Diffusion weighted imaging with special reference to apparent diffusion coefficient (ADC) values in Cholangiocarcinoma- a narrative review

Diffusion Weighted Imaging (DWI) is dependent on micro-movement of water molecules within the intracellular and extracellular spaces. The ADC measures the flow and distance a water molecule has traveled, acting as an indicator of the water’s mobility inside the tissue. Cholangiocarcinomas are hyperintense on Diffusion-weighted imaging (DWI) with low ADC. The ADC values of cholangiocarcinoma might be used as an imaging biomarker to gauge the level of malignancy and the propensity of associated lymph node metastasis. Although repeatable trend of decreased ADC values was found to be associated with poor outcome, the different cut off ADC values in different studies for differentiating cholangiocarcinomas prohibits universal application and warrants further large-scale research with variable demographics.