobserver reliability for wall and necrosis. Conclusion The necrosis/wall ADC ratio appears to be a reliable and promising tool for discriminating lung carcinoma from benign necrotic lung lesions than measuring the wall alone. Level of Evidence: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1001–1006.