Abstract: Objective The aim of this study was to investigate the diagnostic efficacy of apparent diffusion coefficient (ADC) by diffusion-weighted imaging (DWI) of magnetic resonance (MR) in patients with hepatic cystic echinococcosis (HCE) and simple hepatic cyst (SHC). Methods Forty-two patients with HCE and 34 patients with SHC were encountered in our hospital between July 2019 and July 2022, and all underwent MR DWI scan. The ADCs of lesions and livers were obtained when the b were at 500 s/mm² and 1000 s/mm². The diagnostic performance of ADC was analyzed by receiver operating characteristic curve (ROC). Finally, the ADC of MR DWI in the diagnosis of HCE was determined by Kappa consistency analysis. Results When the b equal to 500 s/mm², the focal ADC of patients with HCE was(3.1±0.7), and when the b equal to 1000 s/mm², the focal ADC was (2.4±0.6), both much lower than [(3.6±0.9) and (3.2±0.9), respectively, P＜0.05] in patients with SHC; the ROC analysis showed that when the b=500 s/mm², the optimal cut-off-value of ADC was set as it less than 3.235, with the AUC of 0.743 (95% CI:0.631-0.855) in diagnosis of HCE, the sensitivity (Se) of 0.706 and the specificity (Sp) of 0.690(P＜0.05); when the b=1000 s/mm², the focal ADC≤2.650 was set as the diagnosis of patients with HCE, with the AUC of 0.857 (95% CI:0.771-0.944), the Se of 0.824, and the Sp of 0.762(P＜0.05); the diagnosis of HCE was made when any of the cut-off-value of ADC met the criteria at any b, the consistency analysis confirmed that the diagnostic Se was 0.929, the Sp was 0.971, the accuracy was 0.947, the positive predictive value was 0.975, and the negative predictive value was 0.917 (Kappa=0.894). Conclusion The ADC at b =500 s/mm² or b =1000 s/mm² in lesions of HCE significantly decreases as compared with SHC, and the focal ADC could be applied for the differential diagnosis of the two lesions. We recommend each hospital build up its own cut-off-value of ADC for clinical diagnosis.

Key words: Hepatic cystic echinococcosis, Simple liver cyst, Magnetic resonance, Diffusion weighted imaging, Apparent diffusion coefficient, Diagnosis