Introduction. Despite the use of multiple diagnostic imaging techniques, a non-invasive differential diagnosis of focal lesions in the liver is still a challenging task. It is even more significant, considering the risk of complications related to liver biopsy. On the other hand, the availability of non-invasive radiological and diagnostic imaging methods has resulted in the increased detectability of incidental hepatic lesions. Therefore, further investigation of newer and more effective methods of differentiating benign from malignant hepatic lesions is extremely useful. The aim of the study was to assess the diagnostic value of Diffusion-Weighted Magnetic Resonance Imaging (DW MRI) in differentiating benign from malignant focal lesions in the liver.

Material and methods. Fifty one patients with hepatic lesions detected by magnetic resonance (MR) examination were enrolled in the study. Each lesion was then verified histopathologically, cytologically, or by observation. Ninety five (71 malignant and 24 benign) hepatic focal lesions were analysed. Apart from a standard MR liver examination, an echo planar imaging spin echo diffusion weighted sequence was performed, with a slice thickness of 5 or 6 mm. The maximal b-value was 1000 s/mm² and the minimal 0 s/mm².In the study, the following were assessed: the presence of restricted diffusion, an absolute ADC (apparent diffusion coefficient) value, the decrease of signal intensity in DW MRI with an increase in the b-value.

Results. Confirming or ruling out the restricted diffusion is usually the first effective step in differentiating benign from malignant hepatic lesions, as indicated in the study results. In the material analysed, the diffusion restriction occurred statistically significantly more frequently in malignant (87.3 %) compared to benign lesions (12.5%), (p < 0.0001). Using the diffusion restriction as a criterion for malignancy, 87.4% lesions were correctly classified (62 malignant and 21 benign lesions). In the material analysed, the mean minADC value in malignant lesions (0.92 × 10^-3 mm²/s) was statistically significantly lower compared to benign lesions (1.48 × 10^-3 mm²/s) (p < 0.0001). In clinical practice, it is important to determine the ADC reference values for benign and malignant lesions. The boundary ADC value differentiating benign from malignant lesions estimated when using the ROC curve was 1.04 × 10^-3 mm²/s. Considering lesions with an ADC value > 1.04 × 10^-3 mm2/s to be benign and lesions with ADC value ≤ 1.04 × 10^-3 mm²/s to be malignant, 75.8% lesions were correctly classified.

Conclusions. The results obtained indicate that restricted diffusion, as a marker for malignant lesions, has the highest value in DW MRI in differentiating benign from malignant lesions in the liver.